Contribution of Biogas Slurry-Derived Colloids to Plant P Uptake and Phosphatase Activities: Spatiotemporal Response

Abstract

The bioavailability for varied-size phosphorus (P)-binding colloids (P coll ) especially from external P sources in soil terrestrial ecosystems remains unclear. This study evaluated the differential contribution of varioussized biogas slurry (BS)-derived colloids to plant available P uptake in the rhizosphere and the corresponding patterns of phosphatase response. Keeping the same content of total P input (15 mg kg −1 ), we applied different sizefractioned BS-derived colloids including nanosized colloids (NCs, 1−20 nm), fine-sized colloids (FCs, 20−220 nm), and medium-sized colloids (MCs, 220− 450 nm) respectively to conduct a 45-day rice (Oryza sativa L.) rhizotron experiment. During the whole cultivation period, the dynamics of chemical characteristics and P fractions in each experimental rhizosphere soil solution were analyzed. The spatial and temporal dynamics examination of Ptransforming enzymes (acid phosphatases) in the rice rhizosphere was visualized by a soil zymography technique after 5, 25, and 45 days of rice transplantation. The results indicated that the acid phosphatase activities and its hot spot areas were significantly 1) correlated with the relative bioavailability of colloidal P (RBA coll ), 2) increased with the colloid-free (truly dissolved P) and BS-derived NC addition, and 3) affected by the plant growth stage. With the nanosized BS colloid addition, the RBA coll and plant biomass were respectively found to be the highest (64% and 1.22 g plant −1 ), in which the acid phosphatase-catalyzed hydrolysis of organic P coll played an important role. All of the above suggested that nanosized BS-derived colloids are an effective alternative to conventional phosphorus fertilizer for promoting plant P uptake and P bioavailability.

Microbially Induced Soil Colloidal Phosphorus Mobilization Under Anoxic Conditions

“…The P coll is recognized as a particularly mobile form of P, , contributing significantly to P loss from agricultural systems , and eutrophication of freshwater bodies. , It constitutes a substantial portion of total P in agricultural systems (13%–95%) , and streams (up to 30%). , Soil P coll mobility is influenced by various physical, chemical, and biological factors, , with pH, organic carbon (OC), and elements such as Fe, aluminum (Al), Mn, and calcium (Ca) being significant. , Despite its known importance, P coll behavior under reducing (anoxic) conditions is under-researched. A prior study on grassland soils revealed the anoxia-induced release of colloid- and nanoparticle-bound P < 450 nm, influenced by Fe .…”