Effect of Seed Size on Yield and Yield Parameters of Four Tropical Soybean (Glycine max L. Merrill) Varieties in Nsukka, South-Eastern Nigeria

Abstract

Field studies were conducted to determine the growth response of soybean to seed size at the Teaching and Research Farm of the Department of Crop Science, Faculty of Agriculture, University of Nigeria, Nsukka, Nigeria during the cropping season, June, 2008 to June, 2009.   In this study, four soya bean varieties (TGX 1448- 2 E, TGX 1455-2 E, TGX 1458-2 E and TGX 1497-ID) were used.  The micrometre screw gauge was used to sort out the seeds of each of these varieties into three sizes of small (9.6 g /100seeds), medium 13.3 g/100 seeds and large (16.3g/100seeds)  on the basis of seed weight and mean diameter.  The experiment was laid out as a split-plot in randomized complete block design (RCBD) with three replicates. The four soybean varieties represented the main plot, while the seed sizes represented the subplots.  Our result shows that with the exception of plant height at maturity, seed size was important in the performance of the varietal attributes measured. Plant establishment was ≥ 60% for plants that grew from medium and large seed sizes while small seed size plants had ≤ 55% establishment. Days to 50% flowering and 50 % maturity were 55 days and 122 days for small seed size plants and 50 days and 113days for medium and large seed size plants. Number of nodules /plant averaged 12 nodules for plants that grew from small size seeds, and 15 and 18 nodules for medium and large seed size plants respectively. Number of pods/plant was significantly higher in medium and large seed size plants (43pods/plant) compared to small seed size plants (37pods/plant). An average number of seeds per pod were two seeds for medium and large seed size plants and one seed for small seed size plants. Seed weight per 100 seeds was 10 grams for small seed size plants and 12 and 16 grams for medium and large seed size plants respectively. Seed yield averaged one ton per hectare for medium and large seed size plants and less than one ton (600 kilograms) for small seed size plants. In conclusion, seed size accounted for more than 80 % performance of all the varietal attributes measured in this study. Therefore, in selecting planting material consideration should be given not only to variety but seed size of the planting material.