Annual nut production is only possible if
pecan trees have a sufficient supply of soil nutrients available for uptake by tree
roots. Mid-summer leaf analysis is the best way to assess the nutritional
status of pecan trees and to determine the fertilizer needs. Table 1 provides
the major and minor nutrient sufficiency ranges for pecan trees grown for nut
production. Tables 2-4 provide fertilizer recommendations for the major
nutrients based on leaf test results. At the minimum, pecan trees require
annual applications of nitrogen fertilizers twice a year—in early March and
again in early October. If potassium and
phosphorus fertilizers are needed a single application can be made in the
Spring (March).
Table 1. Leaf Elemental Concentration Sufficiency Ranges for Pecan Orchards
Table 1. Leaf Elemental Concentration Sufficiency Ranges for Pecan Orchards
N% 2.4-3.0
|
P% >0.12
|
K% 0.75-1.00
|
Ca% >0.7
|
Mg% 0.3-0.6
|
Zn ppm >60
|
Fe ppm >50
|
Mn ppm >100
|
B ppm 20-45
|
Cu ppm >7
|
Table
2. Nitrogen fertilizer recommendations based on leaf test results. Nitrogen
fertilizers should be applied both Fall and Spring every year.
|
Pounds of actual N to broadcast per acre
|
|
%
Nitrogen in leaf samples
|
October application
|
March application
|
below 2.0
|
60
|
90
|
2.0 to 2.3
|
50
|
90
|
2.4 to 2.5
|
40
|
80
|
Above 2.5
|
40
|
60
|
Table 3. Phosphorus fertilizer recommendations
based on leaf test results. Phosphorus fertilizers should be applied in the
Spring.
% Leaf P
|
Recommended
P2O5
lbs./Ac
|
< 0.12
|
60
|
0.12 and above
|
none
|
Table 4. Potassium fertilizer recommendations
based on leaf test results. Potassium fertilizers should be applied in the
Spring.
% Leaf K
|
Recommended
K2O
lbs./Ac
|
< 0.75
|
60
|
0.75 and above
|
None
|
Correcting
Other Common Nutrient
Deficiencies
Magnesium. When leaf levels drop below 0.30%, add a
magnesium containing fertilizer to the soil at the rate of 20 lbs Mg/ Acre. Magnesium containing fertilizers include magnesium
sulfate, magnesium oxide, K-Mag, Sul-Po-Mag and kieserite. Dolomitic lime can
be used in acid soils needing a pH adjustment. High N and K fertilization
rates can lead to Mg deficiency.
Zinc. Zinc deficiency problems (leaf Zn < 60ppm) most commonly encountered
on sandy, soils low in organic matter or soils with a pH above 7.2. Increasing
the organic matter in soils and adding Zinc sulfate to the soil at the rate of
5-10 lbs. ZnSO4 / Ac. is recommended for acid infertile soils. In
high pH soils, zinc must be applied annually as a foliar spray. Growers should
mix 2lbs of ZnSO4 per 100 gal of water (or use commercially prepared
liquid Zinc products) and spray their trees starting at leaf burst. Three to
five sprays are needed and should be made at 2 week intervals.