Soil Analysis for Fertility Management in Rainfed Agriculture

Abstract

Soil fertility is one of the important factors that determines the productivity and profitability of crops and crops systems in rainfed agriculture. In simple terms soil fertility is the ability of the soil to provide all essential nutrients required for plant growth in a proper proportion. In order to achieve higher productivity and profitability, every farmer should realize that fertility levels must be measured as these measurements can then be used to manage soil fertility. Currently the tools available for measuring the fertility levels of the fields are: (a) Indigenous knowledge, (b) Plant/Tissue analysis (c) Visual diagnosis, (d) remote sensing and (e) soil analysis. (f) greenhouse pot experiments (g) biological tests. Of all these tools, soil analysis is widely used for measuring the fertility status of the soils as this technique is simple, rapid, cost-effective, accurate, universal, and works for all kinds of soils. Soil analysis and soil testing are two different terms. The former refers any chemical, physical or biological measurement made on a soil, whereas the latter refers to the measurement, interpretation and fertilizer and other recommendations based the result of the analysis and other considerations. However, in this paper the two terms soil analysis and testing will be used as synonymous. The basic objective of soil testing are to : (a) accurately determine the available nutrient status of the soils, (b) clearly indicate to the farmer the seriousness of any deficiency or excess that may exist in terms of various crops (c) forms the basis on which fertilizer needs are determined, and (d) express the results in such way that they permit an economic evaluation of the suggested fertilizer recommendations. A sound soil-testing program requires an enormous amount of background research. This background research should determine, the significant chemical forms of the available nutrients in the soils of the area, the extractants most suitable for extracting all or part of the available nutrient forms, the relative productive capacity of the soils of various crops, the differential response of the various rates and methods of fertilizer applications for different crops, field sampling techniques, test procedures and methodologies. The soundness of the required interpretive judgments will depend almost entirely on the thoroughness and quality of these background studies and it is aptly said that the success of soil testing is directly proportional to its research backing.