Assessing soil health following conversion from forestry to pasture in Canterbury

Soil health was assessed across land conversions from forestry (Pinus radiata) to irrigated dairy pasture.

Samples were collected and indicators of soil fertility, organic matter, soil physical condition and biological activity assessed. Soil health scores were calculated from the indicators and distance from optimum shown in radar plots. Soil health was improved for pastoral land use following conversion from forestry.

The time since forestry ceased and irrigation commenced had a signification effect on indicators of soil health, although many were not optimum even for the sites longest out of forestry/under irrigation.

The main factors contributing to lower scores across all sites were suboptimal fertility, high C:N ratios, high macroporosity, low microbial respiration and low earthworm abundance and diversity.

Some aspects (e.g., fertility) could be managed through nutrient application, while other aspects are more difficult to manage (e.g., C:N ratio and biological activity).

Management targeting these properties may accelerate the path to a healthy and well-functioning soil. The inclusion of a wider range of indicators can help to better understand and manage soils during the conversion from forestry to pasture.

This approach could be useful across all pasture systems to help ensure well-functioning soils.