Meta Analysis On Impact Of Tillage Practices On Yield And Water Use Efficiency Of Spring Maize And Winter Wheat On The Loess Plateau

Maize and wheat are the two most important grain crops in the Loess Plateau.For a long time,the yield of maize and wheat in the dryland of the Loess Plateau is relatively low and varies greatly over the years due to the shortage of water resources.Facing the growing population pressure and increasing demand for food,it is critical to ensure the food security and improve the ecological environment in the Loess Plateau region by seeking a more effective way to improve crop yield and water use efficiency.From the view of tillage measures?planting methods,soil tillage methods,covering methods and rational fertilization?,previous researchers have carried out a large number of experimental researches and achieved positive research results.However,there were many limitations such as the shortage of test sites,small test area,and short duration of single experiment in the previous studies.The results of these studies were not representative and instructive enough to realize balanced increase of maize and wheat yield in a large area.Whereas the accumulated research data provided the basis for systematically analyzing the potential yield increase of grain in the Loess Plateau.Based on the historical data of spring maize and winter wheat in the Loess Plateau in recent 50 years,the effects of different tillage measures?soil tillage methods,covering methods,nitrogen rate?on the yield and water use efficiency of spring maize and winter wheat in different areas of the Loess Plateau were analyzed by means of meat-analysis in this study.At the same time,this study analyzed the potential yield and water use efficiency increase of spring maize and winter wheat in different areas of the Loess Plateau.The results provided the scientific guidance for the construction of the reasonable tillage measures for spring maize and winter wheat in different areas of the Loess Plateau and realizing a balanced grain yield increase in the dryland of the Loess Plateau.The main results of this study are as follows:?1?Increase potential of yield and water use efficiency of spring maize and winter wheat in dryland of Loess Plateau.The results showed that the average yield and water use efficiency of spring maize and winter wheat in the dryland of the Loess Plateau showed a linear trend from 1954 to 2014 because of the use of fertilizers and the application of tillage measure of water collection by mulching?P<0.01?.The average yield and water use efficiency of winter wheat in the whole Loess Plateau from 1954 to 2014 can be divided into three stages: 1954¹962,1972¹993,2001²014,the average yield and water use efficiency of winter wheat in different stages are: 2211kg?hm^-2,3745kg?hm^-2 and 10.24 kg?hm^-2?mm^-1,4357 kg?hm^-2 and 12.19 kg?hm^-2?mm^-1.The average yield and water use efficiency of spring maize in the whole Loess Plateau from 1985 to 2014 can be divided into three stages: 1985 to 2000,2001 to 2010,2011 to 2014,the average yield and water use efficiency of spring maize in different stages are: 6631 kg?hm^-2 and 15.44 kg?hm^-2?mm^-1,7949 kg?hm^-2 and 22.09kg?hm^-2?mm^-1,10485 kg?hm^-2 and 26.97 kg?hm^-2?mm^-1.Under the existing tillage conditions,the yield and water use efficiency of spring maize and winter wheat in the Loess Plateau still have great potential for growth.Compared with the experimental high yield,the increase potential of average yield and water use efficiency of spring maize were 5758 kg?hm^-2 and 17.4 kg?hm^-2?mm^-1 respectively in the whole Loess Plateau,the increase potential of yield and water use efficiency of spring maize were 3472⁵896 kg?hm^-2 and 8.7²0.1 kg?hm^-2?mm^-1 respectively in different areas of the Loess Plateau.The increase potential of the yield and water use efficiency of spring maize in different areas of the Loess Plateau were: middle > east > west > north > south.The increase potential of average yield and water use efficiency of winter wheat were 2683 kg?hm^-2 and 7.5 kg?hm^-2?mm^-1 respectively in the whole Loess Plateau,the increase potential of yield and water use efficiency of winter wheat were 2522²866 kg?hm^-2 and 6.9⁷.9 kg?hm^-2?mm^-1 respectively in different areas of the Loess Plateau.The increase potential of yield and water use efficiency of winter wheat in the northwest area was higher than that in the southeast area.?2?Effects of no-tillage and subsoiling tillage on yield and water use efficiency of spring maize and winter wheat in dryland of Loess Plateau.In different areas of Loess plateau,the adaptability of no-tillage and subsoiling tillage were different.Compared with those under conventional tillage,the yield and water use efficiency of spring maize under no-tillage conditions increased by more than 10% in north and middle of Loess Plateau.The yield and water use efficiency of winter wheat under subsoiling tillage conditions significantly increased in southeast and northwest of Loess Plateau,and it was better than no-tillage.Compared with those under conventional tillage,no-tillage can improve the yield and water use efficiency of spring maize in the different annual precipitation areas of the Loess Plateau,and the increase rate of yield and water use efficiency of spring maize in area with annual precipitation ? 