Meeting Tough Nitrogen Loss Rules

The rapid expansion of dairy farming in Canterbury has put pressure on the environment. Farmers must now comply with increasingly strict regulations to reduce that impact, particularly the loss of nitrogen into groundwater.

Brothers Leo and John Donkers started the Camden Group 25 years ago. They now own four dairy farms and two support farms, as well as being involved in share-milking businesses on three other farms.

“We have to change our management practices to enable us to continue farming in this environment,” Leo Donkers says.

The Camden Group has achieved the 30 per cent reduction in nitrogen losses required of dairy farms well before the 2022 deadline, thanks to changing its repasturing programme and tweaking fertiliser and irrigation practices.

The Selwyn Waihora water zone committee signalled five years ago that tighter controls were coming. The Camden Group took a hard look at its operation and environmental performance.

Changing systems to meet environment regulations

One of the first things they tackled was pasture, which despite being resown in high- performing species wasn’t consistently delivering hoped-for pasture production gains. Part of the problem was the persistence of low-performing native pasture species, so they adopted a new two-year, double-spray strategy, together with a change in species and sowing method.

“We sprayed with glyphosate, direct-drilled an annual and sustained that for a year,” says Leo. “Then at the same time the following year we re-sprayed, cultivated and drilled permanent pasture.

“This one-pass drilling process involved drilling perennial ryegrass in normal rows and then broadcast a tetraploid and white clover mix between the perennial rows to get full coverage.”

Previously browntop would come up between the rows after direct drilling, but under the new system the inter-row space is filled by tetraploid grass species and clover.

New pasture is filled by tetraploid grass species and clover.
“The benefit we got was phenomenal pasture growth,” Leo says. “We grow a lot more grass than we have ever done in the past.”

The tetraploid grasses are cool-season active, which means they soak up nitrogen even when other species’ growth has slowed.

Achieving environmental and production targets

The success of the programme attracted the attention of DairyNZ’s Virginia Serra. She leads the Meeting a Sustainable Future project which aims to foster changes in farm systems to reduce nitrogen losses in the Hinds (Ashburton) and Selwyn Waihora zones.

Serra says the limits are challenging, but the sector is committed to helping farmers achieve them while maintaining resilient businesses.

“This project builds on previous nitrogen loss research. It aims to give farmers confidence the limits are achievable,” says Serra. “Many farmers have been making changes to reduce nitrogen loss for some time and this will continue to build on that.”

Camden Holdings’ Willsden Farm at Te Pirita is now one of two “partner farms” in the project.

Camden no longer applies nitrogen in May because soils get cooler and pasture plant growth slows, and demand for nitrogen decreases. “The worst time for any leaching is in autumn and winter. The unused nitrogen from summer has accumulated in the soil and it gets lost with the winter rains.”

Most dairy shed effluent is spread over about 90 ha of pasture, when conditions are right, using a small spreader, but this year that area is being doubled. Plans are also in train to modify the centre pivot so effluent can be spread from that as well, adding another 140 ha.

Camden Holdings’ Dairy Shed
“We should be to be able to do whole farm over the next two or three years, then we’d have extremely good spread,” says Camden Group operations manager Terry Kilday.

When the farm was first converted, it only had five days’ effluent storage, but now a significantly larger pond has been put in, increasing storage to between 10 and 15 days.

Planning Irrigation

Another area getting close attention is irrigation. Three roto-rainers have been replaced by centre pivots and set sprinklers to allow for greater efficiency and a shorter return, down from 10 days to two to three days. Three roto-rainers are still used on 140 ha, on a seven, seven and six day return.

The completion of the Central Plains Water irrigation project, which replaces water from deep wells with pressurised water drawn from the Rakaia River, backed up by storage in Lake Coleridge, has added to irrigation efficiency.

“We never realised how efficient that would make us because instead of having a push-button system where we are pumping from deep wells and we have all the control, now we have to order water once a day,” Leo Donkers said. “So at three o'clock we've got to make an order for tomorrow which means we need to know where the water is going and how much we need.”

Soil moisture probes are used as a tool to make the correct decision about when to irrigate.

Looking at new technologies and better ways

Achieving a 30 per cent reduction in nitrate leaching – and remaining profitable - has been done without big changes to Willsden’s farming. Terry Kilday is proud of what they’ve achieved.

“We’re looking at new technologies and better ways of doing things. We don't get it right every time but we're getting better and are fast followers of new research and technology changes, which are starting to show real benefits.”

Find out more on the nutrient management rules.

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