Right amount, at the right time

This not only saves on fertiliser costs and enhances soil health but also helps prevent animal health problems and ensures compliance with local rules.

Understanding soil water deficit is crucial to prevent run-off and applying effluent to saturated soils.

There are tools available, such as the DairyNZ farm dairy effluent spreading calculator, to help manage the application of effluent nutrients with precision.

Finally, regular maintenance of your irrigation application equipment is vital for optimal performance.

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 runoff and to avoid applying effluent to saturated soils.

Soil water deficit is the amount of water (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 spreading

New Zealand’s dairy farm systems produce a large amount of nutrientrich 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.

Effluent is commonly grouped into three broad categories based on dry matter (DM) content: liquids (0–5%), slurries (5–15%) and solids (>15%).

Application of effluents is typically via land.

Effluent application to pasture

To get good value out of effluent and reduce environmental risk consider:

• Timing of apllication - 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/capacity available in the soil. If the soil is too wet there will be leaching or run off.
• Rate of application/depth of application - Good practice involves ensuring the effluent is applied at a rate that can infiltrate the soil and not pond or run off, drainage beyond the plant roots is avoided and it is spread evenly.
• Where possible, leave a buffer strip next to waterways and farm boundaries and know your consent conditions and/or regional rules.

Article by DairyNZ.