SOYBEAN (Glycine max L.) RESPONSE TO LIME AND VERMICOMPOST AMELIORATION OF ACIDIC NITISOLS OF ASSOSA, NORTH WESTERN ETHIOPIA

Acidic soils limit the production potential of crops because of low availability of basic cations and excess of hydrogen (H+) and aluminium (Al3+) in exchangeable forms. In the western part of the country such as Assosa and Wellega, soil acidity is a well-known problem limiting crop productivity. A field study was conducted to assess the effects of lime, vermicompost and their combinations on selected soil physic-chemical properties and responses of soybean grown on acidic Nitisols of Assosa area during 2016 main cropping season. Soil samples were collected from the experimental site before planting and from plots after harvesting. The collected samples were analyzed following the standard methods for soil physic-chemical analysis. The treatments were factorial combinations of four levels of lime (0, 1.62, 3.62 and 4.90 t ha-1) and four levels of vermicompost (0, 1.50, 3.00 and 4.50 t ha-1). The experiment was laid out in a randomized complete block design with 3 replications. The data were analyzed using Analysis of Variance in SAS statistical package and treatment means were compared at 5% probability using Tukey’s Test. The results revealed that soil pH increased from 5.2 - 6 pH while exchangeable acidity decreased from 6.4 - 2.16 cmol (+) kg-1 with levels of lime and vermicompost (3.26 with 3 and 4.90 with 4.5) t ha-1 respectively, which resulted in improved soil physic-chemical properties. The combined application of lime and vermicompost also significantly improved the yield related parameters of soybean including: number of nodules per plant, number of pod bearing branches per plant, plant height, number of seeds per pod, grain and biomass yields per hectare. The maximum grain yield (1.95t ha-1) was obtained from the combined application of 4.90 ton lime and 3.00 ton vermicompost ha-1 followed by combined application of 3.26 ton lime with 3.00 ton vermicompost ha-1 with non-significant variation. Therefore, combined application of 3.26 ton lime and 3.00 ton vermicompost ha-1 is a promising alternative amendment for amelioration of acidic Nitisols of Assosa (Amba-12 Kebele) and other similar agro-ecologies for the improvement of soybean production.