Meta-analysis for the impacts of straw return on the diseases of major grain crops in China

Straw returning has been one of the most important practices in agricultural management. At the same time, crop diseases, in this case, have been always concerned in China. It is a high demand to clarify the effect of straw returning on the prevalence of diseases of main grain crops. In this study, a meta-analysis was conducted to determine the overall impact of straw returning on the occurrence of the main grain crop diseases. The key factors were also evaluated in response to various environmental factors and agronomic interventions. The data was collected from the published studies before December, 2021. The effective data was selected from the works of literature including: 1) the experiments were conducted in the croplands of China, and 2) the same experiment needed to include the paired treatment and control group. The treatment group was the straw returning to the field, and the control group was no straw returning. The rest experimental conditions of the treatment and control group were strictly consistent, except for whether the straw returned to the field or not. 3) The collected articles contained the incidence rate or disease index data. 4) The crops and returned straw were set as the main food crops rice, wheat, and maize. A total of 369 data sets were obtained to classify, according to the environmental conditions and agricultural management measures. Specifically, the environmental conditions included the climate type, soil pH, and soil organic matter (SOM). Agricultural management measures included the land use type, crop type, straw type, straw returning amount, and initial C/N. The results showed that the straw returning to the field significantly increased the incidence rate and disease index of the main grain crops, indicating an increase of 9.5% and 12.2%, respectively (P<0.05). There was a most serious increase in the virus and soil-borne diseases. Different environmental conditions and agricultural management practices presented a significant impact on the occurrence of major grain crop diseases under straw returning. Among them, the diseases of returning farmland decreased significantly in the subtropical monsoon climate, whereas, there was an increase in the temperate monsoon climate. Returning rice straw to the paddy field was beneficial to the reduction of the diseases. The disease increased significantly in the dry land, especially the wheat-corn rotation. The disease in the slightly acidic soil was lower than that in the slightly alkaline soil. In addition, the occurrence of diseases significantly increased under the conditions of soil organic matter (SOM), the straw returning amount, and the initial C/N were greater than 15 g/kg, 7 000 kg/hm2, and 15, respectively. The linear analysis demonstrated that there was a strong negative correlation of the annual precipitation and organic matter content with the occurrence of straw-returning disease, whereas, the initial C/N and soil pH presented a substantial positive correlation. Therefore, straw returning to the paddy fields and acidic soil cultivation greatly contribute to the fewer diseases in China with the high annual average rainfall and warmth. At the same time, a better way is to raise the initial application rate of nitrogen fertilizer.