Soil Carbon

Increasing the quantity of carbon stored in agricultural soils has the potential to offset emissions of greenhouse gases to the atmosphere, while soil carbon losses would further add to those emissions.

However, realising this mitigation potential is technically challenging when soil carbon stocks are already high (as they are in New Zealand), potential changes in soil carbon are small and spatial variability is high.

The current NZAGRC programme has three distinct components:

(1) testing specific management practices that may increase the long term soil carbon store in field situations;

(2) developing and using models to predict how a range of management practices may influence long and short tem soil carbon storage; and

(3) identifying those factors that influence the stability of current or newly added soil carbon.

We have also supported international work to map on farm soil carbon and will participate in the international research programme CIRCASA.

Principal Investigators

Dr David Whitehead, Manaaki Whenua - Landcare Research (2010-present)
Professor Frank Kelliher, AgResearch (2010-2017)

Research Stories

Learn Profile - Adriano Nascente

LEARN Research Aims to Give Farmers Options for GHG Reductions

Visiting Brazilian research scientist Dr Adriano Nascente is currently working on a project to help give farmers options for management practices that will reduce nitrous oxide emissions and maintain or increase stocks of soil carbon.

Adriano is visiting under a GRASS Award, one of the awards offered by the New Zealand Government to support the Global Research Alliance on Agricultural Greenhouse Gases. It enables exchanges between New Zealand senior scientists and contemporaries from other GRA member countries to collaborate on livestock greenhouse gas mitigation.

With Dr David Whitehead of Manaaki Whenua – Landcare Research, he is testing the hypothesis that manipulating carbon inputs to soil will modify the microbiological processes that regulate nitrous oxide emissions and soil carbon storage. The carbon inputs are being manipulated using lucerne, with different simulated grazing intensity and sugar addition.

Adriano arrived at the beginning of October 2018 and he has worked at a field site located at Ashley Dene Research and Development Station and Manaaki Whenua – Landcare Research, Lincoln, Canterbury, until the end of this June.

A research scientist with the Brazilian Agricultural Research Corporation (Embrapa), he works at the Embrapa Rice and Beans Research Centre, specialising in agricultural systems that support sustainable social, economic and environmental development.

“I knew David Whitehead from a project supported by Embrapa and the New Zealand Embassy in Suriname, and knew he works with techniques to mitigate greenhouse gas emissions. When I had the opportunity to have a period as a visiting scientist, I asked David if it was possible to come to New Zealand and undertake research together,” says Adriano.

“The project involves the effects of manipulating carbon, adding or removing it from soil while regulating nitrogen and carbon cycles, with the focus being on reducing nitrous oxide emissions.”

The research team is conducting two trials, one long-term and the other short-term.

The long-term trial involves an experimental design of a random block with four treatments of lucerne and four replications of treatments. The four treatments are 1. addition of carbon as sugar; 2. reducing carbon inputs every two weeks by cutting the lucerne at ground level; 3. reducing carbon inputs every two weeks by cutting the lucerne to an average height between a control and ground level; and finally, 4. control with no cutting and no sugar addition.

The short-term trial also involves an experimental design of a random block with four replications. Treatments of lucerne involve 1. addition of carbon as sugar, then 2. control with no sugar added. Measurements at the field site are made every three days.

Starting in November, the carbon availability index was measured every two weeks until differences between treatments were detected, which happened at the end of January. Then, the team quantified in each trial the emissions of N2O and CO2 at the soil surface, the soil nitrate and ammonium concentration, soil temperature and water content, cold and hot water extractable carbon.

“We also extracted DNA for gene copy abundance to quantify specific genes involved in nitrification in the short-term trial,” says Adriano.

Explaining the significance of the work, he adds: “We know that carbon inputs to soil could directly affect microbial activity that regulates nitrogen transformations. We expect that better understanding of these interactions between carbon inputs and nitrogen transformations will lead to improved management practices to mitigate nitrous oxide emissions.”

Knowledge gained from the research will be communicated to scientists worldwide and end users in a report to NZAGRC, a presentation and a peer-reviewed article submitted to a journal.

Adriano says he will use the knowledge gained in New Zealand to further his research projects in Brazil, where work on crop-livestock integration farming is important in recovering degraded pasture.

“There, we are seeking indicators to evaluate the sustainability of agricultural systems. Application of processes related to nitrogen and carbon cycling that we worked on here in New Zealand will be very important for Brazil’s agricultural systems to see if we can reduce greenhouse gas emissions.”

“With David Whitehead, we have opened a door to discussing other projects that could help Brazilian or New Zealand agriculture to reduce greenhouse gas emissions.”

Photo Credit: Bradley White

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