Alfalfa Grassland After Returing To The Dynamic Characteristics Of Soil Water And Nutrient And Biological Yield

Long-term planting alfalfa lead soil desiccation and the physical and chemical properties changes in deep layer in the loess plateau semi-arid areas. This experiment compared the alfalfa planting year relationship with soil moisture recovery, quality and the yield between the farmland which has been planted alfalfa for 30 years and the neighboring conventional ones. Four treatments were set up, Alfalfa ploughing farmland with fertilized (MF), Alfalfa ploughing farmland without fertilized (MO), conventional farmland with fertilized (NF), conventional farmland without fertilized (NO). Field experiment was conducted from plough started in 2010 April to after harvested in 2014 October at the semiarid ecosystem research station of Lanzhou University, all treatments were planted by double ridges and furrows mulched with plastic film,main conclusion as the following:1.Soil water content of after alfalfa ploughed farmland recovered fast in 0-60 cm soil layer, and the soil relative water content in this layer of MF/NF, MO/NO were 80.34% and 82.99% in April 2010, after 5 years continuous planting, which return to 108.01% and 103.04% in 2014 October, respectively, and more than conventional farmland, indicated that soil moisture content has fully recovered; Compared with the soil water content of alfalfa ploughing farmland in 60-200 cm, the soil relative water content in this layer of MF/NF, MO/NO were 76.56% and 74.78% in April 2010, after 5 years continuous planting, which return to 90.78% and 85.67% in 2014 October, respectively, and less than conventional farmland, indicated that soil moisture content has being recovered but not fully.2. From overall,4 kinds of processing experiment of soil organic carbon (SWC), total phosphorus (TP) has a tendency to increase. Total nitrogen (TN) has a tendency toreduce.The difference of available phosphorus content before and after the experiment of a gro wing season will decrease with the increase of the test year,Nitrogen also had the same law. At the beginning, the relative content of available p MF/NF MO/NO were 35.8% and 39.2% respectively in April 2010. The NF of available phosphorus content was significantly higher than that of MF available phosphorus content and the NO of available phosphorus content was significantly higher than that of MO available phosphorus content. After five years of continuous planting crops, the relative contents of available p MF/NF MO/NO were 73% and 47% respectively in October 2014. There was no significant difference between the available p content of NF and the available p content of MF. There was no significant difference between the available p content of NO and the available p content of MO. At the beginning of the mineralized nitrogen relative content MF/NF MO/NO were 39.2% and 22.2% respectively in April 2010. The NF of the mineralized nitrogen content was significantly higher than that of MF mineralized nitrogen content. The mineralized nitrogen content of NO was significantly higher than that of MO mineralized nitrogen content. After five years of continuous planting crops, the relative contents of mineralized nitrogen MF/NF MO/NO were 74% and 260% respectively.There was no significant difference between the mineralized nitrogen content of NF and the mineralized nitrogen content of MF. There was no significant difference between the mineralized nitrogen of NO and the mineralized nitrogen content of MO.3. In 2010 experiment, the corn yield of NF treatment significantly higher than that of MF, the corn yield of NO treatment significantly higher than that of MO. The corn yield of MF accounted for 75.5% the corn yield of NF. The corn yield of MO accounted for 59.6% the corn yield of NO. In 2014 experiment, There was no significant difference between the potato yield of MF and that of NF. There was no significant difference between the potato yield of MO and that of NF. The potato yield of MF accounted for 81.23% the potato yield of NF. The potato yield of MO accounted for 96.59% the potato yield of NO. The difference NF potato yield and MF potato yield is more and more small, NO and MO also had the same law. In 2010 experiment, the water use efficiency (WUE) of NF was significantly higher than that of MF, the WUE of NO was significantly higher than that of MO, the WUE of NF is 1.42 times that of MF, the WUE of NO was 1.58 times that of the MO. In 2014 experiment, there was no significant difference between the WUE of NF and the WUE of MF. There was no significant difference between the WUE of NO and the WUE of MF. The WUE of NF was 1.11 times that of MF and the WUE of NO was 0.79 times that of MO. The difference NF WUE and MF WUE were more and more small, NO and MO also had the same law.