Biochar Amendments for Reducing Nitrate Leaching from Soils of Different Textural Classes in the Nigerian Savanna

This study was carried out with the aim of assessing the effectiveness of four biochar materials; in reducing nitrate leaching from soils of three different textural classes in the Nigerian Savanna region. Soil samples (0-20 cm depth) were collected from three different soil types and three different locations each in the Nigerian Savanna using stratified random sampling. Two hundred and fifty (250) g of soil samples were amended with 0, 2.5, 5, 7.5 and 10 tonha-1 of Maize cob biochar (MCB), rice husk biochar (RHB), cow dung biochar (CDB) and poultry litter biochar (PLB) and were subjected to laboratory leaching experiment. Sixty (60) ml of nutrient solutions containing 300 mgl-1 nitrate using ammonium nitrate (NH4NO3) was applied to each of the laboratory biochar-incubated soil columns to study biochar effect on nutrients retention and transport. The experiment was laid in a Randomize Complete Block Design (RCBD) replicated three times. Leachates were collected and nitrate concentration was determined using a dual beam UV/VIS spectrophotometer. The data collected were analysed using the Generalized Linear Model (GLM) procedure and the means were separated using Tukey’s honest significant difference (SAS version 9.4). Results obtained revealed that there were no significant differences among the biochar treatments on nitrate leaching from Clay loam. However, highest nitrate leaching from Loamy soil of 30.53% was recorded by the application of 2.5 tonha-1 PLB and was significantly different from the application of 2.5 and 5-ton ha-1 RHB and 5-ton ha-1 MCB. Similarly, highest nitrate leaching from Sandy loam of 32.18 % was recorded by the application of 5-ton ha-1 MCB and was significantly higher than 5.94, 2.40 and 7.12 % recorded by the application of 2.5 and 5-ton ha-1 RHB and 7.5 tonha-1 CDB respectively. Therefore, application of 2.5, 5-ton ha-1 RHB and 7.5 tonha-1 CDB can effectively reduce nitrate leaching from Sandy loam. While 2.5, 5, 7.5 tonha-1 CDB and 2. 5 and 5 tonha-1 RHB reduced nitrate leaching from Loamy soils.