Effluent management and operation

Effluent management

New Zealand’s dairy farm systems produce large quantities of nutrient-rich effluent, which is captured from milking sheds, holding yards, feed pads, standoff pads and animal shelters. The average dairy cow produces about $25 worth of nutrients annually as farm dairy effluent (FDE). For a 400-cow dairy herd this represents about $10,000 of nutrients annually. Using effluent to supplement fertiliser presents an opportunity to capitalise on a cost-effective nutrient resource while improving whole farm nutrient use efficiency.

Good effluent management is a combination of having a well-designed effluent system and processes for people that make sure the effluent the system collects is applied to pasture in the right amount at the right time.

On-farm benefits of good effluent management include:

• Fertiliser savings
• Improved soil condition
• Prevention of animal-health issues
• Compliance with council rules or resource consent.

Making good effluent irrigation decisions

The key to good decision making is understanding the soil water deficit. It is essential to prevent ponding and run-off and to avoid applying effluent to saturated soils.

Soil water deficit is the amount of water (ie effluent) which can be applied to the soil before it reaches field capacity (which refers to the amount of water held in the soil after excess water has drained away). If effluent is added at field capacity it will likely result in ponding, runoff or leaching.

Effluent application to pasture

To get good value out of effluent and reduce environmental risk, consider setting up an effluent management plan for your team to use. The management plan should consider:

• Maintenance and performance checks. Good practice is to keep up with maintenance and undertake frequent irrigation bucket tests to ensure your system is operating as intended.
• Timing of application. The best way to ensure that plants can take up nutrients from effluent is to only spread it when there is sufficient soil moisture deficit.
• Rate of application/depth of application. Ensuring the effluent is applied at a rate that can infiltrate the soil and not pond or run off, preventing drainage beyond the plant roots.
• Actively managing storage levels. Ensuring storage levels are monitored and reduced during fine periods to prevent full systems heading into the higher-risk times of the year.

Effluent spreading calculator

The DairyNZ Farm Dairy Effluent Spreading Calculator (app or Excel spreadsheet) allows farmers to easily calculate nutrient loadings and application rates for dairy effluent based on a number of customisable inputs. This means that farmers can manage the application of their effluent nutrients with greater precision.

There are two calculators in this app, the Quick Calculator which is for spray irrigation systems such as travelling irrigators and sprinklers, and an Advanced Calculator which is for slurry tankers and muck spreaders. It is also available as an excel spreadsheet if you prefer to use your computer.

Download this handy app to take the guesswork out of determining your effluent nutrient loadings

• Download for iOS
• Download for Android
• Download as Excel spreadsheet

Irrigation application systems

Keeping on top of maintenance tasks for irrigation application equipment is essential for good performance, and many farmers like to keep a regular check on their application depths and rates.

We have a range of guides that will take farm staff through the important parts of operating and maintaining irrigation systems. They include tips, troubleshooting advice, and an explanation of how to measure application depth and rates.

View our range of irrigation guides