Many Canterbury soils are naturally low in fertility and farming contributes to further nutrient loss. The loss of soil nutrients is a concern where the natural fertility levels are lowered for a period of years or where a loss of fertility reduces the ability of the soil to maintain vegetation, increasing the risk of erosion.

Lowered soil fertility can also allow undesirable plants, such as hieracium, to establish. It is a particular issue for some parts of the high country.

The Cause

Production from the land always results in a loss of soil nutrients by removing vegetation or animal products. Cultivation and vegetation burn-off also reduce soil fertility by removing organic matter from the soil.

We need to replace nutrients if existing ecosystems and agricultural production are to be sustained. We can do this by returning organic matter to the soil, using fertisiler, or using nitrogen-fixing pasture plants. In the extensive high country, such intensive land management practices are often seen as uneconomical, therefore the problems evident in this part of the region.

The Options

In Canterbury, the main sustainability issue associated with a loss of soil nutrients is an increased risk of erosion, so the management options are the same as in the Induced Erosion section. The implementation of these options would focus on the high country.

Provide information and advice on soil fertility management.
Provide information and advice in preparing property plans which incorporate fertility management.
Help with preparing codes of practice for cultivation, grazing and vegetation removal.
Prepare rules that require land uses in at risk areas to maintain soil fertility.