Periphyton‐induced changes in the phosphorus sorption characteristics of a paddy soil from coastal mudflat reclamation

AbstractSoil phosphorus (P) sorption characteristics critically influence P availability to plants; however, the influence of periphyton on P sorption remains unclear. In this study, the P adsorption and desorption characteristics of soil in a reclaimed paddy field were evaluated after periphyton colonization of different substrates, that is, periphyton only (PO), periphyton with straw addition (PS), and periphyton with biochar addition (PB). The results indicate that the addition of straw to paddy soil increased the periphyton biomass, whereas the addition of biochar decreased the biomass. The P availability in the paddy soil significantly increased in all periphyton treatments. Specifically, the content of NaHCO3‐extractable P and readily available P in the paddy soil increased by 5‐, 6‐, and 7.5‐fold and 3‐, 1.5‐, and 7‐fold, respectively, in the PO, PS, and PB treatments. Compared with the control (no periphyton), the maximal P sorption capacity (qm) and equilibrium P concentration at zero sorption (EPC0) of the paddy soil were enhanced in the PO and PB treatments but reduced in the PS treatment. In contrast, the adsorption constant (KL) and maximum buffer capacity declined in the PO and PB treatments but increased in the PS treatment. In addition, the amount of P desorbed from the soil was higher in all periphyton treatments compared with the control. The P content in the periphyton differed among treatments and ranged from 0.6 to 1.6 mg g−1. These findings demonstrate that paddy periphyton has a great impact on the P sorption characteristics of the paddy topsoil. This study contributes not only to a deep comprehension of P cycling in paddy soil containing periphyton or similar aggregates but also to the regulation of soil P availability by periphyton.