OPINION: I saw a headline from OverseerFM that less nitrogen is being lost to the soils across Canterbury dairy farms.
My first thought was, is it simply because of fewer cows per hectare? Have farmers maintained production per hectare while reducing nitrogen losses? If so, cheers to that double success.
The OverseerFM study covered 302,000 hectares of dairy production land and 1269 farm records. This is a chunky 25% of the Canterbury plains. In 2021-22, the average nitrogen loss was down to 46.2 kg/ha, from 63.8 five years earlier.
Nitrogen loss is what is lost into the soil and not used up by any plants. It is not a measure of what might be going into waterways though. That's another whole study.
So how have farmers done it? The short answer is stocking rate per hectare has only dropped one percent over the five years of the study, so it's not a case of simply removing cows.
The OverseerFM Report is clear the drop is not related to changes in dairy farm area or herd size over this period. It says the modelled decrease in nitrogen loss indicates changes in farming practices. Let's hear about these management changes please, as that's a clear win-win.
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