Integration of biochar with animal manure and nitrogen for improving maize yields and soil properties in calcareous semi-arid agroecosystems

•There is a lack of data on biochar amendment of agronomic calcareous soils.•NPK and FYM was applied with or without biochar to alkaline soils in Pakistan.•Biochar amended plots had increased maize yields and retained P and N in the soil.•Biochar amended soil higher concentrations of P and N.•FYM, N and biochar could be integrated into a nutrient management regime for calcareous soils.

Declining soil quality is commonplace throughout Southern Asia and sustainable strategies are required to reverse this trend to ensure food security for future generations. One potential solution to halt this decline is the implementation of integrated nutrient management whereby inorganic fertilisers are added together with organic wastes. These organic materials, however, are often quickly broken down in soil and provide only a transitory improvement in soil quality. Biochar, which can potentially persist in soil for centuries, may offer a more permanent solution to this problem. To address this, we undertook a 2-year field trial to investigate the interactions between conventional NPK fertilisers, farmyard manure (FYM) and biochar in a maize cropping system. Biochar application to the nutrient poor soil increased maize yields after year one by approximately 20% although the yield increase was lower in the second year (ca. 12.5%). Overall, there was little difference in grain yield between the 25 t ha−1 and the 50 t ha−1 biochar treatments. In terms of soil quality, biochar addition increased levels of soil organic carbon, inorganic N, P and base cations and had no detrimental impact on pH and salinity in this calcareous soil. Overall, this field trial demonstrated the potential of biochar to induce short-term benefits in crop yield and soil quality in maize cropping systems although the long-term benefits remain to be quantified. From a management perspective, we also highlight potential conflicts in biochar availability and use, which may limit its adoption by small scale farming systems typical of Southern Asia.