During low allocation years water use efficiency (WUE) of maize is a real plus and with good management many hybrids can be expected to have a WUE of 1.7 to 2.0 tonnes per megalitre of applied irrigation water.

Most maize growers will budget to use eight to nine megalitres of applied water to grow a maize crop with furrow irrigation systems.

"Trial work over the last few years has shown further water savings can be made with all irrigation systems – furrow, spray and drip – on maize grown in the Riverina on five to six megalitres of applied irrigation," district agronomist at Coleambally, Kieran O’Keeffe, said.

"These savings have been made through better soil moisture monitoring and more precise scheduling."

Mr O’Keeffe said district agronomists and irrigation officers had been working with growers to increase the adoption of soil moisture equipment in both summer and winter crops.

"Use of soil moisture probes helps fine tune irrigation timing and can lead to increased water use efficiency," he said.

Even though maize makes efficient use of water, it is considered more susceptible to water stress than other summer crops such as sorghum, because of its unusual floral structure with separate male and female floral organs and the near same time development of florets.

"Maize has different responses to water deficit according to development stages," Mr O’Keeffe said.

"Drought stress is particularly damaging to grain yield if it occurs early in the growing season when plant stands are establishing, at flowering, and during mid to late grain filling."

At the seedling stage, water stress is likely to damage secondary root development.

During stem elongation leaves and stems grow rapidly, requiring adequate supplies of water to sustain rapid organ development.
Water stressed plants are shorter and with reduced leaf area.

Three weeks after the crop emerges is a critical stage for yield when the maize ear is setting the maximum number of kernel rows around the ear.

The following weeks before flowering will determine the length of the ear.

The most critical period for water stress in maize, however, is 10 to 14 days before and after flowering, with grain yield reduced two to three times more when water deficit coincides with flowering, compared with other growing stages.

During this period, ear growth is susceptible to competition from other organs that are still growing, often leading to low grain numbers per ear and occasionally barren ears.

Contact Kieran O’Keeffe, Coleambally, (02) 6960 1300, kieran.o’keeffe@dpi.nsw.gov.au

Further reading

Water research

Maize disorders: the Ute Guide (book)