Agri Science / IBPS AFO / NABARD NOTES

Soil science Important Topic For Competitive Exam

Soil becomes “Saline” in areas where annual evaporation exceeds annual precipitation.
Beans are damaged by chloride in the soil solution at equal ostmatic pressure, which sulphates do not harm the crops.
Grasses are more tolerant to chlorides than sulphates at equal O.P.
At very high O.P, magnesium is more toxic than ‘Ca’ than Na.
A soil which does not permit the normal growth of plant is a “Problem soil”.
Acid soils: Two types in
Laterite soils – These are open textured with “massive structure”.
Ferrugenous red soils – derived from crystalline metamorphic rocks.
Humus is a final product of organic matter decomposition. Lime as a reclaiming agent: calcite limestome – CaCO3,
dolamite limestone – CaCO3 MgCO3.
Quick lime – CaO, Blast furnace slage – CaSiO3 (by product of iron industry).
Due to high soil acidity, Al, Mn, Fe, become highly solubulized and available in toxic amounts.
In acid soils activity of bacteria and actinomycetes is adversely affected. Fungi are active in
acid pH.
All the micronutrients (Fe, Mn, Cu, Zn, Co) except Mo are available in the acid pH. Mo
deficiency has been identified in leguminous crops.

Tillage Implements & their work

Tractor drawn cultivator – Destroy weeds and breaking clods
Sweep cultivator – Harvesting groundnut and used in stubble mulching
Harrows – Preparation of seedbed, destroy weeds
Planker – Micro levelling
Star weeder – Weeding in dry lands and groundnut field

Particle – Diameter(mm)

Stone >20

Gravel 2-20

Fine earth <2

Coarse sand 0.2 -2

Fine sand 0.2- 0.02

Silt 0.02-0.002

Clay <0.002

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