INFLUENCE OF ORGANIC MANURE AND WOOD ASH ON THE ABUNDANCE OF SOIL MICROORGANISMS, ORGANIC CARBON AND GRAIN YIELD OF SOYBEAN (GLYCINE MAX L. MERRILL) IN ACID SOIL

Organic production methods which include the exclusion of chemical approach of soil amendment have been observed to improve plant growth and preserve the soil health and biodiversity of production environment. A study was conducted at the Federal University of Agriculture, Abeokuta, to examine the influence of organic manure and wood ash on the abundance of soil microorganisms, organic carbon and yield of soybean in acid soil. The study consisted of three rates of wood ash (0, 2.5 and 5.0 t ha-1) and three rates of cow dung (0, 5.0 and 10.0 t ha-1) arranged in completely randomized design, replicated three times. Soybean variety TGX 1485 – ID was sown into 5 kg. The results showed that wood ash application at 5.0 t ha-1 significantly increased the soil pH (6.6), organic carbon (7.48) and soil microbial population (110 × 104 cfu g-1) compared to lower rate of 2.5 t ha-1 and control, which resulted in highest number of pods (7.7) and grain yield (14.2 g per plant) at harvest. Cow dung treatment of 10 t ha-1 significantly had highest soil organic carbon (7.39%) at 8 WAP and soil microbial population (21.1 and 91.4 × 104 cfu g-1) at 4 and 8 WAP respectively. These findings indicate that application of wood ash may be an acceptable alternative liming agent to the inorganic soil amendment and higher soybean productivity.