Demonstration Program on Tomato

Background

Demonstration location: JiaGe Town,AnQiu,Shangdong province

Demonstration plant: Tomato

Area of planting: 2 acres(1 for demonstration;1 for comparison)

Fertilizer product: Anlisen and Volger for demonstration;other company’s product for comparison

Fertilization method: Rushing

Time for fertilizing: March 1 to April 3, 2017

We have released a series of new product according to soil issues,such as acidification, compaction, imbalance of nutrition, frequent pests and diseases.Also,we chose alkalescent Anlisen and Volger to do experiment on tomato in Anqiu,Shandong province.It could improve the applicability and reliability of the product in the area of Shangdong.

Notification

We selected five plants Randomly in the area of demonstration and area of comparison,and then measured the size of second ear fruit before and after fertilization.

In the demonstration area,we used Anlisen and Volger. In the comparison area,we chose other company’s fertilizer.

Comparison of the diameter of tomato in 2 areas

Conclusion

(1)In the demonstration area,the fruit grows fast.They are even in size, and there are almost no deformed and hollow ones; the fruit is quite solid,and accumulates enough sugar.Also, the color changes quickly.

  • In the comparison area,the fruit is smaller.Also,the fruit grows and changes more slowly.
  • In the early spring,the temperature of soil is low and the root’s activity is weak.Besides,the rate of absorbationis low.According to the above,we selected Volgar to improve the soil and stimulate the root. Finally,the fruit grows fast and turn color rapidly.

Hello, Philippines! Hello, Davao! Meet us at the 20th Davao Agri Trade Expo,20th~22nd, Sep.

the 20th Davao Agri Trade Expo

Hello, Philippines! Hello, Davao! Meet us at the 20th Davao Agri Trade Expo,20th~22nd, Sep.

Booth number: S3

 

Davao Agri Trade Expo 2018 presents you this year’s Food Security and Infrastructure Conference.The Food Security and Infrastructure Conference is slated on September 20, 2018, 1:00 PM to 5:00 PM. This Conference aims to inform and update on the current state of food security and Infrastructure in Mindanao under the Build! Build! Build! Program of the government.The said conference is to be held at Function Room 3 of SMX Convention Center, Davao City.Each delegate will be assessed a minimal fee of PhP 1,000. This fee includes the conference kit and food.Local Government Units (LGUs), National Government Organizations (NGOs), Civil Society Leaders, Agri-Entrepreneurs, Academes, Farmer Entreprenerus, and Start-Up Entrepreneurs are very much welcome to join us.

How to deal with citrus scab?

citrus scab

How to deal with citrus scab?

Recently, I saw a lot of growers facing the problem with the citrus scrab.

citrus scrab
citrus scrab
citrus scrab
citrus scrab

 

 

 

 

 

 

 

 

 

Why did this happen?

Cause thrips and other bugs attack, during the end of flowering stage, the bugs bite on the flower ovary or baby fruits, then after the fruit grown, there will be a scar on the surface.

How to prevent this?

Solutions:

1.Use Spinetoram, before the followering period, this is the pesticides specialise on thrips. (Of course, imidacloprid or acetamiprid could be a choice, but the dosage should be increased, and these two will cause resistance to drugs)

2.Supply enough Boron and Calcium by foliar, to improve crop resistance to disease. As Andatrace elements, and Megaswell.

Andatrace elements contains of various of trace elements one solution for all crops in different stage. And megaswell products, mostly provide with Ca&Mg.

How to control Tomato Bacterial Wilt caused by Ralstonia solanacearum.

How to control Tomato Bacterial Wilt caused by Ralstonia solanacearum.

  1. Chemical way, by adopting Zinc thiazole, in formula C4H4N6S4Zn.

    Zinc thiazole
    Zinc thiazole
    1. Application method:
      1. Remove diseased plants immediately and do not compost the diseased plants.
      2. Making stock solution by using Zinc thiazole.  Concentration: 1:200~500.
      3. Watering roots. To young plants, normally 200ml stock solution used. To older plants with stronger roots, raising the quantity accordinly.

        watering roots
        watering roots
      4. All the plants should be treated with this methods.
    2. Notification:
      1. Do not irrigate before or after the application. If the plants needs water, try to irrigate with irrigation ditch, with a certain distance to the roots.
      2. Try to applicate in sunny weather.
  2. cultural control, as a reference from https://tomatodiseasehelp.com/treat-bacterial-wilt

    1. Running water can spread the disease to other parts of the garden so rotate your crops regularly away from host plants which could include all of the nightshades (tomatoes, peppers and eggplants), flowers including sunflowers and cosmos and potatoes.
    2. Try raised beds to improve drainage and control root knot nematodes that weaken plants, leaving them more susceptible to disease.
    3. Space plants far enough apart to provide good air circulation.
    4. Have your soil tested and maintain a pH of 6.2-6.5, which is ideal for growing tomatoes and many other vegetables.
    5. Wash your hands after handling infected plants and sterilize any gardening tool that could have been used in infected soil.

Nutritional recommendations for TOMATO in open-field, tunnels and greenhouse

1. About the crop

1.1 Growth patterns-Nutritional recommendations for TOMATO in open-field, tunnels and greenhouse

Tomato cultivars may be classified into three groups by their growth patterns, which are recognized by the arrangement and the frequency of leaves and the inflorescence on the stem.

a) Indeterminate growth – the main and side stems continue their growth in a continuous pattern. The number of leaves between inflorescence is more or less constant, starting from a specific flowering set (Fig. 1a). Cultivars of indeterminate growth are usually grown as greenhouse or staked tomatoes.

b) Determinate growth – the main and side stems stop growth after a specific number of inflorescences that varies with the specific cultivar (Fig. 1b). Processing tomatoes are often belong to determinate cultivars.

c) Semi-determinate growth – branches stop growth with an inflorescence, but this usually occurs at an advanced growth stage. Cultivars of this group are usually grown as out-door, non-staked tomatoes.

Table 1: Number of leaves between inflorescence in different growth patterns

1.2 Growth stages

Growth stages of plants, in very general terms, can be split into four periods:

  • Establishment from planting or seeding during vegetative growth until first flower appears.
  • From first flowering to first fruit set
  • From fruit ripening to first harvest
  • From first harvest to the end of last harvest.

These growth periods also represent different nutritional needs of the plant (see section 3.1).

The duration of each stage may vary according to growing method, variety characteristics and climatic conditions (Table 2).

Table 2: A typical example of a growth cycle in central Israel by growth stages

1.3 Fruit development

After fruit setting, fruit ripens over a period of 45 – 70 days, depending upon the cultivar, climate and growth conditions. The fruit continues growing until the stage of green ripeness.

Three fruit developmental stages are noted.

Ripening occurs as the fruit changes color from light green to off-white, pink, red, and finally dark red or orange. Depending on the distance and time to market, harvest may occur anytime between the pink to dark red stage, the later stages producing more flavorful fruit.

Table 3: Stages of fruit ripening

1.4 Crop uses

Tomatoes are consumed fresh, and are being processed to pickles, sauce, juice and concentrated pastes

Growing conditions

2.1 Growing methods

Soil or soilless, protected crop (greenhouse or high plastic tunnel) or open field.

2.2 Soil type

Tomatoes can be grown on soils with a wide range of textures, from light, sandy soils to heavy, clay soils. Sandy soils are preferable if early harvest is desired. Favorable pH level: 6.0-6.5. At higher or lower pH levels micronutrients become less available for plant uptake.

2.3 Climate

Temperature is the primary factor influencing all stages of development of the plant: vegetative growth, flowering, fruit setting and fruit ripening. Growth requires temperatures between 10°C and 30°C.

Table 4: Temperature requirements during different growth stages:

Light intensity is one of the major factors affecting the amounts of sugars produced in leaves during the photosynthesis, and this, in turn, affects the number of fruits that the plant can support, and the total yield.

2.4 Irrigation

Tomato plants are fairly resistant to moderate drought. However, proper management is essential to assure high yield and quality. The water requirement of outdoor grown tomatoes varies between 4000 – 6000 m³/ha. In greenhouses up to 10,000 m3/ha of water are required. 70% or more of the root system are in the upper 20 cm of the soil. Therefore, a drip system equipped with a fertigation device is advisable. On light soils or when saline water is used, it is necessary to increase water quantities by 20% – 30%. Water requirements will differ at various growth stages. The requirement increases from germination until beginning of fruit setting, reaching a peak during fruit development and then decreasing during ripening. Mild water stress during fruit development and ripening has a positive effect on fruit quality: firmness, taste and shelf-life quality, but may result in smaller fruit. Late irrigation, close to harvesting, may impair quality and induce rotting. Water shortage will lead to reduced growth in general and reduced uptake of calcium in particular. Calcium deficiency causes Blossom End Rot (BER) (see page 15). On the other hand, excessive irrigation will create anaerobic soil conditions and consequently cause root death, delayed flowering and fruit disorders.

Water quality: Tomatoes tolerate brackish water up to conductivity of about 2-3 mmho/cm. Acidic (low pH) irrigation water is undesirable, as it might lead to the dissolution of toxic elements in the soil (e.g. Al3+).

2.5 Specific sensitivities of the tomato plant

Sensitivity to soil-borne diseases

Tomatoes are prone to soil-borne diseases caused by fungi, viruses or bacteria. Therefore it is recommended to avoid growing tomatoes on plots that used for other sensitive crops (peppers, eggplants, Irish potatoes, sweet potatoes, cotton, soybeans and others) on recent years. A regime of 3-year rotation between small grains and tomatoes is recommended.

Sensitivity to salinity

Under saline conditions, sodium cations compete with the potassium cations for the roots uptake sites, and chloride competes for the uptake of nitrate-nitrogen and will impede plant development

(Fig.2) and reduce yield.

Figure 2: Inverse relationship between top dry weight and concentration of plant tissue chloride – the higher the chloride in the plant composition, the lower its dry weight.

