Effects of cropping patterns on rice yield and soil fertility

Field experiments were conducted in double cropping rice field during 2009-2011 to study the effects of different cropping patterns on rice yield and soil fertility. The results show that the yield of the cropping pattern of the milk vetch + double cropping (ZDD) rice is the highest, the yield of the rape + double cropping rice (YDD) is in the middle, and that of the fallow + double cropping rice (XDD) is the lowest. There is not any obvious difference in early rice under different treatments in 2010, but the yield of ZDD in late rice is 3.5 percent and 4.1 percent higher than those of YDD and XDD, respectively. In 2011, the yield of early rice is 6.4 percent and 4.6 percent higher than those of YDD and XDD. The yield differences are mainly caused by the number of effective panicles and grains per spike. The total dry weight of rice roots is in the order of ZDDYDDXDD, and most of the roots is distributed within 10cm soil layer. Two years after the extension of double cropping, compared with XDD, soil organic matter, total nitrogen content, the quantity of microbe and enzyme activity are increased under the treatments of ZDD and YDD. The milk vetch plough substitution of chemical fertilizers is of significant importance of improving rice yield and maintaining soil fertility. The amount of soil organic matter of ZDD treatment is significantly improved, which is 0.58 percent and 0.95 percent higher than those of YDD and XDD respectively. All the three treatments enhance total nitrogen content, ZDD by 6.52 percent, YDD by 2.17 percent, and XDD by 0.72 percent, and among which the difference between ZDD and XDD is most significant. In terms of microbe quantity, extremely obvious differences are noticed, which is ZDDYDDXDD.XDD is most significant. In terms of microbe quantity, extremely obvious differences are noticed, which is ZDDYDDXDD. With the same amount of the fertilization, milk vetch can increase the output of rice, and planting milk vetch and rape in winter improves soil fertility.