Tests to find suitable pasture species mixes on a Waikato farm have produced some unexpected results. By Delwyn Dickey.

The bright and colourful flowers that follow the sun may lift your spirits, but sunflowers in forage crop mixes add little food value to summer pastures.

That was one of the takeaways from recent trials looking at different seed mixes for more resilient summer forage crops.

And while the trial was aimed at feed for dry stock cattle on hill country farms it also had relevance for northern dairy farmers who are experiencing similar problems with feed shortages in summer more often.

“The focus was on designing a mix that had different characteristics that we thought would be important for what we wanted to achieve,” AgResearch Senior Scientist Dr Katherine Tozer says.

“High energy in mid to late summer, good root systems that could explore different parts of soil profile for water and nutrients, and at least one species in the mix that would be rapid to establish and provide really good ground cover to help reduce summer grass weed emergence and establishment.”

Feed pinches in the heat of summer are becoming more common in northern Waikato and up through Northland. Farmers being able to grow their own high-quality feed from resilient forage crops rather than relying on imported supplements, deferred grazing, or single-graze brassica crops could help make farm systems more robust as climate variability increases.

Home-grown forage should also help provide more food security when issues crop up in the global supply chain as seen recently with high import costs of palm kernel in relation to Covid 19, and high fertiliser prices connected to Russia’s war on Ukraine.

A summer crop should provide more nutrition than pasture, which may be poor quality at that time of year. While monoculture brassica crops provide good quality feed they don’t provide as much ground cover as pasture, which increases the risk of phosphorus and nitrogen leaching into waterways, as well as sediment in runoff.

Having variety should also counter some of the metabolic issues that can show up in cattle when only feeding on mono-culture crops.

Run by AgFirst consultant and farmer Phil Weir and AgResearch scientists including Katherine, and Tracy Dale, and with funding from Our Land and Water National Science Challenge, the trial was established on Phil’s finishing property at Te Pahu in the Waikato.

With less of an appetite for bobby calves in the dairy industry the study has now taken on an added dimension for Phil.

“There are going to be more young dairy cross stock grown on in the future,” he says.

Phil is now keen to find relatively easy summer crops that will help take young animals of around 100kg through to 200kg liveweight.

Phil ran dairy calves on the multispecies crops in the trial, with heifers on the monocrops.

While there are many different aspects of what a successful crop could look like, for Katherine, this study was fairly narrow – focusing on the agronomics of the mixes. This covered herbage production, metabolisable energy (ME), weed incursion and production costs.

Kicking off in September 2021, a range of simple four species mixtures along with a couple of hyper-diverse mixtures containing more than 10 species, was compared with a brassica monoculture.

Ideally, they also wanted to see reduced chemical use or no spraying at all.

Rape – a brassica – was the monoculture crop and was also used in the simpler mixes along with a cereal – oats, plantain for ground cover and red clover.

By the time the trial came to an end there had been some surprising results and some lessons learned.

The red clover seed had thrown a small spanner in the works when it failed to germinate. This saw the four-seed mixes performing as three-seed mixes.

While the spring rains got the crop up and running as expected, it turned out to be a very dry summer with little further rain. This may have been behind the plantain failing to contribute drymatter through summer but taking off in late February for a second grazing.

The 21-species mix wasn’t popular with Phil or Katherine.

“A lot didn’t establish and didn’t perform,” Katherine says. “There was also a high proportion of yield from sunflowers – but they’re poor in terms of feed value. Overall in feed value it’s quite limited.”

While cattle will eat the leaves they will sometimes avoid sunflower stalks if there is other feed available, she says.

“The cost of producing metabolised energy with the 21-species mix was more expensive than the rape monoculture because the cost of the seed is so expensive. Even with no weed or pest control, it was still more expensive because of the seed costs.”

The oats proved to be a star performer for suppressing weeds but went to seed well before the rest of the forage, and was in poor condition by the time the stock were put on in mid-January. Both Tozer and Weir agree Triticale might be a better cereal option in the future instead.

There were other surprises.

“Rape is usually grown as a monoculture,” Katherine advised. “In the monoculture trials versus the mixed crops we found rape in the mixture was quite susceptible to being out-competed by the other species and producing a small plant. So, we had to keep a high proportion of it in the mix, to ensure it contributed a biologically significant amount of energy to the mix,” she says.

The oats were also star performers when it came to sowing rates. In one mix they found they could drop back the recommended monoculture sowing rate to about 30% or less, before its contribution to the total yield started dropping off.

“It was very interesting,” Katherine says.

A reduction in the ability to control pest grasses using chemicals was one of the biggest issues for Phil. Having grasses in the mixes meant he wasn’t able to control the rise of other summer grasses that acted as pest weeds, suppressing wanted species.

A positive of having the cover crops in the ground meant when they were grazed off in autumn and when the time came to bring the paddocks back into the grazing round, Phil didn’t need to spray out as he would with a monoculture crop, and simply drilled in Italian ryegrass. This saw the ground continuously covered.

In hindsight Phil reckons they should have used kale instead of the rape, as kale is more flexible with when it can be grazed.

If he were doing another summer crop this spring, Phil reckons he would sow a kale crop. “Keep it clean using chemicals and then just before canopy closure spread fertilizer with chicory seed in it.”

Key findings:

  • Simple mixtures provided a viable alternative to a brassica monoculture based on energy yield and energy costs. The most promising option was a simple rape-dominant mixture which contained rape, plantain and a cereal. It had a high energy yield, low weed abundance and a low metabolisable energy cost.
  • Hyper-diverse mixtures did not provide energy yield or energy cost advantages when compared to a simple mixture.
  • Plantain contributed little to total drymatter in mid-summer but provided forage at the end of February for a second grazing.
  • The cereal established rapidly and reduced weed ingress in the rape-dominant mixture harvested in mid-summer.
  • A diverse mix may have lower weed ingress, but herbicide options are also limited.

Katherine emphasises that while the results are interesting, this was one summer trial on one farm. More research on more farms over several years is needed, she says.

  • Also involved with the project are Agricom New Zealand, PGG Wrightson Seeds, and Farmlands Co-operative Society.