Landcare Greenhouse Gas Research

March 2013

Looking for ways to reduce greenhouse gas production in dairy farming

Landcare Research scientists are looking at the impact of conversion from dryland grazing to high intensity dairying under irrigation and how this affects greenhouse gases. They wanted to be working with the cutting edge of the dairy industry and Synlait offered this farm for the experimental work. The trial work does not influence the way the property is managed, for example its irrigation use, fertiliser use or stocking rates.

John Hunt from Landcare Research says that in the last 20 years there has been a 10-fold increase in dairying in Canterbury. As a result, there has been a large impact on the ecosystems and the transport of water and nutrients, and the researchers want to look at the specific effects of that change.

New Zealand has a strange greenhouse gas footprint with half emissions coming from agricultural production. The researchers want to find some tools for farmers to use to reduce greenhouse gases.

Measurements are being taken on irrigated pasture and adjacent dryland at the same time. There is a triangular area of 25ha of dryland in between two adjacent centre pivot irrigators. The farm has only been converted to dairying in the last four or five years.

A hut has been built on the fenceline, containing about half a million dollars worth of measuring equipment. Cables and wires lead from it to the dryland site 150m away, and to the irrigated site.

Comparisons are being made between the two sites – with the same weather conditions and soils.

One of the reasons the scientists are here is because Lismore soils are very stony and have lower carbon levels, reacting differently to the heavier and deeper soils in the Lincoln district, where a lot of research has already been carried out. Many recent dairy conversions are on Lismore soils.

The research has three main aims:

1. To measure greenhouse gases when land is converted from dryland to dairying.

2. To find the environmental drivers of greenhouse gas emissions and soil carbon storage and how these change season by season. This will be used to develop models to find out what would happen if less fertiliser and less irrigation was used.

3. To develop tools farmers can use to reduce their greenhouse gas emission rates. Emission factors are imposed on farmers but they want to find out if the rates are correct.

They also want to know how conversion affects soil carbon storage.

In the future they hope to take greenhouse gas measurements to find out emissions where lower and higher rates of irrigation are used and where dairy effluent is applied.

Funding for the five-year project comes mainly from the Ministry of Science and Innovation but also from the Ministry for Primary Industry, the Ministry for the Environment and the NZ Agricultural Greenhouse Gas Research Centre.

Five people are working on the project, and almost half a million dollars of equipment is being used to take measurements in the field.

The project is also linked in with a PhD student from Lincoln University and PhD and Masters students from Canterbury University. NIWA is also working on nitrous oxide on the same kind of soils and Waikato University is looking at the effects of pasture species on carbon sequestration in soils.

In this trial three main gases, nitrous oxide, carbon dioxide and methane are measured. Carbon dioxide emissions change on a daily cycle and in relation to the grazing, while methane (from the cow’s breath) is only detected while the cows are in the paddock grazing. Nitrous oxide, produced from urine and fertiliser, is emitted when soil moisture gets above a certain level.

The carbon dioxide is measured using an eddy covariance. This measures the concentration in the air and also windspeed, using a sonic anemometer to tell whether the air is moving up or down.

During the day when plants are taking carbon dioxide out of the air, parcels of air moving down have on average a higher concentration of carbon dioxide than parcels moving up. At night the opposite is true. We measure this 1.5m above the ground, with measurements taken 20 times a second.

At the same time environmental measurements such as water vapour, temperature measurements and windspeed are taken, all of which help show what controls the uptake of carbon dioxide.

They can measure how much water has gone into the ecosystem and how much has evaporated, and so how much is draining into the soil.

Nitrous oxide and methane measurements are taken at heights of 30cm and 1.5m above the ground and happen every six minutes, with recording in the huts. These gases are at much lower concentrations in the atmosphere (100 times less) so more precise instruments are needed.

From the difference in concentrations at these two heights we can work out whether nitrous oxide is going into the ground or coming out. In the same way they measure methane emissions when the cows are grazing.

In future they hope to look at nutrient levels and especially nitrate leaching into the soil.

The farm where this research is taking place is one of the 14 Synlait Farms. Synlait milk a total of 12,000 cows which supply Synlait Milk in Dunsandel.

In 2012 Synlait Farms won the South Island Farmer of the Year award from Lincoln University.

This research site was chosen because it had some dryland adjacent to the irrigated pasture.

It’s a typical dairy system 3, with innovative technologies such as Aquaflex for measuring soil moisture levels, flow metering and a lot of pasture monitoring.

Lucy Johnson from Synlait Farms says “In our group we have a continual improvement programme and use lean manufacturing principles across our business. With our scale we have been able to develop some innovative solutions to dairy farming.

This is important research for us, and we are hoping to get some sound policy which has practical use on our farms with respect to the impact intensification has on our emissions. But this research will be valuable right across the primary sector on any dairy or beef farm. At the moment there are limited options to decrease greenhouse gas emissions on our farms. With more than 40% of NZ’s emissions coming from agriculture, we hope this research will give us a better understanding of the origins of the emissions.”