Effects of tillage practices and microbial agent applications on dry matter accumulation, yield and the soil microbial index of winter wheat in North China

Using microbial agents combined with chemical fertilizers is a promising approach to maintain the soil microbiota balance in continuous wheat-crop rotation fields. Most previous studies focused on microbial agents applied in the topsoil, with limited studies investigating the effects microbial agents under different tillage practices on soil quality and crops growth. In this study, a field experiment was conducted using a two-factor randomized block design (tillage practices and fertilizer applications) with three replicates, the effects of conventional rotary tillage and deep plowing when applying two different types of microbial agents (ETS and JS) on the dry matter accumulation, yield, soil microbial index and soil respiration of winter wheat (Triticum aestivum L.) in north China. The results indicated that wheat grain yield was not decreased after the application of different microbial agents plus 70% of the normal amount of chemical fertilizer and that the straw yield was decreased by 19.1% and 16.4% when ETS and JS, respectively, were individually applied. Additionally, there were no differences in grain and straw yields between the different tillage practices. The aboveground dry matter accumulation increased by 47.5% with ETS application under conventional rotary tillage compared with applications of chemical fertilizer. Under conventional rotary tillage, applications of different microbial agents decreased the microbial biomass C (MBC) concentration by 35.2-42.3% compared with applications of chemical fertilizer, while, the microbial biomass N (MBN) concentration increased by 10.0-18.5% in the 0-20-cm soil layer. With deep plowing, the soil respiration rate was greater than under conventional rotary tillage. In addition, the soil respiration rate after the application of the ETS plus JS combination with deep plowing was greater than after the microbial agents were individually applied during wheat's growth period.