Soil science Important Topic For Competitive Exam

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Soil science

  • 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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