17 1月 2018

Citrus Nutritional Management – Nutrition Supply Analysis and Recommendation

0 Comment

(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.

[top]
About the Author


Leave a Reply

电子邮件地址不会被公开。 必填项已用*标注