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Index >> Soil, Nature Medium For Plant Growth >> Evaluation of Soil Structure

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Evaluation of Soil Structure

	Evaluation of Soil Structure Soil structure is evaluated by determining one or more of the following parameters: (1) size of soil particles using dry or wet sieving methods, (2) pore-size and its distribution in soil, (3) saturated hydraulic conductivity of soil in situ, (4) bulk density of soil in situ. (5) infiltration rates of soil in situ, (6) hydraulic conductivity at compacted minimum bulk density, and (7) energy required to cause aggregate disintegration .
One of the methods followed in the Division of Agricultural Physics, Indian Agricultural Research Institute, for determining soil structure is the aggregate analysis by wet sieving method using a modification of the original Yoder-type sieve-shaker having four nests each containing sieves with apertures ranging from 2.0, 1.0, 0.5, 0.25 and 0.10 mm. Air-dry soil samples (say 50 g each) having aggregates from 5 to 8 mm size are spread on the mesh of top sieve (2 mm) and are saturated with water by gradually increasing the level of water in the tank of the sieve-shaker. Samples are then sieved in water for 30 minutes by shaking at the rate of 33 cycles per minute
The water stable aggregates retained on each sieve are then quantitatively transferred to tared aluminium cans, oven dried and weighed. Oven-dry soil aggregates of various sizes of each sample are transferred to a container having 10 ml of 5% solution of sodium hexametaphosphate with sufficient distilled water to disperse soil particles. After stirring the suspension for 15 minutes, the contents are washed in a stream of water on the same sets of sieves which were used earlier. The primary particles (sand) retained on each sieve are now oven dried and weighed.
Moisture content of soil samples on oven-dry weight is also calculated separately to determine the percentage of aggregates. The calculation is as follows: Percentage of aggregates > 0.25 mm = Based on the above data, aggregation index can be calculated by determining the area between the two curves obtained by plotting the accumulative percentages (fraction less than a particular size) of soil particles and sand against the sieve openings.

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Soil pH Soil Structure Role of Organic Matter Synthetic Soil Conditioners Relation to Root Growth Evaluation Soil Structure

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