The Comparative Study Of Soil Quality And Crop Yield Of The Rotation Plough Land From Alfalfa Grassland And Conventional Cropland

In order to study what long-term effect of crop yield and soil quality will produced after the long duration of alfalfa field rotated to cropland at the semiarid area of China’s Loess Plateau, this study selected30years of alfalfa field ploughing into cropland and make a comparative study with conventional cropland. We set up for Four treatments:treatment one:rotation farmland with fertilization (MF).treatment two:rotation farmland without fertilization (MO).treatment three: conventional farmland with fertilization (NF).treatment four:conventional farmland without fertilization (NO).The rate of fertilization according to the local farmers’standard. The experiment was proceed from2010to2013at the research station of Lanzhou University, which been located in Zhonglianchuan village, Yuzhong county. All treatments during the processing adopts plastic film mulch and tillage, the results are as follows:Maize was planted in2010, the yield of MF was75.5%of NF, and the yield of MO was59.6%of NO. Com was planted in2013, the yield of MF was82.8%of NF, and the yield of MO was84.8%of NO. the yield of MF relative to NF and the yield of MO relative to NO increased by7.3%and7.3%respectively. Potatoes was planted in2012, the yield of MF up to124.3%of NF and MO up to157.5%of NO.In the three years of planting maize, the water use efficiency have no changes between MF and MO. The water use efficiency of MO increased to81.2%of NO in2013.The water use efficiency of MO reached nearly two times of NO.in2012.After harvesting in2013, the soil water content of MF, MO, NF and NO were increased by45.3%,45.3%,34.6%,32.6%in the soil layers of0-200cm, and in200-500cm soil layers, the soil water content of MF and MO was reduced by11.7%and15.8%respectively.After harvesting in2013,in the soil layers of0-15cm,the SOC content of MF, MO, NF, NO was reduced by5.7%,18.6%,18.3%and18.7%, the TN content increased by20.2%,5.6%,7.1%and20.2%respectively, the TP content was stable, the AP content increased by48.1%,76.0%, 95.8%and168.1%respectively.Conclusion:the influence of long duration of alfalfa rotation on crop yields and water use efficiency gradually reduce as increasing of time. The choice of the crop is critical. The soil moisture in0-200cm was recovered, but the soil moisture in200-500cm was decreased.