Adaptations for raising the productivity and profitability of irrigated grains enterprises under future climates
Creators: name: Muleke, Albert
Publisher: name: University of Tasmania
Year: 2024

description: Contemporary scientific literature is laden with evidence suggesting that unabated climate change will have detrimental implications for food security. Australia is expected to experience some of the most severe impacts of the climate crisis, although most previous work has focussed on rainfed farming systems. These trends underscore a need to develop sustainable adaptations that mitigate detrimental impacts of future climates on irrigated agriculture.<br>The thesis first reviewed the impact of climate change on the productivity and profitability of irrigated grain cropping systems. This revealed that average Australian irrigated yield gains plateaued in around 2002, and since then have stagnated. The assessment uncovered a cruel irony that despite having the ability to alleviate water stress, irrigated grain farmers are still reliant on rainfall. The review suggested that integrated and contextualised whole-farm packages, including agronomic, financial and engineering interventions have potential for improving the profitability and water-use efficiency of irrigated crops. In addition, appropriate decision support systems and digital tools may help navigate the complexity of decisions facing farmers for improving economic resilience and reducing climatic risk.<br>One avenue for improving grain production under a changing climate from the review was optimisation of crop flowering times. As such, Chapter 3 examined effects irrigation on the optimal flowering periods (OFPs) of barley, durum wheat, canola, chickpeas, faba bean and maize under climate change, these being prominent crops in the Australian broadacre cropping regions. Chapter 3 revealed that (1) irrigation broadens OFPs, providing greater sowing time flexibility and likelihood of realising potential yields compared with dryland conditions and, (2) for irrigated winter and summer crops, the most preferable maturity durations for maximising yields are early-sown long-season (late) and late-sown short-season (early) maturity types, respectively.<br>To help irrigated grain growers navigate the solution space for tactical and strategic economic decisions, we then co-developed and tested a digital decision framework - WaterCan Profit in Chapter 4. Here, the thesis assessed tactical climate change interventions by optimising manifold variables that drive farm-scale profitability of irrigated grains enterprises. This chapter showed that crop types with (1) higher value per unit grain weight, (2) lower water?use requirements and (3) higher water-use efficiency were more conducive to improving the sustainability and prosperity of irrigated grain production systems under future climates.<br>Chapter 5 details an analysis of long-term (strategic) adaptations to climate change using WaterCan Profit. This chapter examined four whole-farm adaptations (Baseline, Diversified, Intensified and Simplified) and four types of irrigated infrastructure (Gravity, Pipe &amp; Riser, Pivot and Drip) as strategic investments to adapt to climate change. Key findings revealed that: (1) when assessing whole-farm profit, metrics matter: Diversified systems generated higher profitability than Intensified systems per unit water, but not per unit land area; (2) gravity-based irrigation infrastructure required the most water followed by sprinkler systems, while Drip irrigation use the least water; (3) whole-farm adaptation had greater impact on productivity compared with changes in irrigation infrastructure; and (4) only whole-farm intensification was able to raise profitability per hectare under future climates.<br>While previous chapters examined adaptations to climate change, Chapter 6 examined how these adaptations impacted greenhouse gas emissions, and thus their contribution to global warming. In particular, we examined how the whole farm adaptations described in chapter 4 impacted on soil organic carbon (SOC) levels and long-term SOC accrual and net greenhouse gas (GHG) emissions. We found that the potential for improving SOC stocks exists in contexts where antecedent stocks are low (&lt;1%), which may include regions with degradation, chronic erosion and/or other constraints to vegetative ground cover that could be sustainably and consistently alleviated. In contrast, little potential for SOC accrual was evidenced where antecedent SOC stocks were high. This chapter helped clarify some of the confusion amongst practitioners as to how a given practice change may impact on SOC accrual of rainfed and irrigated cropping systems.<br>We concluded that while future climates will challenge the productivity and profitability of irrigated grain cropping systems, appropriate economic, agronomic, technological and environmental interventions may help mitigate detrimental impacts and, in some cases, improve profit. Demand-driven decision support systems can help practitioners determine whether tactical (e.g., changing flowering times) or strategic (e.g., investing in irrigation infrastructure) would best suit their needs. Future adaptation studies may benefit from inclusion of social assessments, such as factors influencing farmer adoption. Taken together, such studies would be expected to help realise sustainable, profitable and resilient outcomes in future.