SOIL AND PLANT ANALYSIS (1+1)

Evaluation of soil structure and Aggregate analysis

Evaluation of soil structure

Soil structure can be evaluated by determining the extent of aggregates, the stability of the aggregates and the nature of the pore-space.
All these characteristics change with tillage practices and cropping systems. The volume

Aggregate analysis
There are generally three techniques that can be followed for the aggregate analysis –
(i) wet and dry sieving
(ii) elutriation and
(iii) sedimentation Direct dry sieving of soils in the field is used to evaluate the distribution of clods and aggregates.

Dry sieving of aggregates gives an important index for characterizing the susceptibility of soil to wind erosion In the wet sieving technique, the soil is slowly wetted by capillarity for 30 minutes and is then transformed onto a nest of sieves immersed in water. The sieves are slowly raised and lowered in the water for 30 minutes. The weight of soil on each sieve is then determined. Elutriation may be used for the separation of aggregates with diameters between 1 and 0.02 mm. Sedimentation methods have been used to determine the aggregate distribution in the finer fractions that cannot be separated by sieving. They are limited to aggregate sizes less than 1 mm. There are generally two limitations of sedimentation method : varying density of particles and possibility of flocculation during sedimentation because of the downward motion of the large aggregates.