Some water quality problems aren't only defined by the borders of a watershed or the banks of a river or lake, rather economic and political boundaries also shape the problem. Manure management is one of those problems.
Some water quality problems aren’t only defined by the borders of a watershed or the banks of a river or lake, rather economic and political boundaries also shape the problem. Manure management is one of those problems.
Concentrated animal feeding operations, or CAFOs, represent a major shift in farming from small family operations raising a few hundred head to large confinements raising thousands of animals at a time. Critics say the sheer concentration of animals makes the farms major environmental hazards: to the air, the land, and the water. Most of the issue, at least where water quality’s concerned, centers on the way confinements manage manure - a potential water pollutant. The farms raise thousands of animals, which produce tons of manure. Animal waste contains nutrients like nitrogen and phosphorous and can contain disease causing bacteria, or harmful amounts of antibiotics. The most common way to manage the manure is to store it in earthen lagoons. A lagoon is a big pit in the earth, sometimes lined with clay or a plastic liner. When a lagoon is full, the mixture is pumped out and sprayed onto fields as fertilizer. But the earthen lagoons aren’t perfect. Lagoon leaks and ruptures in the lining can allow waste to slowly seep into underground water sources. Large spills and lagoon overflows can dump thousands of gallons of waste directly into surface waterways, resulting in huge fish kills and environmental damage.
The threats from storage; the spills and the leaks, aren’t the only problems. Farmers use manure as fertilizer for their fields, and whether the manure comes from a large operation or a small one, it has to be applied correctly. When manure is applied to the land in proper amounts, the nutrients it contains (nitrogen and phosphorous) help crops grow. The land can only absorb so much manure and nutrients. So if too much manure is applied, some of it runs off the land and into waterways. The more animals at an animal confinement, the more manure will be produced, and the more land will need to absorb it. Over-application results in runoff, which can put two major pollutants right into water, excess nutrients or pathogens, both of which are found in animal manure. In states with large agricultural populations, manure runoff is thought to be a major contributing source of bacteria which forced beach closings during the summer.
These confinements also cannot just be shut down. In Iowa, for example, hog production has a 12-billion dollar economic impact, an impact the state can’t afford to lose. Also, not every operation is a threat to water quality. In fact, many farmers are taking the proper steps to protect water, acting as good stewards of our natural resources. Best Management Practices, or BMPs, act as guidelines for manure application. These practices include testing the soil and manure to check current nutrient levels; using only as much manure as the crop needs and the soil can hold; checking soil moisture before applying liquid wastes, and adjusting application rates to avoid runoff; and using raw or untreated manure to reduce odors and nitrogen losses. Because the frozen ground can't absorb liquid and wet ground can't absorb more liquid it is also important for farmers to avoid applying manure to frozen or saturated soils to prevent runoff.
Because of political and economic influences, there are no simple solutions to this problem. Legislation, regulation, management changes, new technologies, are all options that could keep animal manure from threatening water quality.