To avoid crop losses associated with under-watering, growers may routinely overwater. This not only represents a system inefficiency (which is difficult to justify if irrigation supplies are limiting) but can decrease crop growth/quality since inadequate substrate aeration stimulates root production of the plant hormone ethylene. Ethylene limits vegetative growth, stimulates leaf senescence and causes flower/fruit abscission. Reasonably porous growing substrates may overcome this problem, but the lack of a technique to measure rootzone ethylene production prevents identification of suboptimal growing conditions. Recent technological advances now permit on-line rootzone ethylene measurement to quantify ethylene fluctuations in response to soil moisture dynamics. Thus the success (or otherwise) of management techniques (eg. automatic irrigation scheduling, rhizobacterial treatments) to limit ethylene production can be assessed.