Effect of Biochar on Macronutrients Release and Plant Growth on Degraded Soil of Lafia, Nasarawa State, Nigeria

This study consisted of laboratory incubation and pot experimentation. Laboratory incubation was conducted at the Chemistry Laboratory, College of Agriculture, Lafia. The pot experimentation was done in the screen house of faculty of Agriculture, Nasarawa State University Lafia campus during the dry season of 2015 to assess weekly macronutrients (NPK) release in soil amended with locally produced sawdust and rice husk biochar and the growth and nutrient uptake of maize grown on the same soil. The experimental design used was complete randomized design (CRD) and the treatments consisted of three levels of rice and sawdust biochar: 0, 60, 120 g factorially combined to form 9 treatments. The result showed that, in the first week of incubation, 120 g of rice husk and sawdust biochar produced the highest levels of pH (6.58 and 6.69), Nitrogen (0.56 gkg-1 and 0.48 gkg-1), available phosphorus (27.61 mgkg-1 and 27.73 mgkg-1) and potassium (0.26 cmolkg-1 and 0.23 cmolkg-1) respectively. However, the second week of incubation recorded a reduction in nitrogen (0.39 gkg-1 and 0.44 gkg-1) released with application rates of 120 g of both rice husk and sawdust biochars respectively. There was increased in available phosphorus (35.00 mgkg-1 and 37.20 mgkg-1) and potassium (0.26 cmolkg-1and 0.23 cmolkg-1) and soil pH (6.73 and 6.88) respectively in the second week. In the third week of incubation, there was a continuous decline in soil N (0.35 gkg-1 and 0.36 gkg-1) but, P. K and soil pH consistently showed an increase. Rice husk and sawdust biochar applied at 120 g was significantly (p<0.05) higher in a number of leaves (7.00 and 8.00); growth height (50.73 cm and 20.67 cm); fresh weight (102.82 g and 26.18 g); dry weight (15.11 g and 2.69 g) respectively. N P and K uptake by maize plants were also significantly (P<0.05) influenced by rice husk biochar application. 120 g of rice husk biochar produced the highest value of maize uptake of N (2.51 gkg-1); P (62.62 mgkg-1) and K (4.28 cmolkg-1). Then, 120 g of saw dust biochar produced maize that took in the highest values of N (3.70 gkg-1); P (59.40 mgkg-1) and K (4.00 cmolkg-1).