soil fertility evaluation and fertilizer recommendation

2. Soil Fertility Evaluation

3.  Soil Analysis
 Plant Analysis
 Biological methods
 Visual symptoms of nutrient deficiency

4. Soil Analysis

5. Rating limits of soil test values
Nutrient Low Medium High
Organic carbon
(%)
Below 0.5 0.5 – 0.75 Above 0.75
Avail. N (kg ha-1) Below 280 280 – 560 Above 560
Avail. P (kg ha-1) Below 22 22-56 Above 56
Avail. K (kg ha-1) Below 141 141-336 Above 336
Avail. S (ppm) Deficient < 10 ppm Sufficient > 10 ppm

6. 1.plant analysis is an indirect evaluation of soil
2.plant analyses are interpreted on the basis of
critical value approach
Two general types of plant analysis are in use.
1. The Rapid tissue test which is customarily
made on fresh tissue in the field.
2. Total analysis performed in the laboratory
with precise analytical techniques

7. Rapid tissue tests
 Determination of nutrient elements in
the plant sap of fresh tissue.
 Plant Part to be Selected:
◦ In general the conductive tissue of the
latest mature leaf is used for testing.

8. Time of Testing:
 The most critical stage of growth for tissue testing
is at the time of bloom or from bloom to early
fruiting stage.
 Nitrates are usually higher in the morning than in
the afternoon if the supply is short.
 Test for nitrates Diphenylamine
 Phosphates Molybdate + Stannous oxalate
 For potassium Sodium cobalti nitrate

9. Total Analysis:
 Total analysis is
performed on the whole
plant / plant parts
 plant material is dried,
ground, ashed and used
for estimation
 Precise analytical
techniques are used for
measurement of the
various elements

10. Diagnosis and Recommendation
Integrated System
 It considers nutrient concentration ratios rather than
individual element
 The approach measures the relative balance between
nutrients
 Large number of sites is selected at random
 Each element in the plant is expressed in as many ways
as possible
 Ex: Nutrientratios N/P, N/K or products NxP, NxK etc
 NPK requirement of the crop is diagnosed using DRIS
chart

13. Approaches
 Generalized/blanket
Recommendations
 Soil Test Rating and Fertilizer
Adjustment
 Soil test crop response and target
yield concept
 Site specific nutrient management

14. Generalized/blanket
Recommendations
 Uniform application of RDF of a crop.
 RDF Ex.(N, P2O5, K2O Kg/ha)
 Rice :- 100:50:50
 Maize:- 150:75:40
 Red gram:- 25:50:25
 Cotton:- 150:75:75

15. NUTRIENT
Soil Test Ratings Kg/ha
LOW MEDIUM HIGH
N <280 280-560 >560
P2O5 <22 22-56 >56
K2O <141 141-336 >336
S <10ppm 10-20ppm >20ppm

16. RDF (Kg/ha) ADDITION IN RDF AT
LOW FERTILITY
DEDUCTION IN RDF AT
HIGH FERTILITY
NITROGEN
<50 NO CHANGES NO CHANGES
50-100 +12.5 -12.5
100-175 +25 -25
175-250 +37.5 -37.5
250-325 +50 -50
PHOSPHORUS
<25 NO CHANGES NO CHANGES
25-75 +12.5 -12.5
75-125 +25 -25
POTASSIUM
<25 NO CHANGES NO CHANGES
25-50 +12.5 -12.5

17. Soil test crop response and
target yield concept
NUTRIENT REQUIREMENT (Kg/q) =
TOTAL UPTAKE OF NUTRIENT (Kg/ha)
YIELD OF GRAIN (q/ha)
%CS =
TOTAL UPTAKE OF NUTRIENT IN CONTROL PLOTS (Kg/ha)
X 100AVAILABLE SOIL TEST VALVES OF CONROL PLOTS( Kg/ha)
%CF =
TOTAL UPTAKE OF NUTRIENT IN TREATED PLOTS (Kg/ha)
--(AVAILABLE SOIL TEST VALVES OF TREATED PLOTS( Kg/ha) X %CS) X 100
FERTILIZER DOSE APPLIED(Kg/ha)

18. Target Yield Equation
 Using the Basic Data, Fertilizer Dose
Required for specific yield target is
calculated by
F=(NR *T – CS/100*S)*100/CF
F= Fertilizer required kg/ha
NR= Nutrient requirement kg/q
T= Targeted yield q/ha
CS= % contribution of N/P/K from soil
S= Soil test value
CF= % contribution of N/P/K from fertilizer