Pharmacology Journal

AlthoughIndia, in recent years, is emerging as an industrial nation,agriculture remains a key sector in India’s economy, contributing about% of the gross domestic product and employing % of its adultpopulation ICID, . Annual agricultural growth has been modest at .% per annum over the last years IDNP, a.The average Indian farmer is a smallholder owing less than ha ofcultivable land, harvesting one crop a year and striving to harvest asecond crop Pangare et al., .Development plans of the Government of India and State Governments givepriority to alleviate poverty and to create employment, particularly inrural areas. Agriculture depends largely on the monsoon; rains,however, are unevenly distributed in time and space. To sustainagricultural production against these vagaries of rainfall, irrigationhas been created in about million ha, covering about %of the total arable land ICID, .The introduction of irrigated agriculture, however, has resulted in thedevelopment of the twin problem of waterlogging and soil salinization.Considerable areas have either gone out of production or areexperiencing reduced yield. With the misconception, that the more theyirrigate, the more yield they will get, farmers apply huge quantitiesof canal water, e.g. in Segwa, one of the study areas, the actualsupply of mm/year by far exceed the crop water requirementsof mm/year, based on a % application efficiency Ritzema et al., .Furthermore, the introduction of canal irrigation not only brings themuch-needed water, but also imports salts as irrigation water containsconsiderable amounts of salt. In Segwa, the canal water has a salinityof . dS m−, thus an irrigation gift of mm/year will add . t ha−of salts to the soil profile. It is estimated that nearly. million ha of the irrigated lands are affected by soilsalinity and alkalinity, of which about . million ha isalso waterlogged IDNP, a.Drainage,as a tool to combat waterlogging and salinity, has not been givenimportance as much as irrigation by the individual farmers as well asthe governmental agencies. In only about . million ha ofthe affected lands some sort of drainage system has been installed ICID, .Subsurface drainage was introduced only recently. Most systems are lessthan years old and widespread adoption did not take place Gupta, . So far subsurface drainage systems have been installed in about ha Nijland et al., .For the prevailing conditions in India, subsurface drainage systemswith rather deep drains, i.e. drain depth >. m, arerecommended Gupta, . Thisrecommendation is based on the critical depth concept, i.e. to avoidsecondary salinization caused by the upward flux of water once thewater table rises to – m below the soil surface Gupta and Gupta, .These deep drains have their drawbacks. Firstly, the deeper the drain,the higher the installation cost. Secondly, deep drains can onlyeconomically be installed by mechanical construction practices,ignoring the huge employment needs of the rural poor. Thirdly, deepdrains lower the water table during the irrigation season. These lowerwater tables reduce the rate of capillary rise and thus increase theburden on the already poorly performing irrigation systems. Research incountries with similar conditions, i.e. Egypt and Pakistan, indicatesthat shallower drains can maintain salinity levels within safe limitsfor crop production Abdel-Dayem and Ritzema, and Ritzema et al., .Research conducted in various agro-climatic regions in India alsosuggested that the drain depth can be reduced, although the recommendeddrain depth/spacing combinations vary considerably between the variousagro-climatic regions Table .Although sound theories now form the basis of modern drainage systems,there will always remain an element of art in land drainage. It is notpossible to give beforehand a clear-cut theoretical solution for eachand every drainage problem: sound engineering judgement on the spot isstill needed, and will remain so Bos and Boers, .To develop location-specific guidelines for subsurface drainage, theGovernments of India and The Netherlands jointly initiated theIndo-Dutch “Network Operational Research Project on Drainage and Water Management for Control of Salinity and Waterlogging in Canal Commands” IDNP, a. The recommendations and strategies developed by this project are presented in this paper.Table . Recommended drain depth-spacing combinations for various agro-climatic regions in India Agro-climatic regionDrain depth mDrain spacing mReferences Semi-arid coastal plains of Andhra Pradesh.–Rao Semi-arid Trans-Gangetic plains of Haryana.–.–Rao et al. and Achthoven et al. Humid coastal plains of Kerala.Mathew et al. Semi-arid plains of Gujarat.–Parikh et al. Arid lands of Rajasthan.–.–Aheer et al. and RAJAD Sub-humid regions of the lower Gangetic plains in West Bengal.–Rao

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