How Are US Dairy Operations Impacting Water Quality?

ANALYSIS - The tremendous increase in productivity and efficiency in the US dairy industry has also come with an array of negative environmental impacts that are a major challenge from a sustainability perspective, reports Sarah Mikesell, live from the Large Dairy Herd Management Conference held in Oak Brook, Illinois, US.
calendar icon 11 May 2016
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Katharine Knowlton, professor at Virginia Tech

While the productivity progress is important and needed, the industry also needs to work to minimise the negative effects including the impacts on water quality.

Manure is a rich source of nutrients including both nitrogen and phosphorus. Despite the inherent value in fertiliser, spatial intensification of livestock production in recent decades has created problems as the amount of manure produced in a region overwhelms the assimilative capacity of cropland.

Nutrient concentration

“There’s been a tremendous increase in efficiency and productivity in the dairy industry and animal agriculture in general because of increased specialisation, which essentially means that we're bringing feed nutrients in from the phosphate mines in South Florida and the Corn Belt and Wheat Belt,” said Katharine Knowlton, professor in the Department of Dairy Science at Virginia Tech.

“With our current manure treatment technologies, turning around and sending those manure nutrients back where they originally came from is not economically feasible, so over time those nutrients tend to accumulate and concentrate in areas of intensive animal agriculture.”

That creates areas like the eastern shore of Maryland and the Shenandoah Valley in Virginia where animal agriculture is the source of more than 50 per cent of the either nitrogen or phosphorus loading to the surface water in that region, she said.

Phosphorus tends to be a bigger problem than nitrogen. Nitrogen and phosphorus are already in imbalance in manure relative to crop needs, so when we apply the nitrogen that the crop needs we are over applying phosphorus, and that phosphorus can ultimately run off.

Regulatory approaches

There are two different regulatory approaches to nutrient management. One is process based, meaning if we do the right things, we will have the right result.

“Our permit base programme in the US is what I will call process-based. It's built around a nutrient management plan, and it's built around best practices, regular analysis of manure and soil and, in some places, ground water, site-specific crop production and manure application. It's front end,” she said. “The assumption is if we do the right thing, we will have the right result. It’s process-oriented regulations, but it doesn't always work.”

The second approach is more goal or target oriented. In the US, this means that the total maximum daily load is the water quality program where we let the water tell us if it’s working.

“We sample the water and if the water exceeds the state standards then by definition we haven't done enough and we have to go back and ratchet up our process base,” she said.

This approach can be frustrating to producers who believe they are following the rules according to their permit, and are then asked to do more because the water is not clean enough.

“In the US, what we're increasingly seeing is a bit of a hybrid of the two. EPA is telling the state, ‘Your water is not clean enough. We've concluded that your permit program isn't strict enough, so do something about it,’” Dr Knowlton said.


These approaches create a lot of obvious challenges.

Producers don't like it when their management practices don't immediately result in reportable, documentable, nutrient facts and water quality improvement.

Their concern is why bother to do all the work with no results. Regulators don't like it when practices don't translate immediately into water quality benefits because they tend to think enough is not being done.

“There are a lot of reasons why the water quality doesn't immediately reflect the management practices. This is just our best reality and sometimes the regulators have to take a little bit of a pause and wait for the science to catch up,” she said.

The biggest challenge with nutrients and water quality is there can be a decades long lag between changes in management practices that result in changes in surface water quality and ground water quality.

This delay happens for a number of reasons. Nutrient losses are intermittent; they are diffused; they are difficult and expensive to monitor. There is a time lag especially with nitrogen storage in the soils and in aquifers.

A real timeline exists between changes in what we're putting in the soil and what we're seeing running off, and measurements over time are confounded, she noted.

“European research has quantified this decades long lag time, but also demonstrates the problem of confounding,” she said. “In the EU, for instance, increased water quality regulations occurred at the same time as other policy changes like the implementation of the milk quota system in the mid 80s, and cuts in pork and poultry quotas in the 90s.”

Nutrient management can be challenging because it’s rare to see those immediate connections. But Dr Knowlton recommends the industry continue to do the things they know they have to do.

“There are a lot of technologies evolving. We do need continued research in this area, and we have made real improvements. It isn't going to yield immediate water quality improvements, yet over time it generally does improve water quality,” she said.

Sarah Mikesell, Senior Editor

Sarah Mikesell, Senior Editor

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