Effect Of Tartary Buckwheat And Mung Bean Crop Rotation And Fertilizer Application To Alleviate Its Continuous Cropping Obstacles

Tartary buckwheat and mung bean as a functional food with rich nutritional value and a source of organic fertilizer,in China’s northern traditional dryland crop layout occupies an important position,but due to the current reduction in agricultural land and the heavy application of chemical fertilizers,as well as the lack of attention to the planting patterns of small grain crops,resulting in the two appear in the same soil planted one after another and lead to abnormal growth and development of the adverse phenomenon,namely,continuous cropping obstacles.Therefore,it is important to explore reasonable agricultural measures to alleviate the obstacles of tartary buckwheat and mung bean continuous cropping and achieve green and sustainable production of small grain crops.This experiment was conducted in 2020 with tartary buckwheat "Xinong 9940" and mung bean "Xilü No.1" as the test species,selected in the positioning trials established in Yan’an,Shaanxi Province in 2021 and 2022,using a split-zone design,the main zone for three types of planting: Tartary buckwheat continuous crop(CB),mung bean continuous crop(CG)and mung bean-tartary buckwheat(RG-RB)rotation,cleaved area for four fertilizer treatments:no fertilizer(CK),chemical fertilizer alone(NP),organic fertilizer alone(OF),chemical fertilizer reduction 30% organic fertilizer replacement(NPO).From continuous cropping obstacles in tartary buckwheat and mung bean,comparing different cropping patterns and fertilizer application,tartary buckwheat and mung bean farmland soil quality,crop growth and development and photosynthetic characteristics,yield and nitrogen use efficiency changes and differences.The study of buckwheat-bean rotation system and fertilizer application on continuous cropping obstacles in tartary buckwheat and mung bean to mitigate effect,the main conclusions are as follows:(1)In the continuous crop mode,the application of organic fertilizer significantly reduced the tartary buckwheat soil solid phase volume and >0.25 mm aggregates content,increased the mung bean 1 to 2 mm soil aggregates content,increased the tartary buckwheat and mung bean soil gas phase volume,liquid phase volume,relative humidity,field water holding capacity and microaggregates content;compared to the continuous crop mode,the buckwheatbean rotation system effectively increased the tartary buckwheat soil microaggregates content and Mung bean soil solid phase volume,relative humidity,gas phase volume,field water holding capacity,liquid phase volume.Therefore,buckwheat-bean rotation and fertilizer application can effectively improve the compactness and porosity of the soil,improve soil permeability and water content,improve the physical environment of the soil for crop root growth and development,and alleviate continuous cropping obstacles.(2)In the continuous crop mode,with organic fertilizer significantly increased tartary buckwheat and mung bean soil available nitrogen,available phosphorus and organic carbon content,improved soil enzyme activity;compared to the continuous crop mode,buckwheatbean rotation system effectively increased tartary buckwheat and mung bean soil available nitrogen and organic carbon content,increased soil p H,mitigated the acid-base reaction in the soil.The soil urease,alkaline phosphatase,invertase,cellulase enzyme and polyphenol oxidase activities of the buckwheat-bean rotation system increased by 2.80% to 62.69%,12.08%to 23.48%,134.79% to 230.35%,6.74% to 10.44%,26.14% to 35.73% and 5.00% to 7.60%,respectively,compared with continuous tartary buckwheat and continuous mung bean crops,14.69% to 26.27%,89.74% to 144.78%,71.95% to 81.92% and 7.54% to 25.08%,which improved the soil microhabitat environment and enhanced the decomposition and transformation of nutrients in the soil,thus improving soil fertility and alleviating continuous cropping obstacles.(3)Buckwheat-bean crop rotation system and organic fertilizer application effectively increased tartary buckwheat and mung bean plant height,stem thickness,leaf area index and canopy layer photosynthetically active radiation interception rate,effectively improving the continuous crops brought about by plant dwarfism and low photosynthetically active radiation interception rate;improve the relative chlorophyll content of leaves and chlorophyll fluorescence parameters,to avoid damage to the potential active center of PSII,promote photosynthetic primary reaction and photosynthetic electron transfer process,thereby improving the photosynthetic parameters of tartary buckwheat and mung bean leaves and promoting the accumulation of biomass in all organs.Among them,the relative chlorophyll content,net photosynthetic rate and transpiration rate of tartary buckwheat and mung bean leaves increased by 8.75% to 34.18%,9.67% to 91.00%,32.54% to 157.46% and 1.06% to32.71%,6.90% to 65.45%,41.29% to 72.14%,respectively,compared with continuous crop under the polygonum bean rotation system.(4)Tartary buckwheat and mung bean yields and above-ground organ nitrogen content,NRE,NFP,and NHI were correlated to varying degrees.In the continuous crop model,organic fertilizer application significantly increased the nitrogen content of above-ground organs of tartary buckwheat and mung bean,nitrogen use effective,yield and its components;compared to the continuous crop model,buckwheat-bean rotation system of tartary buckwheat and mung bean above-ground organs of nitrogen content,NRE,NFP,NHI,NPE and yield and its components have increased to varying degrees.Among them,tartary buckwheat’s 100-grain weight,grain weight of single plant,yield and mung bean’s grain number of single pod,pods number of single plant,100-grain weight,yield increased by 0.74% to 29.38%,28.39% to79.58%,57.23% to 113.13% and 2.70% to 15.63%,1.22% to 65.63%,1.22% to 11.22%,4.65%to 31.94%,respectively,compared with the continuous crop model.In summary,buckwheat-bean rotation system and fertilizer application can effectively improve the continuous crop of tartary buckwheat and mung bean growth and development,photosynthetic characteristics,and farmland soil physicochemical properties of the adverse effects,improve the nitrogen content of the above-ground organs of both,nitrogen fertilizer utilization and yield,effective mitigation of continuous cropping obstacles,which in the continuous crop pattern,the best effect of organic fertilizer alone.