Biomass accumulation and recovery of dual-purpose crops in a dryland environment.

In the Canterbury region feed deficits occur during summer and winter. Dualpurpose crops (used for forage and grain) such as wheat and oilseed rape, can supply forage during the autumn and winter feed deficit periods and also provide harvestable grain from the mature crop. It may be possible to sow winter type annual crops that require vernalisation very early (> four months early), graze as forage in summer and winter and still harvest grain from the mature crop. A field experiment was conducted to investigate the dry matter production of wheat and oilseed rape under dryland conditions from a range of sowing dates: 15 November 2012, and 23 January, 12 March and 26 March in 2013. Grazing by sheep occurred whenever significant biomass was available and measurements taken included biomass accumulation, recovery and crop development. Oilseed rape produced more biomass in total than wheat, with earlier sowing dates producing greater biomass than later times of sowing. The earliest sowing date (15 November 2012) produced 7342-9749 kg/ha of biomass for grazing, providing 5616-6692 kg/ha of consumed forage. In comparison the latest grazed sowing date (12 March 2013) accumulated 1238-1484 kg/ha of forage in total consumed for both crops. For wheat, grain yields were not significantly different between time of sowing 2 to 4, ranging from 5300 to 5700 kg/ha but time of sowing 1 grain yield was greatly reduced to 2500 kg/ha. Total biomass for oilseed rape was low for all times of sowing in response to grazing. Under dry summer conditions both crops accumulated biomass that enabled grazing to occur and both species did not flower until spring. Therefore forage could be grazed from summer to winter under dryland conditions. There is a significant opportunity for both wheat and oilseed rape to be sown up to four months earlier than grain-only crops in a dryland environment and be grazed throughout the summer and winter period to reduce the impact of feed deficits.