Humphreys Carbon Project 4

Humphreys Carbon Project 4 is a soil carbon sequestration project located in the Shire of Wongan-Ballidu, approximately 45km northeast of the town of Wongan Hills in Western Australia's Wheatbelt region. Registered on June 18, 2025, the project covers a land area of roughly 69.5 hectares. The project is situated in a region heavily utilized for broadacre cropping (wheat, canola, barley) and sheep grazing, typical of the intensive agricultural zone of south-western Australia.

The project operates under the Estimation of Soil Organic Carbon Sequestration using Measurement and Models (2021) methodology. This method credits landholders for increasing soil organic carbon (SOC) stocks through changes in land management. Unlike earlier methods that relied solely on physical sampling, the 2021 determination allows for a "hybrid" approach, using models to estimate carbon change in between physical sampling rounds to reduce costs. Participants typically commit to maintaining the stored carbon for a permanence period of 25 or 100 years, with 25 years being the standard for soil projects to balance flexibility and credit discount.

The local environment in the Wongan-Ballidu shire is characterized by a semi-arid to Mediterranean climate, receiving an average annual rainfall of approximately 350mm to 400mm, predominantly in winter. The landscape features gently undulating sandplains with soil types often consisting of yellow sands, sandy loams, and duplex soils (sand over clay), which can be prone to acidity or salinity. The specific activity for this project involves applying synthetic or non-synthetic fertilizers to address material soil deficiencies, a practice designed to boost plant root biomass and subsequently increase soil carbon levels. The project is developed in partnership with Agriprove, a prominent soil carbon project developer in Australia.