Determining Optimum Water and Nutrients Leaching Requirements for the Saline Areas of Khorezm, Uzbekistan
Irrational water use and mismanagement are at the root of several environmental problems in the Aral Sea Basin, including secondary salinization. Pre-season leaching (February-March) is a common practice of farmers to manage soil salinity challenges. For example, farmers in the Khorezm region tend applying up to 600 mm of leaching volume to prevent accumulation of salts in the root-zone. However, excessive leaching volume causes the water tables to rise at 1-1.5 m depth which are dangerous depths. These shallow groundwater levels cause secondary soil salinization by capillary rise into the rooting-zone, which nullifies pre-season salt leaching efforts, entails yield losses and seriously threatens economic growth and development. (Grieve et al. 1986; Smets et al. 1997; Willis et al. 1997; Christen et al. 2001; Singh 2004; Murtaza et al. 2006). Nitrogen (N) plays an important role in crops grown with irrigation. It is important to use an optimum amount of water and nitrogen for the best management of crop production and in the process avoid nitrogen leaching below the root zone (Gheysari et al., 2009; Wang et al., 2010). Hence, excessive irrigation/leaching amounts can reduce the effectiveness of fertilizer applications by leaching them below the root-zone and thereby causing reduction in crop yield. On other hand, reduced leaching amounts can cause secondary soil salinity in root-zone. This study aims to determine the trade-offs between the amounts of water used for leaching salts to control soil salinity but minimizing nutrient leaching and enhance soil fertility, control water table and increase agricultural water productivity and efficiency.