Biochar Use in Tropical Farming Systems: A Unique Window to Sustainable Intensification of Crop Productivity.

Recent research is proving that biochar inputs to soils in tropical agro-ecosystems can boost crop production by improving key soil fertility functions. Biochar is highly stabilized and can therefore sequesters carbon for very long. Benefits of biochar input on crop production may decline with time, and vary according to the rate and quality, but little information is available about this. This study investigates: 1) the sustainability of biochar effects on crop production and soil C sequestration in maize-soybean rotations, and 2) effective biochar dosage for increasing fertilizer efficiency of maize monocrops. Data from meta-replicated trials was collected in different agro-ecosystems to understand variations of biochar effects. The dose response experiment used a range of rates and feedstocks that resemble what potentially could be produced from local resources in smallholder farming systems.

Biochar input of 10 kg m^-2 during the first year of the long-term experiment generated a positive effect on crop production over 10 years, with and without NP fertilizer. The C content of soils amended with biochar remained largely unchanged after a decade, proving long-term sequestration of biochar. Responses of crop production to different biochar dosages were highly consistent, and did not decline, over the first 3 years. Average maize grain yields achieved in trials receiving NPK fertilizer and 0.1, 0.5 and 1.0 kg m^-2 of biochar measured respectively 1.5, 2.3 and 3.3 times higher than trials receiving only NPK. Inputs of biochar at 0.1 kg m^-2 without fertilizers attained greater yields than when only NPK fertilizers were applied (7.5 g N m^-2 season^-1). Biochar dosages between 0.5 and 1.0 kg m^-2 were most effective for increasing fertilizer efficiency of maize crops across the agro-ecosystems. This study demonstrates that use of biochar offers a unique window to sustainable intensification of tropical cropping systems.