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Every year, landlord Dwan Jantz comes to her field
near Wilbur when the grain is being harvested.

Photo by William Bell




Tillage guidance

Ecology releases first set of ag BMPs to help regulate nonpoint source pollution

Aug/Sept 2020
By Trista Crossley

Back in March, the Washington State Department of Ecology (Ecology) published the initial chapter of their voluntary clean water guidance for agriculture. This draft chapter, which is the first of 13 that the department plans to release over the next five years, covers tillage and residue management.

To help protect water quality, Ecology recommends growers implement a conservation-based tillage system that achieves a residue coverage of 60 percent or more or a STIR value of 30 or less. The STIR value is a soil tillage intensity rating used by the Natural Resources Conservation Service (NRCS) to evaluate the effect of tillage on soil health.

For lower-residue crops that might have a difficult time meeting those values, such as potatoes, peas, beans or lentils, Ecology recommends a set of secondary tillage best management practices (BMPs):

• Minimize tillage to the maximum extent possible and supplement residue cover to achieve 60 percent soil coverage; and

• Use supporting, sediment-trapping BMPs to protect water quality from erosion in cases where it cannot be controlled in the field.

According to the guidance, “Recommending a minimum of 60 percent residue coverage provides a more conservative lower end limit. It achieves an effective erosion control of approximately 90 percent, or more, while limiting soil organic carbon loss. While residue coverage above 60 percent provides for increased erosion control, few crops can generate enough residue to meet those levels. In addition, the types of tillage systems that can be utilized also becomes a limiting factor. The 60 percent residue goal achieves effective erosion control while allowing for a variety of conservation-based tillage options, encouraging greater adoption by more farmers.”

“The goal behind the guidance is to provide more specific guidance tailored to what producers can do to protect water quality,” said Ben Rau, Ecology’s Watershed Planning Unit supervisor. “We are hoping the guidance will be used by both producers and local partners working in watersheds with producers, such as conservation districts and NRCS.”

Under the Clean Water Act, Ecology is required to provide guidance on all nonpoint sources (NPS) of water pollution. The guidance is required to identify best management practices and include measures to control NPS pollution. According to Rau, the other major sources of NPS pollution in the state, such as onsite septic systems and stormwater runoff, already have guidance that is tailored to them or have a regulatory program in place.

“The agriculture sector was really the gap in the guidance that we had,” he said.

Rau stressed that the recommendations are voluntary, and he hopes they become an additional source of information for producers who are making decisions about what tillage practices to use. Ecology worked with NRCS to make sure there wouldn’t be a conflict with NRCS’s recommendations, which aren’t necessarily designed to focus on state water quality standards. Producers who implement Ecology’s recommendations will be assumed to be meeting water quality standards.

“The intent is that if you implement recommendations, you are good to go. If there’s an open complaint and they are implementing these recommendations, unless there’s something that really went wrong with the operation, they are good to go,” Rau said, adding that the recommendations are meant to be flexible, as every farm operation is dealing with different issues. “If you feel like there’s a different way to protect water quality…that’s just as legitimate of an approach. We want to be clear about our recommendations, but also, be clear that people have the option to put together their own system to meet water quality goals. The question at the end of the day is whether the practices being implemented protect water quality.”

This isn’t the first time Ecology has issued BMPs concerning agricultural practices. Rau said they released draft guidance for livestock operations about 10 years ago that wasn’t particularly well received. This time around, the department reached out to agricultural industry groups and their own Agricultural Water Quality Advisory Committee for feedback and came away with two recommendations: to form an advisory group and to include a discussion about implementation of the recommendations.

“I think it’s important that we have both pieces,” Rau said. “We want to have good guidance and how effective the practices are in meeting the end goal, but it’s also important to have the perspective of the producer and what it takes to implement these practices. What might be barriers to them, and what are different ways to address those challenges and barriers?”

The guidance recognizes that conservation tillage practices may not be suitable to all operations or crop types, and the practices that are most appropriate to protecting water quality for any given operation are highly dependent on farm-specific conditions and circumstances and the producer’s priorities, crops and production methods. The guidance also recognizes that there can be a significant monetary cost to adopting conservation tillage. Rau encouraged producers to talk to their local technical assistance providers, such as conservation districts and NRCS, to explore what options are available.

The advisory group includes agricultural stakeholders, stakeholders for local government, local conservation districts, NRCS and Washington State University researchers. The first task was to divide the guidance into manageable chunks. Besides tillage, other chapters will cover crop systems, nutrient and pest management, sediment control, water management and livestock management. Each chapter will be published in draft form so the public will have an opportunity to review the recommendations and provide feedback.

“Our hope is that (the guidance) is useful to conservation districts and NRCS and ends up being something else they can put in front of producers when working with them on that suite of practices they’ll be implementing,” Rau said. “I feel like the more information we can provide for producers, the better they can make informed choices. One of our big goals with the guidance is to provide that information so that individual producers can make those decisions from a really informed place.”

The first chapter of the guidance is available at That page also contains links to an online comment form.