Use of the Enviroscan MULTI™ to Monitor the Basic Seasonal Water Requirements of Allium Cepa Grown in South Australia.

The use of soil water measurement technologies is steadily increasing in commercial agriculture as awareness of the direct and indirect costs of water become known to food industry operators. There is a plethora of examples of water usage optimizations in every crop. What is not always clear is a direct link between yield outcomes and the chain of management decisions taken. Through the use of many different measures and crop inputs, it is sometimes possible to show individual benefits. However, for the grower, such measures are often not practical from a commercial stand-point. Described here is an example where the most basic environmental parameters were used to gain increased understanding and management benefits for a commercial onion crop grown under centre pivot irrigation.

Electronic sensors were strategically placed within and outside the crop, recording the soil water, soil salinity, soil temperature, air temperature, irrigation and rainfall levels in the one electronic data-logging system (EnviroSCAN MULTI™). This data was collected on a continuous basis, day and night, for the complete growing season and was then correlated with evapotranspiration (ET_o) data from a nearby government weather station.

It was possible to study the plant soil water extraction dynamics due to the developing growth stages and changing environmental conditions and to observe the salt leaching effects of natural rainfall.

By focussing on the daily water use of the plant, it was also possible to show periods of stress experienced by the plants through the use of an Evapotranspiration Stress Index (ETSI) calculation.

Taken together, these measured parameters aided in the decision-making processes throughout the growing season and in the lead-up to harvest.

Key words: allium, water, ET, salt, stress, ETSI.