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AVOCADO NUTRIENT REQUIREMENTS

Avocado plantations, originated from Central America, are considered to be far from reaching their full yield potential. Among the yield reduction causes, we could find inadequate fertilizer management.

Avocado nutrient requirements

SALINITY SENSITIVITY

Saline irrigation water, poorly leached soils, under irrigating and over applying of fertilizers causes salt to accumulate in the root zone and thus reaching the leaves. The phenomena of Chloride Tip-Burn can sometimes be wrongly seen as a mineral deficiency, but it’s actually a problem caused by an excess of salinity.    

In many cases, the soil found under the trees that suffers from Tip-Burn, will not be classified as saline.
It is only analysis, of selected injured leaves, that will show the relationship between the total chloride level and the severity of the Tip Burn.

Dealing with the problem, growers can monitor the salinity and leaching affect, practice good irrigation regimes, use salt-tolerant rootstocks and most importantly, create the right fertilization program.

When planting Avocado, placing fertilizers in the planting hole is also not recommended since burning of sensitive roots can occur.

CRUCIAL TIME PERIODS

A worldwide problem, that causes major yield reduction, is flowers & small fruits drop.
This happens when the root system is not capable of providing the needed nutrients at high demand time-periods.

The most crucial time periods are at the Spring Flowering Flush, especially after full bloom, and the Fruit Maturing with emphasis on the second half of the fruit development.

A correct spread of the irrigation system is a key factor that allows the root to maximize their nutrient absorption.
Never the less, imbalance application of fertilizers will lead the tree to stress condition and will result in yield reduction in both quantity and quality.   

ADVANTAGES OF FERTIGATION

Many studies have been made on the different fertilizer application methods, from foliar application through trunk nutrient injection and up to fertigation.

In Avocado, as in many crops, the fertigation method have several advantages:

  •    Water is distributed uniformly
  •    Flexibility in timing application
  •    The wetted root area is being fertilized
  •    Labor costs are lower
  •    On groves with steep slopes, it is the best way to get to all trees

AVOCADO NUTRIENT REMOVAL

Calculating the Avocado nutrient removal is being done in order to establish the amounts of nutrients taken out by the harvested fruits.

Different Avocado varieties have different removal values, as demonstrated below:

Variety/Element

Total N

P

K

Ca

Mg

S

B

Fe

Mn

Zn

Cu

Fuerte

11.3

1.7

19.5

2.08

5.01

8

0.04

0.09

0.02

0.04

0.01

Hass

28

10

67

5.5

11

0.99

0.12

0.02

0.39

0.14

 

Applying Fertilizers based only on the Nutrient Removal is unsatisfactory.

Other data should be implemented as well, such as the amounts of nutrients required to sustain the tree vegetative growth, nutrient loss due to leaf and flower drop, fertilizer loss caused by leaching and more.

When having a full set of data, a Water/Soil/Tissue test is required.

AVOCADO LEAF ANALYSIS

Nutrient levels in 6 month old Avocado leaves have normally reached a steady state and therefore are preferable to soil tests.

Taking a proper sample is the only way to get the benefits of having the leaf analyzed.


Spring cycle leaves, at the age of 6 month, should be sampled from non-fruiting branches.


It is recommended to sample 40 leaves from different trees located is a superior area, and the same number of leaves from a poor area in the plantation.

Placing the leaves in a paper bag, helps to avoid moisture.


Anyways, the leaves should be transferred to the lab as quickly as possible.

The leaf analysis is important as much as the soil & water test results. Creating a nutritional plan that is not suitable for the crop will definitely cause yield reduction and low quality fruits. Therefore, a balanced fertilizer program, must be based on reliable yield estimation and on laboratory tests.


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