Organic carbon and microbial activity in Umbric Rhodic Ferralsol soils under green cane relative to pre-harvest burning of sugarcane

Purpose Pre-harvest burning of sugarcane for easier harvesting and increase sucrose recovery, due to trash removal, may reduce soil quality particularly for Umbric Rhodic Ferralsols that have naturally high concentrations of soil organic carbon (SOC). Harvesting without burning (green cane) retains large quantities of biomass on the surface, which may be an alternative to improve carbon (C) sequestration and microbial activity. In the current study, we examined the effects of green cane relative to burnt cane on SOC concentration and stock, microbial biomass carbon (MBC) and beta-D-glucosidase enzyme activity. Materials and methods Soils under green cane were compared with adjacent burnt cane fields. The soils were sampled, in March 2021, from the 0-5, 5-10, 10-20, 20-30, 30-40, 40-50, 50-60, 60-80 and 80-100 cm depths, using micropits in the top 10 cm and using augers for deeper layers. The soils were analysed for SOC, MBC and beta-D-glucosidase activity. In addition, soil microbial quotient (SMQ) was calculated. Results and discussion The SOC concentration and stock, MBC, SMQ and beta-D-glucosidase activity were significantly higher under green cane than under burnt cane. The SOC under green cane was 24% higher than that under burnt cane. The MBC under green cane and burnt cane constituted 3.52 and 1.25% of the total SOC, respectively. The concentration of all the parameters decreased with an increase in soil depth. The SMQ was not affected by soil profile depth. The beta-D-glucosidase enzyme activity was higher under green cane than under burnt cane in the top 5 cm depth but not at deeper layers. The beta-D-glucosidase activity was positively correlated to the bulk SOC and MBC. Conclusions These findings imply that green cane production increases SOC storage, and microbial activity, when compared with the burnt cane on Umbric Rhodic Ferralsols.