The Effect of Conditioning on Soybean Seed Quality

Abstract

Acceptable quality of soybean [Glycine max (L.) Mer.] seed is hard to achieve when poor growing conditions occur during reproductive development. Seed can be damaged during harvest and any time it is handled. This study was conducted to determine the effect of seed conditioning (the process of cleaning, treating, and preparing seed for planting) on soybean seed quality. We also wanted to determine whether seed quality could be improved or cleanout (the seed and foreign matter removed during conditioning) reduced by different conditioning techniques. Sized seed fractions from seed lots were examined for quality indicators before and after each seed lot was conditioned. Seed quality indicators measured included: seed per pound, seed moisture, damaged seed, standard germination, and germination following accelerated aging. Germination tended to be highest for the middle-sized fractions(14/64 to 16/64 in.). Sizes larger than this tended to have a lower germination when seed moisture content was below 12%. Germination in each small seed fraction was lower (< 13/64 in.) regardless of the moisture level. Seed larger than 17/64 in. had greater seed damage from handling (seed damage as indicated by broken seed coats) in the Clorox test than any other size fraction and showed a significant reduction in germination with increasing seed damage. Germination was reduced by seed conditioning in nearly all lots that had low seed moisture (<10.0%). Decreasing the amount of small seed removed during conditioning can reduce cleanout and tends to improve germination. Research Question Soybean seed quality varies within seed lots by seed size. This research was conducted to determine (i) whether seed quality for various size fractions can be accurately estimated before conditioning and (ii) to quantify the potentially detrimental effect of soybean seed conditioning on each fraction. With this knowledge, seed conditioning could be fine tuned to remove the size fractions with poor quality. Also, size fractions in which conditioning would cause excessive damage could be identified and removed. Literature Summary Germination, one major component of soybean seed quality, has shown a positive correlation with yield. While seed size may be an important component in yield for the individual plant, planting uniformly sized seed normally contributes to higher grain yield per area. Study Description This research was conducted on 27 foundation soybean seed lots harvested in 1991 and 1992 in Kansas. Samples were taken immediately before and after the seed was conditioned. Samples were screened to separate into sized fractions and weighed. The following tests were completed on the original and sized fractions; seed per pound, percentage moisture, Clorox soak test, standard germination, and accelerated aging test. Criteria were then established to condition seed and it was tested by computer simulation. Applied Questions Which seed size fraction had the highest germination? Germination of soybean seed lots tended to be highest in the middle-sized fraction. Lower germination was observed for the largest (< 18/64 in.) and smallest (< 13/64 in.) fractions. Can seed conditioning improve germination? Conditioning soybean seed reduced germination of the drier seed (<10.0% moisture). The lower the seed moisture, the greater was the reduction in germination from seed conditioning. This reduction was not seen in seed of higher moistures (>10.0%). Recommendation Decreasing the amount of small soybean seed that is removed by conditioning will decrease cleanout (the seed and foreign matter removed during conditioning) and may improve germination. The use of the Clorox soak test to identity seed lots with large damaged seed that should be removed can reduce cleanout without reducing germination.