Australian Mungbean Association

Australian-grown mungbeans have quality written all over them!

Irrigation

Mungbeans are highly efficient users of water and usually do not respond to irrigation during podding. They are sensitive to excessive waterlogging and the importance of good layout and drainage cannot be over-emphasised.

Waterlogging events lasting more than five days can cause root nodules to die back, often causing nitrogen deficiency problems in the crop.

 

Furrow irrigation

The following irrigation strategies have been developed to help minimise the impact of waterlogging in pulse crops.

  • select fields with reasonably steep grades
  • fields should not have any low spots. Ideally, they should be laser-levelled
  • form-up high volume hills or beds which drain quickly after rain
  • select fields with short runs (200–400 m)
  • an efficient tailwater system to rapidly drain water away from the paddock
  • irrigate down every second furrow
  • apply water quickly, preferably in 4–8 hours by adjusting the number of siphons per furrow
  • irrigating after light rain can speed up irrigation time
  • the first irrigation should be applied before soil cracks open right up

Nitrogen fertiliser can be used to offset the effects of waterlogging. This can be applied as a foliar urea spray prior to irrigation, or as 15–25 kg urea/hectare in the irrigation water (water run).

Being relatively quick maturing, one of the major advantages of mungbeans is their low water use and relatively high financial returns per megalitre.

A strategy of irrigating at planting and then at budding has been found to be most cost-effective in many situations.

Other points to consider:

  • Crystal offers greater yield potential than other varieties
  • narrow rows will maximise yields under favourable conditions
  • a plant population of at least 30/m2 will maximise yield
  • higher yields will be achieved on 2 m beds than on 1 m hills. The high lodging pressure on 1 m hills can reduce yields by up to 300 kg/ha.
  • irrigating too early can delay or inhibit nodulation
  • the short duration of current varieties places a ceiling on achievable grain yield
  • coordinate irrigation with insect control strategies.

Irrigating too early in the growth of the crop will encourage excessive vegetative growth. The preferred strategy is to pre-water and then plant on a full profile of soil water. The first in-crop irrigation is usually best applied around seven days before the start of flowering, i.e. 30–40 days after planting.

On the heavy black earths (Darling Downs, Emerald, Liverpool Plains), one in-crop irrigation applied around flowering is usually sufficient to achieve reasonable yields. On the lighter grey clay soil types, two irrigations may be required with flood irrigation systems.

Avoid growing hard-seeded lines such as Emerald under irrigation as the hard seeds can cause volunteer problems in cotton farming systems.

 

Spray irrigation

This is an option in some areas and has the advantage of allowing smaller amounts of water to be applied more frequently. This helps reduce waterlogging and can lift yields. Avoid heavy spray irrigation of young plants as the caked-on dirt from mud splash can reduce growth and thin the plant stand (especially in crusting soils). Approximately 50 mm of water per week will normally be required during flowering and pod-fill.

 

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