Nitrogen Application with Microirrigation
contents
Applying nitrogen fertilizers through drip irrigation systems is efficient, effective, economical and convenient. It requires only a fertilizer injector tank with proper accessories, the age of the tree and knowledge of the kind of nitrogen materials available.
The total amount of actual nitrogen applied for the year will depend on the size of the tree. During the first year after planting, about 1/10th of a pound of actual nitrogen per tree is required. The amount increases progressively each year until maturity when 1 to 1 ½ pounds of actual nitrogen per tree per year is required.
From the chart below you can readily determine how much material to add to the injector tank monthly in order to apply the proper amount for the year.
Tree
Age Years 
Actual
Nitrogen/ Tree/ Year 
Amount Per Tree Per Month


Pounds of Material

Fluid Ounces of Material


Urea (46%) Amm Nit (33%) Ca Nit 
Amm Nit Sol (20%) NSol
(32%) 

1

1/10 lb 
.03

.04

.08

0.76

0.45

2

1/5 lb 
.05

.08

.16

1.51

0.90

3

1/3 lb 
.09

.13

.27

2.50

1.49

4

1/2 lb 
.14

.19

.40

3.75

2.26

5

1 lb 
.27

.38

.81

7.57

4.51



1 1/2 lb 
.41

.57

1.21

11.32

6.77

This chart is based on the assumption that nitrogen is applied monthly over an 8month irrigation period  March through November.
How to use: Determine age of tree and find factor for material being used. Multiply factor by number of trees and add that many pounds or fluid ounces (depending on material) to injection tank.
Example No. 1: You have a block of 265 trees, 3 years of age, and want to use urea as a nitrogen source. The urea factor for a 3yearold tree is .09. Multiplying 265 by .09, you get 23.85 pounds  so add that many pounds of urea to the tank once a month for 8 months (March through November).
Example No. 2: You are using NSol 32 instead of urea. The NSol 32 factor for a 3yearold tree is 1.49. Multiplying 265 by 1.49, you get 394.85 fluid ounces  so add 3.1 gallons of NSol 32 solution. There are 128 fluid ounces in a gallon.
Fertilizers are available in many different concentrations and ratios. After a particular ratio of fertilizer has been decided upon, the selection of the fertilizer to use will usually be based on availability and cost. Fertilizers can be compared on the basis of the cost per pound of nutrient element.
Fertilizers with the same ratios can be compared with a simple calculation. For example, the combined cost per pound of nutrient of a 5105 fertilizer can be compared with a 102010 or a 122412 fertilizer.
The relative costs of fertilizers of different ratios can be found by finding the equivalent market values of the fertilizers based on the cost per pound of plant nutrient of ammonium nitrate, treble superphosphate and muriate or potash or other available fertilizers.
Sometimes factors such as availability and ease of handling will determine the fertilizer which will be used.
The approximately percentage of nutrient elements in a few of the common fertilizers are:
N

P

K


Ammonium nitrate 
33.5%





Ammonium sulfate 
21%





UreaAmmonium Nitrate (UN32) 
32%





Urea 
46%





Calcium nitrate 
15.5%





Anhydrous ammonia 
82%





Aqua ammonia 
20%





Single superphosphate 


19%



Trebel superphosphate 


45%



Sulphate of Potash 




50%

Muriate of Potash 




60%