Salinity will result in a potassium deficiency in the tomato plants, leading to a low fruit number per plant. Corrective measures under such conditions must include the following steps:
 Abundant application of potassium, as this specific cation can successfully compete with the sodium, and considerably reduce its uptake and the resulting negative effects. (Fig. 3)
 Abundant application of nitrate, as this specific anion successfully competes with chloride, and markedly reduces its uptake and adverse effects.
 Also, calcium helps suppressing the uptake of sodium. When sufficient calcium is available, the roots prefer uptake of potassium to sodium, and sodium uptake will be suppressed.

Figure 3: ACK01 potassium nitrate reverses the adverse effects of salinity in greenhouse tomatoes

Salination of the nutrient solution markedly decreased dry weight of the plant, fruit size and plant height. The addition of 4 or 8 mM ACKO1 potassium nitrate to the salinized nutrient solution markedly increased EC values of the nutrient solution but reversed the said adverse effects caused by the NaCl. Several parameters were improved even over the control as a direct result of the treatment with ACK01, i.e., fruit size and plant height (Fig. 4).

Figure 4: The effect of salinity and ACK01 potassium nitrate on vegetative parameters and fruit size in ‘Pusa ruby’ greenhouse tomatoes.

Zinc improves tolerance to salt stress.Zinc nutrition in plants seems to play a major role in the resistance to salt in tomato and other species. Adequate zinc (Zn) nutritional status improves salt stress tolerance, possibly, by affecting the structural integrity and controlling the permeability of root cell membranes. Adequate Zn nutrition reduces excessive uptake of Na by roots in saline conditions.

Sensitivity to calcium deficiency. Tomatoes are highly sensitive to calcium deficiency, which is manifested in the Blossom-End Rot (BER) symptom on the fruits. Salinity conditions severely enhance BER intensity. Recently, it was found that manganese (Mn) serves as antioxidant in tomato fruit, hence its application to tomatoes grown under salinity can alleviate BER symptoms in the fruits. Special care must be taken to avoid growing conditions, which enhance BER phenomenon.

Plant nutrition

3.1 Dynamics of nutritional requirements

Nitrogen and potassium uptake is initially slow but rapidly increases during the flowering stages.
Potassium is peaking during fruit development, and nitrogen uptake occurs mainly after the formation of the first fruit. (Figs. 5 and 6).
Phosphorus (P) and secondary nutrients, Ca and Mg, are required at a relatively constant rate, throughout the life cycle of the tomato plant.
Figure 5: The uptake dynamics of the macro- and the secondary nutrients by a tomato plant(Source: Huett, 1985)

Figure 6: Daily uptake rates of plant nutrients by processing tomatoes yielding 127 T/ha (Source: B. Bar-Yosef . (Fertilization under drip irrigation

As can be seen in figures 5 and 6, the greatest absorption of nutrients occurs in the first 8 to 14 weeks of growth, and another peak takes place after the first fruit removal. Therefore, the plant requires high nitrogen application early in the growing season with supplemental applications after the fruit initiation stage. Improved N use efficiency and greater yields are achieved when N is applied under polyethylene mulches via a drip irrigation system. At least 50 % of the total N should be applied as nitrate-nitrogen (NO3 ).The most prevalent nutrient found in the developed tomato plant and fruit is potassium, followed by nitrogen (N) and calcium (Ca). (Figures 7 and 8)

Figure 7: Element composition of a tomato plant. (Atherton and Rudich, 1986)

Figure 8: Element composition of a tomato fruit (Atherton and Rudich, 1986)

3.2 Main functions of plant nutrients

Table 5: Summary of main functions of plant nutrients:

Nitrogen (N)

The form in which N is supplied is of major importance in producing a successful tomato crop. The optimal ratio between ammonium and nitrate depends on growth stage and on the pH of the growing medium. Plants grown in NH4+ -supplemented medium have a lower fresh weight and more stress signs than plants grown on NO3 only. By increasing the ammonium nitrate rates, the EC increases and consequently the yield decreases. However, when doubling the rate of ACK01 potassium nitrate, the EC increases without adverse effect on the yield that increases as well (Table 6).

Table 6: The effect of nitrogen form (NO3 and NH4+) on tomato yield – showing the advantages of nitrate-nitrogen over ammoniacal nitrogen.

Potassium (K)

Ample amounts of potassium must be supplied to the crop in order to ensure optimal K levels in all major organs, mainly due to the key role K plays in tomatoes:

1. Balancing of negative electrical charges in the plant

As a cation, K+ is THE dominant cation, balancing negative charges of organic and mineral anions. Therefore, high K concentration is required for this purpose in the cells.

2. Regulating metabolic processes in cells

Main function is in activating enzymes – synthesis of protein, sugar, starch etc. (more than 60 enzymes rely on K). Also, stabilizing the pH in the cell at 7 – 8, passage through membranes, balancing protons during the photosynthesis process.

3. Regulation of osmotic pressure

Regulating plant’s turgor, notably on guard cells of the stomata. In the phloem, K contributes to osmotic pressure and by that transporting metabolic substances from the “source” to “sink” (from leaves to fruit and to nurture the roots). This K contribution increases the dry matter and the sugar content in the fruit as well as increasing the turgor of the fruits and consequently prolonging fruits’ shelf life. Additionally, potassium has the following important physiological functions:

Improves wilting resistance. (Bewley and White ,1926, Adams et al ,1978)
Enhances resistance toward bacterial viral, nematodes and fungal pathogens. (Potassium and Plant Health, Perrenoud, 1990).

Reduces the occurrence of coloration disorders and blossom-end rot. (Winsor and Long, 1968)

Increases solids content in the fruit. (Shafik and Winsor,1964)

Improves taste. (Davis and Winsor, 1967)

Figure 9: The effect of K rate on the yield and quality of processing tomatoes

Lycopene is an important constituent in tomatoes, as it enhances the resistance against cancer.

Increasing ACK01 potassium nitrate application rates increases lycopene content of the tomato. The function is described by an optimum curve (Fig. 10).

Figure 10: The effect of ACK01 rate on lycopene yield in processing tomatoes

ACK-01 was applied, as a source of potassium, either by itself or blended with other N and P fertilizers, to processing tomatoes. The different application methods, side-dressing dry fertilizers or combined with fertigation, were compared in a field trial (Table 7). ACK-01 increased the yield (dry matter) and the brix level as can be seen in Figure 11.

Table 7: Layout of a field trial comparing different ACK-01 potassium nitrate application methods and rates, as a source of K, combined with other N and P fertilizers:

Figure 11: The effect of application method and rates of ACK-01 potassium nitrate on the dry matter yield and brix level of processing tomatoes cv Peto.

Calcium (Ca)

Calcium is an essential ingredient of cell walls and plant structure. It is the key element responsible for the firmness of tomato fruits. It delays senescence in leaves, thereby prolonging leaf’s productive life, and total amount of assimilates produced by the plans.Temporary calcium deficiency is likely to occur in fruits and especially at periods of high growth rate, leading to the necrosis of the apical end of the fruits and a development of BER syndrome.

3.3 Nutrients deficiency symptoms

Tomatoes are rather sensitive to excess or deficiency of both macro- and micro- nutrients. Examples of common deficiencies, particularly in soilless culture, other than those of N and P, are: K deficiency, affecting fruit quality; Ca deficiency, causing blossom-end rot; Mg deficiency, in acid soils and in the presence of high levels of K; and deficiencies of B, Fe and Mn in calcareous soils.

Nitrogen

The chlorosis symptoms shown by the leaves on Figure 12 are the direct result of nitrogen deficiency. A light red cast can also be seen on the veins and petioles. Under nitrogen deficiency, the older mature leaves gradually change from their normal characteristic green appearance to a much paler green. As the deficiency progresses these older leaves become uniformly yellow chlorotic). Leaves become yellowish-white under extreme deficiency. The young leaves at the top of the plant maintain a green but paler color and tend to become smaller in size. Branching is reduced in nitrogen deficient plants resulting in short, spindly plants. The yellowing in nitrogen deficiency is uniform over the entire leaf including the veins. As the deficiency progresses, the older leaves also show more of a tendency to wilt under mild water stress and senesce much earlier than usual. Recovery of deficient plants to applied nitrogen is immediate (days) and spectacular.

Figure 12: Characteristic nitrogen (N) deficiency symptom

 

Phosphorus

The necrotic spots on the leaves on Fig. 13 are a typical symptom of phosphorus (P) deficiency. As a rule, P deficiency symptoms are not very distinct and thus difficult to identify. A major visual symptom is that the plants are dwarfed or stunted. Phosphorus deficient plants develop very slowly in relation to other plants growing under similar environmental conditions but with ample phosphorus supply. Phosphorus deficient plants are often mistaken for unstressed but much younger plants. Developing a distinct purpling of the stem, petiole and the lower sides of the leaves. Under severe deficiency conditions there is also a tendency for leaves to develop a blue-gray luster. In older leaves under very severe deficiency conditions a brown netted veining of the leaves may develop.

Figure 13: Characteristic phosphorus (P) deficiency symptom

Potassium

The leaves on the right-hand photo show marginal necrosis (tip burn). The leaves on the left-hand photo show more advanced deficiency status, with necrosis in the interveinal spaces between the main veins along with interveinal chlorosis. This group of symptoms is very characteristic of K deficiency symptoms.

Figure 14: Characteristic potassium (K) deficiency symptoms.

The onset of potassium deficiency is generally characterized by a marginal chlorosis, progressing into a dry leathery tan scorch on recently matured leaves. This is followed by increasing interveinal scorching and/or necrosis progressing from the leaf edge to the midrib as the stress increases. As the deficiency progresses, most of the interveinal area becomes necrotic, the veins remain green and the leaves tend to curl and crinkle. In contrast to nitrogen deficiency, chlorosis is irreversible in potassium deficiency. Because potassium is very mobile within the plant, symptoms only develop on young leaves in the case of extreme deficiency. Typical potassium (K) deficiency of fruit is characterized by color development disorders, including greenback, blotch ripening and boxy fruit (Fig. 15).

Figure 15: Characteristic potassium (K) deficiency symptoms on the fruit

Calcium

These calcium-deficient leaves (Fig. 16) show necrosis around the base of the leaves. The very low mobility of calcium is a major factor determining the expression of calcium deficiency symptoms in plants. Classic symptoms of calcium deficiency include blossom-end rot (BER) burning of the end part of tomato fruits (Fig. 17). The blossom-end area darkens and flattens out, then appearing leathery and dark brown, and finally it collapses and secondary pathogens take over the fruit.

