It may come as a bit of a surprise, but the U.S. Department of Agriculture has given a general pat on the back to the nation’s swine industry for its manure management over the past decade.  It is likely more studies will come in the future.  Currently, USDA says pork producers are more likely to have nutrient management plans, and larger hog operations are altering their manure management decisions in response to legal nutrient application constraints, and that environmental policy is contributing to the adoption of conservation compatible manure management practices. 

USDA’s praise of the pork industry comes with the analysis of a series of manure management studies over recent years.  The data in the latest report  documents the current state of manure management and track producers’ manure management practices during a period of rapid change in the hog industry.  Changes to the Clean Water Act, state regulations, and conflicts with nearby residents over odor and air quality are among many issues influencing manure management decisions.  Between 1998 and 2009, the number of hog operations fell by about 60%, and the average head per operation grew from 2,589 to 7,930 head.  Over this period, the number of hog operations producing fewer than 300 animal units declined rapidly, resulting in a shift in production to larger operations.

The aggregation of production paralleled the increased use of contract production, and USDA says, “One issue with production contract arrangements is liability for managing the hog manure. Most contracts require growers to comply with all State, Federal, and local regulations in operating their facilities, and failure to comply can result in contract termination.”  Pork production had been expanding in southern states in the 1990’s, but “Lack of growth in the South could be attributed partly to a 1997 moratorium on the construction of new and expanded hog operations in North Carolina (North Carolina General Assembly, 1997). The moratorium was enacted in response to environmental concerns about managing swine manure from increasingly larger operations.”

At the same time of the structural changes of the pork industry have been state and federal regulations that impact livestock feeding operations, manure disposal, odor issues, and water quality concerns.  While livestock feeding operations are not required to have EPA permits for non-point source discharges of manure, any incidental runoff or accidental spills is considered a violation of the Clean Water Act.  The Clean Air Act also comes into play with the emissions of pollutants that are considered particles, and the emission of ammonia odors is considered a pre-cursor of particulate pollution.  Other environmental laws require local officials to be notified when odor or chemical releases occur on livestock operations that are large enough to meet the CAFO-size standards. 

To be able to exist within this environment of regulations and structural change, pork operations have been challenged in their disposal of manure, whether from lagoons and pumped through irrigation systems, or from pits and injected as part of a crop nutrient management plan.  USDA says by 2009, 62% of hogs were raised on farms using pit/tanks (up from 37% in 1998); in 2009, 34% were raised on farms using a lagoon system (down from 55% in 1998).  Such a shift was the result of regional shifts in production and may have also been encouraged by higher prices for commercial fertilizer.  USDA reports, “The type of manure-spreading technologies used is often related to the scale of production.

Among large farms that applied manure to crops, irrigation was the most common form of manure application, followed by injection of liquid manure. In contrast, smaller operations were more likely to spread solid manure, or to spread liquid manure without injection.”  But another factor was that larger hog operations may have more cropland for feed production, subsequently had more land for manure disposal.  Nevertheless, the typical hog operation by 2009 was only applying manure to one quarter of the cropland it operated, possibly because of the distance required for transporting it.

Among all hog operations, 76% applied some manure on their farms in 2009, a decrease from 82% in 2004.  Part of the overall decline can be explained by the shift to larger operations, which were less likely to apply manure on-farm than smaller operations in each of the three surveys. In 2009, 75% of large farms applied manure on-farm compared with 79% of medium-size farms and 83% of small farms.

Manure management practices and outcomes have changed significantly over the past decade. Many of these trends can be attributed to the pronounced structural changes and regional shifts in hog production that occurred between 1998 and 2009.  The shift to larger operations has meant that an increasing share of production falls under the purview of regulations governing the application of manure nutrients to cropland.  While the manure-nutrient application intensity generally increases with farm size, the decline in application intensity on the largest operations between 1998 and 2009 suggests that environmental policy is contributing to the adoption of conservation-compatible manure management practices.  The research suggests that in addition to the influence of market and structural forces, hog producers have responded to policy incentives that address environmental side effects of manure management.