Suitable drip irrigation amount for summer soybean sown after wheat in Xinjiang

【Objectives】 In order to ease pressure on agricultural water usage caused by the enlargement of winter wheat-summer soybean cropping system in northern Xinjiang, which exacerbated the contradiction between summer soybean and spring crop, this experiment was carried out to find out an appropriate amount of drip irrigation and provide a theoretical basis with water saving, and high yield and quality cultivation techniques for summer soybean. 【Methods】 The field experiment was conducted in summer soybean (Cultivar Heihe 43) field with 4 drip irrigations: 3000, 3600, 4200 and 4800 m3/hm2 by using the randomized block experimental design,and the dry matter accumulation, distribution and nutrient absorption were observed. 【Results】 The results showed that the accumulation amounts of dry matter,N,P2O5 and K2O in plants of summer soybean were fitted in the Logistic equations. The accumulation amounts of dry matter per plant of summer soybean were increased first and then decreased with the increasing of drip irrigation amounts, and the same as N, P2O5 and K2O contents of summer soybean. The fastest accumulation rate of total dry matter of summer soybean was found from 49.5 to 53.0 d after the emergence with the maximum average accumulation rate of 0.48 g/(plant·d), and the rapid growth period of total dry matter accumulation was from 30.3 to 31.9 d. The fast accumulation rates of N, P2O5 and K2O were from 47.1 to 49.9 d, from 44.8 to 45.1 d and from 44.6 to 46.1 d after the emergence,the rapid accumulation periods were from 31.7 to 36.4 d,from 22.2 to 22.4 d and from 28.7 to 31.46 d, respectively, and the average absorption rates were 26.35,8.15 and 9.30 mg/(plant·d). The relationship between the yield and drip irrigation amount at the heading stage could be fitted with a quadratic curve, and the highest yield of 3741.23 kg/hm2 was in 4200 m3/hm2 treatment, which was 30.42%, 13.98% and 8.44% higher than treatments of 3000, 3600 and 4800 m3/hm2, respectively. The fat content in seed was negatively correlated with protein content in seed, and the highest total content of protein and fat was in treatment of 4200 m3/hm2 (53.03%).【Conclusions】 In the 4200 m3/hm2 drip irrigation condition, sowing soybean was not only higher in the dry matter accumulation and yield, but also promoted the absorption of soybean plant nutrients and improved the total content of protein and fat in seed, achieving the purpose of high yield and water saving.