Figure 16: Characteristic calcium (Ca) deficiency symptoms on leaves

Figure 17: Characteristic calcium (Ca) deficiency symptoms on the fruit

All these symptoms show soft dead necrotic tissue at rapidly growing areas, which is generally related to poor translocation of calcium to the tissue rather than a low external supply of calcium. Plants under chronic calcium deficiency have a much greater tendency to wilt than non-stressed plants.

Magnesium

Magnesium-deficient tomato leaves (Fig. 18) show advanced interveinal chlorosis, with necrosis developing in the highly chlorotic tissue. In its advanced form, magnesium deficiency may superficially resemble potassium deficiency. In the case of magnesium deficiency the symptoms generally start with mottled chlorotic areas developing in the interveinal tissue. The interveinal laminae tissue tends to expand proportionately more than the other leaf tissues, producing a raised puckered surface, with the top of the puckers progressively going from chlorotic to necrotic tissue.

Figure 18: Characteristic magnesium (Mg) deficiency

Sulfur

This leaf (Fig. 19) shows a general overall chlorosis while still retaining some green color. The veins and petioles exhibit a very distinct reddish color. The visual symptoms of sulfur deficiency are very similar to the chlorosis found in nitrogen deficiency. However, in sulfur deficiency the yellowing is much more uniform over the entire plant including young leaves. The reddish color often found on the underside of the leaves and the petioles has a more pinkish tone and is much less vivid than that found in nitrogen deficiency. With advanced sulfur deficiency brown lesions and/or necrotic spots often develop along the petiole, and the leaves tend to become more erect and often twisted and brittle.

Figure 19: Characteristic sulfur (S) deficiency

Manganese

These leaves (Fig. 20) show a light interveinal chlorosis developed under a limited supply of Mn.

The early stages of the chlorosis induced by manganese deficiency are somewhat similar to iron deficiency. They begin with a light chlorosis of the young leaves and netted veins of the mature leaves especially when they are viewed through transmitted light. As the stress increases, the leaves take on a gray metallic sheen and develop dark freckled and necrotic areas along the veins. A purplish luster may also develop on the upper surface of the leaves.

Figure 20: Characteristic manganese (Mn) deficiency

Molybdenum

These leaves (Fig. 21) show some mottled spotting along with some interveinal chlorosis. An early symptom for molybdenum deficiency is a general overall chlorosis, similar to the symptom for nitrogen deficiency but generally without the reddish coloration on the undersides of the leaves. This results from the requirement for molybdenum in the reduction of nitrate, which needs to be reduced prior to its assimilation by the plant. Thus, the initial symptoms of molybdenum deficiency are in fact those of nitrogen deficiency. However, molybdenum has also other metabolic functions within the plant, and hence there are deficiency symptoms even when reduced nitrogen is available. At high concentrations, molybdenum has a very distinctive toxicity symptom in that the leaves turn a very brilliant orange.

Figure 21: Characteristic molybdenum (Mo) deficiency

Zinc

This leaf (Fig. 22) shows an advanced case of interveinal necrosis. In the early stages of zinc deficiency the younger leaves become yellow and pitting develops in the interveinal upper surfaces of the mature leaves. As the deficiency progresses these symptoms develop into an intense interveinal necrosis but the main veins remain green, as in the symptoms of recovering iron deficiency.

Figure 22: Characteristic zinc (Zn) deficiency symptoms.

Boron

This boron-deficient leaf (Fig. 23) shows a light general chlorosis. Boron is an essential plant nutrient, however, when exceeding the required level, it may be toxic. Boron is poorly transported in the phloem. Boron deficiency symptoms generally appear in younger plants at the propagation stage. Slight interveinal chlorosis in older leaves followed by yellow to orange tinting in middle and older leaves. Leaves and stems are brittle and corky, split and swollen miss-shaped fruit (Fig. 24).

Figure 23: Characteristic boron (B) deficiency symptoms on leaves

Figure 24: Characteristic boron (B) deficiency symptoms on fruits

Copper

These copper-deficient leaves (Fig. 25) are curled, and their petioles bend downward. Copper deficiency may be expressed as a light overall chlorosis along with the permanent loss of turgor in the young leaves. Recently matured leaves show netted, green veining with areas bleached to a whitish gray. Some leaves develop sunken necrotic spots and have a tendency to bend downward.

Figure 25: Characteristic copper (Cu) deficiency symptoms.

Iron

These iron-deficient leaves (Fig. 26) show intense chlorosis at the base of the leaves with some green netting. The most common symptom for iron deficiency starts out as an interveinal chlorosis of the youngest leaves, evolves into an overall chlorosis, and ends as a totally bleached leaf. The bleached areas often develop necrotic spots. Up until the time the leaves become almost completely white they will recover upon application of iron. In the recovery phase the veins are the first to recover as indicated by their bright green color. This distinct venial re-greening observed during iron recovery is probably the most recognizable symptom in all of classical plant nutrition. Because iron has a low mobility, iron deficiency symptoms appear first on the youngest leaves. Iron deficiency is strongly associated with calcareous soils and anaerobic conditions, and it is often induced by an excess of heavy metals.

Figure 26: Characteristic iron (Fe) deficiency symptoms

3.4 Leaf analysis standards

In order to verify the correct mineral nutrition during crop development, leaf samples should be taken at regular intervals, beginning when the 3rd cluster flowers begin to set. Sample the whole leaf with petiole, choosing the newest fully expanded leaf below the last open flower cluster.

Sufficiency leaf analysis ranges for newest fully-expanded, dried whole leaves are:

Table 8: Nutrients contents in tomato plant leaves

Macro and secondary nutrients

Micronutrients

Toxic levels for B, Mn, and Zn are reported as 150, 500, and 300 ppm, respectively.

3.5 Overall nutritional requirements

Table 9: Overall requirements of macro-nutrients under various growth conditions

(Followed by fertilizer recommendations.)

MAIN DIFFERENCE BETWEEN TWO TYPES OF DIAMMONIUM PHOSPHATE

MAIN DIFFERENCE BETWEEN TWO TYPES OF DIAMMONIUM PHOSPHATE

Normally there is two tyeps of diammonium phosphate in agriculture fertilizer industry.

There main difference is caused by the process and material.

They are obviously different from the apperaence, 18 46, granular, and in brown color. 21 53, crystal, and in white color.

MAIN DIFFERENCE BETWEEN TWO TYPES OF
DIAMMONIUM PHOSPHATE
DAP
Type
RAW
MATERIAL
NUTRITION
CONTAINS
SOLUBILITY HEVEY
METAL
SOIL
FRIENDLY
FOLILAR &Drip USE RELEASE SPEED
18-46-00 wet process phosphate acid 64 min Obviouse Impurities High No No SLOW
21-53-00 purified phosphate acid 74 min 100% water soluble Low Yes Yes QUICK
1, The root difference of these two items comes from the raw material. 21-53-00 type use purified phosphate acid, obviously, purified phosphate acid is more complex to produce, so the cost could be higher. This purification process, makes the 21-53-00 contains less heavy metal and other impurities. So that the 21-53 is soil friendly, and cause no damage to the mother earth. In this reason, the 21-53-00 can by used as foliar fertilizer, which is impossible for 18-46-00.

2, 18-46-00 is often used as base fertilizer in large quantity, as a  result, the fertility of the soil going down and the heavy metal contain is going high, which is not a environmental sustainable solution.
Nowadays, more and more countries realise this problem of 18-46 and grandually reduce the use of 18-46, meanwhile encourage the farmers to use 21-53 as a replacement.

3, To the application, 18-46 is mainly used as the base fertilizer or basal dressing, it used to provide the macro nutrients needed in the WHOLE period of the crops. So, it is used in large quanitty. But due to the diversity of the soil and climate conditions, the absorption of nutrients is different. So, in many cases, even the farmer use a large amount of 18-46, the crops stills performs the lack of Phosphorus.
And also, 18-46 is slow release type. the release is gradually increase of decrease according to the temperature, wet, or other conditions. Some certain period of the growing of crops needs more nutrients, like Mango tree, the sapling period needs more phosphorus than other periods. In this period, if you dont supply Phosphorus quick and fast, the Mango tree will suffer from a bad rooting system.
In this case, 21-53 is needed to supply phosphorus by foliar or driping, quick and fast.
In clusion, 18-46 is a solution for all time.  but 21-53 can provide with a Precision strike solution.

 

Saline-Alkali Soil Reclamation, Suggestion to Imran Baloch from Nawabshah, Sindh, Pakistan

Saline-Alkali Soil Reclamation, Suggestion to Imran Baloch from Nawabshah, Sindh, Pakistan

Recently, Imran Baloch from Nawabvshah, Sindh contact me for suggestion on his soil.

He sent me pictures of his soil, as following (click for HD picture):

From the picture, we can tell. 1.The soil is in heavy Saline-Alkali situation.2.The soil is dry and heavy caking.3.The affecting area is wide.

To figure out the casue, we go to the temerature and rain data of Nawabshan( the temperature in Celsius, rain  in MM ).

The fact is the rain of whole year is less than 100mm, and arround 8 months of a year, the daily Highest temp is over 40 Celsius.

After collecting this facts, we finally understand the main cause of  the 15 hectares Saline-Alkali Soil in Mr Imran’s farm land.

  1. High temperature and low rainfall, cause High evaporation, which is the main cause.
  2. Unreasonale irrigation
  3. Abuse use of insoluble chemical fertilizer.
  4. Other related cause like,low lying land, high river water level, etc.

Before we make the suggestion, we need to come to a consensus that Saline-Alkali Soil problem is a tough problem in agriculral industry worldwide. It can not be 100% solved but only reclamation.

