Sunday, August 14, 2022

On-farm GHG reductions come at a large cost

Science leader Chris Boom, left with DairyNZ extension partner Hamish Matthews and NARF farm manager Kelvin Horton.

The cost of reducing methane and nitrous oxide emissions on the Northland Agricultural Research Farm (NARF) in the 2022 season was 40% of operating profit compared with typical dairy farming in the Kaipara district.

The results of the first season of the four-year Future Farming Systems trial at Dargaville were released at the annual Northland Dairy Development Trust (NDDT) field day.

NARF’s farm and cows have been split into three equalised farmlets, with separate vats, to compare a typical Northland system with one that has 74% of land in tall fescue/cocksfoot-based pastures, and with a third designed to meet greenhouse gas emissions targets (see panel).

Financial analysis of the first season, using a $9.30/kg milk price, showed the “Current” farm was the most profitable with $5040/ha operating profit, followed closely by the Alternative Pastures farm with $4876/ha.

The Low Emissions farm was significantly behind the other two with $3021/ha.

Milk production was the biggest determinant: 1284kg/ha MS on the Current farm, 1213kg on the Alternative Pastures farm and only 794kg on the Low Emissions farm.

The Low Emissions farm had a 33% reduction in methane emissions and 47% reduction in nitrous oxide emissions compared with the Current farm.

“Milk price would have to be as low as $5 before the Low Emissions farm would show a similar profit (or loss) to the Current farm,” NDDT science manager and project supervisor Chris Boom says.

“The pricing mechanism to encourage farmers to reduce emissions has yet to be confirmed, however, it is unlikely the emissions pricing will be near enough to compensate for the significant loss in profit shown in this study.”

Three further years of this study will allow testing of these regimes over different climatic conditions and display any compounding of treatment effects over time.

Pasture growth last season across the three farms was considerably below the historical average due to dry conditions in summer and autumn (13t/ha/year dry matter on the Current farm compared with 15.5t historically).

The fescue/cocksfoot pastures did have higher growth rates during late winter/early spring and there was a lower requirement for supplementary feeding on that farm at that time.

The Current farm grew 1.37t/ha more than the Low Emissions farm, which was the effect of nitrogen.

With 172kg/ha N applied to the Current farm between June and December, the N response was 8kg DM/kg N, lower than expected possibly due to longer rotations and good white clover presence on the Low Emissions farm.

Clover content in pre-graze samples was between 20% and 40% through spring and summer on the Low Emissions farm, compared with under 20% on the other two farms.

The Alternative Pastures farm had significantly lower pasture covers during summer and autumn.

By way of compensation, pasture samples and analysis indicated the Alternative Pastures had higher feed quality through most of the year, apart from the spring.

The crude protein level of pastures that did not receive nitrogen was lower in late winter/early spring and the Low Emissions cows had lower milk production, which may be due to longer rotation or no applied N, or both.

Both the Current and Alternative Pastures farms purchased around 800kg/cow DM of supplement, compared with 67kg for the Low Emissions farm.

The lower stocking rate allowed more silage to be conserved, which was then fed out in late summer/autumn and eliminated the need for imported supplements.

Calculated pasture eaten was three tonnes less on the Low Emissions farm, although that doesn’t mean it grew less, but just had higher grazing residuals, requiring more mulching.

Milk production was always going to be lower, because of the reduced stocking rate, but milk production per cow was also lower (370kg/cow MS compared with 409 and 397).

Greenhouse gas emissions were calculated using Overseer and the Current and Alternative Pastures farms had similar levels. These were up at 9000-plus kg CO2 equivalent per hectare for methane and 2700kg for nitrous oxide.

By comparison the Low Emissions farm generated 6400kg/ha CO2eq of methane and 1484kg of nitrous oxide.

On a per kilogram of milksolids basis, the comparison was 10kg versus 9kg for the Low Emissions farm, which was surprising considering milk production from this farm was 38% lower.

CO2 inputs, not included in He Waka Eke Noa or the Emissions Trading Scheme, were only 335kg/ha for the Low Emissions farm, compared with 2000kg for the other two.

Total income per hectare on the Low Emissions farm was two-thirds that of the other two farms, $8000 versus $12,000.

Total operating expenses were $7739/ha on the Current farm, $7471 on the Alternative Pastures farm and $5055 on the Low emissions farm.

Farm working expenses per kilogram of MS were almost the same across all three, around $5.70.

NARF trial design

The Northland Agricultural Research Farm four-year Future Farming Systems trial is to investigate dairying in a warming climate and when conforming to the Government’s greenhouse gas emissions targets.

NARF is a high-producing dairy farm by Northland standards and has historical average pasture growth of 15.4 tonnes dry matter per hectare a year.

Ryegrass persistence is poor, rust and pest damage are increasing and regression to kikuyu often occurs within three years of sowing new pastures.

The project compares three farm systems:

Current farm

  • Existing ryegrass/kikuyu pastures with imported feed (likely PKE) to fill deficits, at 3.0 cows/ha stocking rate and up to 190kg/ha applied nitrogen.

Alternative Pastures farm

  • At least 75% of pasture in alternative species to ryegrass, including fescue, cocksfoot, legumes and herbs, with imported feed to fill deficits, at 3.0 cows/ha and up to 2190kg/ha applied N.

Low Emissions farm

  • Existing ryegrass/kikuyu pastures, targeting 25% reduction in methane emissions and 50% reduction in nitrous oxide, at 2.1 cows/ha stocking rate, no applied N and little or no imported feed.

The trial measures are pasture and milk production, milk composition, profit and people (labour input and management difficulty).

Alternative species introduction over two years averaged $1138/ha with NARF tractor and man hours and contracted drilling.

Current and Low Emissions farms, plus 25% of Alternative Pastures farm, have approximately 70% kikuyu presence, which requires mulching in autumn and drilling with Italian ryegrass.

This article first appeared in the July 2022 issue of Dairy Farmer.

People are also reading