Herbicide Residue in Soil when Applied to Sorghum in a Winter Wheat-Sorghum-Fallow Rotation

Wicks, G. A.; Fenster, C. R.; Burnside, O. C.

Herbicide Residue in Soil when Applied to Sorghum in a Winter Wheat-Sorghum-Fallow Rotation

1969

Wicks, G. A. | Fenster, C. R. | Burnside, O. C.

Atrazine [2-chloro-4(ethylamino)-6-(isopropylamino)-s-triazine] and propazine [2-chloro-4,6-bis(isopropylamino)-s-triazine] were applied to sorghum [Sorghum bicolor (L.) Moench] at 1.12 to 8,96 kg/ha on separate plots in 1960–63, 1965, and 1966 at 11 experimental locations across Nebraska. Winter wheat was seeded 15 months later. Atrazine, when applied to sorghum at recommended rates, did not affect subsequent winter wheat yields at North Platte on Holdrege loam and Holdrege silt loam. Occasionally, there was winter wheat stand reduction following atrazine and propazine at 4.48 and 8.96 kg/ha. At Alliance on Keith very fine sandy loam, winter wheat fall top growth was reduced by atrazine at 4.48 kg/ha in 1962 and 1963. Thinning of stand did not always reduce grain yields because of subsequent tillering. There was an increase in winter wheat grain yields in 1964 on plots treated with atrazine at 2.24 kg/ha in the sorghum in 1962. At Lincoln, on Sharpsburg silty clay loam, winter wheat yields were reduced from atrazine carryover in 1963 but not in 1964. Under most Nebraska conditions, atrazine applied to sorghum at recommended rates will not persist long enough to cause yield losses of winter wheat in a winter wheat-sorghum-fallow rotation.

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