EFFECT OF PLANT SPACING ON YIELD COMPONENTS AND YIELD OF SOYBEAN [Glycine max (L.) MERRILL] VARIETIES IN DALE SEDI DISTRICT, WESTERN ETHIOPIA

Soybean is an important crop in the tropical, hot sub-moist agro-ecological zone of western Ethiopia. However, the yield of the crop is limited due to lack of appropriate plant density for the varieties. Therefore, the experiment was conducted to determine the effect of inter and intra row spacing on growth, yield components and yield of soybean varieties during 2016 cropping season in Dale Sedi District, western Ethiopia. Four inter row spacing (30, 40, 50 and 60 cm) and two intra row spacing (5 and 10 cm) were evaluated on three soybean varieties (Nyala, Wello and Dhidhessa). The experimental design was randomized complete block design in factorial arrangement with three replications. Highly significant differences were obtained on days to 50% flowering, days to 90% physiological maturity and hundred grains weight (g) due to the main effect of the variety. Variety Nyala was earlier in attaining flowering (57.12 days), physiological maturity (115.6 days) and gave higher hundred grain weight (19.91 g) than varieties Wello and Dhidhessa. The main effect of variety and intra row spacing was highly significant and significant on plant height, where the longest plant height (84.70 cm) and (69.99 cm) was for variety Wello and from 5 cm intra row spacing, respectively. The interaction effect of the variety and intra row spacing was highly significant on number of effective nodules, nodule dry weight and number of primary branches per plant. The highest effective nodules (23.1) were recorded from variety Wello at 10 cm, the highest nodule dry weight (0.345) were recorded from variety Wello at 10 cm and the highest number of primary branches (4.775) were recorded from variety Didhessa at 10 cm intra row spacing. Similarly interaction effect of variety and inter row spacing were highly significant on number of primary branches and number of pods per plant, where the highest numbers of primary branches per plant (4.57) and highest number pods per plant (49.83) were recorded for variety Wello at 60 cm inter row spacing. The three way interaction of variety, inter and intra row spacing was highly significant on crop stand count percentage, where the highest crop stand count at harvest (99.77%) was from variety Nyala at 50 cm inter row spacing and 5 cm intra row spacing. The main effect of variety, inter row spacing and intra row spacing were highly significant on above ground dry biomass and harvest index. The highest above ground dry biomass was from variety Wello (8857 kg ha-1) and inter row spacing of 30 cm (8785 kg ha-1). The highest harvest index was from variety Nyala (44.81%) and inter row spacing of 60 cm (41.9%). The main effect of variety was significant on grain yield where the highest grain yield (3072 kg ha-1) was for variety Nyala whilst the main effects of both inter-row and intra-row spacings were not significant. However, this tentative generalization based one season at one location requires further studies over years and locations to give a valid recommendation.