Legumes have time in the sun

A promising summer legume is on trial in Meckering and could be the key to prolonging the wheat on wheat rotation.

Summer cropping might not be the norm for Meckering farmland, but after three times his average spring rainfall Ray Fulwood took the seeder bar out of the shed and into the paddock.

As well as sorghum and French white millet, Ray and his partner Wendy have sown 100 hectares of cow peas off the back of 150mm of rain between September and the end of November.

Cowpeas are a common summer crop across areas of subtropical Asia and Africa and in Australia are grown mostly in New South Wales, but they're not often seen in WA's Wheatbelt.

WA No-Till Farming Association (WANTFA) research manager Matthew McNee is monitoring the trials and said cowpeas were chosen because they were very drought-tolerant and under the right conditions, good fixers of nitrogen.

"If you got the maximum growth out of these observed in other marginal summer cropping environments, say two tonnes a hectare of dry matter, that's equivalent to about 40kg of nitrogen per hectare that could potentially become available to crops in subsequent seasons," he said.

"Development of a farming system where it is possible to establish cowpeas in most years could reduce fertiliser requirements or allow more wheat crops to be grown in succession.

"An additional benefit might be a soil disease break for wheat similar to that reported when canola is grown before wheat."

Difficulties accessing seed meant the peas weren't sown until a week before Christmas and have had little rain since then, just a couple of millimetres, but are still actively growing on stored moisture.

Two varieties are being trialled - Red Caloona and Black Stallion.

"Both varieties were planted in blocks on both wheat and canola stubble," Ray said.

"The wheat had more visible moisture at seeding and better establishment.

"Our JD Conservapak seeder bar sows to the side of the main tine into undisturbed moist soil and not into the dry soil in the wake of the main tine."

The cowpeas on wheat stubble has thus far out performed those on canola stubble and Ray intends to sow wheat on wheat this season.

A summer legume gives Ray the option replacing summer weeds with a manageable cowpea and using available soil water throughout the year more efficiently.

"We've had no sheep for three years so we don't have any pasture legumes and lupins aren't terribly profitable, only about 15 to 20 per cent of our cropping area is lupins or peas," he said.

"So our legume input is quite low and it seemed the obvious question to ask was - can we grow something over summer on opportunity rain?

"My farming philosophy is to keep the soil covered with plant residues at all times of the year to prevent erosion.

"There is a huge need for summer legumes in WA that are tough as melons and caltrop and will contribute organic nitrogen to our cropping system (but) most research is directed towards grazing animals."

Mr McNee said to be a real success the peas would either have to demonstrate a yield benefit for following crops or allow additional wheat on wheat rotation.

"That would be where you make money out of it, if you could grow it successfully enough so instead of two wheat crops in a row or three, you might get four," he said.

"If you had a productive legume over summer it means you've got one more option to cover your soils and reduce erosion.

"It also means you've got cheap nitrogen when fertiliser prices are getting higher and higher.

"I don't think we'll ever get to the point where you're sowing major areas, mainly because of the logistical problems that presents with harvest and climate variability, but as a tactical option, it would be very significant."

Ray admitted that having the header, seeder and boomspray all going at the same time was a logistical nightmare and said he was already thinking about how it might be done easier.

"We're thinking about trying to sow the cow peas with the wheat and seeing if they will come up in October to try and minimise any input costs, so you get a cheap source of nitrogen," he said.

Summer weeds haven't proven a problem in the cowpeas so far, but Ray believes if they had have been sown in October it might have been a different story.

Mr McNee said in his experience with cowpeas in a marginal summer cropping zone in New South Wales showed they could be grown on 60 to 80mm of in-crop rainfall after harvest, but may also survive well on stored soil moisture after spring rainfall as was the case at Ray's farm this year.

He also said more frequent wet summers could see summer crops increasing.

"With climate change it is expected that there is going to be more summer rainfall, so perhaps these options are going to become viable more frequently than what they once have been," Mr McNee said.

"We're always just testing them out and trying to be ahead of the game so that farmers have options to take advantage of opportunities should they eventuate."