Determining varietal water and nutrient requirements in almond trees in the Murray Darling Basin to optimise plant functioning and mitigate stress responses such as Monterey leafing failure

Almonds are among the highest value and most water hungry crops grown in the Murray–Darling Basin, leaving growers increasingly exposed as water becomes scarcer, more variable and more expensive. This PhD project asks a deceptively simple question: do different almond varieties really need to be irrigated and fertilised in the same way? By measuring how key commercial varieties use water, nutrients and their own stored energy, it aims to give growers variety-specific management strategies that save water, protect yield, and reduce the risk of costly stress disorders such as Monterey leafing failure.

About this project

Why. Almond production is one of the largest and most valuable horticultural industries in the Murray–Darling Basin (MDB), yet it is highly water intensive in a region defined by drought and climatic variability. Most orchards are still managed with generic; one size fits all irrigation and fertiliser recommendations that overlook how individual varieties use water and nutrients wasting water, eroding returns, and leaving trees more vulnerable to stress. Chief among these stresses is Monterey leafing failure, an increasingly common and economically damaging disorder in which dormant buds fail to develop into shoots. Although the cause remains poorly understood, emerging evidence in Australia and California points not only to drought, but also to waterlogging and over irrigation, to depleted carbohydrate reserves after heavy crop loads, and possibly to secondary pathogens.

What. The project determines the variety-specific water, nutrient (nitrogen and potassium) and carbohydrate requirements and the water and nutrient use efficiency of key commercial cultivars grown in the MDB, including Nonpareil, Carmel and Monterey. It identifies the physiological and soil thresholds that trigger stress and leafing failure, with particular attention to how waterlogging, root hypoxia and carbohydrate reserves interact around bloom and leaf-out.

How. Replicated field trials in a commercial MDB orchard combine contrasting irrigation, nutrient and crop load regimes. Trees are monitored across the season using stem water potential, gas exchange, leaf and soil nutrient analysis, non-structural carbohydrate sampling, in soil oxygen and moisture sensors. These data feed statistical analysis and process-based models that translate into practical, variety-specific irrigation and fertiliser guidelines for growers.

Expected Outcomes

The project will deliver evidence based, variety specific best management guidelines that help almond growers lift water and nutrient use efficiency, cut input waste, and reduce the risk of leafing failure and other stress disorders. By clarifying what triggers Monterey leafing failure, it will give industry a proactive tool to protect yield and profitability under a drying climate and provide a transferable framework for managing other high value irrigated perennial crops across the Basin.