Effect of Irrigation Amount and Uniformity on Alfalfa Yield and Quality under Center Pivot System

Abstract. As the center pivot irrigation system has advantages of easy operation and low labor requirement, the alfalfa area irrigated by center pivots has greatly increased to 0.2 million ha in China. Irrigation scheduling and uniformity are two of the most important factors that need to be considered in the design of a center pivot irrigation system for alfalfa producers. In the two-year (2014-2015) field study conducting at Saiwusu, Inner Mongolia Autonomous Region, three irrigation levels (100%ET, 80%ET, 60%ET) and three irrigated areas (A1, A2, A3) were designed for evaluating the effect of irrigation amount and uniformity on alfalfa yield and quality. Annual alfalfa yield was affected significantly by irrigation level, averaging 13063.42, 13047.97, 11179.96kg/ha while irrigation amounts averaged 442.32, 365.17, 288.02mm for 100%, 80%, 60%ET irrigation levels, respectively. No significant difference existed in alfalfa yield between 100%ET and 80%ET irrigation level, but 60%ET level caused an obvious reduction by 14.02% of 100%ET and 14.32% of 80%ET. Crop water productivity significantly decreased with increased irrigation amount. The quadratic relationships between yield and irrigation were established for each harvest. Initial ASW was largely influenced by winter irrigation. Deficit irrigation at 60%ET level was conductive to improve the quality of alfalfa but was of no help to its grade, indicating that yield could be seen as the most important factor to determine irrigation scheduling. Alfalfa yield uniform distribution and quality of different irrigated areas within a center pivot system barely affected by irrigation uniformity with uniformity coefficient of 83.5%, demonstrating that irrigation amount was the most important to design center pivot irrigation systems especially when irrigation uniformity slightly lower than the good value of 85%. Taking all results into account, it was concluded that an irrigation level of 80%ET in the former two harvests and 60%ET irrigation level in the third harvest were recommended due to the present situation of water resources serious shortage in Western Inner Mongolia.