How The Techniques Of Double Ridges And Furrows With Plastic Mulch And Rainwater Harvest With Subgroove Facility Affect Soil Moisture & Temperature, Soil Fertility And Crop Yield In The Semiarid Loess Plateau Of China

In view of natural characteristics of semiarid region of the Loess Plateau and in order to improve the rainwater use efficiency and crop yield,two rainwater-harvesting experiments had been conducted in Beishan of Yuzhong County in combinations of various plastic mulching methods with water-harvesting methods with two aims to maximize field rainwater harvest amount and control rainfall in-place infiltration.In 2006,three treatments were used:(1)flat plot without mulch(CK);(2)two ridges and furrows mulched by one plastic film and maize planted in the furrow between the two ridges(DRM);(3)two rows of maize planted in a ridged bed mulched with plastic (RM).Two additional treatments were tested in 2007:(4)two rows of maize mulched with a 70cm wide plastic film and then 30cm of bare soil alternated(NM);(5)maize planted without ridges in double rows 80cm apart and the whole plot mulched with plastic film(WM).Another experiment was designed from 2005 to 2008 in slope site. There were five treatments:(1)flat plot without mulch(CK);(2)alternating ridges and furrows without mulching(M0C0);(3)alternating ridges and furrows,ridges mulched with plastic film(MC0);(4)altemating ridges and furrows,ridges without mulching,subgroove under the ridge(M0C);(5)alternating ridges and furrows,ridges mulched with plastic film and subgroove under the ridge(M0C).The results as shown follows:(1).Maize yield was highest in the DRM treatment:1150kg ha^-1in 2006 and 6130kg ha^-1in 2007.This was associated with better topsoil moisture in the planting zone and higher soil temperature in the DRM treatment compared with the other treatments. The soil moisture in DRM reached 10.5%and 22.6%,in 2006 and 2007,respectively, the highest of all the treatments.The mean temperature in DRM was higher than in CK and RM by 5.8℃and 4.9℃,respectively in 2006,while in 2007,it was higher than that in CK by 6.1℃in seedling stage of maize.(2).The highest water-use efficiency(WUE)was found in DRM in both years.In 2006,the WUE in DRM was six times greater than that in CK and 9.96%greater than in RM.In 2007,the WUE for grain in the DRM treatment was 16.6kg ha^-1mm^-1, eleven times greater than that in CK and greater than RM,NM and WM by 67.7%, 26.7%and 9.2%,respectively.The yield of maize in DRM was 576%greater than in CK and 2.7%greater than in RM in 2006.It was 64.8%,32.1%,21.9%and 1043.7% greater than in RM,NM,WM and CK in 2007,respectively.Though the costs of labor and the plastic film were also higher than CK,the yield of mulched treatments improved seriously.In this region,the price for corn was on average about 1.4 RMB Yuan kg^-1.In the present study,the economic benefits for CK,DRM,RM,NM and WM were 750.4 RMB Yuanha^-1,7664.5 RMB Yuanha^-1,4347 RMB Yuanha^-1,5883 RMB Yuanha^-1and 6422 RMB Yuanha^-1,respectively(the exchange rate between us＄and RMB Yuan is about 1:6.99).The treatment of DRM takes the largest field and benefit,therefore it can serve as a model for maize establishment on the large scale in this region.(3).DRM,RM,NM and WM could improve the number of the microbial biomass in the soil.The mulching treatments reduced SOC content and light fraction of organic carbon(LFOC).The reduce in SOC negatively correlated(R²=0.84,P=0.0007)with the microbial biomass carbon.The microbial biomass carbon was negatively correlated(R²=0.78,P=0.0007)with mineral N,was positively correlated(R²=0.56, P=0.01)with available phosphorus.The microbial biomass carbon content in DRM was 21.5%to 213%greater in other treatments.But DRM had the least SOC,MN, C/N in all the treatments.They were poor for the soil nutrient.(4).The highest yield of crops appeared in MC all the time.In 2005,the yield in DRM was greater than CK,M0C0,M0C and MC0 by 271%,90.5%,89.2%and 77.4%,respectively.In 2006,that was greater than CK,M0C0,M0C and MC0 by 529%,220%,138.6%and 66.5%,respectively.The yield in DRM was 128%,85.5%, 43.8%and 1.4%greater than in CK,M0C0,M0C and MC0 respectively in 2007,it was was 77.5%,55.1%,41.8%and 19.7%greater than in CK,M0C0,M0C and MC0 respectively in 2008.(5).Ridges mulched with plastic film and subgroove had greater effect on the yield than mulched ridges with subgroove.The subgroove was useful to harvest rainwater in wet years,but it was contrary in drought years. (6).The treatments with subgroove increase SOC content and C/N,but the subgroove was not useful to increase available phosphorus of the topsoil.In conclusion,it was through considerably improving the temperature and moisture of surface soil for the method of double ridges and furrows with whole plastic mulch to increase the yield of crops and accordingly improve the economic output. Nevertheless,this method brought about negative effects on soil quality while it resulted in high yield alike.Only if the subgroove water harvesting method was combined with the method of plastic mulch on the ridges,crop yield can be increased significantly and simultaneously soil carbon contents in subgroove was superior to that of other treatments.