Abstract:
Low soil pH and associated poor soil fertility considered to be among the major challenges to faba bean production constraint in the highland of Ethiopia. The aim of the study was to examine and determine the effects of lime, Rhizobium inoculation and N fertilizer on growth, nodulation yield and yield component of two faba bean (Vicia faba L.) in the high land of Amhara Regional State Gihse District. Before and after harvesting nine representatives composite soil sample were taken at 0-20 cm and selected soil physical and chemical properties were determined. The experiment was arranged in randomized complete block design with three replications by combined application one level of lime, Rhizobium and N fertilizer with two faba bean varieties conducted from June to November in 2016/17 under rain fed conditions. The four treatments were: control (none inoculated, fertilized and limed), lime (6t ha-1) + rhizobium inoculation (LR), lime (6 t L ha-1) + rhizobium inoculation (500gm R ha-1) + N fertilizer (23kgha-1) (LRN) and rhizobium inoculation (R) and Walki=V1 and Dk70=V2 faba bean variety. Per-sowing soil chemical properties at the main cropping season in experimental site indicated that soil pH=5.13, exchangeable acidity=0.47 exchangeable Al= 0.24, exchangeable H=0.23 OC =1.6 total nitrogen =0.097, available P=9.2mgP/kg and CEC=15.3, were recorded. This initial result indicated to needed lime requirement of6ton/ha one month before sowing to improve the pH value the target >5.6 and comforted for root nodulation, growth, yield and yield components. For all experimental plots used 46kg ha-1 basal P2O5 fertilizer uniformly at sowing time. After harvesting the soil analysis result showed that 6 t liming markedly decreased exchangeable Al by 0.37cmol/kg, increased soil pH by 0.9 units and increased available P by 8.27 mg/kg, CEC increased by5.1 cmol/kg. Liming increased soil pH and significant (p<0.001) increment of nodule number/plant, number of pod/plant and number of seed/pod were increased under LRN, LR, and R treatment. The maximum grain yield was 34.13qt /ha and minimum grain yield (28.12qt /ha) was obtained in control (no lime, rhizobium inoculated and N fertilizer) treatments, which has26.45, 22.64, and 10.75% increments on over the control. Lime application and rhizobium inoculated had significant effect on plant height and total biomass. Even though the higher marginal rate of return was recorded at sole application (rhizobium inoculated) of, combined application of lime (L) and rhizobium (R) are economically feasible to improve faba bean yield and yield components on acidic soils of the study area. Therefore, sustainable faba bean production on acidic soil in the central highlands of Ethiopia should involve combined applications of lime and biological fertilizer.