Our suggestion as following:

  1. Hydraulic Engineering. Saperate the irrigation system  with drainage system. Make sure the river water come to your land and flow away, not evaporate. In this process, use the fresh river water to flush the land, water will dissolve the saline alkali material and take them away.  Wash the land two or three times, each time with 1600~2000 metric tons water per hectare, with intervals 5~7days.  And we suggest to process the washing at the period  between the end of November and the end of March. In winter time of Nawabshah, the temperature is low and the evaporating is also at low level.
  2. Agricultural tech. By deep ploughing the soil, filling with heathy soil from other place, and we can also add more crop straw in the soil. Try to promote the Soil permeability.  After, we rapidly fasten the steps of soil washing with 3~4 days intervals and increase the frequency.
  3. Biological method. We can use green manure, straw, bio-fertilizer, plant  salt-tolerant plants, do afforestation and so on, improve soil fertility, improve soil structure, and improve farmland microclimate, reduce evaporation of surface water, prevente the Saline return.
  4. Chemical method. FeSO4·7H2O is recommended to use for reduce the Alkaline and adjust the soil, it can also be a good source of Iron and Sulphur.   Besides, we recommend low pH water soluble fertilzier as the source of macro nutrients, like Urea Phosphate in NPK as 17-44-00, and the pH is extremely low to 1.5~2 and it is also water soluble.  And also stop using Potassium Cloride, Ammonium sulphate., Calcium superphosphate, Magnisum sulpohate.  Use water soluble fertilizer in fertifation and foliar instead.

By the way, our company only focus on water soluble fertilzier, macro nutrients like monoammonium phosphate map 12-61-00, a very good source of nitrogen and phosphorus; monopotassium phosphate mkp 00-52-34, a very good source of phosphorus and potassium; potassium nitrate nop 13-00-46, nitrogen and potassium source. and many other water soluble NPKs and Chelated trace elements,  they all can be used both foliar and irrigation.

You can check the products here: https://www.andagro.com/product/

For more info, you can leave me your message here, or directly send me email chao.h@andagro.com or chao.h@anda-chem.com. I will reply as soon as I can.

Citrus Nutritional Management – Nutrition Supply Analysis and Recommendation

(Former Chapter please check Citrus Nutritional Management – Nutrition Function )

Citrus Nutritional Management – Nutrition Supply Analysis and Recommendation

2.4  Special sensitivities of citrus

2.4.1 Salinity

Citrus is sensitive to high concentrations of salt (sodium chloride) in the soil or in irrigation water. Salt toxicity causes leaf burn and yellowing, starting near the tip. Leaf drop is heavy and dieback follows. Older leaves show the symptoms first.

Citrus is moderately sensitive to salinity: Sensitivity Threshold = 1.7 dS/m; Yield decline slope (beyond threshold) = 16 % / EC unit (Fig. 31 – 35).

Figure 31: The effect of chloride on citrus fruit yield

Figure 32: Salinity-resulted tip burn

Figure 33: Salinity – Twig dry out

Figure 34: Twig dry out

Figure 35: Wide areas of chlorosis along the margins and between veins of lemon leaves due to high salt concentrations

Symptoms of salt toxicity often begin as yellowing and grey or light-brown burn of the leaf tip. The burn extends back from the tip and then develops along the edges of other parts of the leaf edge. A variable degree of yellowing can develop ahead of the burnt tissue. The tolerance limit of salinity in the root-zone for ‘Valencia’ oranges is estimated at an EC of 2.5 – 3.0 ds/m. The growth of citrus species and their fruit yield is generally reduced at soil electrical conductivities (EC) above 1.4 ds/m. Salinity, not only reduces growth and yield due to the osmotic potential effect, but for the same reasoning salinity delays and depresses emergence, reduces shoot and root biomasses. The use of more tolerant scions and salt-excluding rootstocks helps minimize salt injury to trees and loss of production. Lemons are more susceptible than grapefruits or oranges. Citrus on rough lemon rootstock are more susceptible to salt toxicity than those on Troyer or Carrizo citrange, with sweet orange stock being the most tolerant of the stocks commonly used for oranges. Poncirus trifoliata rootstock allows high levels of chloride to accumulate in the tree, whereas Rangpur lime and Cleopatra mandarin stocks are the most effective in excluding chloride, where their use is appropriate.

ACK-01 (Anda Classic Potassium Nitrate – KNO3) combats successfully salinity by suppressing the uptake of chloride and sodium. The antagonistic effects of nitrate-nitrogen (NO3-) and potassium (K+) suppress these ions, Cl- and Na+. The higher concentration of ACK-01 in the soil solution, the better results of combating salinity can be expected (Fig. 36-37).

Figure 36: The Effect of ACK-01 ANDA CLASSIC Potassium Nitrate on chloride content of a citrus leaf under saline conditions. ACK-01 treatment: constant concentration of 200ppm in the irrigation water.

Figure 37: ACK-01 Anda Classic potassium nitrate increases nitrate content in citrus leaves under saline conditions. ACK-01 treatment: constant concentration of 200ppm in the irrigation water.

High sodium level in the soil damages its particles structure and reduces water penetration. High sodium competes with potassium uptake, leading to potassium deficiency and upset tree nutrition. Correcting the salinity often restores normal potassium nutrition. When applying potassium fertilizer in saline areas, ACK-01 (potassium nitrate – KNO3) should be used and not potassium chloride (muriate of potash). This is an effective way to minimize the salinity problem, due to the antagonistic effect, will successfully suppress the uptake of sodium (Na+) and increase the K+ in leaves (Fig. 38-39) and in results,ACK-01 increases yield (Fig. 40).

Figure 38: ACK-01 potassium nitrate reduces Sodium (Na) content in citrus leaves under saline conditions. ACK-01 treatment: constant concentration of 200ppm in the irrigation water.

Figure 39: ACK-01 potassium nitrate increases K content in citrus leaves under saline conditions. ACK-01 treatment: constant concentration of 200 ppm in the irrigation water.

Figure 40: The Effect of ACK-01 potassium nitrate on the yield of citrus under saline conditions

2.4.2 Salt injury

Many salinity-induced symptoms are similar to drought stress symptoms, including reduced root growth, decreased flowering, smaller leaf size, and impaired shoot growth. These can occur prior to more easily observed ion toxicity symptoms on foliage. Chloride toxicity, consisting of burned necrotic or dry appearing edges of leaves, is one of the most common visible salt injury symptoms. Actual sodium toxicity symptoms can seldom be identified, but may be associated with the overall leaf “bronzing” (Fig. 41) and leaf drop characteristic of salt injury. Slightly different symptomology may occur depending on whether injury is due to root uptake or foliage contact. Excessive fertilizer applications, highly saline irrigation water, and storm-driven ocean sprays can all result in salinity-induced phytotoxic symptoms.

Figure 41 a-b: Salt injury

2.4.3 Copper toxicity

Symptoms can include thinning tree canopies, retarded growth and foliage with iron deficiency symptoms. Feeder roots may also become darkened, and show restricted growth. When extractable copper exceeds 100 pounds per acre, (1.12 kg/ha) trees may begin to decline. Old citrus land should be checked for soil copper before replanting. High soil copper levels may be ameliorated by liming to pH 6.5. The rootstock Swingle citrumelo is known to be quite susceptible to high soil copper.

2.4.4 Boron toxicity

Early stages of boron toxicity usually appear as a leaf tip yellowing or mottling (Fig. 42). In severe cases, gum spots appear on lower leaf surfaces (Fig. 43) with leaf drop occurring prematurely. Severe symptoms can include twig dieback .

Figure 42: leaves showing the signs of boron toxicity

Figure 43: Gumming on underside of leaf

Figure 44: Necrosis at the tips and chlorosis beginning between the veins of Valencia orange leaves due to excessive boron.

High boron level in the irrigation water or in the soil may be problematic for growing citrus. Only in cases where the soil is the source of high boron, leaching irrigations and improved drainage will control the problem. Rootstocks and scions differ in their susceptibility to boron toxicity. Citrus on rough lemon stock are more affected than those on sweet orange or Poncirus trifoliata rootstock. Lemons are the most susceptible scion, followed by mandarins, grapefruit and oranges.

2.4.5 Manganese toxicity

Manganese toxicity symptoms are occasionally found in citrus growing in very acid soils (usually below pH 5.0). The soil may be naturally acidic or have become acidic through continued heavy applications of strongly acidifying fertilizers, particularly ammonium sulfate.

Yellowing around the outer part of the leaves, especially of the older leaves, is the most characteristic effect of manganese toxicity in lemons. The yellowing is very bright and is described as ‘yellow-top’ (Fig. 45). Affected oranges and mandarins develop dark brown spots 3-5 mm in diameter, scattered over the leaves (tar spotting) (Fig. 46).

Figure 45: Manganese toxicity in lemons

Figure 46: Manganese toxicity signs on orange leaf

Toxicity is more common in loamy soil than in sands. Damp, poorly drained soil encourages the build-up of soluble manganese. Lemons, oranges, mandarins and grapefruits are all affected. Trees on P. trifoliata rootstock are affected worst, but the problem is also found in trees on rough lemon stock. Applications of ACK-01 potassium nitrate, whenever K fertilization is required, help to increase the soil pH and may help to prevent the manganese toxicity phenomena.

 

2.4.6 Biuret toxicity

Biuret is an impurity in urea fertilizer, which may be avoided using only guaranteed low-biuret urea products, particularly for foliar sprays. Leaf symptoms appear as irregular, yellowish-green interveinal chlorotic areas appearing first at leaf tips and spreading over the entire area of the leaf surface (Fig. 47). As severity increases, only the midribs and parts of the major veins remain green.

Figure 47: Lemon leaves with signs of biuret toxicity

Fertilization recommendations

The recommendations appearing in this document should be regarded as a general guide only.The exact fertilization program should be determined according to the specific crop needs, soil and water conditions, cultivar, and the grower’s experience. For detailed recommendations, consult a local AndaChemicals representative. Disclaimer: Any use of the information given here is made at the reader’s sole risk. Shifang Anda Chemicals Co., Ltd. provides no warranty whatsoever for “Error Free” data, nor does it warrants the results that may be obtained from use of the provided data, or as to the accuracy, reliability or content of any information provided here. In no event will Shifang Anda Chemicals Co., Ltd.  or its employees be liable for any damage or punitive damages arising out of the use of or inability to use the data included.

