WORDS AND IMAGES SUPPLIED BY HEATHER CHALMERS, FOUNDATION FOR ARABLE RESEARCH.
North Otago mixed arable farmer Peter Mitchell says he is reconsidering where ryegrass fits in his rotation and is looking for ways to extract more value from the crop.
With limited crop options, ryegrass has been a “poor man’s break crop” on his farm before going into wheat, Peter says.
The rolling downs property near Oamaru grows wheat, barley, ryegrass, and radish, as well as sunflower and canary seed for the family’s bird seed business. About 140 beef cattle are finished as well as 4000 to 5000 lambs in winter.
Other potential crop options like maize or clover seed can’t be grown because the farm’s location doesn’t have the heat units for reliable economic yields and heavy clay soil makes harvesting difficult. The heavy clay also rules out peas. Burning of crop residue is not an option because of the number of lifestyle blocks and roads near the farm.
In a presentation at FAR’s ARIA event at Chertsey, Peter said he was interested in the results of a FAR project aiming to extend the value of ryegrass seed crops by adding legumes into post-harvest regrowth. While he hasn’t tried this, he is looking at ways to increase winter feed quality in post-harvest ryegrass, while reducing the weed burden and his N fertiliser spend for the following crop.
On his farm, ryegrass, as a break crop, is failing to control grass weeds, particularly hairgrass and brome grasses, and now increasingly ryegrass itself, Peter says. “We have had a rethink of where ryegrass fits in our rotation.”
Ryegrass is now kept for 18 months, rather than the previous 12 months, and utilised for lamb finishing after harvest.
“An advantage of this is that we get a big strike of hairgrass in winter which is grazed by lambs.”
The challenge is the current low trading margin for lambs, although in most years it is profitable.
Nitrogen is applied at about 80 to 100 kg N/ha after harvest to boost ryegrass regrowth.
Terminated in late spring with glyphosate, the former ryegrass crop is usually sown in summer forage rape for grazing. However, this year a small paddock has been sown in Balansa clover to gauge how much nitrogen the N-fixing legume will contribute.
“It is important from an economic point of view to know what amount of N is being fixed. “We also want to see whether we will get better weed control in the following crop.
“For 12-month ryegrass, we are relying too much on the chemical drum and there is still too much carry-over of weeds.
“On one side of the paddock we had ryegrass which had been carried over and grazed in the winter then cut for silage in spring and early summer, while the other side was grazed in the winter and then terminated and planted in summer rape for grazing. The grass weed pressure in the following wheat crop was significantly less in the summer rape rotation, so this is encouraging.”
An extreme solution in some years may be to quit ryegrass seed production and only grow a ryegrass, white clover pasture for grazing and/ or silage, so it never seeds. However, it is a question of what gives the best return.
Peter says that when he did the sums four years ago, the seed option made more than silage. “But if we could add some N through N-fixing and get that benefit then maybe this tips the balance financially.”
This year he has tried spinning clover on before harvesting ryegrass, to see how the clover might establish with the ryegrass following harvest.
Managing herbicide resistance is a big challenge for arable growers, he says.
“While acknowledging that average wheat yields have increased, I remember in the mid-1990s when I grew a crop of wheat that only needed three sprays – one herbicide in autumn, one wild oat spray in spring and one flag leaf spray and job done, but it’s completely different now.
“My view is that we need to introduce more cultural controls and consider wider and more diverse rotations, but at the same time remain profitable.
“We need to know the benefits that grazing and adding legumes to ryegrass post-harvest will give the following crop and the bottom-line financials. There is a challenging future in relying solely on herbicides.”
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