Growing carbon in HB soils

Our nation’s farmers have a key role to play in how New Zealand addresses climate change and contributes our constructive part in mitigating the global predicament. Thus a topic of great interest to New Zealand farmers these days, especially those raising livestock, is whether carbon can actually be ‘grown’ in the soil and used to offset harmful climate-warming emissions. 

Leading edge farmers using regenerative farming practices insist this can be done. Everyone from the Government to Beef+Lamb NZ to Greenpeace is looking for the evidence.

Here in Hawke’s Bay, dairy farmers John and Donna Kamp – working with farm consultants Phil Schofield and Paul Smith – are on that path and beginning to show promising signs. John and Donna have shouldered most of the cost involved in this research, with some support for the sampling analysis from the Hawke’s Bay Future Farming Trust. Here’s what they’re up to.

BayBuzz: John, can you give us an overview of your farming operations?

John: Donna and I are currently farming on three farms totalling 1,080 hectares in Patoka – ‘The Incline’ (farmed regeneratively since 2007 and organically since 2016), ‘Huiarangi’ (purchased in 2016 and now farmed regeneratively and organically), and ‘Raumati’(purchased in 2019 and undergoing organic conversion).

The farms are in close proximity and share soils, geology and climate. They also share a prior history of intensive farming employing chemical ‘best practice’ as prescribed by conventional agribusiness.

I’ve had a ‘career’ in farm renovation since 1988. In 2007 prompted by ill health and a growing recognition of the links between soil, environmental, animal and human health, we decided to adopt a biological/regenerative approach. Phil Schofield has been our soils mentor since 2008, with Paul Smith now involved as well.

BayBuzz: What are you trying to achieve that prompted this research project? 

John: We see soil microbiology as the basis of healthy living soil and the foundation of productive pasture and livestock. We believe our regenerative practices will add to our soil carbon stocks, mitigating against climate change, improving water infiltration and retention, and yielding more profitable farming.

Paul Smith: Phil and I had been looking for an opportunity to measure soil carbon stocks on grazing farms that had different pasture management, but were essentially the same in other respects – soils, contour and climate. When John bought Raumati it presented a really great opportunity to do this. His three farms represent a progression from high input farming to lower input regenerative farming. We don’t have good research on this in New Zealand and, given that soils contain more carbon than the atmosphere and vegetation combined, it’s important that we learn more about how our farming practices effect this vast resource. 

We know that increased carbon in the soil has to come from CO2 in the air. We also know that soils with higher carbon hold more water and nutrients. If it can be shown that some farming practices improve soil carbon then we can use this to sustainably produce great food and help save the planet at the same time, and we won’t need to plant trees on good, productive farmland. 

BayBuzz: Describe the basic framework for this project – what did you set out to measure, why and how?

Phil Schofield: We were seeing differences in the soil health, pasture quality and pasture root length and density on the three farms so we wanted to see if those differences could correspond to differences in the soil carbon levels.

Paul has been working for years on verified soil carbon measurement methodology and was a co-author on MPI’s newly minted Technical Paper on soil carbon benchmarking. He enlisted the leads on this paper, Paul Mudge and Stephen McNeill from Manaaki Whenua Landcare Research, to help with the sampling design and make sure it was done properly. We measured Total Nitrogen stocks as well because it is environmentally important to know if soils can hold more nitrogen.

36 individual sites were sampled on each farm. Each core was divided into one 0 to 300 mm depth sample and a 300 to 600 mm depth sample making a total of 72 samples analysed per farm. The bulk density, total N and total C was measured for each sample at the Manaaki Whenua Landcare Research lab in Palmerston North. 

BayBuzz: And so what have you found? What’s the headline out of this?

Paul: Keeping in mind that Incline has been under ‘regenerative’ management for at least the last 10 years, Huiarangi for 5 years, and Raumati about 12 months, we see significant differences in soil carbon and nitrogen, as this table indicates. Total C and Total N stocks are expressed in tonnes per hectare for the full 600 mm depth.

Overall there is 64 tonne/ha more carbon and 5.2 tonne/ha more nitrogen 

in the top 600 mm of the soil at Incline compared to Raumati and the C and N levels at Huiarangi are in between Incline and Raumati. The soil carbon levels we found are fairly high by world standards. Soil carbon concentrations of approximately 8% (Incline) and 5.5% (Raumati) were found in the top 300 mm of the soil profile on the farms. The general consensus is that NZ’s soil carbon levels are high and therefore we won’t be able to improve them; these results put that in doubt. 

I wasn’t expecting that we would find so much more nitrogen held in the Incline soils, especially as no fertiliser nitrogen has been applied for over 10 years.

Phil: The differences we have found in soil carbon levels and total N levels on the farms correspond to our field observations. Visual soil assessment (VSA) methods show us that Incline has a deep pasture root system. Compared to Incline the soils at Raumati are more compact, less porous and there are fewer earthworms present. The VSA measurements at Huiarangi are not as good as we find at Incline and better than at Raumati. 

