Forage-based dairying in a water-limited future: Use of models to investigate farming system adaptation in southern Australia

Abstract

The irrigated dairy industry in southern Australia has experienced significant restrictions in irrigation water allocations since 2005, consistent with climate change impact predictions for the region. Simulation models of pasture growth (DairyMod), crop yield (Agricultural Production Systems Simulator, APSIM), and dairy system management and production (UDDER) were used in combination to investigate a range of forage options that may be capable of sustaining dairy business profitability under restricted water-allocation scenarios in northern Victoria, Australia. A total of 23 scenarios were simulated and compared with a base farm system (100% of historical water allocations, grazed perennial ryegrass pasture with supplements; estimated operating surplus $A2,615/ha at a milk price of $A4.14/kg of milk solids). Nine simulations explored the response of the base farm to changes in stocking rate or the implementation of a double cropping rotation on 30% of farm area, or both. Five simulations explored the extreme scenario of dairying without any irrigation water. Two general responses to water restrictions were investigated in a further 9 simulations. Annual ryegrass grazed pasture, complemented by a double cropping rotation (maize grown in summer for silage, followed by either brassica forage crop and annual ryegrass for silage in winter and spring) on 30% of farm area, led to an estimated operating surplus of $A1746/ha at the same stocking rate as the base farm when calving was moved to autumn (instead of late winter, as in the base system). Estimated total irrigation water use was 2.7ML/ha compared with 5.4ML/ha for the base system. Summer-dormant perennial grass plus double cropping (30% of farm area) lifted operating surplus by a further $A100/ha if associated with autumn calving (estimated total irrigation water use 3.1ML/ha). Large shifts in the forage base of dairy farms could sustain profitability in the face of lower, and fluctuating, water allocations. However, changes in other strategic management policies, notably calving date and stocking rate, would be required, and these systems would be more complex to manage. The adaptation scenarios that resulted in the highest estimated operating surplus were those where at least 10 t of pasture or crop DM was grazed directly by cows per hectare per year, resulting in grazed pasture intake of at least 2 t of DM/cow, and at least 60% of all homegrown feed that was consumed was grazed directly.

Management opportunities for boosting productivity of cool-temperate dairy farms under climate change

“…Growth is restricted during winter due to low temperatures and in summer primarily due to insufficient rainfall, occasional heat waves and high vapour pressure deficit (Chapman et al, , 2011(Chapman et al, , 2012Cullen et al, 2009;Doyle et al, 2000). In north-western Tasmania, perennial ryegrass is generally most productive in spring as temperatures climb after winter and pastures utilise frequent rainfall and soil water that often accumulates over winter.…”

Year-Round Forage Yield Stability through a System Combining Triple-Maize Crops with Winter Barley in Kyushu, Japan

“…In southern Australia, irrigation on dairy farms has been restricted since 2005, consistent with anticipated climate change impacts. Annual-ryegrass grazed pastures, complemented by a double maizeBrassica or ryegrass rotation on 30% of the farm area, were estimated to lead to an operating surplus, combining with halving irrigated water use (Chapman et al, 2012). In northern China, wheat-maize double cropping has been innovated by intercropping watermelon with maize to get more than a 50% gross margin, though at higher irrigation and labor input, which should alleviate rural poverty in the region (Huang et al, 2015).…”

Use of the Comprehensive Climate Index to estimate heat stress response of grazing dairy cows in a temperate climate region

“…In our study visual observations were only undertaken until 20 : 00 h. In general, cattle reared in temperate zones are not used to experience heatwaves regularly. Thus, changes in behaviour must be evaluated further since high temperatures are expected to increase due to climate change in the coming years (Chapman et al ., 2012; Gauly and Ammer, 2020). We observed a decrease of overall activity during the hottest hours of the day (12 : 00 and 18 : 00 h), which agrees with other reports (Cook et al ., 2007; Allen et al ., 2015).…”