Effect of different Rates of Wood Ash on Exchangeable Aluminum, Growth, Nodulation, Nitrogen Accumulation and Grain Yield of Soybean (<i>Glycine Max </i>(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.