By Delwyn Dickey for the Our Land and Water National Science Challenge
Phil Weir is a busy man. Along with running a family drystock farm in the Waikato he is also a farming advisor with AgFirst and has recently completed a Nuffield Scholarship.
With a changing climate that is becoming more variable, and seeing warmer and drier summers with droughts becoming more common in northern Waikato and Northland, Weir sees a need to move farm systems away from using supplements over these drier months.
“Every time you turn on your tractor to feed out, in a drystock context you’re losing money,” he said.
His operation grows dairy and dairy-beef calves year round. Summers have become tough as pasture quality suffers in the dry and the heat.
“Summers are hard for all animals, but particularly on calves,” he said. “Trying to increase their weight from 100kg to 200kg over the first summer can be difficult.
“All the options available for feeding in summer create an imbalance in your workload. You’re losing your repair and maintenance time or having to take on casual staff. Ideally we’re looking for an in situ crop instead,” he said.
Weir sometimes grows a monoculture crop like kale for his animals. He hopes that adding multiple species of plants that grow well in the area will result in less pest pressure, less weed burden, less spraying and more dry matter. Less tractor use would also mean lower emissions.
Weir believes that with more calves likely to be coming onto the market due to Fonterra signalling changes with bobby calves, there needs to be a way of making it easier. This is what prompted him to get involved with AgResearch scientists Katherine Tozer and Tracy Dale to find summer-safe multispecies mixes for summer forage crops as part of a Rural Professional Fund project funded by Our Land and Water, with trialling carried out on his farm.
The study was narrow, focusing on the agronomics of the various mixes. A range of simple four-species mixtures, along with a couple of hyper-diverse mixtures containing over 10 species, were compared with a brassica monoculture.
The most diverse mixture included 21 species: rape, oats, plantain, red clover, cocksfoot, prairie grass, chicory, tall fescue, meadow fescue, sulla, sunflower, perennial ryegrass, hybrid ryegrass, lupin, lucerne, timothy, strawberry clover, crimson clover, balansa clover, white clover and vetch. The 11-species mixture included: rape, plantain, red clover, chicory, buckwheat, phacelia, pea, crimson clover, white clover, vetch and Triticale kudos.
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.
Preparation for the trial involved spraying off the site with a mixture of both a non-selective herbicide and insecticide, with fertiliser applied a week later. Discing, power harrowing and rolling followed.
In mid-October, multiple plots of about 20sqm were established. Seeds were drilled in at a depth of 1cm with a width of 1.5m and row spacing of 15cm.
There were multiple plots, including a monoculture plot of rape, oats, plantain and red clover. Some had each of the species dominating the mix at a ratio of 61% by weight and 13% for each of the rest. Another had equal amounts of the seed. As there were concerns some of the seed could be buried too deeply, this wasn’t rolled. Diammonium phosphate was hand broadcast and an application made of Slugout.
The seed bed on the two paddock-scale case studies, which were about 1.3ha in size, was prepared the same way as the smaller plots. A Kuhn Triple disc drill was used to sow seed in the paddocks. The first paddock was rape-dominant with the second the 11-species mix.
Sprays to control broadleaf weeds and insects were used in November with the monoculture rape crop sprayed for white butterfly in January.
It became clear things weren’t going quite to plan when the red clover seed had a very low germination rate – less than 25% compared to well over 70% for the other seeds, and 97% in the case of oats. This saw the four-seed mixes become three-seed mixes. This would normally be picked up through emergence testing of the seed in a glasshouse prior to the trial getting underway. But covid restrictions stymied this step, with testing taking place at the same time as the start of the trial.
While there was more rain than usual during spring, which got the plants up and running, a dry summer followed. This may have been behind the plantain failing to thrive over the heat of summer, only coming into its own in late February for a second grazing.
Before the crops were ready for grazing in mid- January, samples were taken to determine how much dry matter was produced across each of the plots and what that meant for metabolisable energy. This saw plant matter cut to ground level, weighed, shredded and dried.
Many of the species in the 21 species mix didn’t perform well.
“A lot of the species established, but then died and contributed little to the overall yield,” said Tozer. “There was also a high proportion of yield from sunflowers, but they’re poor in terms of feed value.”
While the 21-species mix had reasonable dry matter and metabolisable energy, sunflowers can be a bit “hit and miss” with cattle. “While cattle will eat the leaves, they will sometimes avoid sunflower stalks if there is other feed available,” she said. The stems make up a big portion of the sunflowers’ dry matter.
Adjustments for this saw the mix slide in energy value as a consequence.
“The cost of producing metabolisable energy with the 21-species mix was more expensive than the rape monoculture because … seed is so expensive. Even with no weed or pest control, it
was still more expensive because of the seed costs,” Tozer said.
Oats in mixes proved to be very effective at suppressing weeds, even at low sowing rates. But oats fell down in a big way by going to seed well ahead of the rest of the forage crop. By the time the stock were put on in mid-January it was in very poor condition.
Both Weir and Tozer recommend that Triticale should be looked at as the cereal in the mix in the future. It might not be as aggressive at suppressing weeds, but its seedhead timing fits better.
By the end of the trial the most promising option was a simple rape-dominant mixture that contained rape, plantain and a cereal. It had a high energy yield, low weed abundance and a low cost per unit of metabolisable energy.
Tozer 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 said.
