Frost risk associated with growing maize for silage on Tasmanian dairy farms

The practice of growing maize silage for dairy cows is increasing in popularity within Tasmania. However, due to the relatively high cost of production, the long growing season (c.a. 20 weeks), frost exposure and yield variability, maize is considered precarious to grow. This study explored how long term yield, yield variability and frost risk is mediated by sowing date and maturity type in four dairy regions of Tasmania, Scottsdale (41.17S, 147.49E), Bushy Park (42.71S, 146.90E), Edith Creek (40.99S, 145.08E) and Cressy (41.72S, 147.08E), using the biophysical crop model APSIM. Yields in all regions decreased with later planting dates (median yields decreased from 27 to 14, 23 to 13, 27 to 15 and 25 to 13 t DM/ha with sowing dates of November 12 compared to January 7 for Scottsdale, Bushy Park, Edith Creek and Cressy respectively). Variability in yield increased as sowing was delayed. The regions of Bushy Park and Cressy were identified as locations with a high frost risk while Edith Creek and Scottsdale are relatively risk free. The use of early maturing hybrids reduced the frost risk by 20, 30, 30 and 17% for Scottsdale, Bushy Park, Edith Creek and Cressy respectively. Sowing crops earlier also reduced the risk of frost across all locations. Earlier sown crops and quicker maturing hybrids were also higher yielding than later sown crops and slower maturing genotypes. It is concluded that using early maturing hybrids and early sowing dates are both viable options to manage the risk of frost in maize crops grown in Tasmania.