DairyNZ’s sustainable team leader Dr Theresa Wilson said farmers were now very switched on about effluent management and were asking better questions before installing or upgrading systems on their farms.
“We’re also getting a wider range of products and there’s more competition within the different technology which helps with price,” she said.
The big push now for farmers was linking dairy effluent with their nutrient requirements on the farm.
“Farmers are getting more aware of the soils on their farms and they know what they are putting on with effluent, so can balance out their fertiliser applications.”
Soils are a crucial factor when designing an effluent system and the majority of properties have information about their soils online at smap.landcareresearch.co.nz. If it’s not there, or there are still questions about the complexities of the soil, it might pay to contact a soil expert, especially in a catchment where soil risk is specified in the consent.
Wilson said regional councils also had soil maps, while the latest data coming through from various agencies would produce even more detailed soil maps within the next few years.
DairyNZ had extensive information on effluent design and maintenance on its website and advises using an accredited farm dairy effluent company that understands the dairy farm effluent code of practice and design standards.
That gives farmers the assurance their investment will be right for their farming environment and farming system, as well as complying with regional council requirements when it is managed correctly.
A list of accredited companies is available at effluentaccreditation.co.nz. So far 14 companies are accredited around the country, with another seven going through the accreditation process.
Then it’s a matter of working through the scenarios and factors to future-proof the system for whatever lies ahead. Dairy effluent infrastructure needs to be a system that caters for the farm tomorrow. Is it possible cow numbers will increase in the future, more supplements be fed to the cows, or a feedpad or a wintering pad added?
When selecting a site for effluent storage and disposal, Wilson said farmers needed to consider their neighbours and wind drift that could carry effluent odour. An effluent storage pond too close to lifestyle blocks was not a good choice. And farmers needed to think about how they would manage objectionable odour in their storage system if it arose.
For that reason, DairyNZ suggested removing solids before storing effluent in the pond and then frequent stirring to aerate the liquid. Today there are a range of options for removing solids such as weeping wall systems of slope screens which are considered a passive separation, or rotary screens and screw presses which are all mechanical separators. There are pros and cons to both types of separators and while the mechanical methods require a smaller area and filter the effluent better, they also have ongoing mechanical maintenance and energy costs.
If planning a feedpad, intensive feeding system or large herd, a solid separator should be considered to deal with the increased amount of solids in the effluent.
Storage is the single biggest cost in an effluent system and it has to have the capacity to store sufficient effluent to allow a farmer to irrigate it onto the pasture at a time it suits both them and the soils, as well as maximising its nutrient and water value.
The Dairy Effluent Storage Calculator is a software tool to help determine each farm’s storage requirement and though it is not an absolute or final figure, it helps farmers make an informed decision.
It uses 30 years of daily climate data and individual farm details to provide recommendations for the volume of storage required.
When constructing a pond, there are obvious considerations such as suitable clay or a synthetic liner over a geomembrane underlay to ensure there’s no leakage. Just as important is the safety of the pond.
An effluent pond is a dangerous place and both clay and synthetic liners provide no grip for someone to climb back out if they fall in.
Systems need to be planned and put in place to help people climb back out of a pond, using materials that last in corrosive effluent. Fencing around the pond should be aimed at keeping people out of the pond. It’s about minimising risk and farmers should have a health and safety plan in place as soon as the pond begins filling.
In high rainfall regions, ponds or tanks collect an enormous quantity of rain, which is why several farmers have added floating covers to their tanks. Wilson said it was one of the latest innovations for farmers to consider in those climates. Otherwise there’s a huge range of stormwater diversion designs available, including manual and mechanical. Care needs to be taken to manage the stormwater diversion correctly and DairyNZ advises installing an automatic facility or warning device.
The final component of an effluent system is the form of application, which could include pivots, travelling irrigators, slurry tanker, low-rate application systems such as pods, or a contract spreader. The choice is going to depend on a number of factors such as topography, soils and how it fits into the overall farming system.
Poorly drained soils, sloping land, high rainfall or sensitive catchments all need a low-rate application system, and a sprinkler-type system is best.
Once the dairy effluent system has been completed, appropriate manuals and training should be provided that cover both operation and maintenance.
There should also be a commissioning report that describes the system, including the evaluation of its performance, and an accurate plan with all the key items located and the dimensions of all key components.
Managing dairy effluent is not just about designing and constructing a good system. Any system needs to follow good practice to be effective. With good management, dairy effluent is a valuable resource that can increase pasture production and reduce fertiliser costs.
Poorly managed, it becomes both an environmental and business risk.
The farm team needs to be trained in the operation and maintenance of the system and be familiar with health and safety plans. A lack of time or knowledge are key causes of system failure and potential noncompliance. DairyNZ has a good practice guide to managing farm effluent on its website which includes guidelines for the farm team.
Before tackling a new project the best idea is for farmers to get out there and talk to people – experts, effluent companies and most importantly other farmers in the area who have installed different effluent systems and know at grassroots how each aspect performs.
Wilson said there were many good system upgrades going in and she had noticed a lot more on farms recently, which she attributes to a higher payout and systems that keep getting better.
