Restriction of soil bacteria promoting high yield of super hybrid rice in the Huaihe Valley in central China by conventional ploughing intensity

Abstract

Fields used to grow ‘Super rice’ rice bred to meet the rising food demand in China are typically ploughed before seedling transplantation. However, conventional tillage, i.e. shallow ploughing (SP) to < 15 cm depth, limits further improvements in yield and fertiliser use efficiency in paddy soils of central China. Microorganisms drive soil nutrient transformation and can be manipulated by cultivation practices. However, little is known about the extent and biological mechanisms of the soil microbes responsible for the rice yield limitation. Our results showed that tillage was a primary factor affecting paddy soil microbial communities. Shallow ploughing affected the diversity and composition of soil bacteria communities, while deep ploughing resulted in closer, more competitive soil bacterial networks with 1.64-folder higher negative connection among bacterial taxa. Shallow ploughing resulted in 10.5 % lower relative abundance of Nitrospirae and higher abundances of denitrification pathway genes (nirS, nirK, and nosZ) of soil microbes, as well as greater nitrogen loss through N2O, leading to a lower rice yield. Our results indicated that the conventional tillage intensity has negative effects on the composition and network of soil bacteria, particularly affecting nitrification and limiting the achievement of high yield in rice paddies. This finding provides a theoretical basis underlying a microbiological mechanism that will be useful in proposing a novel tillage practice for high-yield rice cultivation in the Huaihe Valley in central China.