joy, with nitrates leaching into the poor soils of the canterbury plains and polluting waterways.ystems here? mike: light stony soils, lots of cows on it, a lot of fertilizer and palm kernel going on to feed them. lots of urine going out and down through those soils, into the rivers; the aquifers and rivers really all acting as one here, moving out towards the coast and you're getting the nitrate levels just rising and rising and rising really quickly. great for farming, but not so great for fresh water. yaara: back on the ground at this dairy, 600 cows are coming in for their daily milking. john sunckell is a third-generation farmer. like many in the canterbury region, he converted from traditional mixed farming to dairy. john: it provides a future for my family and for the generations that have come before. i have five full-time staff on farm. it puts bread on their table, and it bolsters and builds communities. ♪♪♪ ♪♪♪ john: so we, you know, rotate, so it's rotational grazing. we run a-- yaara: john is showing me around his 500-acre property. in the economic downturn of the lat