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 Al³⁺ 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 Al³⁺ indicated values of r² = 0.973** for soil pH and R² = 0.944** for exchangeable Al³⁺. 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.

KEY WORDS: Soil Acidity, Wood Ash, Growth, Nodulation, Grain Yields, Southeast, Nigeria.