Best practices for optimal pasture application
Good effluent management on a dairy farm combines a well-designed system with proper processes to ensure the right amount of effluent gets applied to pasture at the right time.
Storage facilities must be sealed so they do not allow contaminants to leak out; all areas where effluent is stored should be sealed to prevent leachate losses to groundwater.
Farmers should avoid locating effluent storage facilities at sites with high water tables or a risk of flooding.
The use of well installed and guaranteed synthetic (e.g. plastic, rubber or concrete) liners is recommended. Farmers may be asked for a producer statement to confirm the pond and liner will meet the construction and sealing requirements of district or regional councils.
It is also vital to manage storage volumes and pond levels throughout the year; an empty pond gives a farm adequate capacity for when the farmer cannot irrigate because of unsuitable conditions, or when extra storage is needed, e.g. at calving.
A full pond may overflow or cause odour problems, and may result in financial loss as a farmer loses control of effluent and the capital investment tied up in the pond.
Seasonal targets
Spring: the pond is filling with effluent, particularly during wet weather, or when the farmers are too busy to manage the effluent system. Small volumes of effluent can be irrigated as soil water deficits allow.
Summer: the pond should be kept as empty as possible.
Autumn: the pond should be maintained at a low level. Try to empty the pond while conditions allow.
Winter: ideally keep the pond empty, or at a low level. Where possible prevent stormwater entering the pond, off unused yard areas, etc. Areas contaminated with dairy effluent cannot be diverted. Consider using the safety escape ladder for pond level marking system.
Storage capacity
You need enough storage for:
- Rainy periods when the soil is too wet to irrigate
- Busy periods when farm labour is stretched and you do not want to irrigate
- Equipment failures (pumps or irrigator), when you cannot irrigate. Adequate storage will allow you to keep effluent for use when nutrients are most needed (i.e. drier months or when putting down a crop).
- An empty pond will give the capacity for when you can’t irrigate because of unsuitable conditions, or if you have factored in extra storage for times of year such as calving.
- A full pond may overflow or cause odour problems, and may result in financial loss as you lose control of effluent and capital investment tied up in the pond.
