Influence of Seed Ageing on Growth and Yield of Soybean

Effect of seed ageing on stand establishment, growth and yield of three soybean varieties was studied. Treatments consisted of three varieties viz. Shohag, Bangladesh soybean 4 and BARIsoybean-5 with four levels of seed ageing viz. 20, 12, 8 and 2 months aged seed. Seed germination and field emergence percentage decreased but electrical conductivity of seed leachate increased with increasing seed age in all the soybean varieties. Irrespective of varieties, plants grown from 20 months aged seed accumulated more dry matter per plant but crop growth rate (CGR) were lower than the other ageing treatments. The highest dry matter accumulation and CGR were found in BARIsoybean-5 and lowest in Bangladesh soybean 4. Irrespective of varieties, crop grown from 2 months aged seed produced significantly the highest seed yield (1981 kg/ha) which was at par with the yield obtained from 8 months aged seed; and the lowest (811 kg/ha) was grown from 20 months aged seed. Among the varieties, significantly the highest seed yield (1615 kg/ha) was obtained from BARIsoybean-5 which was identical with that of Bangladesh soybean 4. Results further revealed that Bangladesh soybean 4 can be grown up to 12 months aged seed without significant reduction in seed yield. Introduction Quality seed is the prime factor for crop productivity. Seed quality, as measured by its vigour and viability, plays a major role in establishment of seedling as well as higher crop yield. A major cause of low vigour has been identified as seed ageing (Mathews 1980). In recent years, soybean has become an important oilseed crop in Bangladesh for increasing demand of poultry feed. Soybean seeds contain about 42 to 45% proteins as well as up to 22% edible oil (Mondal et al. 2002). However, non-availability of good quality seed remains one of the major constraints of soybean cultivation. Soybean seed germination and vigour potential is short lived as compared to other grain crops and it is often reduced prior to planting time (Byrd and Delouche 1971, Justice and Bass 1978, Nkang and Umoh 1996). Its seed is rapidly deteriorated by high temperature and high relative humidity during storage. Seed deterioration leads to reductions in seed quality, performance and stand establishment (McDonald 1999). No systematic studies have been carried out on seed quality aspects of soybean in Bangladesh. The present study was conducted with a view to evaluating the effect of seed ageing in determining stand establishment, growth and yield of three soybean varieties. Materials and Methods The experiment was conducted at the Central Research Farm, BARI, Joydebpur Gazipur during Rabi 2006-07. The experiment was laid out in a split plot design with three replications. Four levels of seed ageing viz. A1 (20 months), A2 (12 months), A3 (8 months) and A4 (2 months) were placed in the main plot and three varieties viz. V1 (Shohag), V2 (Bangladesh soybean 4) and V3 (BARIsoybean-5) were placed in the subplot. Different aged seeds were collected from the harvest of rabi 2004-05, Kharif II 2005, Rabi 2005-06 and Kharif II 2006. Seeds were cleaned, properly dried (7.5 to 8% moisture content) and stored in tin containers under ambient temperature for 20, 12, 8 and 2 months. For germination percentage and electrical conductivity of seed leachate, the seeds were tested at laboratory prior to sowing. For electrical conductivity measurements, seed leachates were made by soaking 100 seeds in de-ionized water