Conservation strip-till modifies rhizosphere ammonia-oxidizing archaea and bacteria, increases nitrate accumulation and promotes maize growth at grain filling stage

Strip-till (ST) is a conservation tillage wherein the “inter-row” is not tilled and remains covered with protective residues, while the “row zone” is strip tilled. In comparison to conventional ridge tillage (CT), maize yield under ST is maintained due to its growth recovery at grain filling stage (GFS), though its growth lag at early growth stage in cold regions. To explore microbial mechanisms underlying the growth recovery, compared with CT, we investigated relationships among rhizosphere ammonia-oxidizing archaea and bacteria (AOA and AOB), rhizosphere soil characteristics, and maize growth under ST through a two-year field experiment in a Mollisol of Northeast China. Compared with CT, ST led to rhizosphere NO3--N accumulation at 0–5 cm location, which positively correlated with maize N accumulation and growth at GFS. ST significantly affected rhizosphere AOA and AOB communities at 0–5 and 20–30 cm locations, and decreased AOA abundance, norank_p_Thaumarchaeota relative abundance and bio-markers, but increased AOB abundance, richness, Nitrosospira relative abundance and bio-markers at 0–5 cm location. ST obviously increased the number of OTU hubs belonging to AOB Nitrosospira in networks and their complexity at 0–5 cm location. AOB community play a more important function role than AOA at 0–5 cm location. Rhizosphere NO3--N accumulation, maize N accumulation and growth recovery were closely related with AOB (especially Nitrosospira), but not AOA. It is concluded that, in contrast to CT, ST mainly stimulate rhizosphere AOB activity at 0–5 cm location (especially Nitrosospira) during grain filling stage, which contributes to more rhizosphere NO3--N accumulation and maize N absorption and faster growth. Our findings provide a theoretical basis for efficient crop-soil management to increase maize productivity under conservation tillage system.