Subject: Irrigation Engineering, Class: B.Tech IInd Year Course teacher: Dr.S.K.Sharma Title: Land Grading Land grading is reshaping of land surface to a planned grade. It is necessary in making a field surface to control the flow of water, to check soil erosion and provide for surface drainage. Usually field is not graded to a level surface, but a gentle uniform slope is maintained to meet the requirements of irrigation and drainage. Irrigated areas benefit greatly from land grading since the ground in its natural state is seldom suited for the efficient application of water. When an uneven land is irrigated the high spots are watered too little and the low spots too much. This results in uneven crop, reduced yields and loss of water. A properly graded land surface ensures unobstructed smoth flow of water into the land, without eroding the soil and ensures uniform distribution of water throughtout the field. Criteria for Land Levelling or Grading Criteria for land grading are influenced by the characteristics of the soil profile, prevailing land slope, rainfall characteristics, cropping pattern, method of irrigation and other considerations. 1. Soil profile condition: A soil survey of the area to be levelled is necessary before undertaking the leveling work. The soil survey map will show the nature of the top soil, the subsoil and the material under the subsoil. It will show the depth to sand, hard pans, rock or other material that might limit the depth of cut as well as the extent of such areas. Alkali spots will be outlined and depth to water level shown. The information will aid in planning the best possible layout for land leveling. Soils that are shallow have limitations in the depth of cut that is allowable. Deep cuts in such cases may expose inert material which may not grow cops. In deep soils, however, cuts into subsoil may not be harmful because organic matter can be added t o build up its fertility quickly. Soil survey will furnish information relative to infiltration and hydraulic conductivity. If the sub soil and substratum are sand or sandy loam and the infiltration rates are high the irrigation runs must be shorter than if there is clay loam or clay underlying the surface.
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Title: Land Grading Course teacher: Dr.S.K.Sharma Subject ...jnkvv.org/PDF/04042020083154Land grading.pdfCriteria for land grading are influenced by the characteristics of the soil
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