Weed control during production

Because of the Importance of weed parts as a trash component, weed and grass control during the production phase is extremely Important. It may be concluded (12) that if there is grass in the field, there is likely to be grass in the fiber. Broad-leaf-weed and grass control in the field provide, therefore, the first effective opportunity available to reduce the foreign matter content of ginned fiber. 

Petroleum products such as stove oil were used as selective herbicides in fields of guayule—a rubber-bearing shrub—grown experimentally in California and the Southwest during World War II. Mineral spirits are used rather extensively for weed control in cranberry bogs in the lake states and in the Northwest. 

The move into continuous cereal production and away from mixed farming with firm rotations meant that farmers could cultivate high value crops on all available land without the need for fallow. This could not have been achieved without the use of chemical herbicides. The movement of people from the land to the urban environment during the industrial revolution and thereafter reduced the available labour for hand weeding and weed control became a real problem for the farmer. The revolution was the introduction of 2,4-D and MCPA that allowed broad-leaved weeds to be controlled selectively in the previously dirty cereal crops. 

On the other hand, the broad weed control spectrum of chloramben, which was introduced in 1959, brought with it widespread acceptance. As an over-the-row band for control of both broadleaf and grass weeds, cost was minimized. With good crop tolerance, chloramben dominated the early soybean herbicide market. During 1972, 85% of the product was applied as the granular formulation (Table 4.2). However, as application practices changed for the soybean crop, banded applications became an inconvenience. Herbicides such as metribuzin (a triazine herbicide), linuron, and bentazon, which could be applied as an affordable broadcast treatment, soon became products of choice, and the marketing of chloramben was eventually discontinued in 1990. 

During 1995-1997, the information from past studies, almost 5000 field trials, new surveys of growers, and a weed control model developed by Dr. David Bridges (Bridges, 1998) were used to provide USEPA with estimates of the economic benefits of triazine and atrazine on all crops labeled with these products in the United States. A summary of the economic and biological models and some of the components are available (Bridges, 1998 Carlson, 1998). 

Inununoassay and GC/MS (gas chromatography/mass spectrometry) analysis for triazine herbicides were compared in order to evaluate the potential of Inununoassay as a screening tool. Water samples were collected at 146 sites on streams In a 10-state region of the midwestern United States during 1989 before and shortly after application of pre-emergent herbicides that were used for weed control in the production of corn and soybeans. The sites were sampled a third time in fall 1989 during a low streamflow period. 

Pre-sowing treatments, using contact-acting products like glyphosate, may be required to kill weeds that have not been controlled during seedbed cultivations. 

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