Regulating Effects Of Different Conservation Tillage On Wheat-Maize Production In The Dryland Region Of Western Henan Province

In the semi-arid region of North China,the production of crop is decreasing due to water deficiency,for lack of irrigation and rainfall.And excessive plowing is another reason for crop failure.In order to improve water use efficiency,which is crucial to crop yields in rain-fed areas,it's necessary to balance the dislocation between precipitation and wate the crop needed,and to develop the conservation tillage techniques.It is believed that conservation tillage has the capacity to change soil physical and chemical properties,as well as ecological environment of crops.However,these studies were mainly focused on high-yield farming areas ruther than low-yielding fields,or in a crop rotation system.In this study,three kinds of conservation tillage patterns were applied in the dryland of agricultural areas in Western Henan since 2004(Luoyang),namely summer Free Autumn Free(NTSM),Xia Songqiu Free(SSM)and ridge for cover(RSM),with conventional tillage(CT)ascontrolled.The effects of different conservation tillage on soil properties,water use of wheat and maize,root growth,photosynthetic characteristics and grain yield were investigated in the four consecutive years from 2008 to 2012.The main results are as follows:1.The long-term experiment results showed that SSM and RSM in 2012 had increased soil organic matter(OM),total nitrogen(TN),total phosphorus(TP)and total potassium(TK)contents at different levels,compared with those in 2004.However,CT and NTSM did not have obvious impact on these contents of nutrient.Three conservation tillage patterns,especially for SSM and RSM,significantly increase contents of soil available phosphorus(AP)and potassium(AK).The content of AP and AK under SSM treatment increased by 95.8%,54.0%,while under RSM those nutrients were improved by 94.7%and 40.0%,respectively,compared with CT treatment.2.Soil microbial quantity and enzyme activity decreased with the increase of soil depth.The number of microorganisms in soil layer of 0-20cm was significantly larger than that of 20-60cm.With the development of wheat growth,the number of bacteria,fungi and actinomycetes increased significantly in three conservation tillage treatments,and the enzyme activities of urease and protease also improved with wheat growth.The order of soil enzyme activities and soil microbial quantity in different treatments was showed as follows:RSM>SSM>NTSM>CT.Soil microbe quantity and enzyme activity of RSM patterns increased significantly,especially at late growth period of wheat development,compared with CT.The increased soil microbial activity and number may accelerate crop decomposition and corruption processes,resulting in accelerated transformation of carbon and nitrogen cycles,thus to increase the accumulation of soil organic matter and soil fertility.3.NTSM,SSM and RSM improved the photosynthetic performance of wheat leaves,especially the RSM treatment.When compared with CT,the values of SPAD and canopy PAR under RSM treatment were significantly increased in the late growth of wheat development.Besides this,the net photosynthetic rate(Pn),stomatal conductance(Gs),transpiration rate(Tr)and intercellular CO2 concentration(Ci)of wheat and maize were significantly higher than those under the CT treatment.4.Conservation tillage had significant regulating effects on the growth of wheat root.Root parameters(total root length,total root surface area,root diameter and root total volume)were significantly increased under the conservation tillage treatments,especially under RSM treatment.For root distribution,the total root length,total root surface area,root diameter and root total volume in 0-60 cm soil layer increased with the development of wheat plant.However,these parameters of wheat roots decreased with the increase of soil depth under all treatments.RSM treatment significantly increased root distribution in deep soil layer,relatively to CT treatment.5.Water use efficiency(WUE)of wheat was correlated to annual rainfall and the rainfall in wheat growth period.While for maize,WUE was closely correlated to the seasonal distribution of precipitation.Three conservation tillage significantly improved WUEs of wheat,maize and the annual production.Compared with CT,WUE was improved by 9.0-25.3%,9.8-26.6%and 12.2-17.8%,respectively under the NTSM,SSM and RSM treatments.Effect of conservation tillage on WUE showed in the order:RSM>SSM>NTSM>CT.In addition,all three conservation tillage significantly improved the yield of wheat and maize and annual production.They were increased by 7.9-12.0%,13.4-24.6%and 12.3-16.9%,respectively compared with CT.The improvement of yield under the RSM and SSM treatments was much greater.6.The DSSAT model was used to simulate the annum production of wheat(Luohai 5)and maize(Luoyu 5)under different tillage treatment in the semiarid area of Western Henan Province.The result showed that differences between the value of simulated and trueduring the crop growth were only 1-2 d for wheat and 2-3d for maize,respectively.And the NRMSE between simulated and true of wheat and maize yield were 2.7%and 5.1%,respectively.This result indicated that the growth,yield of wheat and maize and soil water content in the semi-arid area of Western Henan Province could be simulated by the DSSAT model established.