Little is known about the interactive effects between biochar application and phosphorus (P) fertilization on plant growth and P uptake. For this purpose, five wheat straw biochars (produced at 25°C, 300°C, 400°C, 500°C and 600°C for 4h) with equal P (36mgkg(-1)) amount, with and without additional P fertilization (100mgkg(-1)) were applied in a pot experiment to investigate the growth of Suaeda salsa and their uptake of P from biochar and P fertilization amended saline sodic soil. Soil P fractions, dry matter yield, and plant P concentrations were determined after harvesting 90days. Our results confirmed that relatively lower pyrolysis temperature (<400°C) biochar retained P availability and increased plant growth. The plant P concentration was significantly correlated with NaHCO3-Pi (P<0.05), and NaOH-Pi (P<0.1) during early incubation time (4days) for biochar amended soil. As revealed by statistical analysis, a significant (P<0.05) negative (antagonistic) interaction occurred between biochar and P fertilization on the biomass production and plant P concentration. For plant biomass, the effects size of biochar (B), P, and their interaction followed the order of B×P (0.819)>B (0.569)≈P (0.568) based on the partial Eta squared values whereas the order changed as P (0.782)>B (0.562)>B×P (0.515) for plant P concentration. When biochar and P fertilization applied together, phosphate precipitation/sorption reaction occurred in saline sodic soil which explained the decreased plant P availability and plant yield in saline sodic soil. The negative interaction effects between biochar and P fertilization indicated limited utility value of biochar application in saline sodic soil.
Keywords: Bioassay test; Biochar; Interaction effect; Phosphorus; Saline sodic soil.
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