INFLUENCE OF TILLAGE METHODS AND WOOD ASH APPLICATION ON SOIL PROPERTIES AND SOYABEAN (Glycine max (L) Merrill) PERFORMANCE IN ADO-EKITI, SOUTH WESTERN NIGERIA

Abstract

The study aimed at developing a soil management package for soyabean cultivation on an alfisol in the rain forest zone of Nigeria. A three season experiment was conducted at the Federal Polytechnic, Ado-Ekiti (FPA) and Ago Aduloju Settlement (AGO) in Ado-Ekiti Local government area of Southwest Nigeria. Five tillage practices namely (a) Manual clearing MC, (b) Herbicide based zero tillage (ZT), (c) Disc ploughing (PL), (d) Ploughing plus harrowing (PLH) and (e) Ploughing plus two passes of disc harrow (PL2H). These were combined with no ash and application of wood ash at 4t/ha giving 10 treatments on the whole. The treatments were replicated three times and applied to soyabean plants at the two sites. Three consecutive crops were involved in each site from 2008 to 2010. The experimental design was a Randomised Complete Block Design. The soil chemical properties, physical properties, growth, yield parameters, and nodule counts of soyabean were determined. Data were subjected to Duncan Multiple Range Test (DMRT) for test of significant at 5% level of probability. The pre-planting soil chemical analysis data indicated that PLH had the highest values of OM, P, K and Ca. At harvest, PLH also had highest values for OM, N, P, K and pH. The PL2H had least values of soil chemical properties in pre-planting and harvest determinations. Generally, soil chemical properties were similar among MC, ZT, and PL. Soils had suitable pH for soyabean while P status was adequate. Soils required amendment for Ca and OM. The ZT had relatively high soil bulk density and lower total porosity that was matched with lower moisture content. The PLH and ZT gave highest leaf count, plant height, pod weight, pod count and seed weight while PL+2H gave least values of the parameters. ZT followed by PLH had highest root and nodule count. Ash application obliterated effect of high soil bulk density and lower porosity associated with ZT. The ZTA therefore had least soil bulk density. The wood ash also increased soil pH, OM, N, P, K. Ca, Mg and CEC significantly. The ZTA had highest values of soil chemical properties among the 10 tilla ge cum ash treatments. Ash significantly increased plant height, number of leaves. It increased root count by 100%, nodule count by 258%, seed weight by 103% and pod count by 43%. The ZTA followed by PLHA had highest values of pod weight and seed weight while PL2H and MC had least values.