Reduced-tillage systems

Doupnik Jr., B., and M.G. Boosalis (1980). Ecofallow A reduced tillage system - and plant diseases. Plant Disease, 64 31-35. 

Wicks, G.A. (1976). Ecofallow A reduced tillage system for the Great Plains. Weeds Today, 7(2) 20-23. 

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. 

Burnside, O.C. and G.A. Wicks (1980). Atrazine carry-over in soil in a reduced tillage crop production system. Weed Sci., 28 661-666. 

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. 

Conservation tillage is one of the most practical and economical ways to reduce soil erosion. Surface crop residue protects the soil from the erosive impacts of wind and rain. Reductions in erosion are proportional to the soil coverage of crop residue. From 78% to 89% of the variance in erosion between tillage systems is explained by the percentage of soil coverage by plant residue (Laflen el al, 1978). No-till systems, which leave nearly all surface plant residue in place, usually reduce erosion by 90% or more. 

Tillage and the multiple machinery passes used in conventional tillage systems can lead to soil compaction, which increases water runoff, alters the desirable mix of air and water in soil pores, and reduces crop yields. Tractor wheel traffic reduced corn yields by as much as 50% in a Canadian study (Raghavan et al, 1978). 

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