| More concern has been exerted on the suitability of sprinkler irrigation in arid regions with increasingly shortage of water resources. Water consumption and growth of crop was affected by environmental factors. So, research on the suitability of sprinkler irrigation in different climatic regions is essential to establish proper irrigation and fertigation schedule. At present, most of the studies about sprinkler efficiency were insufficient for without considering the effect of crop characteristic, and lack of analysis of effects of environmental factors using statistical method. Sprinkler efficiency was difficult to determine accurately during crop growing season. A proper understanding of suitability of sprinkler irrigation in arid regions is important for determining the coefficient of sprinkler uniformity. So it is essential to examine the sprinkler efficiency and affecting factors in arid regions.Field experiments were conducted in arid and semiarid region, during the growing season of wheat to investigate the effects of environmental factors on sprinkler efficiency, and to evaluate the effects of sprinkler uniformity on distribution of soil water and nitrogen, and to investigate the response of crop yield on sprinkler uniformity and soil variation. Major results of study were listed as follow.1. The results showed that sprinkler efficiency varied from 0.65 to 0.97 during growing season of spring wheat. A greater sprinkler efficiency exceeding 0.9 was obtained when sprinkler irrigation was performed in evening or wee hours. The environmental factors of higher air temperature, low relative humidity and high wind could result in the decreasing of low sprinkler efficiency. Wind velocity was found to be the predominant factor affecting application efficiency, followed by the relative humidity, while air temperature had the least effect.2. More uniform distribution of water was obtained in soil than on the field surface. A coefficient of sprinkler uniformity lower than 60% still produce a coefficient exceeding 90%, which can be attributed to the redistribution of water in soil.3. Sprinkler irrigation affected the coefficient of soil water uniformity in 45 cm layer apparently. The coefficient increased with depth above 45 cm soil layer, and almost no change below 45 cm soil layer. Sprinkler uniformity could not affect the uniformity of soil water significantly. Therefore, in spite of the large variation sprinkler uniformity in growing season, coefficient of soil water uniformity has always kept a high value above 90%.4. Variation of nitrate in soil was affected by many factors including irrigation, fertigation, and crop uptake. Distribution of nitrate and ammonium nitrogen was random in soil. Strong variation of nitrogen uniformity in soil was observed with time and soil depth. Coefficient of nitrate and ammonium nitrogen ranged from 23%～97% during the winter wheat growing season, and coefficient of variation ranged from 0.04～1.06 and 0.04～1.00 respectively. Uniformity of nitrate distribution in soil depended on the uniformity of sprinkler irrigation and fertigation, and affected by the initial distribution of nitrate in soil.5. Coefficient of variation of water was biggest in 60-80 cm soil layer. Field capacity obeying normal distribution and lognormal distribution increased with content of fine particle in soil. Coefficient of uniformity of yield and component part was less than the coefficient of cumulative irrigation. Both the dispersion degree of soil characteristics and irrigation would induce the increase of dispersion degree of yield. |
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