Soil texture refers to the relative percentage of mineral particles (sand, silt and clay) in a soil. The size of particles in mineral soil is not subject to ready change.
In other word, the size of soil particles and their spacing determine how much water can flow through the soil. The larger the spacing, or pore size, the greater the infiltration rate of soil. Thus, sandy soils will have high infiltration rates because pore sizes are larger and there are no finer materials to block the pores.
Thus, it is considered as a permanent feature and a basic property of a soil. Soil texture is an important physical property of soil because it will partly determine water intake rates (absorption), water storage in the soil, the tillage operation, aeration status of soil etc.
Natural soils are comprised of soil particles of different. Soil texture combinedly influence soil fertility. As for an example, a coarse sandy soil is easy to cultivate or till, has sufficient aeration for good root growth and is easily wetted, but it also dries rapidly and easily loses plant nutrients through leaching, whereas in case of high – clay soils ( > 35 % clay ) have very primarily small particles that fit tightly together, leaving very little pore and spaces which permits very easy of the little room for water to flow into the soil. This condition makes soils difficult to wet, drain and till.
As the soil is a mixture of various sizes of soil separates, it is therefore, necessary to establish limits of variation for the soil separates with a view to group them into the different textural classes. Texture is a basic property of the soil and it can not be changed.
Soil texture is an important property of soil that drives crop production and field management. Soil particles may be either mineral or organic but in most soils, the largest proportions of particles are mineral and these soils are therefore referred as “mineral soils.”
Various dimension particles interconnect different types of soils.
The following groups of soil have been divided on this basis:
(1) Sandy Soil – 85% Soil Balter + 15% Smooth Soil or Silt.
(2) Loamy Soil – 70% sand + 30% smooth clay or lap.
(3) Silt – 90% silt + 10% sand.
The soil texture directly affects the organization of Soil Water. It also affects the basic growth and soil air at the same time. It also affects the soil’s food-level.
Three broad and fundamental groups of soil texture:-
Sands – The sand group includes all soils of which the sand separates make up 70 percent or more of the material by weight. Two specific classes are recognized sand and loamy sand. Sand particles are little big in size.
The pore spaces between the particles in sandy soils are also little large. This allows water to drain quickly and air to move in the soil. Sandy soils tend not to get water logged in winter but can be subject to drought during the summer time.
Loams – Loamy soils containing many sub division does not exhibit the dominated physical properties of any these three soil separates sand, silt and clay. An ideal loam soil may be defined as a mixture of sand, silt and clay particles which exhibited light and heavy in equal proportions. Loam particles are small for us to see with the eyes. Loam soils have much smaller pore spaces but a lot more of them.
Clay – Clay particles commonly are platy in shape and higher plastic when moist. A clay soil must carry at least 35 percent of the clay separate and in most cases not less than 40 percent. They have highest surface area since surface area is inversely related to size. Clay particles are very smaller in size less than 0.002 mm in diameter. Clay soils are poorly drained and hold on to the water in their pore spaces for longer time. However, they become very hard if they dry out.
Rice, cotton, sorghum etc. are grown on heavy textural soils which include clay, loam, silty clay loan, silty clay and clay. Medium textured soils like loams, silt loams, silts and sandy loams are suitable for most of the crops. Sandy, loamy sand and sandy clay are light textured soils. these are suitable for groundnut, potato, tobacco, pearl millet and fodder crops etc.
Determination of textural class:-
There are mainly two methods employed for the determination of textural class :-
Feel method – In the field, texture is commonly determined by the sense of feel. The soil rubbed between thumb and fingers under wet conditions. Sands feel gritty and its particles can be easily seen. The silt when dry feels like flour and talcum powder and is slightly plastic when wet. Clay particles feel very plastic and exhibit stickiness when wet and are hard under dry conditions.
Laboratory method – A more accurate and fundamental method has been devised by the U.S Department of Agriculture for the naming of soils based on a mechanical analysis.
Additional Methods – There are several additional quantitative methods for the determination of soil texture. Some examples of these methods are the pipette method, the particulate organic matter (POM) method, and the rapid method etc. from whicj we can determine the soil texture.
Depending upon the perimeter of particles of the International Society of Soil Science, Soil has been divided into the following parts:
- Clay Soil – 0.002 min. I Less than.
- Silt – 0.02 min. I 0.002 min from I Less than.
- Fine sand – 0.20 min. I 0.020 mins from I Less than.
- Coarse Sand – 2.0 min. I 0.20 mins from I Less than.
- Finely Gravel – 5.0 min. I 2.00 mins from I Less than.
- Gravel – 5.0 min. More than m.
Soil texture can influence whether soils are free draining, whether they hold water and how easy it is for plant roots for the growth.