Evapotranspiration Point Wise Notes For Competitive exam

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• Evapotranspiration losses can be reduced by mulches, antitranspirants, wind breaks and weed control.

• About 60 to 75 % of the rainfall is lost through evaporation.

• Mulch is any material applied on the soil surface to check evaporation and improve soil water.

• Application of mulches results in soil conservation, moderation of temperature, reduction in soil salinity, weed control and improvement of soil structure.

• If the surface of the soil is loosened, it acts as mulch for reducing evaporation. This loose surface soil is called soil mulch or dust mulch.

• Soil mulch helps in closing deep cracks in vertisols.

• Crop residues like wheat straw or cotton stalks etc. are left on the soil surface as a stubble mulch.

• If straw is used as mulch, it is called straw mulch.

• In plastic mulching plastic materials like polyethylene, polyvinyl chloride used as mulching materials.

• Subsoiling is the most effective method of breaking hard pans to improve root penetration, aeration and water percolation.

• Effects of subsoiling are not long lasting.

• Slots left by the subsoiler are closed and sealed off within a few months.

• In order to prolong the beneficial effect of subsoiling vertical mulching is adopted.

• The objective of vertical mulching is to fill slots with organic matter and keeping them open and functional for a longer period.

• In black soils infiltration of water is slow and rainfall is lost as runoff.

• To improve infiltration and storage of rain water in black soils, vertical mulches are formed.

• In vertical mulching narrow trenches are dug across the slope at intervals and placing the straw or crop residues in these trenches.

• Nearly 99% of water absorbed by the plants is lost in transpiration.

• Antitranspirant is any material applied to transpiring plant surfaces for reducing water loss from the plant.

• Fungicide like phenyl mercuric acetate (PMA) and herbicides like Atrazine in low concentrations function as stomatal closing antitranspirant.

• Stomatal closing antitranspirants reduce photosynthesis.

• Mobileaf, hexadecanol, silicone are film forming type of antitranspirants. They also reduce photosynthesis.

• 5% kaolin spray, diatomaceous earth product (celite) are reflectant type of antitranspirants. These are white materials.

• Cycocel is a growth retardant. It reduces shoot growth and increase root growth. It also induces stomatal closure.

• Wind breaks are any structures that obstruct wind flow and reduce wind speed.

• Shelterbelts are rows of trees planted for protection of crops against wind.

• The direction from which wind is blowing is called windward side.

• The direction to which wind is blowing is called leeward side.

• Shelterbelts give protection from desiccating winds to the extent of 5 to 10 times their height on windward side and up to 30 times on leeward side.

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