We’re often asked if it’s safe to spread effluent over calving paddocks, and yes, you definitely can, but not too much. As with any paddock, adding too much brings the risk of nitrate poisoning, and paddocks with pregnant stock should keep a close watch on the nutrient levels entering the soil.
How much is too much?
Hill Laboratories suggest a nitrate-N level 0.10 - 0.15% or 1000 - 1500 mg/kg (or ppm), or 0.44 - 0.66% nitrate is safe to feed non-pregnant animals. So to ensure you’re not adding too much nitrate to the soil, it’s important to test the levels in your slurry. While there are laboratories that can do this, having your own testing kit can be a very cost effective option which enables you to test yourself on a weekly basis and adjust your spreading accordingly. A test usually only takes around 5 minutes to conduct.
What happens if I spread too much?
Spreading too much can result in excessive levels of nitrate in the soil, which is then absorbed by the plants and passed on to grazing cattle. When too much nitrate is absorbed by the plant, it can’t convert the nitrate into protein fast enough. Once consumed by cattle, it converts in the rumen, and then binds to haemoglobin in the blood, stopping the haemoglobin from carrying oxygen. This is where death can occur rapidly from suffocation.
Pregnant or lactating cows have a higher risk of nitrate poisoning as they tend to consume higher amounts of feed within a short time.
How do I reduce risk while spreading?
- Test your nutrient levels before spreading
- If your slurry has a high level of nutrients be sure to spread over a larger area or speed up your irrigator or slurry tanker for a lighter application.
- Don’t over saturate your cow paddocks – in a calving paddock keep the nutrient level below a nitrate-N level of 0.15% or 1500 mg/kg (or ppm), or 0.66% nitrate.
Where calving paddocks are where the irrigation system is you may need to reduce the amount being spread throughout the calving season. In this situation it is important to have adequate storage and/or an alternative way to spread out to other paddocks such as a slurry tanker or drag hose system.