3.1  Many benefits with Anda quality fertilizers

Either soil application, fertigation or foliar treatments, Anda provides quality products to benefit of any citrus grower.

Fertigation

ACK-01, Anda Pro, Anda Classic MAP and Anda Classic MKP are water soluble fertilizers, containing major macro and minor plant nutrients. Due to the compatibility and the solubility of these fertilizers, can be fertigated in the most effective way and with most beneficial results.

Foliar applications:

Anda Trace Bonus affects the external and internal fruit quality: increases size and weight, prevents creasing and splitting, improves soluble solids and vitamin C content. In addition, correct quickly and effectively plant nutrient deficiencies.

Anda Pro available in many N-P-K ratios to deal with an effective way to prevent and to cure plant nutrient deficiencies.

3.2  Summary of recommended applications with Anda Chemicals fertilizers

Table 10: Summary of recommended applications with Anda fertilizers

* For detailed recommendations, refer to the relevant paragraph in the following chapters

* For detailed recommendations, refer to the relevant paragraph in the following chapters.

* For detailed recommendations, refer to the relevant paragraph in the following chapters.

* For detailed recommendations, refer to the relevant paragraph in the following chapters.

3.3  Plant nutrients requirements

The tree age and the expected yield are two important parameters in determining the required plant nutrients (Table 11).

Table 11: Required rates of macro and secondary plant nutrients according to growing stages and expected yield .

3.4  Soil analysis

This is useful for measuring pH, available P and certain exchangeable cations, notably Ca and Mg.

Table 12: A standard soil test, using Mehlich-1 extractant, interpretation and phosphorus recommendations for commercial citrus orchards, 1-3 years of age.

Application of high rate of magnesium (Mg) fertilizers, may suppress the uptake of potassium (K) due to their cationic competition.

Table 13: The standard Mehlich-1 soil test interpretations and magnesium recommendations for commercial citrus orchards.

However, because citrus trees are grown on a wide range of soil types, it would be difficult to establish standards for all soils. They are therefore usually developed for certain soil types in a given region. It is usually more difficult to assess the N and K status in the soil because both these elements are subject to leaching, especially in humid regions.

3.5  Plant analysis data

Leaf analysis is an essential tool to determine the required plant nutrients (Table 14). According to leaf analysis results, the fertilization rates and the correct ratio of plant nutrients can help to schedule the fertilization program.

Table 14: Leaf analysis standards for mature, bearing citrus trees based on 4 to 6-month-old, spring-cycle leaves from non-fruiting terminals.

3.6  Nitrogen

The form of a nitrogen, either ammonium (NH4+), nitrate (NO3) or amide (NH2), plays an important role when choosing the right fertilizer for fertigation of citrus trees.

Nitrate-nitrogen is a preferable source of nitrogen as it suppresses the uptake of chloride (Cl-) and at the same time promotes the uptake of cations, such as potassium (K+), magnesium (Mg2+) and Calcium (Ca2+). In addition, the nitrate form of nitrogen increases the pH of soil solution near the root system, especially important in acidic soils.

The nitrogen in ACK-01 (potassium nitrate, KNO3) is entirely in nitrate form, which makes it a suitable fertilizer for fertigation.

Table 15: Nitrogen requirements and recommendations for the first three years after planting

\

* Other water-soluble N fertilizer may be added and ACK-01 rate should be reduced accordingly.

Table 16: Nitrogen requirements and recommendations for trees aged 4-7 years, by variety

* Other water-soluble N fertilizer may be added and ACK-01 rate should be reduced accordingly.

Table 17: Nitrogen requirements and recommendations for trees eight years and older

* Other water-soluble N fertilizer may be added and ACK-01 rate should be reduced accordingly.

3.7  Phosphorus

Table 18: Test interpretations and phosphorus recommendations for commercial citrus orchards, ages 4 and above.

3.8  Potassium

Potassium recommendations also depend on the age of citrus trees. During the first 3 years after planting, K2O should be applied at the same rate as N (g K2O/tree). For orchard ages of 4 years and above, K2O should be applied at the same rate as N (in Kg K2O/ha).

Table 19: K recommendations for the first three years of orchard-age

Table 20: K requirements and recommendations for trees aged 4-7 years,

Table 21: K requirements and recommendations for trees eight years and older

3.9  Fertigation

Application of water-soluble fertilizers through the irrigation system is the optimal method for providing balanced plant nutrition throughout the growth season. A balanced Nutrigation™ regime ensures that essential nutrients are placed precisely at the site of intensive root activity and are available in exactly the right quantity – when plants need them.

3.9.1 Fertigation recommendations for young trees

  • Soil type: Light to medium
  • 240 irrigation (application) days per year. If more application days, calculated daily rates should be reduced, accordingly
  • Rates are based on N: K2O ratio 1: 1

Table 22: Fertigation recommendations for young trees

* In fertile soils and irrigated water with high content of plant nutrients, rates of fertilizers should be reduced, accordingly.

Table 23: Recommended applications of Anda Classic MAP (12-61-0) when soil test is not available

* Estimated 240 irrigated days.

3.9.2 Fertigation recommendation of bearing trees

    • Soil type: light to medium
    • Tree population: 400-600 trees/ha
    • Expected yield: 40 t/ha

The recommended average rates of nutrients (Kg/ha):

Nitrogen: The recommended amount is based on the nitrogen consumption of 4-6 Kg N/ ton of fresh fruit. 75% of the entire amount of nitrogen should be applied from early spring to the mid-summer. It is recommended to split this amount of nitrogen and to apply it proportionally in each one of the irrigation cycles. The rest 25% can be applied in autumn, after color breaking, or as post-harvest fertilization.

Phosphorus: One or two applications at the beginning of spring.

Potassium: It is recommended to divide the entire amount of potassium and to apply it proportionally in each one of the irrigation cycles from early spring to early summer irrigation.

Fertigation Schedule:

Table 24: Fertigation schedule on bearing trees:

Recommendations for Bearing Trees (higher yield)

  • Soil type: light to medium
  • Plant population: 440 trees / ha
  • Expected yield: 60 ton / ha

The recommended average rates of nutrients (Kg/ha):

Table 25: Fertigation schedule of total plant nutrients per seasonal application

* Split into low rates and applied weekly ; ** Split into 1-2 applications

3.9.3 Proportional Fertigation

Proportional Fertigation, (constant concentrations of plant nutrients during the entire irrigation session) is a beneficial tool, mainly when growing on sandy soils (Table 26).

Table 26: Proportional Fertigation

* P in orthophosphate form serves as a buffer.

3.9.4 Fertigation practice in Israel

Non-bearing citrus trees

Table 27: Recommended rates of N, P and K, on young – non-bearing citrus trees:

When proportional fertigation is used, the concentration of N, the irrigated water in non-bearing orchard should not exceed 200 ppm (200 g N in 1000 L water). In fruit bearing orchards grow where leaf analysis is not available, it is recommended to apply 200 kg N /ha/yr, 180 Kg K2O/ha/yr and once in three years 60 Kg P2O5/ha. Applications of potassium may vary according to soil texture; in light texture soils, low rates of phosphorus in each fertigation may be added, similarly to N, while in heavier texture soils higher rates of P may be applied once a week.

Bearing citrus trees

Apply N throughout the irrigation period according to the harvesting time of the fertigated variety. Varieties that are having color breaking difficulties, it is recommended to complete the N fertigation in mid-summer. When proportional fertigation is used, the concentration of N, the irrigated water bearing orchard, should not exceed 50 ppm N (50 g N in 1000 L water). Phosphorus should be applied, as needed, during the entire fertigated period in equal rates. If orchard is not fertigated, phosphorous should be applied in one portion in either spring or fall. Applications of potassium may vary according to soil texture; in light texture soils, low rates of phosphorus in each fertigation may be added, similarly to N, while in heavier texture soils higher rates of P may be applied; once a month.

Recommendations according to leaf analysis

Table 28: Recommended potassium application rates according to leaf analysis, for oranges, (Shamuti, Washington navels, Valencia), lemons and tangerines:

Table 29: Recommended potassium application rates according to leaf analysis, for grapefruits:

Potassium: should be applied in the same rates and methods as nitrogen.

Table 30: Recommended phosphorous application rates according to leaf analysis, for oranges, (Shamuti, Washington navels), lemons and tangerines:

Table 31: Recommended phosphorous application rates according to leaf analysis, for grapefruits and Valencia oranges:

Phosphorous: When drip irrigation is practiced, it is recommended to apply the phosphorous as a full-soluble product, such as Anda Classic MAP or Anda Classic MKP, at a constant concentration, during the entire irrigation season. When leaf analysis is unavailable, it is recommended to apply 200 kg/ha of nitrogen, 180 kg /ha of K2O and once every three years, 60 kg/ha of P2O5.

Citrus Nutritional Management – Nutrition Function

Growing citrus

1.1  Growing conditions

Being a tropical and subtropical crop, citrus can be grown in a belt between 40 °N and 40 °S, except at high elevations. Minimum temperature and its duration time are the limiting growth factors sensitivity depends on variety, rootstock, dormancy of the trees and the absolute minimum temperature and its duration.

Intensive citrus cultivation requires the use of fertilizers, close monitoring and control of pests, diseases and weeds, effective irrigation and control of tree size. The trees begin their productive life on the third year, and peak productivity takes place when the trees are 10-30 years old, average yields under these conditions are 30-60 t/ha.

Extensive citrus cultivation requires with the use of fertilizers, but only moderate monitoring and control of pests, diseases and weeds. They are generally rain-fed only. Their productive life starts on the fourth year, and peak productivity takes place when the trees are 8-15 years old, average yields under these conditions are 15-25 t/ha.

1.2 Soil type

Citrus can be grown on a wide variety of soils, from sand to loam and clay. Both acidic and alkaline soils are acceptable.

1.3 Varieties

The genus Citrus is an evergreen tree belonging to the family Rutaceae. It has about 150 genera and 1500 species, all native to the tropical and subtropical regions of Asia and the Malay Archipelago.

