Effect of straw pulverization and concentrated deep-buried into field on growth and yield of maize

Abstract: In recent years, the environmental pollution caused by straw burning is becoming more and more serious. Therefore, straw utilization is concerned by all walks of life. From the present situation of the 70%-90% of straw returning in developed countries, the most effective way to use straw is to return the soil. The amount of straw returning in China is low. At present, the model of straw returning to the field is mainly divided into three major categories, including covering the field, the return of straw to the plough layer, and returning straw into the field through deep ploughing. Covering soil with straw has the effect of maintaining soil moisture, but it reduces the temperature of the ground and cause the delay of crop emergence. The return of straw to the plough layer can improve soil nutrients and change the physical structure of soil, but it can cause the soil to be fluffy and reduce water-retaining property. The straw is often accumulated in the plough layer, which leads to the poor quality of mechanical sowing and the low emergence rate. As the two returning approaches have some drawbacks, our group proposed the technology of returning straw to subsoil. This technique can avoid the problem of low ground temperature and postponing the sowing date in spring in the cold area and avoid the problem of low quality of mechanical sowing and low emergence rate. Meanwhile, it could improve the physical and chemical properties of soil. Dou Sen and other studies also show that straw depth can also effectively improve soil organic matter, promote the formation of aggregates, and change the overall environment of the soil to the direction that is beneficial to the growth of the crops. Although returning straw into the field through deep ploughing can also overcome the unfavorable factors of covering the field, the return of straw to the plough layer, the popularization of straw returning technology is still limited. The main reason is that the corresponding machinery has not been developed. In this paper, in order to solve the problem of mechanical and technical non matching and the low ratio of straw returning to the field, on the basis of the concept of returning straw into the field through deep ploughing, the technology of straw concentrated into a strip returning was developed. According to the idea of this technology, the supporting machinery of straw concentrated into a strip lateral returning, and supporting five plow tillage synchronizations, were designed and developed, which realized the corresponding field operation. A field comparative experiment was conducted with three treatments: normal tillage (control CK), the return of straw to the plough layer, two steps straw concentrated into a strip returning for three years. The results showed that straw concentrated into a strip returning did not reduce the seed emergence rate compared with CK. The seedling rate of the return of straw to the plough layer was reduced by 3.3%-3.5%, and the difference was significant (P< 0.05). Compared with CK and straw concentrated into a strip returning, the corn height of the return of straw to the plough layer at seedling stage decreased by 3.1-4.5 cm, stem diameter decreased by 2.3-2.5 mm, dry matter quality decreased by 15.8% - 17.2%, plant height decreased by 13.3 - 17.9 cm at maturity, stem diameter decreased 3.1 - 4.0 mm, dry matter quality decreased 8.0%-10.8%, total root length and total root length decreased, and there was no difference (P > 0.05) between CK and straw concentrated into a strip returning. Compared with CK, the three year yield of straw concentrated into a strip returning increased by -0.64% - 2.45%, and the yield increased with the number of years of returning to the field. The yield of the return of straw to the plough layer for three years was significantly (P < 0.05) reduced, the yield reduction was 3.95%-8.84%, and the difference was significant (P < 0.05). The two steps straw concentrated into a strip returning can overcome the problems of the return of straw to the plough layer and not reduce the yield, which can make the straw return to the soil effectively.