Ways to keep nutrients out of waterways

AgResearch scientist Tom Orchiston. Photo: Nicole Sharp
AgResearch scientist Tom Orchiston. Photo: Nicole Sharp

How can we reduce sediment, phosphorus and E. coli getting in to waterways?

AgResearch scientist Tom Orchiston put the question to farmers along with giving advice on good management practices onfarm at Dairy NZ’s Farmers Forum on May 4.

Sediment in waterways reduced the habitat and disrupted the eco-system in streams, he said.

When it came to phosphorus, it only took a small amount to have a large impact on the water way, and if E-coli was in water ways it could impact human health, he said.

Good management practices could reduce the amount of nutrients leaching into water ways.

The main piece of advice Dr Orchiston gave to farmers was to strategically graze winter crops, as it could reduce both run off and sediment loss.

An example of this was a study run at Telford, a division of Lincoln University, where two similar paddocks were grazed in the same and different ways to test the impact.

The study was completed as part of Pastoral 21.

Strategic grazing meant avoiding critical source areas, selecting winter grazing paddocks that would minimise nutrient loss, considering soil, slope, moisture and stock management before sowing, grazing top to bottom, back fencing regularly and keeping stock out of damp areas, Dr Orchiston said.

Strategic grazing could reduce sediment losses by 70-80%, he said.

Dr Orchiston also encouraged farmers to think more about how, where and why when it came to applying fertiliser.

‘‘Make sure you are not applying to pugged or compacted soil. Heavy soils and sloping carries more of a risk.’’

Out of all nutrient losses, phosphorus could be one of the most damaging.

‘‘Small increases in the amount of P in water ways can have a significant impact on water quality . .. Keep the P [phosphorus] on the paddock, it means you are fertilising your paddock rather than your stream.’’

DairyNZ senior scientist Ina Pinxterhuis spoke about how farmers could reduce nitrate leaching from grazing animals.

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