Growth of Sorghum and Soybeans in Picloram-treated Soil
1975
Bovey, R. W. | Miller, F. R. | Baur, J. R. | Meyer, R. E.
Picloram (4-amino-3,5,6-trichloropicolinic acid) residues in soil may occur as a result of weed control practices on cropland and injure subsequent crops. This study was conducted to determine how soil residues of picloram affected the growth and dry matter production of sorghum (Sorghum bicolor (L.) Moench) ‘Topland’ and soybeans (Glycine max (L.) Merr.) ‘Hill’ grown in soil at various time intervals after picloram had been applied. The potassium salt of picloram was applied at 1.12 kg/ha and incorporated by disking into a Wilson clay loam soil 1 ½, 3, 6, 7, 12, 14, 16, 19, and 26 months before planting of sorghum and soybeans in the Spring of 1972 and 1973. Soil, sorghum, and soybeans were analyzed for picloram content at time of harvest. After maturing, crop plants were counted and harvested by clipping two rows, 4.1 m long at the soil level in each plot. Plants were weighed and oven-dried for dry matter determination. Germination tests were conducted with harvested sorghum seed. Sorghum was grown on picloram-treated soils 12 months after application without reduction in plant numbers, dry matter production, flowering, or germination. No picloram was detected in sorghum seed (immature and mature) produced by plants seeded 6 or 12 months after application of herbicide to the soil. Because soybeans were sensitive to small amounts of picloram in the soil, they should not be grown in a picloram-treated clay soil for at least 2 years after application. Earlier planting risks possible reduction in stand and dry-matter production in situations similar to this study.
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