Soil is the thin layer on earth’s crust made up of disintegrated and decomposed rocks containing complex mineral compounds, organic matter, air and living organisms like bacteria, fungi, insects, worms, etc. It is the soil that supports the growth of plants on earth’s surface and supply the nutrients required by the plant. Soil is the most important medium for the whole agricultural system.

Soil contains many important plant nutrients, the principal being nitrogen, phosphorous and potash. These are the three plant foods, largely drawn from the soil by growing plants. Repeated removal of these essential elements leaves the soil in poor condition and hence unable to produce optimum crop. Besides these, the plants also require secondary nutrients like calcium, magnesium and sulphur in smaller amounts. Plants also require micronutrients like boron, zinc, copper, iron, manganese, molybdenum and chlorine.

To have a successful crop in medium or poor soils one has to replenish the deficient plant nutrients. Soil is chemically an active material and engage in many reaction. The reaction of soil is measured by a scale called pH. If pH is 7 it represents neutral soil, pH below 7 are acidic soil and above it are alkaline soil.

Crops like tea, coffee, pineapple, camellia grow luxuriantly only in acidic soil. Tea and coffee prefer a pH range from 4.5 to 5.5. Again there are some other crops such as grapes, mulberry, pear, etc which prefer alkaline soils. Due to preference of crops for various pH, range correction of soil pH is very essential for a profitable cultivation. So there should be a close watch on the pH factor of soil along with other parameters for greater success in farming.

Just like human beings, plants also need balanced diet. One has to know that each nutrient has a definite role in plant nutrition and no single nutrient can be substituted for another. But all nutrients must work together to produce best crops. The actual basis of fertilization therefore consists in preparing the soil with a balanced supply of nutrients to get best yield. The balanced supply also tends to make plant more resistant to disease and pest attack.

Just by looking at a plot of land no one can tell the correct amount of essential plant nutrients the soil contains and its right proportions. That can only be done by analysis of top soil and subsoil. This is the only way to know the status of the soil. Soil testing is the key to efficient crop production and efficient production is the key to increased profit.

The primary objective of soil testing is to make fertilizer and lime recommendations that will produce maximum economic returns under prevailing conditions. It is important to note that the profits are reduced by use of either inadequate or excessive amount of fertilizer or lime. Soil testing is the best and most reliable basis of determining fertilizer and lime needs.

Soil testing results can be used mainly: a) to identify nutrient problems in soils comparing the nutrient contents; b) to diagnose nutrient deficiencies; and c) to monitor fertilizer programmes. There are three main steps in soil testing — collection of representative soil samples, laboratory analysis and the interpretation of the analysis to generate a recommendation for fertilizer use. The gardeners and farmers have the responsibility of the first one i.e. collection of representative samples. The other two steps are taken care of by the soil testing laboratory and the scientist responsible for an appropriate recommendations.

Soil testing should be done regularly in at least every three or four years interval. This will give a moving picture of soils producing capacity and the progress that is being made in keeping proper soil management practices as moving ahead. Regular soil testing is required to continue building fertility to the desired level.

Short cut in sampling such as taking soil sample from only one or two spots, a handful of soil, contaminating the sample and equipment with fertilizer, etc will give quite misleading results.

By applying fertilizers or soil ameliorants after proper soil testing carried out in a reputed soil testing laboratory, one can achieve greater productivity than those areas where fertilizers and ameliorants are applied on the basis of guess work.

Neoland Technologies on RG Baruah Road, Guwahati is the only reputed private sector laboratory in the entire Northeast, which was established in 1997. It is recognized by Tea Board of India, Government of Assam and Assam Agricultural University, Jorhat, where analysis of soil and water are carried out by some competent analysts, led by soil paedologist Dr DN Chakravarty, retired dean, AAU, Jorhat and soil scientist Dr H Goswami, who retired from Tocklai Experimental Station, Jorhat.

Simanta Bhagawati