Increasing production of an annual medic–wheat rotation by grazing and grass removal with herbicides in the Victorian Mallee

Abstract

Summary. The productivity of an annual medic-based pasture–pasture–wheat rotation in response to chemical grass control and stocking rate treatments was evaluated over 3 years.

Fluazifop applied in 1991 reduced the annual grass component during the pasture years (to <2% in 1991 and <5% in 1992) and grass densities in the 1993 wheat phase. This improved winter herbage production in 1992 (>50%) and the 1993 wheat yield (>40%). Glyphosate applied during the winter of 1991 reduced the grass component and the winter and total herbage production in that year, and grass populations in 1992. Glyphosate applied during the spring of 1991 reduced the medic seed yields and the grass and medic densities in 1992. There were no pasture or cereal production benefits measured from the 1991 glyphosate applications. All the above comparisons were made with no herbicide in 1991 followed by glyphosate applied during the winter of 1992, a common district practice.

Stocking at twice the district average, over all herbicide treatments, reduced the 1991 winter herbage production but maintained or improved the 1992 winter and total herbage production, compared with the district average stocking rate. The high stocking rate resulted in lower grass densities in the 1993 wheat crop and increased the wheat grain yield by 0.5 t/ha.