Virginia Ishler Livestock & Environment

At the third Waste to Worth conference in mid-April in Raleigh, North Carolina, one of the topics covered was evaluating agricultural best management practices in the Chesapeake Bay program.

A major objective is to bring science-based facts to support the use of practices that will improve the watershed and be reflected in the bay model.

Jeremy Hanson from Virginia Tech presented on how the bay program is using an expert panel to review the relevant literature and develop recommendations on best management practices and how they should be incorporated into the bay model.

This expert panel functions as independent peer reviewers. It presents its findings to Chesapeake Bay partnership groups, and once the findings are approved they are built into the modeling tool.

One of the panel’s challenges is the availability of published literature. Even in topic areas where there may be a lot of research, there are still gaps.

This approach is a step in the right direction, but even with today’s advances in technology, there are limitations to what is supported by scientific fact or best professional judgment.

The second speaker in this series was Doug Hamilton from Oklahoma State University, whose task was to determine nutrient removal potential from manure treatment technologies.

Based on his panel’s assessment, the focus of technologies has been to reduce odor, solids and organic matter from the manure system.

There have been only minor reductions in nutrient loading. Instead, the greatest effect of treatment technologies is the transformation of nutrients to more stable forms.

Robb Meinen from Penn State University presented on injected manure. One of the aspects was providing a definition on injected and incorporated manure.

Manure injection is defined as the mechanical placement of manure into the root zone with surface soil closure at the time of application and soil surface disturbance of 30 percent or less.

Manure incorporation enters the soil profile within a specified period of time. It was divided into high disturbance: 30 percent or more residue retention and low disturbance: 30 percent or less retention.

A lot of research has been conducted comparing injected manure versus incorporation and the reflected reduction in nutrient loss.

Based on the expert panel’s review, the reduction of nitrogen and phosphorus derived from the literature is varied.

In some of the reports, research was conducted on small plots with simulated rainfall. Some professional judgment was used within injection and incorporation categories to determine loss reduction efficiencies to be used in the bay model.

The report on manure injection and incorporation was accepted by the Chesapeake Bay Program’s Agricultural Workgroup in December 2016. The values will be used in Phase 6 of the Chesapeake Bay Watershed Model.

A lot of time and effort is being devoted to trying to perfect the effect of best management practices in the Chesapeake Bay watershed.

A recent study by the University of Waterloo in Ontario investigated the time it takes to observe positive water quality changes in a watershed.

That study showed that time lags between implementation of conservation measures and real improvements in water quality are often on the order of decades.

They saw that where nutrient inputs have been decreasing since the 1980s, the water quality has been slow to respond.

Livestock producers have made tremendous strides in managing nutrients and implementing environmentally friendly practices.

Realistically, however, it may be some time before the benefits are realized, which could cause some to lose focus because there is no short-term fix to improving impaired watersheds.

Virginia “Ginny” Ishler is a nutrient management specialist and the manager of Penn State University’s dairy complex.


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