The effectiveness of effluent management

L to R: Dr David Houlbrooke, Dr Richard Muirhead and Dr Ross Monaghan

AgResearch’s Dr David Houlbrooke is leading some of the research into why the same effluent management practices can produce good results on some farms but poor ones on others.

The management of dairy effluent in New Zealand has typically involved the daily collection of wash down effluent to a concrete sump and then applying it to the pasture using a twin boom travelling irrigator.

Factors affecting the effectiveness of effluent application include the volume of effluent, the types produced, the use of pond storage and control of application depths and rates. But understanding how various soil and land types process effluent at a farm scale is where more work is necessary.

Generally well drained soils perform well in their ability to filter faecal microbes and attenuate applied nutrients. However, well drained soils can deliver greater amounts of drainage water than poorly drained soils and can provide more opportunity to leach nitrate if total nitrogen (N) inputs to the effluent block are excessive. This can occur where paddocks receive both effluent and N fertiliser inputs.

Land which is rolling or sloping also has less capacity to absorb and process waste mater, compared to well drained flat land with fine to medium soil structure. The effect of these conditions can be made worse by climate.