Review on Effects of Inter and Intra Row Spacing on Yield and Yield Components of Soybean (Glycine max (L.) Merrill) in Ethiopia

Plant density and arrangement of plants in a unit area greatly determine (i) resource utilization such as light, nutrients and water, (ii) the rate and extent of vegetative growth and development of crops particularly that of leaf area index, plant height, root length and density, (iii) yield components and yield, (iv) development of important diseases and pests, and (v) the seed cost. Plant density affects early ground cover, competitive ability of crops with weed, soil surface evaporation, light interception, lodging and development of an optimum number of fruiting sites in a crop canopy. It also affects canopy development, plant architecture and distribution of pods. Use of proper agronomic practices is one of the important factors which contribute for the increase of yield per unit area. Plant density is one of the essential agronomic practices as it is a major management variable used in matching crop requirements to the environmental offer of resources. Plant density is determined either by seed rate (for broadcast planting) or by inter- and intra- row spacing (for row planting). The density depends on the germination percentage and the survival rate in the field. Establishment of required plant density is essential to get maximum yield. For example when a crop is raised on stored soil moisture under rain fed conditions high density will deplete moisture before crop maturity, whereas low density will leave moisture unutilized. Hence, optimum density will lead to effective utilization of soil moisture, nutrients, sunlight etc. In Ethiopia, studies showed that plant spacing recommended for early and late maturing varieties was 40 cm x 10 cm and 60 cm x 5 cm, respectively. However, use of below (30cm x5cm spacing for all varieties, indiscriminately) and above the recommended spacing have effect on the yields of soybean in Ethiopia. Keywords: Intra row spacing, Inter row spacing and plant densit