Subsoiling tillage with straw incorporation improves soil microbial community characteristics in the whole cultivated layers: A one-year study

Abstract The subsoiling tillage managements have been recommended to remediate subsoil compaction and maintain crop production. These practices can improve soil properties and fertility due to soil loosening and straw incorporation, and further affect soil microbial community characteristics. However, the response of soil microbial community structure to subsoiling tillage managements is still poorly understood. The objective of this study was to examine the effects of tillage practices (conventional tillage, CT; subsoiling tillage, ST; subsoiling tillage with straw incorporation, STS) on soil microbial community characteristics. Topsoil (0–20 cm) and subsoil (20–35 cm) samples were taken from a 360–day in−situ field experiment in northeast China. Microbial community characteristics were determined by the phospholipid fatty acid (PLFA) method. The contents of subsoil bacterial PLFAs and fungal PLFAs were lower in the ST treatment than those in the other treatments within 60–360 days, and gram−positive (G+) bacteria were more abundant in the subsoil of ST treatment than those in the subsoil of STS treatment. In contrast to the other treatments, the STS treatment had the larger total PLFAs content and the higher ratio of fungal to bacterial PLFAs (F/B) in the subsoil during the whole incubation period, and fungi played a dominant role in straw degradation of subsoil. Compared with the other treatments, the STS treatment had a lower cyclopropyl to precursors (cy/pre) ratio in the subsoil on the 30th day, suggesting that the STS treatment provided more K2SO4−extractable organic carbon (EOC) and some available nutrients (nitrogen, potassium and phosphorous) for soil microbes. The STS treatment relative to the other treatments increased the bacterial PLFAs and fungal PLFAs contents in the topsoil, which were associated with the increase in the EOC/SOC ratio. Accordingly, STS practice had a great potential for improving subsoil and topsoil microbial community characteristics.