Studies On Water-Saving Irrigation Of Cotton In Arid Desert Areas

Minqing oasis lies in lower reaches of Shiyang river, where surface water is overmuch exploited and is shortage. Maintainable development of agriculture depends on rational exploitation of water resource. So water-saving irrigation is one of main measures under condition of shortage water. In the oasis, trial of irrigating cotton is done by three different ways, which is drip irrigation, semifixation spray irrigation and seepage-preventing ditch irrigation. Thereinto, drip irrigation is divided into three treatments of different ration. Tectorial and untectorial treatment are adopted to semifixation spray irrigation. At the same time, seepage-preventing trial is done. By study of one growth season, it shows that the indexes, such as percent of mature cotton boll, quantity of cotton boll, seed quantity, weight of cotton boll and seed yield, of drip irrigation and semifixation spray irrigation are all lower than them of seepage-preventing ditch irrigation. However, the indexes, such as ginning exponent, ginning outturn, fibre length, yield and production efficiency of water, of drip irrigation are higher than them of semifixation spray irrigation and seepage-preventing ditch irrigation. In drip irrigation trial, every index all decreases with reducing of irrigation ration. Treatment of 60% irrigation ration restricts growth and development of cotton plant in higher degree in period of flower boll, so in which the ration irrigation shouldn't,be adopted and irrigation ration should be increased properly. The connection between cotton yield and quantity of irrigation and water deprivation, between production efficiency of water and quantity of water deprivation, is both approximate conic. It has best significance difference among unit yield of using differentirrigation ways. The highest yield is in irrigation treatment of 80% field moisture capacity, it is secondary in seepage-preventing ditch irrigation treatment and is the lowest in spray irrigation treatment. The effect to yield is obvious in drip irrigation treatment of different irrigation ration. Yield decreases with reducing of irrigation ration. Yield of different drip irrigation ration all can be inosculated by quadratic equation with quantity of irrigation and water deprivation. And yield can be forecasted by planting density, and efficient cotton boll quantity of individual plant and quantity of individual cotton boll. The equation is y=-4046.21+0.04468xt+ 393.78x2+820.23x3 and its complex correlation coefficient is R=0.903. Comparing with flood irrigation, water-saving technique has the effect of increasing production and harvest, economizing water, energy sources and field, saving work, time and power. Seepage-preventing ditch irrigation economize 40.4% water, drip irrigation economize 49-55.6% water and spray irrigation economize 59.2% water comparing with flood irrigation. Seepage-preventing ditch irrigation, drip irrigation and spray irrigation save work respectively 14.4%, 47.0% and 36.1%, economize electricity respectively 29.2%, 38.5% and 31.1%. Furthermore, drip irrigation and spray irrigation save field about 5-7% comparing with seepage-preventing ditch irrigation and flood irrigation. The result of water-saving irrigation of oasis cotton shows that drip irrigation and seepage-preventing ditch irrigation have obvious effect and can apply in this region. And yet semifixation spray irrigation need to experiment unceasingly. It suggests semifixation spray irrigation should be introduced cautiously.