Land reclamation increased organic P fractions and phosphatase activities, and strengthened the co-occurrence networks of phoD community in calcareous soils

Abstract

Organic phosphorus (Po) is an important constituent of P pool. Soil phoD community is primarily involved Po transformation. However, influences of agriculturally-driven land-use change on different Po fractions, phosphatase activities and phoD community are largely unknown. Here, an investigation was carried out containing three treatments: vegetable field (VF), cropland (CF) and uncultivated land (UL). Various Po fractions were measured by Hedley’s sequential extraction and 31P-NMR methods. The activities of alkaline phosphomonoesterase (ALP), acid phosphomonoesterase (ACP), phosphodiesterase activity (PD) and phytase were assayed; the abundance, and diversity of phoD community and its co-occurrence networks were analyzed. Compared with the UL treatment, soil total organic P (total-Po) in the VF and CF treatments significantly increased by 75.9% and 53.0%, respectively, mainly attributed to the increases in NaHCO3-Po, NaOH-Po and C.HCl-Po. 31P-NMR spectra showed that, when land was reclaimed from uncultivated land into agriculture fields (i.e., VF and CF), myo-inositol hexaphosphate (myo-IHP), α-glycerophosphate (α-glyc) and β-glycerophosphate (β-glyc) were increased by 9.5, 3.9 and 2.0 times, respectively. The activities of ACP, ALP and PD in the VF and CF treatments were higher than in the UL treatment. The α-diversity of phoD community was also significantly increased by land reclamation. Moreover, the linkage between soil Po and Po-cycling-related biological parameters (ACP, ALP and PD and phoD community) was more pronounced by NaHCO3-Po and NaOH-Po than the Po fractions measured by 31P-NMR method. Topological parameters (edges, node degree, and betweenness centrality) of phoD community’s network in the VF and CF networks were higher than in the UL network, implying that land reclamation favored to construct a more cooperative network of phoD community. Collectively, our findings demonstrated that when uncultivated land was converted to cropland, soil Po was notably increased, and phoD community’s co-occurrence network was also strengthened. The outcomes of this study emphasize that when land was reclaimed from nature (uncultivated land) into agriculture fields, the fertilization strategy of organic combined with chemical fertilizers application was beneficial for improving P fertility and assembling organic P-cycling related community.