Wise fertiliser use can save farmers money
With the warmer weather, farmers have been busy either putting fertiliser on their paddocks or preparing to do so.
It’s important to use fertiliser wisely to avoid unnecessary spending and potentially negative impacts on water quality.
If farmers apply too much fertiliser or apply it in the wrong place or at the wrong time, this resource can become a contaminant, polluting ground water and promoting algal growth in waterways.
Before buying fertiliser, I recommend farmers look at their nutrient budget and talk to a fertiliser representative about the issues involved to ensure they apply only enough fertiliser to grow the pasture or crop needed. That will help minimise impacts on both the economics of the farm and the surrounding environment.
Importantly, if farmers don’t already have a nutrient budget, they should ask their fertiliser representative or consultant to prepare one for them.
There are potential risks involved with fertiliser application and there are strategies farmers can use to help avoid these problems. Nitrate leaching Pasture plants need nitrogen for healthy leaf growth. But N is an extremely mobile nutrient.
If farmers apply more nitrogenous fertiliser than plants can take up, the excess N ends up leaching through the soil into ground water or surface water.
An important reason for inefficient N cycling in grazed pastures is nitrogen deposited by the grazing animals, in concentrated urine patches.
Farmers can reduce the amount of N leaching from pasture by:
Avoiding fertiliser application when plant uptake of nitrogen is low.
Applying fertiliser in split dressings.
Making sure farm dairy effluent is applied to a large enough area.
Adjusting fertiliser policy for effluent irrigated areas.
Standing cows off pasture during wet weather and capturing the effluent for later application.
Phosphorus behaves differently to N because it binds with the soil and only dissolves slowly in water over time.
This means it doesn’t readily leach to ground water but it can still pollute waterways through surface run-off and soil erosion.
As with nitrate leaching, farmers can reduce the amount of P running off pasture by ensuring they don’t apply phosphate fertiliser when heavy rain is forecast. Farmers should also: Follow the NZ Fertiliser Manufacturers’ Research Association code of practice for nutrient management.
Apply fertiliser when the grass is in a growing phase.
Make sure fertiliser isn’t applied near waterways.
Leave a grassed buffer strip between paddock and waterway.
Control run-off from tracks, races, feed and stand-off pads.
To summarise – large nutrient surpluses can hurt the environment and mean a waste of farmers’ hardearned cash on fertiliser.
Bala Tikkisetty is a sustainable agriculture coordinator at the Waikato Regional Council.