Long-Term Land Use Affects Phosphorus Speciation and the Composition of Phosphorus Cycling Genes in Agricultural Soils

Abstract

Agriculturally-driven land transformation is increasing globally. Improving phosphorus (P) use efficiency to sustain optimum productivity in diverse ecosystems, based on knowledge of soil P dynamics, is also globally important in light of potential shortages of rock phosphate to manufacture P fertilizer. We investigated P chemical speciation and P cycling with solution 31P nuclear magnetic resonance, P K-edge X-ray absorption near-edge structure spectroscopy, phosphatase activity assays, and shotgun metagenomics in soil samples from long-term agricultural fields containing four different land-use types (native and tame grasslands, annual croplands, and roadside ditches). Across these land use types, native and tame grasslands showed high accumulation of organic P, principally orthophosphate monoesters, and high acid phosphomonoesterase activity but the lowest abundance of P cycling genes. The proportion of inositol hexaphosphates (IHP), especially the neo-IHP stereoisomer that likely originates from microbes rather than plants, was significantly increased in native grasslands than croplands. Annual croplands had the largest variances of soil P composition, and the highest potential capacity for P cycling processes based on the abundance of genes coding for P cycling processes. In contrast, roadside soils had the highest soil Olsen-P concentrations, lowest organic P, and highest tricalcium phosphate concentrations, which were likely facilitated by the neutral pH and high exchangeable Ca of these soils. Redundancy analysis demonstrated that IHP by NMR, potential phosphatase activity, Olsen-P, and pH were important P chemistry predictors of the P cycling bacterial community and functional gene composition. Combining chemical and metagenomics results provides important insights into soil P processes and dynamics in different land-use ecosystems.

Widespread detection of Candidatus Accumulibacter phosphatis, a polyphosphate‐accumulating organism, in sediments of the Columbia River estuary

“…comm. ; Liu et al, 2018). Extracted P in our samples constituted > 10% of total sediment P and, therefore, we estimate that SE was approximately 9%, or 2.73-3.27 mg kg −1 for the dawn sample and 4.7-5.7 mg kg −1 for the dusk sample.…”

“…; Liu et al, 2018). In part, this arises from the large sample sizes that are needed for detection of different P forms due to the relatively low sensitivity and high detection limits of the method; this can lead to the pooling of samples that limits resolution, particularly in space.…”

Options for Improved Phosphorus Cycling and Use in Agriculture at the Field and Regional Scales

“…The same trend was demonstrated in commercial fields, where phoD and phoC gene abundance and phosphatase activity in bulk soil were negatively correlated with labile P values (Fraser et al, 2017). Liu et al (2018) used metagenomic sequencing to demonstrate an increased genetic capacity for P cycling in the annual cropping systems, based on the presence of microbial genes responsible for phosphoesterase, phytase, phosphonate degradation, inorganic PO 4 − solubilizing, P transport, and Pho regulation, compared with grasslands and roadside ditches. Although the grassland sites had fewer microbial P cycling genes, there was increased acid phosphatase activity in these soils and higher concentrations of Po, as shown by 31 P NMR (Liu et al, 2018).…”

“…Liu et al (2018) used metagenomic sequencing to demonstrate an increased genetic capacity for P cycling in the annual cropping systems, based on the presence of microbial genes responsible for phosphoesterase, phytase, phosphonate degradation, inorganic PO 4 − solubilizing, P transport, and Pho regulation, compared with grasslands and roadside ditches. Although the grassland sites had fewer microbial P cycling genes, there was increased acid phosphatase activity in these soils and higher concentrations of Po, as shown by 31 P NMR (Liu et al, 2018). The positive correlation between substrate (orthophosphate monoesters) and enzyme may be due to root phosphatase activity rather than microbial activity, thus demonstrating the role of plant species in P dynamics and the potential importance of different mechanisms in contrasting management systems.…”

Soil phosphorus availability, dynamic and speciation in long-term high fertilized soils

“…Much of the development of Brazilian agriculture production is based on research on the dynamics and availability of P in tropical soils, since this nutrient is the most limiting for agricultural production in the tropics . Modification in soil management practices and land-use is expected to change soil P dynamics and alter soil physical, chemical and biological properties, and thus the chemical nature soil P species that governs their bioavailability (Abdala et al, 2018;Boitt et al, 2018;Liu et al, 2018).…”