Combining biochar with low rate of chemical fertiliser boosts maize biomass yield, regardless of tillage system, under humid conditions

Biochar application to soils increases biomass and crop yields, especially with rates higher than 100 t ha−1. Yet, there is limited knowledge on the combined effect of biochar and chemical fertiliser under different tillage systems. The objective of this study is to investigate the effect of maize-cob biochar (BC) (rates of 5 and 10 t ha−1) combined with chemical fertiliser micro-dosing (MD) at a rate of 25% of the recommended quantity on total shoot dry matter (DM) and plant height of maize cultivated under flat (F) and tied-ridge (R) practices during a humid season in Tanzania. The results indicate that combining 5 t ha−1 BC with 25% MD increases DM at harvest by 83% (4.16 t ha−1) compared to the control (2.27 t ha−1) and was in the same range as the DM obtained from the treatment with the recommended fertiliser rate (100% FD). The treatments with single applications of 25% MD, 5 t ha−1 BC, and 10 t ha−1 BC only tended to exceed the control of DM yield. Therefore, we recommend that small-scale farmers aiming at DM for livestock or grain yield with limited access to chemical fertilisers to combine biochar with 25% MD, rather than applying biochar or low chemical fertiliser rates alone.