Impact Of Straw Return On Diseases,Pests And Weeds Of Main Grain Crops In China:A Meta-Analysis

Straw returning has become a widely used agricultural management practice in China’s farmland today and has a significant effect on crop yield.However,the effects of straw returning on diseases,pests and weeds under different environmental conditions and agricultural management practices across the country are unclear and controversial.In this study,using an meta analysis approach,we collected data from the published literature until December 2021 to quantify the total effect of straw return on the occurrence of diseases,pests and weeds in rice,wheat and maize,the main grain crops in China,and further analyzed the effects of different environmental conditions(climatic conditions,soil texture,soil organic matter content(SOM),soil p H,initial C/N)and agronomic management measures(straw return pattern,straw type,crop type,land use type,amount of straw return)on the occurrence of diseases,pests and weeds,and the key modifiable factors were clarified using linear regression analysis.The main findings are as follows:1.straw return to the field significantly increased the incidence and disease index of main grain crop diseases in China by 9.5%and 12.2%respectively(P<0.05),mainly increasing virus diseases and soil-borne diseases.The disease was significantly reduced under subtropical monsoon climate,significantly aggravated under temperate monsoon climate,favored under paddy field,and significantly aggravated under dryland,especially under winter wheat→spring maize rotation,and lighter under slightly acidic soil than slightly alkaline soil.In addition,the conditions of SOM>15 g/kg,amount of straw>7000kg/hm~2 and initial C/N>15 all aggravated the disease of grain crops.Linear analysis found that the effect of straw return to the field on disease was significantly positively correlated with initial C/N(P<0.05),extreme significantly positively correlated with soil p H(P<0.01),extreme significantly negatively correlated with average annual rainfall(P<0.01),and significantly negatively correlated with organic matter content(P<0.05).2.The overall effect of straw return on the occurrence of insect pests of main grain crops in China was not significant.However,the soil type was loamy and p H>7.5 significantly increased the number of nematodes by 16.8%and 25.2%respectively(P<0.05);in addition,the straw returned to the field was rice straw significantly reduced the number of nematodes by 66.1%(P<0.05).3.straw returning to the field significantly reduced the number of weeds and weed quality of grass infestation of main grain crops in China by 45.8%and 65.8%respectively(P<0.05).In the subtropical monsoon climate and temperate monsoon climate returned to the field weed damage significantly reduced,in the temperate continental climate returned to the field weed damage weed number significantly increased,SOM15-25 g/kg returned to the field weed number significantly reduced,while the SOM<15 g/kg conditions returned to the field weed number significantly increased.The weed infestation was significantly reduced when the soil was alkaline and the texture was loamy.In paddy fields,the straw was returned to the field to significantly reduce the number of weeds and weed quality,and in drylands,the straw was returned to the field to significantly reduce the quality of weeds and weed diversity,and the best weed suppression effect was achieved when the crop was rice and the straw was wheat.The amount of straw returned to the field>4000 kg/hm~2 significantly reduced the weed damage,and both mulching/burial returned to the field significantly reduced the weed damage.Linear analysis revealed that rainfall,temperature and straw return were extreme significantly negatively correlated with the occurrence of grass damage(P<0.01).Considering the combination of diseases,pests and weeds,it is recommended that in regions of China with high average annual rainfall and average annual temperature,paddy fields with medium organic matter and neutral or slightly acidic soil conditions can reduce both diseases and weeds.Moisture,temperature,initial C/N,p H,return amount and SOM are the key control factors affecting the occurrence of pests,diseases and weeds,and the actual production can reduce the occurrence of diseases,pests and weeds by increasing the initial Nitrogen fertilizer dosage,adjusting soil acidity and alkalinity,and straw return amount.