IV. Soil Testing

IV. Soil Testing

  • A soil test is a chemical method for estimating the nutrient supplying power of a soil. It is much more rapid and has the added advantage over other methods of soil fertility evaluation. One can determine the needs of the soil before the crop is planted. A soil test measures a part of the total nutrient supply in the soil.
  • Soil testing plays a key role in today’s modern and intensive agriculture production system as it involves continuous use and misuse of soil without proper care and management. Soil analysis is helpful for better understanding of the soils to increase the crop production and obtaining sustainable yield. Soil testing is an indispensable tool in soil fertility management for sustained soil productivity.
    Objective of soil testing
      a. To evaluate fertility status of soil by measuring available nutrient status
      b. To prescribe or recommend soil amendments like lime and gypsum and fertilizers for each crop
      c. To assess nutrient deficiencies, imbalances or toxicities in soil and crop
      d. To test the suitability of soil for cultivation or gardening or orchard making
      e. To know acidity, alkalinity and salinity problems
      f. To know morphology, genesis and classification of soil
      g. To find out the effect of irrigation on soil properties.
      h. To prepare a soil fertility map of an area (village, taluk, district, state)
  • In the soil testing programme, “soil sampling” is most important step to be followed for getting accurate results. Soil sampling is a process by which a true representative sample of an area or orcahrd can be obtained. The soil sampling must be done scientifically by adopting appropriate time and depth of sampling given for each crop for accurate analysis of soils.
    Interpretation of soil test results and critical levels of nutrients in soils.

    Nutrients

    Low

    Medium

    High

    Avail. Nitrogen(Kg/ha)

    280

    280-580

    >580

    Avail.Phosphorus(P2O5 Kg/ha)

    22.5

    22.5-55

    >55

    Avail. Potassium(K2OKg/ha)

    125

    125-300

    >300

    Organic carbon (%)

    0.5

    0.5-0.75

    >0.75

    pH

    <6.5        =   Acidic
    6.5-7.5    =Normal/Neutral
    7.5-8.5    = Saline
    >8.5        =Alkaline

    EC(dSm-1)

    <0.80      = Normal
    0.8-1.60  = Critical for some crops
    1.6-2.5    = Critical for salt tolerant crops
    >2.5        = Injurious to all crops

    Ca

    <50% of CEC

    Mg

    <4% of CEC

    S

    <10ppm

    Zn

    <0.6 ppm (0.5-1.2ppm)

    Fe

    2.5-4.5 ppm

    Mn

    <2 ppm

    Cu

    <0.2 ppm

    B

    <0.5 ppm(WS)

    Mo

    <0.2 ppm

    Cl

    <2 ppm(WS)
Last modified: Wednesday, 7 December 2011, 5:45 AM