Date of this Version
Thesis (M.S.)--University of Nebraska--Lincoln, 1949. Department of Agronomy.
Wider adaptation of 2, 4-D (2, 4-dichlorophenoxyacetic acid) had become possible through its use as a pre-emergence treatment. Pre-emergence treatment is the application of an herbicide to the surface of the soil after a crop is planted, but before it has emerged. Higher rates of application per acre are usually required than for foliage spray. Plants are most subject to injury during the germination period. Some advantages of pre-emergence are that smaller amounts of 2, 4-D per plant are required to kill weeds when they are germinating than at later stages of development. Thus, pre-emergence treatment will control both broad-leaved and grass species in large seeded crops. Certain crop seeds planted at a greater depth than where weed seeds normally germinate are not greatly affected by the herbicide and may be more resistant to 2, 4-D than weed seedlings. 2, 4-D leaves a toxic residue in the soil for a relatively short period of time when applied to warm, moist soil at recommended rates. Since it has a lethal effect when in contact with certain germinating seeds during the period which it persists in the soil, pre-emergence treatments may prove an effective measure of weed control.
The purpose of this study on germination and seedling development of crop seeds was to determine possible differences due to formulations, differences in tolerance between crops and crop varieties, and the different amounts of 2, 4-D required to give comparative effects in a germinator in the greenhouse and in field plots.