Assessing the Nitrogen Leaching Potential of the Njala Soil Series Amended with Biochar

Abstract

Upland gravelly soils of Sierra Leone pose serious challenges to agriculture due to their low ability to retaining nutrients and water. Their highly weathered states, dominance of low activity clays and low organic matter content exacerbates their nutrient retention capabilities leading to high leaching of essential nutrients. However, there little knowledge about the magnitude of nutrient loss on Njala soils. This study was therefore conducted to quantify leaching losses of nitrogen from urea fertilizer in soils treated with and without biochar. In this study, four treatments were used to set up leaching columns: (i) Soil without Biochar (Control), (ii) Soil+Biochar, (iii) Soil+Fertilizer, and (iv) Soil+Biochar+Fertilizer.  Each treatment was replicated three times. Leaching experiment was conducted daily for seven days. Leachates were collected daily and analyzed for total Nitrogen.  The results showed a high rate of nutrients loss in soils not treated with biochar than soils treated with biochar.  Hence, the study has revealed the magnitude of nitrogen loss from applied urea fertilizer is 74.1% while the addition of biochar can reduce the loss significantly to 40% on the gravelly upland soils of Njala.  The study showed the vulnerability of nitrogen loss on the Njala uplands and the role of biochar in minimizing such loss.