Soil Testing is well recognized as a sound scientific tool to assess inherent power of soil to supply plant nutrients. The benefits of soil testing have been established through scientific research, extensive field demonstrations, and on the basis of actual fertilizer use by the farmers on soil test based fertilizer use recommendations. Soil testing was initiated in the country in the beginning of planning era by setting up of 16 soil testing laboratories during 1955. Aim is to increase the soil analyzing capacity in the country.
The numerical strength does not, however, decisively indicate the quality and success of the programme. Planners and agriculturalists have recognized the utility of the service fully but it suffers due to inadequate scientific support in its execution.
It may be pointed out that the methods to extract available nutrients from the soil are rather old in terms of their enunciation, being mostly given out in the years as early as 1940s and 50s but are still popular and being followed world over. What has fundamentally changed is to categorized the available nutrients extracted by these methods into the limits of sufficiency, deficiency or somewhere in between in relation to present day crop varieties and soil nutrient status. This is achieved through extensive research trials by ICAR and SAUs system to establish a correlation between soil test values so obtained and crop response to applied fertilizers. Thus, the critical input in improving the soil test based fertilizer use recommendation would be ‘ratings’ given to these values. Another aspect of latest scientific input in the soil testing programme would be to analyze these extracted amounts of nutrients by modern, heavy duty and fast analyzing equipment so that the capacity and accuracy of the soil testing laboratories could be enhanced.
Conception of Soil Testing
In most of the soil testing laboratories in India, the soil pH, electrical conductivity, oxidizable organic carbon, available nitrogen, available phosphorous and available potassium are determined by chemical analytical methods within a short period. Hence, Soil testing is the rapid chemical analysis of a soil to estimate the available nutrient status, reaction and salinity of the soil.
Objectives of Soil Testing
The objectives of soil testing area as follows:
1. To estimate the available nutrient status, reaction (acidic/alkaline) of a soil.
2. To evaluate the fertility status of soils of a country or a state or a district.
By soil test summaries the fertility status i.e., available nitrogen status or available phosphorous status or available potassium status expressed as HIGH, MEDIUM or LOW. A soil fertility map showing such fertility status can be prepared. The soil fertility map can be used for -
- Delineating areas of nutrient (e.g.,N, P, K) sufficiency or areas of nutrient (e.g.,N, P, K) deficiency,
- Studying soil fertility changing pattern due to crop cultivation over a period of years,
- Determining nutrient (e.g.,N, P, K) requirement for the deficient areas etc.
3. To prepare a basis for fertilizer recommendation, lime recommendation or gypsum recommendation.
Soil Testing Programme
A soil testing programme has four phases as follows:
- Collection of soil samples.
- Analysis of soil samples.
- Calibration and interpretation of the results of soil analysis.
Before giving the soil samples to a soil testing laboratory for chemical analysis, collection and preparation of soil sample should be done with perfection.
Rating of Soil Test Results- On the basis of soil test results, the soils are grouped into different categories. The categories with respect to organic carbon, available PO, KO and N are a follows:
|Categories||Organic Carbon(%)||Available N (kg ha-)||Available PO (kg ha-)||Available O (kg ha-)|
|High||Above 1.5||Above 450||Above 90||Above 340|
|Low||Up to 0.75||Below 280||Below 45||Below 150|
For Soil Testing, CSC SPV is developing a software jointly with NIC and will implement it in CSCs to give fertilizer recommendation based on the soil testing values (NPK, Organic Carbon and pH) obtained from soil testing kits deployed at CSCs. We are procuring soil testing kits from Agriculture University, Raipur.