Optimizing Phosphorus Fertilizer Use in Wheat Production through Biochar Amendment: Mechanisms of Availability, Uptake and Yield Response

Abstract

Phosphorus (P) deficiency limits wheat productivity in alkaline soils due to rapid P fixation. This field study evaluated the effect of wheat straw biochar (2% w/w, ~40 t ha⁻¹) on soil P dynamics, P uptake and wheat growth in a slightly alkaline soil (pH 7.55) of subtropical China. Biochar significantly improved soil properties: total organic carbon (+31%), soil organic matter (+31%), water holding capacity (+12%) and total P (+15%). Vertical distribution analysis (0–60 cm) showed enhanced P retention in the root zone with reduced leaching potential. Biochar increased plant height (12%), spikelets per panicle (33%), grains per spike (25%), 1000-grain weight (15%) and grain yield (16%). Physiological parameters improved with SPAD chlorophyll (+29%) and relative water content (+17%). Straw and grain P concentrations increased by 17% and 21%, respectively, with 22% higher total P uptake. These benefits resulted from synergistic mechanisms: direct P addition, reduced fixation, enhanced solubility, improved water relations and microbial P mobilization. Biochar amendment at 40 t ha⁻¹ effectively enhances P availability and wheat productivity in alkaline soils, offering a sustainable strategy for reducing chemical fertilizer dependence while maintaining crop yields.