Sewage sludge biochar: effects on soil fertility and growth of radish

Biochar has been presented as a viable alternative for the sustainable use of sewage sludge (SS) in agriculture. However, there are still doubts about the nutritional effects of biochar on short-cycle crops. The objective of this study was to evaluate the effect of different doses of SS biochar on soil fertility components and agronomic development of the radish, Raphanus sativus L. (Brassicae). An experiment was conducted in a greenhouse, whose experimental design was completely randomised with six treatments and four replications. Soil properties were evaluated before and after cultivation of radishes. The variables tested responded positively to the increase in biochar dose from 10 to 30 g kg−1, and a slight decrease was observed from 30 g kg−1. There was an enrichment of nutrients in the soil receiving biochar, especially phosphorus, available nitrogen and exchangeable cations (calcium and magnesium). Biochar also increased soil fertility indicators including sum of bases and base saturation, and the cation exchange capacity, and had no effect on the components of soil acidity. In general, the biochar was able to supply nutrients to plants in a short period resulting in increased radish productivity.