Wastewater is “used water from any combination of domestic, industrial, commercial or agricultural activities, surface runoff or storm water, and any sewer inflow or sewer infiltration”.
By definition, dairy effluent is wastewater. I think this depends on how you use it. When managed correctly, you could call dairy effluent, “beneficial water”.
According to DairyNZ, the average dairy cow produces about R350 worth of nutrients yearly as dairy effluent. When this is treated as wastewater it is about figuring out how to get rid of it. When viewed as beneficial water, it is about viewing the opportunity cost of these nutrients. If you take a herd of 800 dairy cows, there is an opportunity cost of R280 000 a year from effluent.
Benefits of spreading effluent
- Source of nutrients: Effluent contains nutrients such as N, P, K, Ca, Mg, S, and trace elements which are all important for soil health.
- Source of organic matter: Improve soil life, structure, aeration, drainage, water holding capacity, and nutrient holding capacity.
- Source of moisture for soil: Dairy effluent adds to the moisture content of the soil, especially important in drier regions.
- Reduced animal health disease: Effluent that is left in a pond over long periods is a breeding ground for diseases.
Things to consider before applying
- Soil fertility: It is important to assess dairy effluent and soil sample results before applying effluent, in order to prevent oversupplying of nutrients.
- Soil moisture: Effluent must not be applied during periods of high soil moisture content, as it will end up in water sources, causing pollution and wasting farm nutrients.
- Soil infiltration: The speed at which water enters the soil will determine how much effluent can be put down at a time.
- Topography: The slope in the area should be taken into account when planning effluent application rates. Over application of effluent on steep areas will result in deposition of nutrients and water at the bottom of the slope.
- Rooting zone: It is important to know how deep the rooting zone is, in order to supply nutrients and moisture to the roots of the plants.
- Time of year: Effluent must be applied mainly during summer and autumn months when the soil moisture content is low. This will also help boost winter growth.
When farmers manage dairy effluent in the correct manner, it can be beneficial water instead of wastewater!
- https://en.wikipedia.org/wiki/Wastewater – Accessed 21 January 2019
- https://www.dairynz.co.nz/environment/effluent/managing-and-operating-effluent-systems/ – Accessed 21 January 2019
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