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Importance of research to Soybean farmers
Farmers experience a significant amount of green or semi-green soybeans in their harvested soybean when an early frost occurs. This research provides helpful information for farmers on how to manage green and semi-green soybeans in the field prior to harvest and during storage.
Research Conducted
An early frost on soybeans was mimicked by killing the soybean plants using a herbicide at the growth stages of fully developed seed (R6) and beginning maturity (R7). The killed plants were left out in the field to dry and harvested with the mature seeds (R8). The soybean seeds conditioned to 12 and 17% moisture. The seeds were stored in airtight plastic bags in opaque plastic pails at 4 °C and 23.5 °C for six months. The moisture and color of the seeds were checked during field drying and in addition mold counts, and quality of oil were evaluated during storage.
Research Results
Weather conditions after being frozen are crucial to the moisture and color of harvested soybeans. Soybeans harvested ten days after killing at the R6 growth stage showed significant fading of the green color, under good weather conditions and exposure to sunlight on the field, approaching that of mature soybean, Fig 1. Soybeans harvested at the R6 (Fig 2) and R7 growth stage exposed to snow, freezing temperatures, and wet weather after the desiccation still had a green tone and discoloration. Despite the green seed color, no green color was observed in the extracted oil from the seeds after field drying or during storage. Hence, the chlorophyll content of all seeds was at low levels. Very little change in the golden green color of 17% moisture R6 and R7 soybean seeds during 4°C storage. Mold development was observed on 17% moisture seeds at 23.5 °C within a couple weeks of storage. Both peroxide and free fatty acids of oil extracted from all seeds were at acceptable levels during storage.