Effect of different Rates of Wood Ash on Exchangeable Aluminum, Growth, Nodulation, Nitrogen Accumulation and Grain Yield of Soybean ( Glycine Max (L.) Merrill) in an Acid Ultisol

Abstract

Response of soybean grown on acidic soil to wood ash applied at 0, 2, 4, 6, and 8 t ha-1 was studied in two field experiments in 2003 and 2004 at Umudike in the rainforest zone of Southeast Nigeria. Treatments were fitted in a randomized complete block design (RCBD) replicated three times. Effect of treatments on some soil fertility and productivity parameters were evaluated. The wood ash contains 64.30 g kg-1 Ca, 12.20 g kg-1 Mg, 9.03 g kg-1 K, 8.75 g kg-1 P and 4.84 g kg-1 N, and had a pH of 11.07. Soil pH increased significantly from 4.80 to 6.40, while levels of exchangeable Al 3+ correspondingly decreased from initial values of 2.50 cmol kg-1 to 0.21 cmol kg-1 when 4 t ha-1 of wood ash was applied. Estimation of linear and quadratic curves respectively for soil pH and exchangeable Al 3+ indicated values of r 2 = 0.973** for soil pH and R 2 = 0.944** for exchangeable Al 3+. Significant increases (P < 0.01) in soil Ca, P, K, status relate to patterns of growth, nodulation, nitrogen accumulation and grain yield of soybean. The application of 4 t ha-1 wood ash gave grain yield of 2028.34 kg ha-1 compared with 0 t ha-1 ,and this was significantly (P < 0.01) higher than values obtained from either 2, 6 or 8 t ha-1. Thus, the effect of the application of 4 t ha-1 was more outstanding and is recommended if high grain yields are to be obtained.