By Delwyn Dickey for Our Land and Water
Agricultural emissions targets could be met by 2030 by increasing brassica and grains in cattle diets by 20-30%, with stocking rates reduced just 5%, a new agricultural model developed for the New Zealand arable farming sector has found.
Cattle grazing on lush green pastures under clear blue skies is an iconic rural NZ image – and it resonates with consumers, giving the country’s beef and butter a marketing edge compared to product from intensive feedlots in the United States and indoor farms in Europe.
But pastoral farming has some surprising drawbacks. When looking through a climate change lens, our cattle are probably releasing 20% more methane from their pasture diet than their factory-farmed counterparts with diets high in grains. Pasture species also produce more protein than grain feed. The excess returns to the paddock as nitrogen in urine, leading to additional nitrous oxide emissions.
With consumers, food manufacturers and retailers increasingly considering the emissions footprint of food, the country’s agricultural products run the risk of becoming seen in a negative light, despite its free-range model.
The government has set goals of reducing methane by 10% from 2017 levels by 2030, and 24–47% by 2050. Nitrous oxide needs to drop to net zero by 2050.
Those targets could be met by reducing stock numbers, but this may not be the whole solution, Ivan Lawrie, general manager at the Foundation of Arable Research (FAR) said.
“Keep the pastoral system, but balance out the diet with an increase of low-protein supplemental feeds. Grains fit well and can be grown on farm, in the same livestock or dairy systems we currently have,” he said.
A new agricultural model developed for the NZ arable farming sector, with funding from the Our Land and Water National Science Challenge, has combined recent studies’ evidence to show stocking rates could reduce 5% or less and still meet emissions targets in 2030, providing there was an increase of alternative feed (brassica and grains) of 20–30% in cattle diets.
The model also suggests that reducing stocking levels 10% while increasing alternative feed intake at least 10% would enable 2030 emission targets to be met.
Emissions targets for 2050 could be achieved by reducing herd numbers between 10–15%, combined with an increase of 30% of the alternative diet.
Although thousands of hectares will be needed to produce the alternative fodder crops and grain, most could be grown on farm, Lawrie said.
“The grain crop could also be used to mop up excess nitrogen in the soil from urine and fertiliser,” he said. Home-grown alternative feeds could also reduce our reliance on imported palm kernel extract, which produces even higher levels of methane than pasture when digested.
The modelling suggests that introducing wheat production in a dairy system has a positive environmental impact, producing almost eight times less CO2-e biogenic emissions and using a third less water for irrigation than dairy.
Farms would, however, need more infrastructure for grain storage and could face an increased workload.
The NZ Agricultural Greenhouse Gas Research Centre has researched the amounts of methane and nitrogen cattle produce as they digest different pasture and forage species. Replacing pasture with brassica crops, such as rape and plantain, helps reduce methane from the rumen of cattle. Low-nitrogen crops like fodder beet can reduce nitrous oxide emissions when carefully managed.
But farmers may be understandably reluctant to apply this knowledge on farm, until they can see the flow-on effects of the system changes. Modelling these effects makes it easier to make decisions and plan to produce food sustainably while maintaining good returns.
Scientists at University of Canterbury and Manaaki Whenua Landcare Research developed a model specifically for NZ’s agricultural systems and conditions, with data from NZ’s Arable Food Industry Council, StatsNZ, and the Food and Agriculture Organisation of the United Nations. It is one of few agricultural models anywhere in the world that have been designed to combine production methods, emissions, energy, land use, water use, fertiliser use and profitability.
Aimed at national and regional policy makers, and agricultural industry leaders, the model has used real-world questions and scenarios, said modelling scientist Dr Clémence Vannier of Manaaki Whenua Landcare Research.
As well as looking at mitigating climate change, the researchers modelled two further scenarios for arable agriculture in NZ: one looking at alternative protein production, and another on self-sufficiency for wheat.
