Can we regenerate soil carbon in soils used for intensive field cropping?
To scientifically test regenerative farming principles within a typical New Zealand cropping system, we have established a six-year trial on the Heretaunga Plains. The trial at the LandWISE MicroFarm is a collaboration with the Hawke’s Bay Future Farming Trust. The information produced will increase understanding of benefits, impacts of conversion, support the development of decision-making tools, and increase confidence in regenerative farming principles through the value chain.
Our trial is a systems comparison, evaluating differences between a conventional high input, high output cropping system and a system producing the same crops managed according to regenerative practice principles. A third ‘hybrid’ treatment can adopt practices from either system, evaluating the effectiveness of selecting only some new practices, or aiming to model a transitional approach to conversion from conventional practice to a regenerative one.
Strict definition of regenerative cropping has been deliberately avoided in favour of adherence to generally agreed principles: minimise soil disturbance, keep the soil covered, keep living roots in the soil at all times, grow a diverse range of crops, and introduce grazing animals. Additional principles are to minimise the use of artificial fertilisers and sprays. Importantly, there is no “ban” on any practice should it be deemed an appropriate management response.
The trial site has moderately degraded soils after almost ten years continuous cropping. It has been split into 12 mini-paddocks, each 12 m wide and 90 m long. This provides four replicates of each treatment. The width enables use of conventional process cropping machinery, fitting 12 m, 6 m, 4 m, 3 m or 2 m equipment. The length ensures equipment is functioning correctly and sampling can avoid ends of rows.
Key parameters measured include soil factors such as carbon stocks, labile carbon, visual soil assessment (VSA), aggregate stability, and worm counts. Also measured are crop development, yield and quality, and profitability assessed via gross margins using input costs and standard contractor rates.
Project establishment saw baseline measurement via an EM map at 50 and 120 cm, and VSA soil quality assessments. Carbon stocks and labile carbon (HWEC), total nitrogen and labile nitrogen (HWEN) and Olsen P were measured to 90 cm in four depth bands. The EM map shows a high degree of homogeneity across the trial site. The VSA tests were also consistent, showing the soils to be in “moderate” condition, neither good nor poor. This allows for the imposed management to either further decrease quality or regenerate it.
The first crop planted was process sweetcorn for McCain Foods, an industry partner. Land had come out of 18-month pasture that was sprayed out. Everything was strip-tilled, then the conventional treatment also power harrowed. Compost, Trichoderma and biostimulants were added to the regenerative plots. The crop emerged quickly and evenly in all treatments, although slugs and pükeko caused some early damage. During Cyclone Gabrielle, the site was inundated with relatively clean flood water for less than a day. The crop remained healthy.
After winter cover crops, a Kraft-Heinz Watties tomato crop is planned for 2023-24. The project is supported by McCain Foods, Kraft-Heinz Watties, BASF Crop Protection and others.
More information at the Carbon Positive page
Members wanting more involvement, contact Alex, the Project Manager