Biochar‐based nutrient management as a futuristic scalable strategy for C‐sequestration in Semi‐arid Tropics

Abstract Climate and agriculture experts emphasize the need to develop a carbon sink in the soil to help alleviate the effects of climate change. A 2‐year field experiment in semiarid tropical drylands tested sustainable nutrient management approaches to sequester carbon in the soil. We analyzed nine different treatments, including chemical fertilizers (as blanket and soil test‐based [STB] recommendations), sole organic (biochar and compost), and their combinations (with 75% and 50% STB recommendation) as integrated applications (integrated nutrient management [INM]) in the maize–chickpea cropping sequence. We report that biochar treatments show higher (24%–30%) organic carbon stock in the top layer of soil than the respective compost treatments. Furthermore, the biochar‐based INM showed the maximum residual effect in chickpea ( Cicer arietinum L.) crops. The system equivalent yield showed the best results (8 Mg ha −1 ) for 50% need‐based fertilizer and 50% biochar. Although we observed that sole‐biochar sequestered the highest amount of soil organic carbon (0.69%) in the topsoil compared to the other treatments, it was not scalable due to the lower yield for maize crops. Similarly, composts showed more labile carbon concentrations as microbial biomass but lagged behind biochar treatments for organic carbon storage. The system performance expressed as net returns and benefits–cost ratio also showed better results for biochar‐based INM. The findings show that drylands facing widespread land degradation in terms of nutrient imbalances and low C levels will benefit from an integrated approach of need‐based fertilizer with biochar application. Therefore, this might be a long‐term sustainable strategy for C‐sequestration and food security for semiarid tropical drylands.