Meta analysis of straw returning technology to improve soil physicochemical properties and increase the yield of main cereal and oil crop

Straw returning is one of the most important modes in agricultural production, in order to improve the growth of crops, as well as the physical and chemical properties of soil. In this study, Meta analysis of straw returning was carried out to improve the soil physicochemical properties and yield of the main cereal and oil crop. A systematic investigation was also made to clarify the influences of different straw returning years on the comprehensive fertility of cultivated soil. The data was selected from the journals and papers that were published from 2000 to 2023. The research scope was limited in the application efficiency of straw-returning technology in the field of agricultural production. Four major crops were taken as corn, wheat, rice, and rape. The search area and field experiments were confined to China. The search terms included the amount of straw return, depth of straw return, ways of straw return, and their combination. This basic database was constructed after searching. The non-returning straw treatment was taken as the control group. A total of 152 literatures were retrieved and 676 data groups were selected for the different measures of straw returning, such as the amount, depth, and years of returning. According to the published literature data over the past 20 years, the Meta analysis was made to explore the effects of different straw returning measures (returning years, modes, and amount) on the soil's physical and chemical properties, comprehensive fertility index, and crop yield of major grain and oil crops (maize, wheat, rice, and rape) in China. Various indexes of soil nutrients were graded and then standardized, according to the grading standard of the Second National Soil Census. A systematic evaluation was then performed on the soil comprehensive fertility and technical measures for straw returning, from the perspective of crop productivity and soil fertility. The results showed that the years, amount, mode, and depth of returning straw dominated the high yield of main grain and oil crops. The best years of returning straw to corn, wheat, rice, and rape were larger than 10 years, where the yield increased by 15.4%-18.3%. The optimal amount of rice and rape was larger than 6 000-9 000 kg/hm², while the suitable amount of maize and wheat was larger than 9 000 kg/hm². Indirect tillage was the best mode of straw returning to the field. The three major grains (crops, corn, wheat, and rice) were mainly returned to the field with > 10-20 cm, while the rapeseed was suitable for the deep tillage with > 20-30 cm. It was recommended to use the straw returning technology with the years of straw returning > 10 a, the amount of straw returning > 9 000 kg/hm², indirect mode of straw returning and the depth of straw returning > 10-20 cm, in order to significantly increase the contents of soil organic matter, total nitrogen, available phosphorus and available potassium. At the same time, the straw-returning technology significantly reduced the soil bulk density. There was an outstanding increase in the soil comprehensive fertility index. More attention should be paid to the straw returning strategy during production and fertilizer. The finding can also provide the scientific basis and data support for the technical model of scientific straw returning to the field.