Sensible effluent spreading ensures farms benefit - Waikato Regional Council

For sound environmental reasons, effluent is often talked about as a contaminant, with a focus on the risks involved if spreading it is done when conditions are not suitable.

But the Waikato Regional Council also recognises clearly the positive potential of effluent given the ability of the nutrients it contains to boost farm productivity and keep fertiliser costs down.

The key, of course, is to spread it sensibly when chasing such gains, so as to protect waterways but also to ensure maximum on-farm benefit.

One of the main aspects of a well-designed effluent system is the ability to spread nutrients when they are able to be taken up to increase plant-growth.

In order for this to happen, effluent should be spread at depths and rates which do not create ponding.

If it's not, liquid effluent and the associated nutrients will end up draining through the top soil layer and beyond the root zone of plants meaning it is not able to be used for plant growth.

The council's farming services team is finding that many farmers that have upgraded their effluent systems enjoy the fact that they have more flexibility to spread effluent when they want to spread it, rather than when the pond or sump is full.

This helps them avoid ponding, allowing them to make the most of the nutrients.

The DairyNZ Facts and Figures booklet shows the level of nutrients available in effluent. It shows that effluent from 100 cows in a pasture-only system equates to 590 kilograms of nitrogen per year, 70kg phosphorus/year and 540kg potassium/year.

Not unexpectedly, the levels of nutrients tend to increase as the amount of supplementary feed increases.

Different farmers choose to use their effluent in different ways with some, for example, preferring to store it for long periods of time and spreading on to crops to increase germination activity. Others prefer the little and often approach throughout the year.

The general feeling within the industry is that if farmers started thinking about effluent more in regards to it being 'nutrients' rather than a 'contaminant' the attitude around the way it is managed will continue to change for the better.

A system that both protects waterways while also improving the farm system - by reducing fertiliser costs and spreading nutrients when they are most beneficial to the environment - should be something that all farmers aim towards.

Often improvements in one area may have detrimental effects to other parts of a system.

But the environmental and economic co-benefits of effluent upgrades is often what gets farmers over the line when it comes to seeing a net benefit from such expenditure.

They can see that while the initial cost can, at times, be high the payback period for some of these systems is often not as bad as initially thought.