Soil testing is mainly for the purpose of agriculture. In agriculture, the soil testing is the analysis of a soil sample to determine nutrient content, composition and other characteristics, including contaminants. Tests are usually performed to measure the expected growth potential of a soil. The soil testing helps us in knowing fertility of the soil. People use "law of the maximum" to perform the soil test.
The farmers find it extremely difficult to know the proper type of fertilizer, which would match his soil. In using a fertilizer he must take into account the requirement of his crops and the characteristics of the soil. The basic objective of the soil-testing programme is to give farmers a service leading to better and more economic use of fertilizers and better soil management practices for increasing agricultural production. High crop yields cannot be obtained without applying sufficient fertilizers to overcome existing deficiencies. Apart from this, soil testing is also used for construction purpose.
Soil testing characteristics can vary significantly from one spot to another, even in a small garden or field. Taking samples everywhere in the field is crucial to get the most accurate measurement of nutrients and other organisms. An example of this is along gravel roads where the soil could have more lime from the dust from the roads settling down in the soil, or an old animal feedlot where phosphorus and nitrogen counts could be higher than the rest of the field. There are various methods to collect the soil sample in the field, around 40 acres of land it is advisable to take a soil teat with the sample at least in 20 different areas so that the average value of fertility in the land can be found.
Equipment used to take the soil test Spade, Polythene bucket, 12 inches scale, Ball point pen/Lead pencil, A sheet of thick paper, Polythene sheet (2ft x 2ft).
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.
- Collection of soil samples.
- Chemical analysis of soil samples.
- Calibration and interpretation of the results of chemical analysis.
There are various nutrients available in the soil like nitrogen, phosphorus, and potassium, secondary nutrients sulphur, calcium, magnesium, minor nutrients iron, manganese, copper, zinc, boron, molybdenum, aluminum
- Select the plot unit
- Make a traverse over the soil unit (or plot).
- Clean the site from where soil sample is to be collected.
- Insert the spade into soil.
- Standing on opposite side, again insert the spade into soil.
- A lump of soil is removed.
- A pit of V shape is formed.
- Take out the soil-slice (like bread-slice) of ½ inch thick from both the exposed surface of the pit from top to bottom. This slice is also termed furrow-slice. To collect the soil-slice spade may be used. Collect the soil samples in a polythene bucket.
- Collect furrow-slices from 8-10. Select the sites at random in a zigzag manner. Distribute the sites throughout the entire soil unit (plot). In lieu of spade auger may be used. Do not take the prohibited samples and local problem soils.
- Furnish the following information in two sheets of thick paper with the sample. One sheet is folded and kept inside the bag. Another sheet is folded and attached with the bag.
Thus soil testing helps to diagnose soil health and evolve soil specific and crop specific solutions. It helps to identify problematic soils, their nutritional status, texture and structure. Based on the analysis, farmers are advised on soil fertility management through rational use of manure, fertilizers and amendments to make agriculture more productive and sustainable. Thus soil testing serves as a useful tool for all the farmers.