Tillage systems weed control

Table I. The Effect of Tillage and Rye Residue (Above- and Belowground) on Weed Control Averaged Across Three Cropping Systems at Clayton, NC, in 1982 and 1983...

Organic farming systems rely more on mechanical weed control and in certain crops on considerably more intensive soil tillage as the use of synthetic herbicides is prohibited. This can have negative effects on other key species of soil meso-fauna, i.e. a reduction of population of Collembola with organic cultivation (Krogh 1994). 

The benefits of the triazines in multiple cropping systems range from their application flexibility, effective weed control, soil residual activity, and crop selectivity to their important role in resistance management and conservation tillage. The triazines also have made a major impact on agricultural sustainability and crop yields, as evidenced by the use of atrazine, especially in com. 

The triazines have played a significant role in the transformation of agriculture in Europe and were key components of weed control systems for many crops within the European Union. In 2005, 21 EU countries were using one or more triazine herbicides. These products are primarily used in combination with other active ingredients for broad-spectrum weed control in various tillage systems employed in the economic production of many crops. 

Wicks, G.A., O.C. Burnside, and W.L. Felton (1994). Weed control in conservation tillage systems. In P.W. Unger, ed., Managing Agricultural Residues. Boca Raton, FL Lewis Publishers, pp. 211-244. 

Tillage compatibility Because atrazine provides both postemergence and residual preemergence weed control, it fits well into conventional, minimum, and no-till production systems. Research indicates that dependency on atrazine increases when tillage is reduced, and in fact, currently available data indicate that 67.6%, 70.1%, and 81.5% of conventional, conservation, and no-till com acreage, respectively, is treated with atrazine (Doane Marketing Research, 2000). 

No one herbicide will do the job and control all of the many weeds in most fields. Farmers require combinations of effective and dependable herbicides that will work under a wide variety of weed species and densities, soil types, and climatic conditions. Many years of research, trial, error, and experience have been required for farmers to arrive at the greater than 22% of all corn acreage in no-till, and 112.6 million A (45.6 million ha) or more than 40% of our total United States cropland acres in some form of conservation tillage systems in 2004 (CTIC, 2004). Table 33.1 shows the trend toward various types of conservation tillage in recent years. 

Triazine herbicides are particularly well suited for conservation tillage because they provide foliar and residual control of a broad spectrum of weeds. Atrazine, simazine, and metribuzin are used in com, atrazine and propazine in sorghum, metribuzin in soybean, and simazine reduces tillage required for weed control in many perennial and tree crops. Atrazine is also used extensively in chemical fallow cropping systems in rotations involving corn, sorghum, and wheat. Cyanazine was also used extensively in corn and cotton until 2002. 

Triazine herbicides have been important tools in the development and implementation of conservation tillage systems. Postemergence and residual activity, low vapor pressure, weak adsorption to surface crop residue, root uptake, broad weed control spectrum, and crop safety make these herbicides compatible with the high crop residue conditions of conservation tillage. 

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