Tillage systems for summerfallow preparation in north-central Saskatchewan
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This paper examines the agronomic and economic performance of seven summerfallow - spring wheat tillage systems studied over a 18 year period on a highly fertile silty clay loam soil at Melfort, Saskatchewan. During 1969-76, areas planted to wheat had the seedbed prepared with a cultivator and harrow; since 1977 one-half of each plot area received conventional seedbed preparation, the other half was sprayed with herbicide and zero till seeded. Overall, wheat yields averaged 3239 kg ha-1 for tillage alone, 3280 kg ha-1 for reduced tillage (combinations of tillage and herbicides), and 3347 kg ha-1 for herbicides only. On an annual basis, method of summerfallow preparation significantly influenced grain yields in only 6 of 18 years. In 3 of these years yields were lowest for tillage alone and highest for herbicides only; in 2 years yields were lowest for reduced tillage, and in 1 year yields were lowest for herbicides only. During 1977-86, preparation of the seedbed by tillage significantly increased yields (compared to zero till seeding) in 6 of 10 years, but it resulted in significantly lower yields in 4 of 10 years. Volume weight, protein content, and % P concentration in the grain were unaffected by the method used for fallow or seedbed preparation. Results of the economic analysis showed that total costs for the complete rotation systems were lowest for the all tillage treatment (average: $109 ha-1), intermediate for reduced tillage (average: $129 to $158 ha-1), and highest for herbicides only (average: $179 ha-1). Although the substitution of herbicides for mechanical tillage provided resource savings in the range of $2 to $10 ha-1, this was more than offset by the increased expenditures for herbicides. Net returns (income above all costs) were highest for tillage alone (average: $129 ha-1) and lowest for the herbicide only treatment in which paraquat or glyphosate was used in combination with dicamba (average: $54 ha-1) . The reduced tillage systems generally produced a net return that averaged $18 to $44 ha-1 lower than the traditional system. The maximum expenditure that could be made for herbicides to break even with the traditional system ranged from $22 to $29 ha-1 for the reduced tillage systems, and from $31 to $37 ha-1 for the herbicides only treatments. The study concluded that although the substitution of herbicides for some or all of the mechanical tillage is attractive to producers from an agronomic and soil conservation perspective, the present economic conditions and in particular, the high cost of herbicides, remains a major deterrent to widespread adoption.
Part OfSoils and Crops Workshop
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