Rotational diversity shapes the bacterial and archaeal communities and confers positive plant-soil feedback in winter wheat rotations

Plant-soil feedbacks drive productivity in winter wheat (WW; Triticum aestivum L.) rotations. Although this is a frequent observation, the underlying plant-soil-microbe interactions remain unclear. We aimed to investigate the effects of WW rotational positions on soil bacterial and archaeal communities, as well as nitrogen (N) cycling, as potential drivers of WW yield decline in successively-grown WW. WW following oilseed rape (W1; Brassica napus L.) was compared with WW in self-succession (W2) in a rhizotron study using agricultural soil with a sandy loam texture. Samples were collected at tillering and grain ripening. At tillering, we found a higher NO3- content in W1 soil, especially in the 60-100 cm subsoil layer, associated with the N-rich residues of the preceding oilseed rape crop, while this trend was reversed at grain ripening. Analysis of enzyme kinetics revealed an increase in leucine aminopeptidase activity in W1 and an increase in beta-glucosidase activity in W2 at tillering, possibly related to the residue quality of the preceding crop. No differences in bacterial and archaeal alpha diversity were observed at both sampling times, but beta diversity showed a significant role of both rotational position and soil depth in shaping the microbial community. The gene copy numbers of amoA genes of ammonia-oxidizing bacteria (AOB), nifH and nirS were significantly higher in W2 compared to W1 at tillering, suggesting a strong effect of rotational position on N cycling of the following WW. The abundances of amoA (AOB) and nirS were also higher in W2 at grain ripening. Our results highlight the persistent soil legacy of the preceding crop on both nutrient cycling and bacterial and archaeal community composition, contributing to yield reduction in successively grown WW. Understanding plant-microbe interactions and keeping them at the center of productive WW rotations is, and will continue to be, critical to future agriculture.