Understanding water, and how it moves through soil and landscapes, is crucial to understanding Aotearoa’s current freshwater crisis.
Soil microbes can convert various forms of nitrogen into nitrate. Having nitrate available in soils is good for farming, as it’s the easiest form of nitrogen – essential for growth – for plants to take up. However, nitrate is not easily held in the soil. The nitrate ion has a negative charge – so it doesn’t get electrically held in place by clays or organic matter. Nitrate is also water-soluble. So nitrate easily gets flushed into groundwater and surface water. This is the crisis that is now percolating through much of New Zealand’s water supply.
The cause
The cause of the crisis is well known: synthetic nitrogen fertiliser. New Zealand’s dairy herd nearly doubled in three decades, from 1990 to 2019, according to Stats NZ. That growth was built on a huge uptick in the use of synthetic nitrogen fertiliser, which increased more than 600 percent during the same period. Nitrogen can spark quick grass growth, allowing farmers to pack more cows into their paddocks. However, any
