Productivity,Water And Nitrogen Use Under Spring Wheat-forage Crop Rotation In The Longdong Loess Plateau

The traditional planting system in the Loess Plateau of Longdong is dominated by winter wheat.The yield of this system is unstable and resources are inefficiently used due to its simple structure and variable climate.The application of crop-forage rotation system could increase crop productivity and resources use efficiency compared with traditional cropping systems.However,its application in this area has not been fully studied.This study was carried out in 2014 and 2015 at the Qingyang Loess Plateau Experimental Station of Lanzhou University to investigate the effects of spring wheat-forage crops rotation on crop productivity,water and nitrogen use efficiency.The spring wheat was firstly introduced to the Longdong Loess Plateau,through evaluated its performance.The rotation of spring wheat and eight kinds of annual forage crops were set up.The responses of the crop productivity,forage nutritive quality,water and nitrogen use efficiency of those rotation systems were determined.The main results are as follows:1.Through two years of field experiment,spring wheat in Longdong dryland area can finish the whole growth stages,the local temperature conditions can meet the heat requirement of the growth and development of spring wheat.With the extension of the growth period,the growth rate was faster in the vegetative period,reached 8.66 g·m-2·d,and slowed down during the reproductive growth period,reached 1.52 g·m-2·d.The soil moisture at the early winter period had a positive effect on the early vegetative growth of spring wheat.The yield of grain could be harvested 1.52 t·hm-2 and 1.78 t·hm-2 in 2014 and 2015 years,respectively,and the harvest index were 0.27 and 0.29.2.In the rotation systems of spring wheat-annual forage,the plant height and aboveground biomass of the eight different annual forage grasses increased with the progress of their growth,while the leaf area index was increased and then reduced.The leaf area index and aboveground biomass of sudangrass was the maximum among the forage crops,and the yield of sudangrass was reached 6.4 t·hm-2 at the flowering stage,indicating that sudangrass is suitable for autumn planting to alleviate the winter and spring forage shortage.3.With the progress of forage,the crude protein content of pea reached 29.05%,and was the maximum in eight kinds of annual forage grasses.The NDF and ADF of millet reached 62.28 and 50.54,respectively,and were the maximum.The DDM,DMI,TDN,RFV and RFVY of sudangrass were greater than the other forage crops.4.Compared with the summer fallow and spring wheat continuous cropping,the yield,water use efficiency and nitrogen uptake efficiency of the spring wheat and annual crop rotation system were promoted.In terms of total system yield,the total dry matter yield and crude protein content production,dry matter water use efficiency and crude protein crude water use efficiency of the spring wheat-sudangrass rotation were the greatest among the nine different rotation,and also greater than that of recreational and spring wheat(P <0.05).In summary,the performance of spring wheat was evaluated on the loess plateau system of Longdong Loess Platea.The productivity,quality and utilization efficiency of nitrogen and water resources of spring wheat and annual forage rotation systems were studied and identified the optimal cropping system.Results of this study could be used as a guide in the improvement of cropping systems on the Longdong Loess Plateau.