Katherine Dunsford1, James Nuttall1, Roger Armstrong1 and Garry O’Leary1
1 Agriculture Victoria, 110 Natimuk Road, Horsham, Victoria, 3400, email@example.com
Recently, there has been renewed interest in long (18-month) fallowing as a means of managing risk in Australian dryland cropping systems. Traditionally, wheat was grown after long fallows, however, given the high commodity value and rotational benefits of crops such as canola and pulses, the contribution of long fallow to additional yield potential warrants exploration. We used a crop simulation modelling approach to assess the yield benefits of growing canola (Brassica napus), lentil (Lens culinaris) and wheat (Triticum aestivum) after either an 18-month fallow or wheat crop (i.e. 6-month fallow) using initialisation data from a long-term rotation experiment (Sustainable Crop Rotations In Mediterranean Environments; SCRIME) in the Wimmera region of Victoria. Secondly, we simulated a three-phase rotation to see whether the benefits of fallow would persist beyond the first season. Long fallowing provided large yield benefits to wheat (17%) and canola (14%) and to a lesser extent in lentils. Additional soil water was observed (31 mm) after fallow/lentil. The soil water and nitrogen benefits of the fallow/lentil rotation persisted to third phase wheat crop and increased yield. On average, however, continuous cropping including a pulse crop (i.e. wheat/lentil/wheat) yielded more but was subject to greater risk of crop failure. Consequently, given the high value of canola and lentil, it is worth considering the benefit of using a long fallow ahead of these crops to maximise yield potential and stability. Next steps include assessing the net economic benefit of these proposed rotations, where long fallow equates to lost income in that year.