Land use and biochar effect on nitrate leaching in a Typic Haplustert of central India

Studies on the effect of biochar on nitrate leaching are few. Hence, a laboratory column experiment was conducted using surface (0-20 cm) soil from three different land uses of a Vertisol, to investigate the effect of biochar amendment on leaching behaviour of nitrate and salts. The three selected land uses were: thick forest, agriculture land use with good soil fertility and good crop production history and agriculture land use with low soil fertility and poor crop production history. Biochar was added at 0, 0.5, 1.0 and 2.0% (w/w) to the soil in the upper half of the columns. The treatments were taken with three replications in a factorial completely randomized design. The PVC made columns (40 cm height and 11 cm internal diameter) filled with soil to a bulk density of 1.2 Mg m−3 were leached with deionized water once a week for 15 consecutive weeks. Nitrate in form of KNO3 was added at the rate equivalent to 100 mg N kg−1 soil (220 kg ha−1) at each application in the 1st, 8th and 11th week. The forest soil showed significantly higher salt and NO3−-N leaching. Biochar amendment @ 0.5% or at higher level showed a significant reduction in NO3−-N leaching in the forest and good agriculture soil, whereas, in the poor agriculture soil, no significant effect was observed even at 2.0% biochar amendment level. With the highest level of biochar amendment (2%, w/w), reduction in NO3−-N leaching to the extent of 27% and 23% was observed in the forest and good agriculture soil, respectively. Biochar application significantly reduced salt leaching in the forest soil at 0.5% amendment level, and in the good agriculture soil at 1.0% level. At 2.0% biochar amendment, reduction in salt leaching to the extent of 18% and 16% was observed in the forest and good agriculture soil, respectively.