500 mm was significantly higher than that in area with annual precipitation ?500mm.In the areas with different annual precipitation of the Loess Plateau,the yield and water use efficiency of winter wheat under subsoiling conditions increased significantly,and the increase rate was higher than that under no-tillage conditions.Compared with those under conventional tillage,the yield and water use efficiency of spring maize significantly increased under no-tillage conditions in area with annual average temperature?10?.In the areas with different annual average temperature of the Loess Plateau,the yield and water use efficiency of winter wheat under subsoiling conditions increased significantly,and the increase rate was higher than that under no-tillage conditions.?3?Effects of different mulching methods on yield and water use efficiency of spring maize and winter wheat in dryland of Loess Plateau.The effects of different mulching methods on the yield and water use efficiency of spring maize and winter wheat in Loess Plateau were different,and the effect of plastic film mulching was better than that of straw mulching.For spring maize,the effect of flat film mulching in autumn on the yield and water use efficiency of spring maize in the Loess Plateau was the best.For winter wheat,the effect of flat film mulching in a whole year on the yield and water use efficiency of winter wheat in the Loess Plateau was the best.The best mulching methods of spring maize in different areas of the Loess Plateau were different.In middle area of the Loess Plateau,the effect of ridge-furrow film mulching in autumn on spring maize yield and water efficiency was the best;in west and south areas of the Loess Plateau,the effect of ridge-furrow film mulching in sowing was the best;in east and north areas of the Loess Plateau,the effect of flat film mulching in sowing was the best.The best mulching methods of winter wheat in different areas of the Loess Plateau were different.In southeast area of the Loess Plateau,the effect of ridge film mulching on yield and water efficiency of winter wheat was the best;in northwest area of the Loess Plateau,the effect of flat film mulching in a whole year was the best.?4?Effects of different nitrogen rates on yield and water use efficiency of spring maize and winter wheat in dryland of Loess Plateau.Under no mulching conditions,the suitable nitrogen application rate of winter wheat in dryland of Loess Plateau was 169.4¹91.1 kg?hm^-2,and the average yield and water use efficiency of winter wheat were 4100 kg?hm^-2 and 12.05 kg?hm^-2?mm^-1 respectively under suitable nitrogen application rate.Under no mulching conditions,the suitable nitrogen application rate of spring maize in dryland of Loess Plateau was 255³00 kg?hm^-2,and the average yield and water use efficiency of spring maize were 7928.7 kg?hm^-2 and 19.42 kg?hm^-2?mm^-1 respectively under suitable nitrogen application rate.Under plastic film mulching,the suitable nitrogen application rate of spring maize in dryland of Loess Plateau was 228²33 kg?hm^-2,and the average yield and water use efficiency of spring maize were 10718.9 kg?hm^-2 and 30.06 kg?hm^-2?mm^-1 respectively under suitable nitrogen application rate.?5?The suitable tillage measures of spring maize and winter wheat in different areas of Loess Plateau.In middle area of the Loess Plateau,the suitable tillage measures for spring maize were no-tillage combined with ridge-furrow film mulching in autumn,and with 228²33 kg?hm^-2 nitrogen application rate.In east and north areas of the Loess Plateau,the suitable tillage measures for spring maize were no-tillage combined with flat film mulching in sowing,and with 228²33 kg?hm^-2 nitrogen application rate.In west and south areas of the Loess Plateau,the suitable tillage measures for spring maize were ridge-furrow film mulching in sowing combined with 228²33 kg?hm^-2 nitrogen application rate.In southeast area of the Loess Plateau,the suitable tillage measures for winter wheat were subsoiling tillage combined with 169.4¹91.1 kg?hm^-2 nitrogen application rate.In northwest area of the Loess Plateau,the suitable tillage measures for winter wheat were subsoiling tillage combined with flat film mulching in a whole year,and with 169.4¹91.1 kg?hm^-2 nitrogen application rate.