The principal citrus scions are:

Orange (C. sinensis Osbeck)
Mandarin (C. reticulata Blanco)
Lemon (C. limon [L.] Burm.)
Lime (C. aurantifolia [Christ.] Swing.
Grapefruit (C. paradisi Macf.)
Pomelo (C. grandis [L.] Osbeck)
The most commonly used rootstocks are:
Rangpur lime (C. limonia Osbeck)
Rough lemon (C. jambhiri Lush.)
Sour orange (C. aurantium L.)
Cleopatra mandarin (C.reshni Hort.)
Trifoliata (P. trifoliata [L.] Raf.)

1.4 Climate

Both arid and humid climates are acceptable. As citrus trees are sensitive to low temperatures, the limiting parameter for growing citrus is the minimum temperature prevailing in winter time.

1.5 Irrigation

Irrigation is one of the most important factors in producing a good yield of quality citrus. Irrigation scheduling, knowing how much water to put on and when, has a direct impact on tree health as well as fruit yield, size and quality. Without correct irrigation scheduling, orchard is more susceptible to nutrient deficiencies, physiological disorders, pests and disease.

Correct irrigation scheduling requires an understanding of:

How much water can be held in the crop root zone

How much water the crop uses each day

How much water the irrigation system applies.

Shallow root system

Citrus have a shallow root system. It is important to aim irrigation at the effective root zone, minimizing the amount of water leaching past. For citrus, the effective root zone is usually in the top 30 to 40 cm, depending on the soil type.

How much water can the root zone hold?

The amount of water that can be held in the root zone and thus available to the tree varies with the irrigation system, soil type, depth of the effective root zone, and proportion of stone or gravel in the soil.

Examples of water holding capacity

Both trees in this example (Fig. 1) are the same size (9 m2 canopy area) growing in a hedge row in a loam soil. The root-zone depth of both trees is 30 cm. One tree is irrigated with two drippers, the other with a fully overlapping micro sprinkler system. The tree irrigated with two drippers has only 34 liters of readily available water. The tree irrigated with the fully overlapping sprinkler system has a much larger volume of readily available water (189 liters). The more soil is wetted within the root zone, the greater the volume of readily available water.

Figure 1: Example of water holding capacity

Citrus tree water holding
Citrus tree water holding

Scheduling irrigation

To schedule irrigation, the amount of water available in the crop root zone with the tree’s daily water requirement should be compared. If the daily water requirement exceeds the amount of water that can be held in the root zone, there will be a need to irrigate more than once a day. If the soil can hold more than the daily water requirement, there is an option of irrigating when the available water is depleted (this may be every second or third day).

Rainfall during the irrigation season may reduce the irrigation requirement of trees. Not all rainfall is available to the trees; some is lost to run-off, percolation below the root zone, and interception by leaf litter or mulch.

Over-irrigation, especially surface irrigation, may wet the trunks of the trees and increase the incidence of root rot caused by Phytophthora. Lime-induced chlorosis can be aggravated by over-irrigation, and tends to be reduced by drip irrigation. Irrigation timing is considered crucial for reproductive development, fruit set and fruit enlargement. However, cropping in one season influences both root extension and top growth, often with a carry-over effect on yield in the successive year.

Recommendations

The following recommendations are for healthy and productive orchard. Citrus orchards that above average yield is expected, there is a need to increase the irrigated water quantity by 10% as of the bearing fruit stage (early summer).

Irrigation schedule should start according the soil moisture that can be determined by soil samples with auger or tensiometers (a moisture measurement tool). It directly measures the physical force that the root system must overcome in order to access water held in the soil (also known as matric potential).

Placement of tensiometers in the orchard, according to the irrigation method:

Drip irrigation – 15-20 cm of the second emitter from the tree’s trunk.

Micro-sprinkler – 0.5 m from the mini sprinkler.

Sprinkler – 1 m from the sprinkler.

Depth placement of tensiometers:

Upper – 20-30 cm deep (most of the active root zone) and the reading from this tensiometer with determine the irrigation schedule. Lower – 50-60 cm deep, verifies the irrigated depth.

Irrigation intervals will be determent by the age of the citrus orchard or tree size, irrigation method, soil type and the daily water requirement (Table 1).

Table 1: Irrigating intervals (days):

Irrigation of young orchard (up to 4 years from planting):

The water quantities are per single tree and related to irrigation method to the tree size.

Table 2: Drip irrigated young citrus orchard (up to 4 years from planting)

Irrigation of bearing trees

Due to the variation in water consumption between different growing areas, varieties, expected yield, soil type, drainage problems and so on, it is impossible to provide irrigation schedule that will fit all citrus orchards.

It is important to use additional parameters to determine irrigation schedule:

1.Soil sampling auger

2.Tensiometers

3.Measuring fruit size

How to calculate the water requirement

The daily required amount of water is calculated by multiplying the seasonal irrigation factor, varies from area to area and differs according to varieties, by transpiration factor generated from a Class ‘A’ Pan Evaporation data. To determine the required water quantity, the daily quantity should be multiplied by number of days from the last irrigation (irrigation cycle).

Irrigation factor – is the correlation between the transpiration from the tree and the evaporation from Class ‘A’ Pan (Evapotranspiration) of a citrus orchard during a particular period.

Group A: Varieties no fear of too large fruit size and plots with above average yield.

Group B: Varieties with low yield and fear of oversized fruits.

Group C: Late grapefruit varieties – yield less than 60 ton/ha, Topaz variety yields less than 40 ton/ha.

Group D: As of late spring, irrigation according to fruit size.

Table 3: Irrigation factors according to different citrus groups

Example of calculation:

0.55 (irrigation factor) X 7 mm (daily evaporation data from Class ‘A’ Pan) X 4 days irrigation interval = 15.4 mm, or X 10 = 154 m3 water/ha.

1.6 Planting density and expected yield

Tree spacing is affected by factors such as the species of citrus concerned, the cultivar, type of rootstock, environment, size of the orchard and the management practices the grower will be using. For example, if a grower uses machinery, he must leave enough space between the rows for the machines to pass when the trees are mature. Site quality in terms of soil characteristics and water availability should be considered. Expected lifetime of the orchard is also important and may be influenced by freeze potential, disease incidence, or non-agricultural development potential. Thus, decisions must be based on a number of situations.

Spacing of 6 – 7.5 m between rows and a middle width of 2 to 2.5 m provides adequate access for production and harvesting operations. Within this range, more vigorous trees, such as: grapefruit, lemons, tangelos, and other varieties with more spreading growth habits should be planted at wider spacings than oranges.

Spacing wider than 7.5 m take longer to fill their allocated space, thus reducing early yield potential.

Spacings between rows as close as 4.5 m can be managed with conventional production equipment with timely row middle hedging, however, fruit handling at these closer row spacings becomes a problem.

Spacing in the row of 3 to 4.5 m is considered suitable for new plantings. Tree vigor, site selection and external fruit quality requirements again are important considerations within this range. With the rapid tree growth occurring in many new plantings, trees at this spacing will grow together to form a continuous hedgerow relatively early in the life of the planting.

Spacings less than 3 m in the row have been tried experimentally and in a few commercial plantings. However, trees planted too closely may compete with each other for space at such an early age (before significant production) that the advantage of the higher density does not justify the additional cost of trees. Spacing trees at regular intervals in the row is preferable to grouping trees. For example, regular 3 m spacing is more desirable than grouping two trees 1.5 m apart and then skipping 4.5 m, even though the tree density per an area is the same.

Tree densities range from 286 trees per hectare for the 4.5 X 6.5 m spacing, to 540 trees per hectare for the 3 x 6 m arrangement. Small acreages of densities of up to 865 trees per hectare might be considered on a trial basis.

Tree vigor is of fundamental importance in determining the tree spacing, density, topping, and hedging in new citrus orchards. Citrus tree are flexible and adapt to arrangement of space allocations. Adaptability is limited, however, and maximum economic returns are generated only when tees perform well within their allocated space.

Plant nutrition

Main functions of plant nutrients

Table 4: Summary of main functions of plant nutrients

Nutrient demand/uptake/removal

Removal of mineral elements in the harvested fruit is one of the major considerations in formulating fertilizer recommendations. The table below shows the quantities of nutrient elements contained in one metric ton of fresh fruit. The large amounts of K reflect the high K content of citrus juice.

Table 5: Nutrients removed from the orchard by the fruit

Table 6: Micronutrients removal from soil, by fruit, of different citrus varieties

2.2.1 Leaf analysis as a guidance tool for the nutrition of citrus

Using leaf analysis as one of the guides in planning citrus fertilizer programs has yielded a considerable cultivation progress. The table below relates to spring flush leaves, 4-6 months old, from non-fruiting terminals. Leaves from fruiting terminals (used in S. Africa and some S. American countries) have lower N, P and K, and higher Ca and Mg contents than leaves of the same age from non-fruiting terminals, a fact which should be borne in mind when interpreting leaf analysis data. It is common to sample spring flush of healthy, undamaged leaves that are 4-6 months old on non-fruiting branches (Fig 2a). Selecting leaves that reflect the average size leaf from the spring flush. Typically, 75 to 100 leaves from a uniform 5-hectare block of citrus are sufficient for testing.

In some countries, it is recommended to sample spring grown leaves from bearing shoots, nearest to a fruit (Fig 2b).

Figure 2a: Sample leaves from the middle of non-fruiting shoots as shown above

Figure 2b: Sampling spring grown leaves nearest to fruit

Table 7: Leaf analysis standards for Citrus (Florida)

2.3  Nutrient deficiency symptoms in citrus

Nutrient deficiency symptoms appear on different plant parts, most frequently on leaves, fruits and roots. The mobility of nutrients is an important property from this point of view. Therefore, nutrients undergoing redistribution process e.g., when plant enters into reproductive- from vegetative phase. Accordingly, various nutrients are classified as very immobile (B and Ca), very mobile (N, P, K, and Mg), immobile (Fe, Cu, Zn, and Mo), and slightly mobile (S). Symptoms are noticed on fruits for immobile nutrients like B and Ca. Development of visible symptoms is accountable to metabolic disorders, which cause changes in micro-morphology of plants before these symptoms are identifiable.

