Understanding irrigation requirements

25 May 2015 | AgFirst | Australian Fruitgrower / Future Orchards® article

Effective irrigation depends on understanding both what the crop is likely to require and what is actually happening in the orchard. This AgFirst article recommends using soil-moisture monitoring together with a basic water budget rather than relying on either tool alone.

A water budget accounts for evapotranspiration, rainfall, irrigation applied and an appropriate crop factor. The article notes that mature apple and pear trees commonly use a crop factor around 0.7, while stressing that the appropriate value varies with canopy, planting system, irrigation design and local conditions. OrchardNet® can be used to compare irrigation, rainfall and evapotranspiration over the season.

Three case studies show why cross-checking matters. One well-managed Cripps Pink block produced more than 99 t/ha with average fruit size of 172 g. In an under-watered Gala block, gross production fell from 43 to 28 t/ha and average fruit size from 160 to 141 g. A Fuji block that was over-irrigated reached yield and fruit-size targets but had poor dry matter and colour.

The article’s practical message is to use water budgeting to plan and check irrigation, then use soil-moisture observations to fine-tune the schedule block by block.