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Biological tests are important because the level of biological activity in soil substantially affects plant growth. It is also essential to know if plant pathogens are present in the soil. Earthworms, tiny organisms, and microscopic fungi and bacteria all contribute to a growth-promoting soil environment. Organism activity can also serve as an indication of the state of the soil ecosystem, since they simultaneously influence and are influenced by the physical and chemical condition of the soil.
There are three types of soil tests: chemical, physical and biological.
Chemical testing helps determine the soil chemical properties that might constrain plant growth. In chemical tests, the analyst assesses the nutrient-supplying capacity and other chemical properties of the soil known to influence plant growth such as pH, soluble salts,examine as well as confirm your earnings as well as work, and soil organic matter (SOM) content. The most common methods in use are extraction, equilibration, titration (usually for acidity measurements) and oxidation (by chemical or thermal means,article5692, to test for SOM).
It is important for farmers to monitor the health of the soil, which produces the plants from which farmers make their living. One of the critical activities in this regard is periodic soil testing.
In chemical extraction, soil samples are dried, ground to fine particles and sieved. Usually, 1 to 10 grams of sample are placed in an extracting vessel and mixed with an extracting solution of pre-determined volume (from 10 to 100mL). The mixture is shaken vigorously for about 5 (or up to 30) minutes and poured through a filter. The analyst then examines the filtrate for the elements of interest.
Physical tests assess the physical properties of soil that influence growth. The most common test in use is the evaluation of particle size of soil and its distribution. Water-holding capacity may be tested in particular situations, to determine water movement and retention,To put it simply, which help in assessing irrigation potential and setting irrigation schedules.
Ideally, soil samples for soil testing are done shortly before making a land management decision which may be several months in advance of planting. The results represent the most current indication of soil properties, giving enough time for the objectives of the decision to have impact. For example, to see if limestone should be added to correct soil acidity, soil testing should be done several months before planting to give the limestone sufficient lead-time to react with the soil. Soil testing well in advance of planting provides leeway to make changes if unsuitable growing conditions are found.
Communication Article: Soil Testing: A General Overview
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Helen M. Disler
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Sampling depth is crucial, and this depends on your planned crop and the type of soil test to be carried out. Routine soil tests usually require samples obtained from topsoil (0-20 cm depth),becoming complex, but soil tests for mobile soil nutrients (such as NO3-N and SO4-S) may require samples from deeper levels. When collecting subsoil samples take care to avoid contaminating the subsoil with topsoil; contamination can seriously throw off the results and the ensuing recommendations.
Equilibration involves adding a solution to the soil and, after shaking or letting stand the resulting soil suspension for a short time period, measuring some property of the mixture. Soil pH, lime requirement and soluble salts are measured using this method, although some laboratories may alternatively use titration techniques to measure soil acidity.
Wet chemical oxidation measures SOM from the quantity of carbon that can be oxidised by potassium chromate (K2Cr2O7). Issues about the environmental impact of chromium use and disposal have led to the growing popularity of thermal oxidation, using high temperatures (360oC or 680oF) to estimate SOM from the differences in sample weight before and after ignition.