Colorado Regulation 85 and Large-Scale Plant Growers

Source: Colorado State University Extension and Colorado Department of Public Health & Environment

Colorado passed Regulation 85 in 2012 to reduce nutrient pollution in lakes, rivers, and streams.

The regulation does not currently regulate agriculture or other horticultural crop growers, but recommends voluntary action to avoid future regulation after 2022.

In Colorado and across the United States, farms are being identified as one source of nutrient pollution. Nutrients such as nitrogen and phosphorus can run off fields and accumulate in surface waterways and groundwater, causing water quality issues. Excess nitrogen and phosphorus in water sources can cause:

  • algal blooms
  • reduced dissolved oxygen content
  • harm to aquatic plants and animals
  • impaired drinking water supplies


“Nutrients in water can affect downstream users, diminish aquatic life and may increase the need for treatment of water,” said Troy Bauder, Water Quality Specialist at Colorado State University Extension. “In Colorado, we are really fortunate that a lot of water large municipal water supplies are above agriculture and in the mountains. Most often, towns and cities use water first for drinking supplies. Then, it goes through treatment plants and into rivers.”

Currently, Regulation 85 places the most requirements on wastewater treatment plants. The plants are responsible for removing excess nitrogen and phosphorous from water before returning it to the watershed. In some cases, water utilities are required to upgrade facilities to meet discharge limits.

Regulation 85 does not have any mandatory requirements of crop growers currently. Instead, plant producers are encouraged to adopt best management practices (BMPs) that can help reduce nutrient pollution in surface waterways.

Implementing BMPs & Sharing Information Could Prevent Future Regulation

Regulation 85 sets a 2022 deadline for evaluation of the current voluntary approach for limiting nutrient pollution. The Water Quality Control Commission from the Colorado Department of Public Health and Environment will assess the nutrient levels in waterways and the extent contributed by farmers and plant growers. This assessment will include the review of agricultural and horticultural practices, surface water quality data, and related testimony. Additional regulations may be considered, depending on the success of voluntary efforts in limiting nutrient levels in waterways.

“If growers implement BMPs now, talk about them and show their efforts to their customer base, they can show what that industry is doing to be good stewards,” Bauder suggested. “We don’t tell our story really well. We go about our work to get through the growing season. We’re all busy. Someone may point a finger at us, and say, ‘You are an environmental problem; you need to clean up your act.’ We need to show we are implementing best practices already, and make sure the positive actions that the industry is taking are well known.”

Implementing the 4Rs to manage nutrients

He pointed to a concept called 4R nutrient management, that has been around for about a decade in the agronomic world. Also applicable to the horticulture industry, the four R’s are:

  • Right source: use the correct formulation of fertilizer for each situation,
  • Right amount: use the correct amount for your production goals and make sure through soil testing,
  • Right place: use a fertilization distribution method that is most appropriate for the situation so it stays where it is needed, and
  • Right time: distribute fertilizer when the plant needs it and can use it most effectively.

Implementing the Four R’s to Manage Nutrients

Doing a site assessment is most important for growers, so they can understand their site characteristics. “It’s important to know where the runoff is going during rainstorms. Does it go to a dry gully or stormwater collection point? What is the field’s proximity to a stream, lake or other water body? Depending on the answers, the grower might want to think about ways to mitigate the situation,” he said.

The goal is to design the site for minimum runoff. Grass strips and places where water can flow through before leaving the site can act as filters. But, care should be taken when collecting water so as not to run into water rights laws, he added.

Then, growers should assess their fertilizing practices such as whether nutrients being supplying to the soil in fields and pots is reasonable and whether people applying fertilizers are trained. “I think most of our growers with high-value horticulture crops typically are pretty aware of their inputs and applying them judiciously,” he commented.

“We nearly always recommend soil tests annually in field situations,” he said. “Also when growing in pots, you want to know the numbers. If suppliers of potting mixtures are not providing information on the soil nutrient content, I recommend testing random samples as the batches come in. Soil test fees are under $20 and sometimes as low as $12. The labor costs are probably bigger than the actual test fees. Test kits may also be an option”

Example filter strip, a best management practice with water quality monitoring equipment installed

Soil tests will tell you one of three things: your inputs of nitrogen and phosphorous are correct, you’re putting on too much and need to cut back on how much you fertilize, or you aren’t putting on enough and need to increase fertilizer or compost for better production. If you have been using too little or too much, you will have an economic gain by finding that out and adjusting.

Site management is also important for the horticulture industry, including paying attention to storage of compost, soil and fertilizers. “Does the pile have containment around it? At large operations, is your fertilizer mixing and loading over a pad spills and runoff aren’t falling on the ground? It really takes only one spill to mess up a situation,” he said.

For landscapers, this may even be more important. Keeping fertilizer off of hard surfaces when landscaping at a business or residence is necessary to prevent it from entering waterways.

“In Colorado we don’t treat stormwater by and large. Cities have permits to allow certain amounts of pollution in stormwater,” he said. “Landscaping crews should be trained to spread fertilizer carefully, keeping it on the soil and cleaning up if it falls on hard surfaces.”

More information and resources related to Regulation 85, agricultural water quality and BMPs: and