Irrigation requirements of wheat and cotton under different water table conditions
2001
Qureshi, A.S. (International Irrigation Management Inst., Lahore (Pakistan))
Water availability to major crops from different water table depths has been studied by various organizations in Pakistan. The results of these studies reveals that high water tables were not conducive for successful agriculture yet crop production appeared to be a feasible proposition provided irrigations are controlled to judicious requirements, rainfall is evenly distributed over the year and ground water quality is good. The general practice of applying 5-6 irrigations to wheat and cotton crops proved wasteful and unproductive on soils having water tables less than 3 m from the surface. Good yields of cotton and wheat could be obtained with 1-2 irrigations (where each irrigation measures about 7.5 cm) at water table depth of 1-2 m, 2-3 irrigations at water table depth of 2-3 m and 3-4 irrigations at water table depth of 3-4 m provided groundwater quality is within safe limits. To accomplish efficient use of scarce water supplies and avoid undue addition to the water table, research results suggest a significant cut to the present application levels under high water table conditions. The extent of irrigation supplement towards crop consumptive use depends mainly on crop root system and soil type. On the basis of this analysis, it can be concluded that drainage system should be installed to maintain water table between 1 m to 1.5 m provided groundwater quality is within use able limits. This depth of water table will not only maximize the sub-irrigation but also control the salinization of the soil profile. Moreover, shallow drains will reduce the volume of drainage effluent and installation and system costs.
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