Conception of Soil Testing
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:
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 -
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:
Before giving the soil samples to a soil testing laboratory for chemical analysis, collection and preparation of soil sample should be done with perfection. Method of Collection of Soil Samples - Collection for field crops Equipments
Procedure
Informations
Collection for plantation crop
Collection for local problem soils - Local problem soils are treated as separate soil units (plots). Hence, separate composite samples are collected from problem soils. The problem soil samples are not mixed with normal soils (i.e., non problem soils). Both surface soil and subsoil samples are collected. Collection of surface soil sample-Take 10-30 furrow-slices or cores that extend through A1 horizon. Collection of Subsoil sample Dig a well (i.e. pit) of 1 meter depth. Take soil-slices of ½ inch depth below A1 horizon from different depths as follows: 0-15, 15-30, 30-60, 60-100 cm Fertilizer Recommendation 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:
The categories of soils with respect to soil pH are as follows:
The categories of soils with respect to conductivity (total soluble salts) in mmhos/cm (dSm-1) followed are as follows:
Finding the Rate of N, P2 and KO Application from Recommendation Table Some soil testing laboratories in India use a table that contains the rate of N, PO and KO application on the basis of soil test results as a tool for fertilizer calculation. One example of such table is given bellow.  | |||||||||||||||||||||||||||||||||||||||||||||
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