The way in which the symptoms develop and manifest on younger or older leaves, or the fruits, gives a reliable indication about the cause of nutritional disorders. Both deficiency and excess of nutrients can lead to reduction in crop yield, coupled with inferior fruit quality. Mild visible leaf symptoms, for some of the essential element deficiencies, can be tolerated without a reduction in yield in some citrus varieties, but not in others.

Various forms of deficiency symptoms are usually summarized as:

  1. Stunted or reduced growth of entire plant with plant remaining either green or lacking in normal green luster or the younger leaves being light colored compared to older ones
  2. Older leaves showing purple color, which is more intense on the lower side
  3. Chlorosis of leaves either interveinal or the whole leaf itself, with symptoms either on the younger and/or older leaves or both
  4. Necrosis on the margins, or interveinal areas of leaf, or the whole leaf on young or older leaves
  5. Stunted growth of terminals in the form of rosetting, frenching, or smalling of leaves coupled with reduced terminal growth, or subsequent death of terminal portion of plants

2.3.1 Nitrogen (N)

Function: Nitrogen is one of the primary nutrients absorbed by citrus roots, preferably in form of nitrate (NO3 -) anion. It is a constituent of amino acids, amides, proteins, nucleic acids, nucleotides and coenzymes, hexosamines, etc. This nutrient is equally essential for good cell division, growth and respiration.

Deficiency Symptoms: Deficiency is expressed by light green to yellow foliage over the entire tree in the absence of any distinctive leaf patterns. With mild deficiency, foliage will be light green progressing to yellow as conditions intensify (Fig. 3a, 3b). New growth usually emerges pale green in color, but darkens as foliage expands and hardens. With yellow vein chlorosis, the midribs and lateral veins turn yellow, while the rest of the leaf remains with normal green color (Fig. 4). This chlorosis is frequently attributed to girdling of individual branches or the tree trunk. It may also occur with the onset of cooler weather in the fall and winter, due to reduced nitrogen uptake by the plant from the soil. Nitrogen deficiency is also associated with senescing foliage, which can develop a yellow-bronze appearance prior to leaf abscission (Fig. 5). Nitrogen deficiency will limit tree growth and fruit production, while high nitrogen applications produce excessive vegetative growth at the expense of fruit production, reducing fruit quality and threatening groundwater, particularly on vulnerable soil types.

Figure 3a: Nitrogen deficiency (Dark green leaf is normal; the other two leaves are deficient.)

Figure 3b: Nitrogen deficiency (Aging, senescing leaves.)

Figure 4: Pale new growth under N deficiency

Figure 5: Nitrogen deficient lemon foliage. Note that deficiency appears on the older leaves.

2.3.2 Phosphorus (P)

Function: Phosphorus is one of the three primary nutrients, and is absorbed by citrus roots in the form of orthophosphate (H2PO4-) or HPO42-. It is a component of sugar phosphates, nucleic acids, nucleotides, coenzymes, phospholipids, phytic acid, etc. It plays a key role in the reactions involving ATP. The element is necessary for many life processes such as photosynthesis, synthesis and breakdown of carbohydrates, and the transfer of energy within the plant. It helps plants store and use energy from photosynthesis to form seeds, develop roots, speed-up the maturity, and resist stresses.

Deficiency Symptoms: Phosphorus has the tendency to move from older to younger tissues; therefore, symptoms appear first on older leaves, which lose their deep green color. Leaves turn small and narrow with purplish or bronze lusterless discoloration. Some leaves may later develop necrotic areas, and young leaves show reduced growth rate. Fruits are rather coarse with thick rinds (Fig. 6) and have lower juice content, which is higher in acid. Although rarely observed, foliage may exhibit a bronze appearance. Phosphorus deficiency is unlikely to occur in orchards that have received regular P applications in the past.

Figure 6. Phosphorus deficiency symptoms on fruits

2.3.3 Potassium (K)

Function: Potassium (K) is required as a cofactor for 40 or more enzymes. It is required for many other physiological functions, such as formation of sugars and starch, synthesis of proteins, normal cell division and growth, neutralization of organic acids, regulating carbon dioxide supply by controlling stomatal opening and improving efficiency of sugar use, overcoming environmental stress such as frost by decreasing the osmotic potential of cell sap.

Due to higher ratio of unsaturated/saturated fatty acid, a role in imparting drought tolerance, regulation of internal water balance and turgidity, regulating Na influx and/or efflux at the plasmalema of root cells, chloride exclusion behavior through selectivity of fibrous roots for K over Na, and imparting salt tolerance to cells to enable holding the K in the vacuole against leakage, when Na incurs in external medium.

Table 8: Positive effect of K on yield, fruit size and quality in sweet oranges

Deficiency Symptoms: Early K-deficiency symptoms are commonly in the form of stunted growth, sparse somewhat bronzed foliage, and a lusterless appearance of leaves. Under acute K-deficiency, the leaves wrinkle and twist, and only weak new lateral shoots emerge, because of lack of mechanical strength. Other symptoms are: reduced fruit size (Fig. 7a, 7b) with very thin peels of smooth texture, premature shedding of fruits (Fig. 11), leaf scorching, appearance of resinous yellow spots, and shoots turning S-shaped.

Figure 7a: K affects the size of orange fruit

Figure 7b: Potassium deficiency symptoms on fruits (Left one is normal and smallest fruit is the most K-deficient).

Figure 8: K affecting the rind – have smoother, thinner rinds, susceptible to diseases Plugging – removal of the peel in the stem-end area of the fruit; increases incidence of postharvest decay.

Figure 9: Creasing – rind disorders, albedo breakdown, causing narrow sunken furrows on the rind surface as the peel disintegrates easily.

Figure 10: Splitting – vertical split at the styler or blossom-end and opening longitudinally towards the stem end.

Figure 11: Fruit drop – early fruit drop may occur when K is deficient.

Fading of chlorophyll, appearing as blotches, takes place in distal half of leaf. These blotches appear pale yellow at first, but later deepen to bronze, as they spread and coalesce, with leaf tips turning brown, showing abnormally variegated chlorosis in the form of amarelinho. Appearance of yellow to yellow-bronze chlorotic patterns on older leaves, along with corky veins, is also seen (Figs. 12a-c).A screw-type of curling towards the lower leaf surface, particularly on lemon is more common. Many a times, fruits attain more growth in the longitudinal direction leaving restricted fruit growth equatorially; eventually fruits turn elliptical in shape.

Figures 12a-c: Chlorosis of older leaves. K-deficient leaves turn golden yellow, and bend downward at the tip and margins

Potassium deficiency is likely to occur on calcareous soils due to elemental antagonism, and where large crops of fruit are produced with high nitrogen rates. A rarely observed bronzing of foliage may sometimes be observed, particularly on lemons. Potassium deficiency is associated with accumulation of cadaverine, acid invertase, lysine, histidine, arginine carboxylase, and reduced activity of carbamyl putrescine amine hydrolase, and pyruvate kinase. These are considered useful biochemical markers for establishing K-deficiency in citrus.

Table 9: Response of citrus yield and quality parameters to K fertilization as indicated by leaf K *

Thicker arrow = more pronounced effect

2.3.4 Calcium (Ca)

Function: Calcium is one of the secondary nutrients, absorbed by plant roots as Ca2+. Calcium is a constituent of the middle lamella of cell walls as Ca-pectate. It is required as a cofactor by some enzymes involved in the hydrolysis of ATP and phospholipids. It is an important element for root development and functioning; a constituent of cell walls; and is required for chromosome flexibility and cell division. Calcium deficiency appears to be a special case in which leaf chlorosis indeed reflects a broader interference involving alterations in nitrogen metabolism. The reduced activity of pyruvate kinase is considered an indicator of Ca-deficiency.

Deficiency Symptoms: Deficiency of Ca is mainly characterized by fading of chlorophyll along the leaf margins and between the main veins, especially during winter months. Small necrotic (dead) spots develop in the faded areas. Small thickened leaves cause loss of vigor and thinning of foliage under severe conditions. Twig die-back and multiple bud growth develop from new leaves with undersized and misshapen fruits having shriveled juice vesicles, commonly referred as bronzing or copper leaf.Chlorosis along leaf margins, leaves misshapen, often abscise rapidly.Roots underdeveloped, may decay .Tree shows dieback and stunted Breakdown’ Fruits show creasing and cracks form underneath the rind, with splitting and separation of the rind (Fig. 13).

Figure 13: Creasing resulted by calcium (Ca) deficiency

2.3.5 Magnesium (Mg)

Function: Magnesium is another secondary macronutrient absorbed as Mg+2. Magnesium is a central constituent of the chlorophyll molecule. A large number of enzymes involved in phosphate transfer require it nonspecifically. It is involved in photosynthesis, carbohydrate metabolism, synthesis of nucleic acids, related to movement of carbohydrates from leaves to upper parts, and stimulates P uptake and transport, in addition to being an activator of several enzymes.

Deficiency Symptoms: The deficiency of Mg is commonly referred to as bronzing or copper leaf symptoms. Symptoms of Mg-deficiency occur on mature leaves following the removal of Mg to satisfy fruit requirement. Disconnected yellow areas or irregular yellow blotches start near the base along the mid-rib of mature leaves that are close to fruits. These blotches gradually enlarge and coalesce later to form a large area of yellow tissue on each side of the mid-rib. This yellow area gradually gains in size, until only the tip and the base of the leaves are green, showing an inverted V-shaped area pointed on the mid-rib. With acute deficiency, leaves may become entirely yellow-bronze and eventually drop (Fig. 15 a-c). Seedy fruits are more severely affected than cultivars producing seedless fruits. Within the tree itself, heavily fruited limbs develop extreme Mg-deficiency symptoms, and may even become completely defoliated, while limbs with little or no fruits may not show deficiency symptoms. An increase in concentration of alkaline invertase is considered biochemical markers of K-deficiency in citrus.

With acute deficiency, leaves may become entirely yellow-bronze and eventually drop (Fig. 13). Magnesium deficiency occurring in calcareous soil may have to be corrected with foliar applications. Spraying Magnisal®, magnesium nitrate, is an effective treatment to correct Mg2+ deficiency.

