Effluent tests as fertiliser

Dairy effluent could have lots of benefits for cropping farms, but it is important to understand how its nutrients are released, according to Craig Tregartha, of Plant and Food Research.

Mr Tregartha was a speaker at the Foundation for Arable Research's Arable Research in Action field day at the Chertsey trial site recently.

Every effluent was different and it was important to know the nutrient composition when deciding on application rates. It also released nutrients more slowly than chemical fertilisers.

Understanding the rate of release was a critical factor that influenced the amount of extra fertiliser that could be required to reach yield targets.

Solid effluent had advantages over liquid or slurry, Mr Tregartha said, in that it was lighter to transport and it could be stored before being spread.

Applying a more concentrated effluent with less water could reduce the cost of application and potential delay before a paddock could be planted.

He said about a quarter of dairy farmers in Canterbury now had solid effluent separators.

It had more benefits than just as a fertiliser, with its organic matter improving soil structure and its range of nutrients being in organic form.

The amount of effluent which may be applied to cropping paddocks was controlled by regional council rules. These set the total amount of nutrient (and nitrogen in particular) that can be applied during a year.

Solid effluent waste is being used on crops at the site in a trial funded by the Ministry of Primary Industries sustainable farming fund.

Five plots are under scrutiny, one with half the effluent applied in autumn, one with half applied in spring, one with it only applied in spring, one with urea applied and one with nothing applied.

At this stage the urea plot was ahead but it was early days, Mr Tregartha said.

By Maureen Bishop.