Chemical aids to drying seeds of beans (Phaseolus vulgaris) before harvest

SUMMARY The effects on seed moisture content of seven different chemical formulations applied to bean (Phaseolus vulgaris) crops in two successive years were observed. Those containing bipyridyl herbicides caused the biggest effects. In 1974, diquat (0–59 kg a.i. ha‐1), applied to a French bean crop cv. Processor 26 days before harvest, decreased seed moisture content by 98 mg g_1 dry weight below a control value of 438 mg g_1. In 1975, diquat applied at the same rate to a navy bean crop cv. Seafarer 16 days before harvest, decreased seed moisture content by 123 mg g_1 below a control value of 364 mg g_1. Diquat applied at a lower rate (0–3 kg a.i. ha‐J) caused a decrease of 79 mg g_1 and paraquat decreased seed moisture by 147 mg g_1. In both years smaller effects were observed for dimexan (15 kg a.i. ha‐1) which decreased seed moisture content by 32 mg g‐1 in 1974 and 72 mg g_1 in 1975 and for ethephon (1‐0 kg a.i. ha‐1) which caused decreases of 78 mg g_1 in 1974 and 31 mg g_1 in 1975. In 1975, metham‐sodium (70 kg a.i. ha‐1) a soil sterilant, proved almost as effective as the bipyridyls, decreasing moisture content by 105 mg g_1. Trimming the roots mechanically reduced seed moisture by 67 mg g_1. Other chemical treatments, tried in 1975 only, were less effective and decreased seed moisture content by 31–60 mg g_1. These were Wiltz‐65 (pentanoic and hexanoic acids, 14‐6 kg a.i. ha‐1), N252 (dihydro‐dimethyl‐dithiin tetroxide, 0–56 kg a.i. ha‐1) and an application of diquat (0–3 kg a.i. ha‐1) to plants treated 10 days before with ethephon (1‐0 kg a.i. ha‐1)‐ In addition to the effects on seed moisture content, all treatments decreased seed yield. The largest decreases were caused by diquat and were attributable mainly to effects on mean seed weight. The paper concludes with an economic analysis which shows that at present prices chemical drying of beans in the field is not worthwhile because the yield loss nullifies any savings in drying costs.