Lysimeter Techniques and Application in Indiaby S. P. Bhardwaj, Central Soil & Water, Conservation Research & Training, Inst, Dehra Dun, India,
Abstract: Water is the most important resource and limiting factor for crop and industrial production in India, and agriculture is the largest consumer of water. The measurement of evapotranspiration (ET) of farm crops was started precisely in the 1940's using gravimetric analysis of soil. Non-weighing type and constant water table lysimeters were installed during the 1960's. Lack of precise daily/weekly (ET) data led to installation of about 40 weighing type lysimeters during 1975. Five simple and improved mechanical weighing type lysimeters using a 120 cm3 undisturbed soil monolith were developed and installed. The system has a sensitivity of 200g (0.14 mm water) with the provision of hourly/daily monitoring of the complete hydrologic cycle (rainfall, dew, soil profile moisture, run-off, seepage and ET). Total ET values (mm) (in an unstressed condition) were found for crops such as corn (385), paddy (499), soybean (545), sesamum (355), cowpea (354) during the rainy season (June - September); and wheat (507), barley (440), alfalfa (1057), sugarcane (1375), lentin (324) and potato (191) during the post-rainy season (November-April). Water Stress reduced the yield of wheat. The daily/weekly correlation of ET with various meteorological parameters were developed. Fourteen models were used for computing potential ET (ETp) and values were compared with observed ETp. Seven models were improved to suit local conditions. The study gave added importance to lysimeters as a tool for budgeting three major natural resources of crop production namely water, solar radiation and nutrient elements. More than 100 centers in the country are using pan evaporation data for optimizing irrigation schedules in their studies. The availability of ET values gave definite improvement in their studies of water use efficiency, crop yield, water resource development and management.
Subject Headings: Crops | Measuring instruments | Water resources | Developing countries | Water conservation | Evapotranspiration | Soil analysis | India | Asia
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