Plant Population Density Effects on Yield and yield components of Soybean (Glycine max. L.)  Varieties in Ethiopia- A Review

Soybean is the most important oil seeds and grain legume crop in the world, in terms of whole
manufacturing and international trades. Appropriate plant density is a key for production of soya bean in various environments of Ethiopia. This paper reviews on effect of plant population density on yield and yield components of soybean in Ethiopia. Under these review recent literatures concerning on effect of plant population density has been covered. Optimizing plant population per unit area is one of the best agronomic practices to increase soybean production and productivity. Improvements of inter and intra row spacing practices are important for land productivity to soybean varieties based on the varieties architecture and the environmental yield potential of the land. The yield and yield related parameters of a single plant can be increased by optimum plant population density. As the review indicates most yield components of soybean were affected by different plant population densities due to resource competition that can be affects the grain yield. Normally as population increase yield also increases proportionally. However, after it reached a certain level the yield declines. Population density is also dependant on the moisture availability and nutrient status of the soil. Soybean tolerates considerable variation in plant population density and there is a tendency for higher yields with narrow rows. Several experiments conducted on row and plant spacing under different soil and climatic conditions indicated higher yield and yield components for high planting densities than for low planting densities.
The optimum plant population for Soybean could vary depending on geographical locations, morphological characteristics, length of maturity. In Ethiopia, recent studies showed that plant spacing 30-40 cm inter row spacing with 5cm intra row spacing was recommended and economical for early and medium maturing soybean varieties.

Keywords: Population, density, soybean, spacing, and yield