Inside the Barn: Canterbury Composting Barn Roadshow

John came south from the Waikato because he hated mud and then found a wet Canterbury winter could be just as bad. Wintering on a support block meant kale and fodder beet, and club root was hitting the crop. The turning point came in a muddy paddock when he met his sharemilker, both of them loaded up with standards and reels.

The site and the build

John wanted the barn close to the shed so the cows can walk straight out to milking. The Faulkner composting barn sits 700 mm above ground on heavy soil, with a hard-packed dirt base, no drainage under the bedding and poplar and pine chip about a metre deep. The holes for the tallest poles, 13.4 m high, kept coming out too big, so the team switched to a sleeve system.

It was 14 months from earthworks to completion. John expected chaos, but the cows looked at the roof, found the feed and settled.

The first winter: what he’s still working out

John was open about what took adjusting. Tilling came first. He now tills twice a day, about an hour with the cows out, and a probe in the pack has mostly read 52 to 60 degrees.

Feed was the second. Top-quality silage at about 33% dry matter left the dung looser than he wanted, and that goes straight into the bedding, so next season he’s aiming for 45 to 48%. Rene Vos found something similar with a wet summer crop at our Waikato stop.

What farmers asked about the Culverden composting barn

Most questions came back to John’s first winter: what changed on the farm, what it takes to look after the bedding and what to sort out before you build

Calving, weather and labour

Springers calve inside, and a dedicated tractor picks up the calves twice a day. John called it “a very fluid, easy system”. When a weather event hits, the whole herd comes in and an electric wire splits the barn into pens. Staff numbers haven’t changed, but the team usually finishes by about 11 am.

Condition, production and animal health

Cows reached calving condition score in about 20 days in the barn. John said production was about 18% ahead for the season, mostly from using the barn at the end of last season to keep cows milking longer. Animal health was good through winter and he hasn’t seen the mastitis some people warn about.

Consents

John needed a building consent, a farm system change consent from his irrigation company and an Environment Canterbury consent for discharge to air. Harry Miller from Rural Consulting said the rules are fairly permissive, and Rural Consulting offers a free planning assessment on every Aztech build.

The environmental side

Getting cows off winter crop in the high-drainage months is where the environmental case comes from. Harry’s modelling of three West Coast barns found nitrogen losses 25 to 48% lower, though not from the barn alone, since less winter grazing and less nitrogen fertiliser played a part too. John’s own modelling puts his at about 850 kilograms less nitrogen reaching waterways.

What would John change, and what’s next?

The barn holds about 550 cows and John winters about 590, so there’s no spare room. He’s also looking at what else it could do. Grazing is getting harder and dearer to find in Canterbury, and his young stock currently travel all the way to Timaru, so he’s weighing up whether the barn could take them too, run almost like a feedlot. If El Niño brings the hot days forecast, he also plans to bring the cows in during the day to stop them panting.

His advice to other farmers is to lean on people who’ve done it before.

Five years in: Murray Coates at Prospect Farms

Murray Coates from Prospect Farms on the West Coast was also at the Culverden event. John visited his barns before building his own, and in the Q&A Murray shared what about five years of running them has taught him. With nearly a metre of rain since calving, he put it simply.

Moisture is still his biggest challenge, and the soak pits the council asked for pushed groundwater back up through the bedding, so his advice was to get water well away from the barn. Once a year a contractor screens the barns and swaps the wetter feed-lane bedding with the drier outer material, and John plans to flip his the same way.

In summer, Murray brings the cows in once it hits about 22 degrees, and his empty rate in hot years has dropped from 18 to 20% to around 10%.

Why the design is what makes the system work

Billy Gibbs, our regional sales manager, took farmers through the seven design points we’ve found make or break a composting barn, using John’s barn as the example. It starts with space and depth.

We design for about 8 square metres per cow and at least 600 mm of bedding, typically 700, and the consultants on the day said that’s what gets farmers five to seven years out of their chip. Then comes tilling, which tied straight back to John’s lesson.

Airflow and protection do the rest. The 18-degree roof pitch draws fresh air in from the sides and up through the ridge vent, taking moisture and odour with it. The solid steel roof has one clear light per bay to keep direct sun off the cows, and large overhangs and covered gable ends take the worst of the weather. A 3 m concrete strip at each end slopes away from the bedding, so any driving rain runs off. A farmer also asked about closing off the north-west wall, and the advice was that a windbreak is fine as long as the airflow keeps going.

All seven points are in our free composting barn guide, which went home with everyone.

Thank you to John and his team for hosting, to everyone who came along, to Murray for sharing his barn experience, and to our partners DeLaval, Webline, Headlands Consultancy and Rural Consulting. If there’s one thing to take from Canterbury, it’s that a composting barn is a farm system that depends on how well the bedding is run, so plan for both before you build.

Wondering how a composting barn would fit into your own farming system? Talk to the Aztech Buildings team about your farm, herd and what you want to achieve.