No silver bullet for phosphorus
In New Zealand’s soils, phosphorus does a great job at growing plants but unfortunately it does the same thing if it makes it into our water.
Water efficiency is now a catch-cry and the dairy sector is being urged to lessen its water ‘footprint’.
Crucial to this challenge is how effluent is managed. Recycling and reusing the nutrients in dairy shed effluent is good practice, showing that dairy farmers are doing the right thing. This comes with a price tag: 70% of dairy farmers’ environmental spending goes on effluent management (see graph).
Challenge to status quo
Well-managed effluent forms a key part of the nutrient cycle onfarm, but in spring when cows are calving and spring rains keep falling, effluent ponds can fill and the traditional and viable method of irrigating or spreading of effluent can become a headache.
This can lead to accidental breaches of discharge, resulting in potential leaching or run-off of nutrients into surface water, perhaps damage to a farmer’s reputation and the risk of a hefty fine. In a cold wet winter, spreading effluent nutrients to keep ponds under control can also increase the potential for nitrate leaching.
If farmers are also looking to use feed pads more in the winter to avoid pugging, as a way to mitigate potential phosphate run-off, then effluent capture, treatment and reuse becomes even more important.
Recycling and reusing water
There are a few reasons why the ponds are at risk of filling up too fast – reaching the danger zone. Without tackling the root cause, the temptation can be simply to build a bigger pond with all the costs and risks entailed.
Now a new generation of storage ponds is on its way which, with reporting, management and decision support technology, a farm would be able to easily track, show and improve its nutrient efficiency and water efficiency– a win-win for all.
• Jamie Thompson is a Ravensdown effluent technology manager. This article first appeared in Ground Effect autumn issue.