Figure 14: Severe (left) and moderate (right) Mg deficiency

Figure 15 a-c: Magnesium (Mg) deficiency symptoms on citrus leaves

2.3.6 Iron (Fe)

Function: Iron, a micronutrient, is a constituent of cytochromes, non-haeme iron proteins, involved in photosynthesis, and N2 fixation and respiratory linked dehydrogenises. Iron is also involved in the reduction in nitrates and sulfates, the reduction in peroxidase and adolase. The increase in carbonic anhydrase activity is considered effective marker of Fe -deficiency.

Deficiency Symptoms: Lime induced Fe-deficiency is the most common form of deficiency. Interveinal white chlorosis due to Fe-deficiency appears first on young leaves. In mild cases, leaf veins are slightly darker green than interveinal areas with symptoms appearing first on new foliage (Fig. 16). In severe cases, interveinal areas become increasingly yellow with entire area eventually becoming ivory in color with emerging foliage, which is smaller. In some cases, leaves remain completely bleached, and margins and tips are scorched. In acute cases, the leaves are reduced in size, turn fragile and very thin, then shed early (Fig 17).Trees dieback severely from the periphery, especially at the top, and some trees have dead tops with the lower limbs showing almost normal foliage. Trees may become partially defoliated with eventual twig and canopy dieback. Iron deficiency is usually an indication of calcareous soil condition and is more likely to be expressed on high pH-sensitive rootstocks like Swingle citrumelo. An early expression of flooding damage to roots and of copper toxicity may be iron deficiency symptoms.

Figure 16: Iron (Fe ) deficiency symptoms on young citrus leaves

Figure 17: Development of iron (Fe) deficiency in lemon. Left- healthy leaf; right- severe deficiency

Figure 18: Iron (Fe) deficiency symptoms on lemon foliage. Note that leaves are young, but are generally full size.

2.3.7 Manganese (Mn)

Function: Manganese is one of the redox micronutrients, absorbed by the plant roots in the form of Mn+2. It is required for the activity of some dehydrogenases, decarboxylases, kinases, oxidases, peroxidases, and non-specifically by other divalent, cation-activated enzymes, and is required for photosynthetic evolution of O2, besides involvement in production of amino acid and proteins.

Manganese has equally strong role in photosynthesis, chlorophyll formation and nitrate reduction, and is indispensable for the synthesis of ascorbic acid, emerging from secondary effects of the fertilizer. A metalloenzyme peroxidase concentration is considered the marker of Mn deficiency. Accumulation of xylose and increased activity of peroxidase are considered useful biochemical markers of Mn deficiency in citrus in addition to reduced activity of phenylanine lyase, tyrosine ammonia lyase, and polyphenol oxidase.

Deficiency Symptoms: Deficiency appears as dark green bands along the midrib and main veins surrounded by light green interveinal areas (Fig. 19) giving a mottled appearance (Fig. 20). In more severe cases, the color of leaves becomes dull green or yellowish green along the mid-rib, and main lateral veins turn pale and dull for the interveinal areas. Chlorosis appears first on younger leaves, then spread gradually to older leaves (Fig. 21. Stems remain yellowish green, often hard and woody. Young leaves commonly show a fine network of green veins on a lighter green background, but the pattern is not distinct as in Zn and Fe deficiencies, because the leaves remain green. Both manganese and zinc deficiencies may occur on calcareous soil and may be more severe on trees with highly pH-sensitive rootstocks. Incipient manganese symptoms may sometimes disappear as the season progresses, so leaves should be observed several times before remedial action is taken. Soil and foliar applications may be effective in correction of manganese deficiency.

Figure 19: Manganese (Mn) deficiency

Figure 20: Mn deficient leaves show mottled appearance

Figure 21: Manganese deficiency symptoms in lemon, showing normal leaf (left) and typical interveinal chlorosis (right).

2.3.8 Zinc (Zn)

Function: Zinc deficiency is a common problem world over. It is an essential constituent of many enzymes such as alcohol dehydrogenase, glutamic dehydrogenase, lactic dehydrogenase, carbonic anhydrase, regulating equilibrium between carbon dioxide; alkaline phosphatase, carboxypeptidase, and other enzymes such as dehydropeptidase and glycylglycine dipeptidase for protein metabolism. It also regulates water relations, improves cell membrane integrity, and stabilizes sulflahydryl groups in membrane proteins involved in ion transport.

Deficiency Symptoms: Little leaf, rossetting, mottle leaf, frenching etc. The young leaves from vegetative shoots are more affected than reproductive shoots. The symptoms of Zn-deficiency are also characterized by irregular green bands along the mid-rib and main vein on a background of light yellow to almost white (Fig 22). Relative amounts of green and yellow tissue vary from a condition of mild Zn-deficiency showing in small yellow splotches between the larger lateral veins, to a condition in which only a basal portion of the mid-rib is green and the remainder of the leaves remain yellow to white. In severe Zn-deficiency, the leaves turn abnormally narrow and pointed with the tendency to stand upright coupled with extremely reduced size (Fig 23). As the deficiency progresses, the leaves are affected over the entire periphery of the tree, and the twigs become very thin and later dieback rapidly. A profuse development of water sprouts takes place. Some of the metallo-enzyme viz., carbonic anhydrase, nitrate reductase, and indole-acetic acid are suggested as biochemical markers of Zn-deficiency.

Figure 22: Zinc (Zn) deficiency

Figure 23: Leaves showing symptoms of severe Zn deficiency

2.3.9 Sulfur (S)

Function: Sulfur is essential for protein formation, as a constituent of the three amino-acids cystine, cysteine and methionine. Sulfur is required for the formation of chlorophyll and for the activity of ATP – sulfurylase. These essential functions permit the production of healthy and productive plants, which are capable of giving high yields as well as superior quality.

Deficiency Symptoms: When plants do not get enough S, they may show visual symptoms of S deficiency. The classical symptom is a yellowing of younger leaves while old leaves remain green. Plants deficient in S often mature late. Symptoms of S deficiency occur particularly in plants well supplied with nitrogen but are sometimes confused with that of nitrogen. In this instance, leaf analysis can be invaluable. Symptoms: Yellowing of new growth smaller leaves and abscise prematurely. Dieback of new shoots. Fruit undersized and misshapen (Fig. 24)

Figure 24: Sulfur (S) deficiency

2.3.10 Copper (Cu)

Function: Copper plays an active role in enzymes performing key functions like respiration and photosynthesis and Cu-proteins have been implicated in lignification, anaerobic metabolism, cellular defense mechanism, and hormonal metabolism. Known forms of Cu in the plants comprise cytochrome oxidase, diamine oxidase, ascorbate oxidate, phenolase, leccase, plastocyanin, protein having ribulose biphosphate carboxylase activity, ribulose biophosphate oxygenase activity, superoxide dismutase, plantacyanin, and quinol oxidase. Copper proteins exhibit electron transfer and oxidase activity. Ascorbic acid oxidase is widely distributed and responsible for catalysing oxidation of ascorbic acid by oxygen. Copper is also a constituent of cytochrome oxidase and haeme in equal proportions. It also acts as a terminal electron acceptor of the mitochondrial oxidative pathway.

Deficiency Symptoms: copper deficiency is commonly known as exanthema. Wilting of terminal shoots, frequently followed by death of leaves is usually seen in Cu-deficiency.

Mild copper deficiency is usually associated with large, dark green leaves on long soft angular shoots. Young shoots may develop into branches, which appear curved, or “S-shaped,” referred to as “ammoniation” usually resulting from excessive nitrogen fertilization (Fig. 25). Twigs can develop blister-like pockets of clear gum at nodes (Fig. 26). As twigs mature, reddish brown eruptions may occur in the outer portion of the wood. Severely affected twigs commonly die back from the tip with new growth appearing as multiple buds or “witches broom”. Necrotic-corky areas on the fruit surface may sometimes occur in extreme situations (Fig. 27) . Copper deficiency is more likely to occur in new plantings on previously uncropped soils, which are usually deficient or totally lacking in copper.

Figure 27Copper (Cu) deficiency – necrotic-corky areas on the fruit surface

2.3.11 Boron (B)

Fruit symptoms most indicative of boron deficiency include darkish-colored spots in the white albedo of fruit and sometimes in the central core (Fig.28). Fruit may be somewhat misshaped with a lumpy surface. Young leaves are dull brown/green, water soaked areas may develop. Leaves are thick, curled with pronounced veins on upper surface. Bark of twigs may split, fruits are small (Figs. 29 a and b).Unlike other micronutrient deficiencies, boron can affect fruit quality and therefore should be avoided. On the other hand, even slight excess of boron can cause toxicity (see page 30), so maintenance or correctional applications should be done very carefully, involving either soil or foliar applications, but not both.

Figure 28: Boron deficiency symptoms in red grapefruit

Figure 29 a-b: Boron deficiency symptoms on leaves

2.3.12 Molybdenum (Mo)

Deficiency of molybdenum in citrus is rare. It can occur under acidic soil conditions. The most characteristic field symptoms are large yellow spots on the leaves that appear first as less defined water-soaked areas in spring (Fig.30), later developing into distinct larger interveinal yellow spots.

Figure 30: Molybdenum deficiency symptoms

 

The 19th Shanghai CAC Show, 7th~9th Match. See you there!

The 19th Shanghai CAC Show, 7th~9th Match. See you there!

Booth Number: N5K13

 

18th Shanghai CAC in 2017
18th Shanghai CAC in 2017

China International Agrochemical & Crop Protection Exhibition (CAC) is organized by CCPIT Sub-council of Chemical Industry every March in Shanghai. Having experienced 18 years’ development since first launched in 1999, CAC has become world largest agrochemical exhibition and a UFI approved event in 2012. Integrating new product display, technical exchange and trade talks together, CAC  serves as world largest one-stop platform with the most active transactions for agrochemical trade, exchange and cooperation involved in pesticides, fertilizers, seeds, beyond-agriculture, production & packaging equipment, crop protection equipment, logistics, consultancy, laboratories and supportive services. It opens a window for Chinese agrochemical enterprises to march into the international market, and is the annual get-together for global agrochemical business performers.