Recovery dynamics of rainfed winter wheat after livestock grazing 1. Growth rates, grain yields, soil water use and water-use efficiency

Abstract

Detailed information on the growth dynamics, yield responses and soil water use of dual-purpose cereal crops after grazing is often required to devise guidelines for profitable grazing management. To increase the availability of such data, grazing experiments with winter wheat (Triticum aestivum) were conducted near Canberra, Australia. In 2007, cultivar Mackellar was grazed at low-short (LS, 33 sheep/ha for 31 days), heavy-short (HS, 67 sheep/ha for 31 days) or low-long (LL, 33 sheep/ha for 62 days) intensity-durations. In 2008, cultivars Mackellar and Naparoo were grazed at the HS intensity-duration. Aboveground net primary production (ANPP) of ungrazed Mackellar crops averaged 1181 g/m2. LS and HS grazing did not affect ANPP in 2007, but LL grazing in 2007 and HS grazing in 2008 treatments reduced ANPP by 20% (which included biomass removed by livestock). Average grain yield (381 g/m2) was not significantly affected by grazing. Grazing increased the proportion of water lost through soil evaporation but decreased transpiration, reducing shoot dry matter production per unit evapotranspiration by up to 22%. However, grazing did not affect grain yield per unit evapotranspiration. For rainfed wheat crops grown in temperate environments, greater biomass production occurred with shorter rather than longer grazing durations, irrespective of grazing intensities.