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Bezborodov G.A.,Uzbek Cotton Growing Research Institute | Shadmanov D.K.,Uzbek Cotton Growing Research Institute | Mirhashimov R.T.,Uzbek Cotton Growing Research Institute | Yuldashev T.,International Center for Agricultural Research in the Dry Areas | And 3 more authors.
Agriculture, Ecosystems and Environment

Water scarcity and the predicted impact of climate change will necessitate the use of alternate available water resources in agriculture, such as saline water, to narrow the gap between demand and supply of freshwater. Saline water, in combination with freshwater or alone, is used to irrigate cotton (Gossypium hirsutum L.) in Central Asia in summer when there are often severe freshwater shortages. The use of saline water without appropriate management can result in the accumulation of salts in the root zone with associated negative impacts on crop productivity. The accumulation of salts in surface soil layers can be managed by reducing evaporation from the soil surface. A 3-year field study on a saline soil (ECe=13.9dSm-1; SAR=3.1) in the Syr-Darya River Basin of Uzbekistan was undertaken to evaluate the effects of wheat straw mulching on alternate irrigation furrows (1.5tha-1) and different levels of irrigation water salinity (4.0, 6.2, and 8.3dSm-1) on soil salinity and sodicity dynamics, cotton yield, and crop water productivity. Compared to the pre-experiment status in 2005, the average increase in salinity in the upper 0.15m layer of post-cotton 2007 soil under mulching treatments was significantly less than the non-mulching treatments. On average, there was a 20% increase in surface soil salinity of the non-mulching treatments compared to the mulching treatments. These treatment differences were less with increasing soil depth. Similar trends were observed with respect to changes in soil SAR in the top soil and across the soil profile. Cotton yield and water productivity under mulching treatments were significantly greater than non-mulched treatments at a given irrigation water salinity level. In addition, cotton yields were up to 800kgha-1 higher and crop water productivity (lint+seed) up to 0.47kgm-3 greater in the mulching treatments than the farmers' managed fields with conventional practices in the same region. These results suggest that by using appropriate combinations of water quality and mulching, there could be substantial increase in crop yield and water productivity resulting in water savings of up to 0.5m3 for each kg of cotton produced. When translated on a broader scale, such water savings are significant in a region where freshwater supplies are constrained and salt-induced water quality deterioration is widespread. © 2010 Elsevier B.V. Source

Sommer R.,International Center for Agricultural Research in the Dry Areas | Glazirina M.,International Center for Agricultural Research in the Dry Areas | Yuldashev T.,International Center for Agricultural Research in the Dry Areas | Otarov A.,Kazakh Research Institute Of Soil Science And Agro Chemistry After U U Uspanov | And 16 more authors.
Agriculture, Ecosystems and Environment

Climate change (CC) may pose a challenge to agriculture and rural livelihoods in Central Asia, but in-depth studies are lacking. To address the issue, crop growth and yield of 14 wheat varieties grown on 18 sites in key agro-ecological zones of Kazakhstan, Kyrgyzstan, Uzbekistan and Tajikistan in response to CC were assessed. Three future periods affected by the two projections on CC (SRES A1B and A2) were considered and compared against historic (1961-1990) figures. The impact on wheat was simulated with the CropSyst model distinguishing three levels of agronomic management. Averaged across the two emission scenarios, three future periods and management scenarios, wheat yields increased by 12% in response to the projected CC on 14 of the 18 sites. However, wheat response to CC varied between sites, soils, varieties, agronomic management and futures, highlighting the need to consider all these factors in CC impact studies. The increase in temperature in response to CC was the most important factor that led to earlier and faster crop growth, and higher biomass accumulation and yield. The moderate projected increase in precipitation had only an insignificant positive effect on crop yields under rainfed conditions, because of the increasing evaporative demand of the crop under future higher temperatures. However, in combination with improved transpiration use efficiency in response to elevated atmospheric CO2 concentrations, irrigation water requirements of wheat did not increase. Simulations show that in areas under rainfed spring wheat in the north and for some irrigated winter wheat areas in the south of Central Asia, CC will involve hotter temperatures during flowering and thus an increased risk of flower sterility and reduction in grain yield. Shallow groundwater and saline soils already nowadays influence crop production in many irrigated areas of Central Asia, and could offset productivity gains in response to more beneficial winter and spring temperatures under CC. Adaptive changes in sowing dates, cultivar traits and inputs, on the other hand, might lead to further yield increases. © 2013 Elsevier B.V. Source

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