BayBuzz: What are the farming practices that account for these results?

John: We’re implementing four basic practices, our version of regenerative farming:

• Do no harm: Use no synthetic fertilisers or chemicals that can compromise microbial life or animal health. Organically approved fertiliser is applied to achieve mineral balance and stimulate microbial life.

• Encourage pasture diversity: Every plant species uniquely adds to the complexity and proliferation of soil microbial life (i.e. soil health)… the same way eating a diversity of healthy whole foods forms the basis of a functioning human microbiome to promote good health and vitality. 

• Intensive grazing with ruminant animals: High stock density with frequent shifting and long pasture recovery time. 

This replicates the deep soil building processes of the North American bison herds and wildebeest herds of Africa (kept compact by predators) that grazed, trampled, defecated, urinated and salivated their way across abundant grasslands adding fertility, composting in situ, re-inoculating and stimulating soil microbiology as they went. Fenced paddocks with water supply replace the predator effect in the NZ pastoral setting.

• All grass farming with minimal soil disturbance: This reduces soil loss through wind and rain and encourages mycorrhizal fungi growth – filaments that bridge soil microbes to plants, creating a resource trading ‘internet’. The plant offers photosynthetically derived sugars (from atmospheric carbon) in exchange for essential minerals delivered by the soil’s wide fungal network. 

The result of these practices is in situ composting and carbon trading, sequestering carbon deep in the soil as stable humus … the essence of live healthy soil. 

BayBuzz: How conclusive are these findings?

Paul: We wish we had gone deeper; we found bigger differences between the farms at depth than expected. We were trying to keep control of costs as we didn’t have any funding to start with, and still only have lab costs covered.

Comparing the farms at this stage is tricky, the benchmarking process is really designed to be the first stage in a monitoring process that measures soil carbon change on a set piece of land over time. We will know more about how the farming practices are affecting soil carbon when we have done another couple of rounds of measurements. We are hoping to be able to retest these farms in 2023 and 2026 so that we can pick up trends and quantify the rates of soil C and N sequestration.

That said, the farms are close together and so have the same climate, they have similar contour, the same soil type, and, because of the extensive VSA monitoring that Phil and I have done on a number of neighbouring farms over the last 10 years, we have some confidence that the topsoil depths would have been fairly similar across them when they were all sheep and beef farms. The data set was also very tight, with clear differences between the farms. I think we can say that the results are indicative, they give us a good “heads up” of what is happening.

In the meantime we hope to do some soil C testing on farms that neighbour the three farms we have benchmarked. This will help shed light on whether the differences we have found are due to historic soil differences or are resultant from the pastoral farming system being employed.

BayBuzz: So what are the implications of your findings?

Paul: Finding that there is 64 tonne/ha more soil carbon on Incline than on Raumati, on soils that are likely to have had similar levels prior to conversion, is nationally important. To put this into perspective, it converts to 235 tonnes of CO2-e, or roughly the same as a pine forest would accumulate in 8 years. If we can show, with more measurements over time, that these sorts of changes are due to the farming methods employed then the industry can start to incorporate some of these methods into best practice and begin to recognise gains as GHG offsets.

If we were able to achieve even a small portion of this change over NZ’s pastureland it would have a huge impact on our GHG profile. The great thing with soil carbon, compared to forestry, is that you can claim the GHG benefit, keep the carbon in the ground where is improving the water holding and nutrient holding ability of the soil, and keep growing low GHG food on the land – there aren’t too many downsides.

Phil: In addition, Incline has 5.2 tonnes per ha more nitrogen present in the soil (humus complex) than Raumati. If the different management systems employed on these farms for the last 10 years has resulted in the observed differences in soil nitrogen then a very significant environmental benefit can be obtained by holding more N in the soil rather than losing it to groundwater or having it volatilise to N2O, a potent greenhouse gas. This increased N, bound to the soil organic matter and derived entirely through natural processes (no N fertiliser is used) is available to support dairy production with no detriment to the environment. 

Phil: This study offers very positive news for pastoral farmers. The benchmarking shows that we can have big differences in soil C in NZ soils under pastoral farming management. There is a strong indication from our historic soil quality monitoring that managing pastures using regenerative farming methods can result in soil carbon sequestration and Nitrogen attenuation at rates that are highly significant from an environmental management viewpoint. We plan to continue the research so that we can establish whether NZ pastoral farmers should have soil carbon projects where they can use the C sequestered as an income stream or an offset in the ETS. 

BayBuzz: John, what happens next for you on these farms? 

John: The benchmarking results very closely match what we expected from our visual soil assessments and will enable us to monitor ongoing changes over time. We believe that Raumati, starting from a lower soil carbon base and being farmed regeneratively for the shortest period should record the most dramatic changes. 

The outcome will be largely determined by the daily grazing management of Jeremy and Sheree Wapp and their staff who contract milk on all three farms.