Preparation of Soil Test Results and Fertilizer Recommendation:
Preparation of Soil Test Results and Fertilizer Recommendation:
Correct interpretation of soil analysis is an essential part of soil testing programme. The data obtained from soil analysis would be meaning less unless they are correlated with crop yield.
On the basis of soil testing results, the recommended fertilizer does for the crops are modified for making fertilizer recommendations to the farmers.
Preparation of Soil Test Report:
The format of soil test report should content following four parts.
1. Information about cultivator and field.
2. Soil test values with corresponding classification in 6 tier system of each of the nutrients.
3. Nutrient dose for a particular crop as per requirements of the cultivator.
4. Calculation of the fertilizer to apply essential nutrients. Salinity and alkalinity problems and steps taken to overcome them.
Recommendation of Fertilizers:
Step 1. Find out the range in which the given soil fits e.g. any one of the very high, high, moderately high, medium low and very low.
Classification Chart for Soil Test Data:
|
Category |
Org.C (%) |
Av.N (Kg/ha) |
Av.P (kg/ha) |
Av.K ( kg/ha) |
|
Very Low |
< 0.20 |
<140 |
<7 |
<100 |
|
Low |
0.21-0.40 |
141-280 |
Aug-14 |
101-150 |
|
Moderate |
0.41-0.60 |
281-420 |
15-21 |
151-200 |
|
Moderately High |
0-61-0-80 |
421-560 |
22-28 |
201-250 |
|
High |
0.81-1.00 |
561-700 |
29-35 |
250-300 |
|
Very High |
Above 1.00 |
>700 |
>35 |
>300 |
Step 2:
Increase or decrease the recommended dose of the nutrient according to the category.
1. Very high: 50% less
2. High: 25% less
3. Moderate: Recommended
4. Moderately high: Recommended
5. Low: 25% more
6. Very low: 50% more
Step 3:
Calculate the quantity of straight fertilizers based on above example.
Step 4:
Calculate the gypsum or lime for problem soils.
Problem:
Calculate fertilizer dose (kg ha-1) for sorghum as per six tiers system of fertility rating from given information. Recommended dose of fertilizer 80: 40:40.
Soil Available N= 82
Soil Available P= 10
Soil Available K= 206
Solution:
As per six tier system soil is very low in N content, low in P content and moderate in K,
According to six tier system one should apply 23% more P and recommended dose for K
Fertilizer doses will be
For N = 80 + (50 % of 80)
= 80 + 40 = 120 kg
For P= 40 + (25% of 40)
= 40 +10 =50 kg
Now fertilizer dose will be 120:50:40.