Deep phosphorus application changed bacterial structure and functional genes, improved phosphorus availability but decreased organic carbon content in soil

Deep fertilisation is considered an effective strategy for optimising fertilisation because deep phosphorus application promotes root growth and enhances soil phosphorus availability. However, information on potential mechanisms for enhancing phosphorus availability and the response of soil bacterial communities and functional genes to deep phosphorus application remains limited. This study used metagenomics to comprehensively investigate how soil bacterial communities and phosphorus cycling genes changed at three different depths of phosphorus application (8, 16, and 24 cm) and how these changes influenced soil phosphorus fractions. The results showed that deep phosphorus application complicated bacterial and phosphorus cycling gene networks, increased the relative abundance of gcd and phoD genes within the 16-24 cm soil layer, and enhanced inorganic phosphorus dissolution and organic phosphorus mineralisation. Total, available, and microbial biomass phosphorus in fertilised soil layers increased by deepening phosphorus application. However, the abundance of carbon degradation-related genes and soil organic carbon content decreased. This study provides important theoretical information for the optimisation and improvement of deep phosphorus fertilisation.

深层施肥被认为是优化施肥方式的有效策略，因为深层施磷可促进根系生长并提升土壤磷素有效性。然而，目前关于深层施磷提升磷素有效性的潜在机制，以及土壤细菌群落和功能基因对深层施磷的响应的相关研究仍较为匮乏。本研究采用宏基因组学（metagenomics）技术，系统探究了在3种不同施磷深度（8、16、24 cm）下，土壤细菌群落与磷循环基因的变化特征，以及这些变化如何影响土壤磷组分。研究结果表明，深层施磷可复杂化细菌群落与磷循环基因的共调控网络，提升16~24 cm土层中gcd与phoD基因的相对丰度，并增强无机磷溶解与有机磷矿化作用。随施磷深度增加，施肥土层中的总磷、有效磷与微生物生物量磷含量均显著提升。但与此同时，与碳降解相关的功能基因丰度与土壤有机碳含量均有所下降。本研究可为深层施磷技术的优化与改良提供重要的理论参考依据。