In conservation tillage systems

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. 

In the direct drilling (no-till seeding) practice in the united Kingdom/ straw residues from the preceding crop are usually burnt because poor crop establishment and yields can result/ particularly on heavy soils in wet years (10). Similar problems can occur in the conservation tillage systems oF the Pacific Northwest (L.F. Elliott and H.-H. Cheng/ this volume). 

Conservation agroecosystems developed in the Great Plains of the U.S. to control soil erosion are characterized by the presence of varying quantities of plant residues on the soil surface. This residue mulch protects the soil from the erosive forces of wind and water, resulting in improved stream water quality and soil conservation. Conservation tillage systems also help maintain soil productivity and reduce energy requirements of crop production (15). However, crop yield reduction has been observed with conservation wheat production in some areas of the U.S. (16-18) and with rice culture in the Far East (, 20). 

Allelopathic problems have been especially troublesome with conservation tillage systems (6.7.9). An example is the reduced growth of winter wheat when it is direct-drilled into stubble (Figure 1). In the heavy residues (left), the plants grew poorly. 

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 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. 

Fawcett, R.S. (1987). Overview of pest management for conservation tillage systems. In T.J. Logan, J.M. Davidson, J.L. Baker, and M.R. Overcash, eds., Effects of Conservation Tillage on Groundwater Quality. Chelsea, Mich. Lewis Publishers, pp. 19-37. 

Cultivators or other mechanical weed control options should remain available. Conservation tillage systems may not always be an option in situations where resistance is a problem. 

Conservation tillage systems are gaining in popularity in areas subject to soil erosion. Conservation tillage, which includes minimiun till, no till, and other forms of maintaining residue on the soil surface, has enabled farmers to increase their production options in response to their specific challenges. These systems became feasible with the advent of speciahzed equipment and new herbicide chemistry that reduce or eliminate the need for extensive tillage. 

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