Biochar improves phosphorus use efficiency of organic-inorganic fertilizers, maize-wheat productivity and soil quality in a low fertility alkaline soil

Abstract Low and declining soil organic matter contents pose a significant threat to soil fertility, crop productivity and economic returns in arid and semi-arid agroecosystems. Holistic approaches are required to build and sustain soil organic matter in such soils to enhance nutrient use efficiencies and meet food security. Biochar is emerging as an attractive option for multiple benefits to soil-plant systems and carbon sequestration, especially in low fertility soils. We conducted a two-year maize-wheat rotation field experiments during 2015 and 2016 to test the effects of biochar on crop productivity, soil properties and phosphorous use efficiency (PUE) when applied with organic P sources as either farmyard manure (FYM) or poultry manure (PM) and diammonium phosphate (DAP) chemical fertilizer. Biochar was applied at two rates (0 and 10 t ha −1 ) whereas percentage of organic-inorganic P sources were 0, 25, 50 and 100% respectively. Biochar and manures were incorporated only once at the start of the field experiments whereas chemical fertilizers were applied during each crop cycle. Analysis of the two-year data revealed that biochar and P sources significantly and positively changed crop and soil quality attributes. Application of biochar significantly increased biological and grain yields of maize and wheat, soil organic carbon (SOC), and available nitrogen (N) and P contents without any negative effects on soil pH and electrical conductivity (EC). Addition of 50% P each from organic (FYM or PM) and chemical fertilizer increased biological and grain yields of maize, however, wheat biological and grain yields were higher with 100% PM or FYM in the presence of biochar. SOC and P contents were the highest when biochar was integrated with 100% P from FYM under maize crop. Biochar enhanced PUE from organic P sources more than the chemical fertilizer for both crops. Grain and biological yields of both crops correlated positively with SOC, soil N and soil P contents. We also found strong correlations between SOC, PUE and harvest index (HI) suggesting the benefits of increasing SOC contents under biochar-related integrated nutrient management practices. Overall results from these field experiments indicate potential of biochar to enhance plant nutrition, crop productivity and soil quality in nutrient poor alkaline calcareous soil under maize-wheat cropping system. Long-term farmers’ participatory field experiments, however, are required to extrapolate the potential of biochar integrations into current cereal-based cropping systems of Pakistan.