Irrigated peanuts: It only hurts a bit

Kevin Norman: irrigation essential to achieve yield potential.

Even peanuts need to be put under a bit of stress to achieve top performance. But not too much, not too little and at the right time!

Kevin Norman, North Queensland-based agronomist with the Peanut Company of Aust-ralia (PCA), told advisers at the GRDC-sponsored Kingaroy Research Update seminar about the latest techniques in peanut irrigation.

He said peanuts have natural drought tolerance and water efficiency that can be tricked into helping produce top yields.

The trick was to apply water stress by limiting irrigation as a peanut crop began the stage of vegetative growth before peg initiation, "persuading" the peanut plants to put more effort into nut production and less into plant structure.

Experiments in North Queensland had achieved the same stress effect with light applications of herbicide to slow the growth of peanut plants.

Once pegging — the start of the exponential growth phase of the plant — began, a peanut crop would maximise yield only if it was never short of moisture.

Growers should try to fill the soil profile at that time — centre pivots perhaps needing two or three revolutions in quick succession.

"Then keep topping it up," advised Mr Norman. "Keep the soil environment constant if you can. If you start and stop you increase the potential for disease, such as white mould."

Irrigate but don't overdo it

He said irrigation is essential to achieve yield potential, quality and maximum profitability. It also reduces risk of crop failure and aflatoxin development. Irrigation is the single most important key to yield; it can deliver 7 t/ha under full irrigation management.

Mr Norman said even supplementary irrigation — just two or three wettings — in a good season on the Atherton Tableland boosted yields from 5 t/ha to 6.2 t/ha with very little extra cost.

However, another North Queensland trial — applying twice as much irrigation as the regular schedule called for — failed to deliver any extra yield, proving again that peanuts are a very water-efficient plant.

Start your crop on good soil moisture

An irrigated peanut crop should be established on good soil moisture — preferably a full profile — because a peanut seed would take up 50 per cent of its own weight in water for germination.

"We need to use the available tools and information like the DPI Q-NUT model to know how much water is in the soil during the life of the crop," Mr Norman said.

"I like to start farmers with an evaporation plan as the start of a water budgeting system. They are simple to use and generally deliver a greatly improved understanding of what is happening to moisture."

Field Intelligence

Kevin Norman, agronomist with the Peanut Company of Australia (PCA), sees a technologically advanced future for the irrigated peanut industry, including:

  • precision farming, using computer and satellite technology to treat different areas of paddocks according to their needs
  • "chemigation" and "fertigation", efficient systems, particularly for the application of fungicide against Sclerotinia in peanuts; variable rate applications possible
  • irrigators with computer-aided management systems, the computers programmed for one or more paddocks and operated from a base station through remote links like mobile telephones
  • low energy, precision application of irrigation, reducing losses from wind and evaporation
  • trickle irrigation, already in use by some farmers and delivering water savings of up to 40 per cent and lending itself to permanent beds
  • soil-moisture monitoring tools like Environscan and Gopher.

Region North, South, West