Effects of growth stage and soil type on the secretion of biological nitrification inhibitors from sorghum

Abstract

Sorghum can secrete biological nitrification inhibitors (BNIs), whereas maize lacks this capability. In this study, we selected two different types of soil, sandy soil dominated by ammonia-oxidizing archaea (AOA) and silty soil dominated by ammonia-oxidizing bacteria (AOB), to investigate the effects of sorghum cultivation on soil nitrification microbial abundance and community composition at different growth stages (seedling, jointing, and flowering stages). The results indicated that, compared with maize cultivation, sorghum cultivation significantly reduced the soil nitrification rate. This effect was particularly pronounced during the jointing and flowering stages in sandy, AOA-dominated soil. In silty, AOB-dominated soil, both the nitrification rate and potential nitrification decreased only during the jointing stage. During the flowering stage, sorghum cultivation reduced the abundance of the AOA amoA gene in silty, AOB-dominated soil, whereas in sandy, AOA-dominated soil, sorghum cultivation suppressed the AOB amoA gene abundance, reducing it by 38 % and 29 % during the jointing stage and the flowering stage, respectively. Sorghum cultivation significantly altered the AOB community structure but did not affect AOA. During the flowering stage, sorghum cultivation significantly decreased both the richness and diversity of the AOB community in sandy, AOA-dominated soil, particularly reducing the relative abundance of Nitrosospira Cluster 2a.1 compared with that under maize cultivation. In silty, AOB-dominated soil, sorghum cultivation significantly reduced only the relative abundance of Nitrosospira Cluster 1. Overall, the secretion of BNIs was greatest in the jointing stage, which potentially regulated the nitrification rate by inducing niche differentiation between AOB and AOA. The AOB community exhibited greater sensitivity to the secretion of BNIs than did the AOA community, particularly in sandy, AOA-dominated soil. These findings provide critical evidence for the functional utilization of the BNIs in sorghum.