Biomass burning in windrows after clearing a tropical rainforest: Effects on soil properties, evaporation and crop yields

Abstract

Burning is a widely used practice to clear fields of felled vegetation after forest clearing. Effect of vegetation-burning on soil properties and crop yields, however, has received limited attention. Two months after clearing a rainforest by the shear-blade method, dry-biomass was windrowed (4 windrows per plot) and burnt. Changes in soil properties, evaporation and crop productivity in windrows (burnt area) one year after burning the felled biomass were investigated. There were considerable increases in the amounts of exchangeable cations in the top 30-cm soil layer after burning. Consequently, soil pH increased from 5.7 to 7.0 in the 0–10-cm layer, from 5.6 to 6.5 in the 10–20-cm layer, and from 5.4 to 5.9 in the 20–30-cm layer. Burning and conversion of biomass to ash increased the availability of major nutrient elements. Bulk density was lower in the burnt area. The equilibrium infiltration rate was 106 and 13 cm h −1 in the burnt and unburnt areas, respectively. The rate of water evaporation and, thus, cumulative evaporation was higher from the burnt area. Rice (cultivar UPL-Ri-5) and plantain yielded significantly more in the burnt compared with the unburnt sites. Corn and cassava also yielded more in the burnt area, though differences were not significant. Growth and yield of cowpea was not affected. The results indicated that biomass should not be burnt in windrows in order to avoid introducing fertility variation in otherwise uniform fields.