Soil Sample before you Crop
From an agriculture perspective, soil has been the second most important criteria, after the weather. The nature of soil determines the type of crops those can be grown with best yield. In ancient time, in absence of scientific methods, the soil quality was primarily determined by its physical characteristics. While those methods were sufficient then, as the necessity of fertilizers to generate maximum crop in limited timeframe or resources wasn't a factor, the modern expectations are to generate maximum produce within available resources and hence the soil selection after thorough testing comes into picture. The modern soil testing involves chemical and physical analysis that later becomes an input for crop nutrient selection. For example, acidic soil adversely affects roots and it is important to conduct a lime treatment of the acidity in soil. Similarly, alkaline soil from less rainfall areas is treated with conditioners like sulphur or gypsum.
The top layer of soil usually contains fertilizers and other nutrients or crop residuals as compared with the deeper soil, it is important to pick the sample carefully to get the accurate result. Ideally deeper soil samples provide a uniform sampling as compared with gathering surface samples, for example with a shovel. Similarly, the samples should be gathered from different areas of the field to assess the variation. As soil is not just a mixture of minerals, but a heterogeneous complex of organic and inorganic compounds or even living organisms and they can significantly vary depending upon depth and width of the sample and could accordingly impact the test results and analysis. Most of the situations, lab errors are often found caused due to invariability of soil samples.
Some of important soil sampling criteria from agriculture and industrial perspective are the evaluation of fertility, dirt classification, organisms nature and density, pH value, acidic/alkaline nature, mineral and chemical composition analysis, compaction, shearing strength and infiltration.
Variability in Soil
Depending upon the crop being grown in an area and agricultural practices, the property of soil can be affected in multiple ways. Changes in soil texture and composition are observed when plan residue remains in the ground after harvesting.
It is observed that good top soil is often eroded from highlands and ridges and is found deposited in the lower areas. This causes acidic variation in soils at different heights.
Cropping and Tillage practices.
The distribution of soil nutrients, and thus the preparation of soils, vary among those which are heavily tilled and those which are worked only slightly or not at all.
It is important to gather samples from different fields to assess the effect of various cultivation techniques on the soil. Regardless the variations caused by vegetation, topography or cropping practices or the combination. In fact, higher the variation more should be the number of soil samples.
Renu Joshi, Ph. D.