AgResearch Invermay soil scientist Ross Monaghan is running a nearly $1 million project to explore whether dairy cows grazing on pasture in winter can reduce nitrogen leaching and mud compared with being on traditional forage crops.
The Soil Armour Project was launched in October 2020.
Experiment sites are live on a dairy farm on the Telford campus near Balclutha and Freedom Acres Dairy Farm at Wendonside.
Dr Monaghan said research at Freedom Acres was evaluating a winter bale-grazing method, which aimed to maintain a level of soil armour.
Hay bales were laid on pasture in a checkerboard formation for cows to graze on.
“We think that this protection can help to reduce some of the environmental impacts of cow wintering and improve welfare outcomes.”
When compared with a traditional forage crop wintering system, bale grazing had reduced soil and pasture damage, resulting in less mud and a relatively rapid recovery of plant growth and nitrogen uptake in spring.
The provision of hay provided forage and a resting area which encouraged cows to lie for longer.
Residual hay might have additional benefits for stimulating soil biological processes that could help to retain nitrogen deposited in the urine of the grazing cows.
Freedom Acres Dairy Farm owners Dylan and Sheree Ditchfield hosted an open day about the system last month.
Mr Ditchfield said bale-grazing originated in the United States, as part of regenerative farming systems. It was used to winter feed livestock and improve soil outcomes, mostly from the bale litter left behind.
Bale litter has seeds which germinate.
The grasses established from the bale litter, combined with the increasing temperatures, broke down the litter to feed the biology in the soil, he said.
Benefits of bale-grazing included the soil being biologically active and improved nutrient availability, soil structure and pasture growth, Mr Ditchfield said.
In their first season of bale-grazing, they trialled three paddocks, on which they calved their cows.
Most calved on bale litter, resulting in fewer calf deaths and better cow health.
After calving cows on the bale-grazing paddocks in August and early September, those paddocks were normally back into rotation by mid-October.
For pasture repair, perennial pasture seed was direct-drilled at full sowing rate where pasture damage has occurred, which was between 2% and 3% of the total area.
Where there was mild pasture damage — between 8% and 10% of the area — perennial pasture seed was direct-drilled at half sowing rate.
For the second season, half the herd was wintered on bale grazing. This season all the young stock were wintered on bale grazing.
“We plan to be 100% bale grazing all livestock once the AgResearch trial finishes after its third year.”
Cows walked less in a bale grazing system compared with wintering on a traditional crop, thus decreasing pasture damage, because they were fully fed and often ruminating on the hay.
In cold conditions, cows seem “more settled with full bellies” on bale grazing than on conventional winter crops.
The bale litter insulated the soil, which encouraged cows to lie on it rather than bare ground, so they needed less energy to maintain body condition and temperature.
For bale grazing, paddocks had to be shut up early enough to grow up to 4000kgDM/ha pre-grazing cover before grazing in March or early April.
About 30 bales per hectare was placed in a grid formation, about 20m apart.
Placing bales in different positions on the same paddock the following winter meant the whole paddock would eventually be covered with bale litter.
A herd of 100 cows were offered half a hectare every three days.
In adverse weather events, cows were moved to the next break and returned to the unfinished break once the soil dried out.
The benefits of bale grazing included reduced nitrogen leaching; a live plant in the ground year round; minimal pasture damage; very little to no sediment runoff; no cultivation, sprays and crop establishment costs; improved and better functioning soil; easy wintering with shifting cows every three days; better livestock welfare; no massive feed transitioning for cows and less feed being required to maintain body condition.
A drawback included the system needing more area than a conventional crop wintering system.
Southern farmers could include bale-grazing in their wintering system, Mr Ditchfield said.
“Be careful not to let the myth that you can’t winter cows on grass in Southland or South Otago dominate your thinking.”
Freedom Acres Dairy Farm
Area: 163ha effective/158ha milking platform.
Runoff (lease): 128ha effective.
Stock: 410 crossbred cows and 100 Friesian crossbreed heifers.
Production: 172,000kg of milksolids.
Staff: Three permanent.
Pastures: 30% multi species, 70% perennial ryegrass and white clover.
Soil: Mataura silt loam.
Wintering: 80% bale grazing and 20% kale crop.
shawn.mcavinue@alliedpress.co.nz
Southern Rural Life
