Contrasting maize responses to soil phosphorus and potassium availability driven by biochar under reduced irrigation

Background and aimsBiochar is increasingly recognized for its potential to enhance soil water retention and improve soil fertility in agricultural systems; however, few studies have evaluated the effects of biochar on nutrients from an integrated perspective. This study aims to investigate how biochar affects soil phosphorus (P) and potassium (K) availability and their effects on plant growth, especially under reduced irrigation conditions.MethodsMaize plants were grown in split-root pots with full (FI), deficit (DI) and alternate partial root-zone drying (PRD) irrigation under 2% (w/w) softwood (SWB) and wheat-straw biochar (WSB) for three successive growth cycles.ResultsWSB amendment decreased soil P availability and resulted in a decrease in plant P content. However, WSB amendment significantly enhanced soil K availability inducing higher plant K content under reduced irrigation, thereby enhancing the biomass and harvest index of maize plants irrespective of growth cycles, especially with PRD. WSB amendment significantly enhanced P use efficiency due to lower plant P content and higher biomass in the initial growth cycles. Adding SWB decreased plant growth under reduced irrigation by inhibiting plant K content in the second growth cycle, which was mitigated by PRD by enhancing root growth.ConclusionCollectively, despite negative effects on soil P availability and plant P content, WSB combined with PRD could be a promising strategy in sustainable maize production under drought stress.