Effects of delaying chemical fallowing in pasture rotations on pasture quality and wheat yield in the Victorian Wimmera

Abstract

The effects of delaying chemical fallowing in a pasture rotation on pasture quality and subsequent wheat yield were investigated at sites near Minyip and Charlton, Victoria, in 1983 and 1984. Three chemical fallows were commenced at different times and were compared with a conventionally cultivated fallow. The earliest chemical fallow was established, together with a conventional fallow, at the end of winter. The second chemical fallow commenced towards the end of the rapid spring growth period in mid-October (early hayfreezing), and the third in mid- November (late hayfreezing) on a grass-dominant pasture. The pasture in spring ranged from 51 to 72% digestible dry matter (DDM) but the quality declined to 42-50% DDM by the end of the fallow treatments in autumn at each site in both years. Weathering of the pasture over summer reduced it to roughage. In contrast to a conventional fallow, early hayfreezing of pasture reduced the yield of subsequent wheat crops at Minyip by 14% in 1984 and 26% in 1985. Late hayfreezing caused losses of around 35% in each year at Minyip. At Charlton yield losses were much lower with only 14% loss observed from late hayfreezing in 1985. Because the feed produced by hayfreezing was of very poor quality, hayfreezing cannot be recommended as a viable fodder conservation method as it could not adequately compensate for any yield loss.