July 2010, Volume 16, Number 3
Sustainable Agricultural Systems
The World Commission on Environment and Development in 1987 defined sustainable agricultural systems as those that use land, air, water and other resources to meet current needs for food and fiber without compromising the ability of the agricultural system to meet future needs for food and fiber. In agriculture, sustainability has been defined as food security, or having enough food at affordable prices now while ensuring there are sufficient resources to produce affordable food in the future.
USDA publishes periodic reports on the resources used in and affected by agricultural production (www.ers.usda.gov/publications/arei). The report covers two major resources, land and water, charting trends in land use and land values as well as the availability, cost, and quality of water and the status of wetlands. USDA then turn to other resources, from R&D to productivity growth, and covers farm management practices to deal with pests, soil nutrients and waste water. USDA concludes with an assessment of government conservation programs.
Land. Land may be the easiest resource to assess. There are three major uses of US farm land? for pasture and range, forests and wood land, and crop land. The 48 US states have about 1.9 billion acres of land, and 585 million acres were used for pasture and range land in 2002, 560 million for forests (including parks), and 440 million for crops. Urban areas used 60 million acres (more than double the 25 million acres in 1960), and the remaining land was desert and marshes and used for purposes ranging from transportation to industrial and military purposes.
Not all crop land is planted and harvested. Some is placed in USDA's Conservation Reserve Program (35 million acres in recent years), some is not planted to allow moisture to accumulate, and some crops fail. About 300 million acres of crop land are harvested, and 80 percent were four crops: corn (25 percent), soybeans (23 percent), hay (21 percent) and wheat (15 percent). Less than five million acres of fruits, nuts, vegetables and melons are harvested.
Water. About 90 percent of the water used in the US is from renewable surface- and ground-water supplies; 10 percent depletes stored ground water. Water availability and water usage rates are diverging as a result of population growth in the arid west and southwest, where water supplies are limited and irrigated agriculture uses most of the available water. The US has about 55 million acres of irrigated land, and farmers apply an average 20 inches of water a year to their crops.
The 2010 Rabobank US Farm & Ranch Survey (www.rabobankamerica.com/survey) reported that 70 percent of the 600 farm operators who responded have embraced some form of sustainable farming, such as direct seeding (64 percent), minimizing use of chemicals (42 percent), crop rotation or diversification (39 percent) and reduced energy inputs (39 percent).
Amish. Amish farmers in Lancaster county generally farm with horses rather than tractors. However, runoff from manure and the use of artificial fertilizers to boost yields winds up in the Chesapeake Bay, reducing oxygen rates, killing fish and creating a dead zone that has persisted since the 1970s despite off-and-on cleanup efforts.
Amish farmers own more than half of the 5,000 farms in Lancaster county, which generates more manure than any other county in the Chesapeake Bay watershed. The EPA is trying to persuade Lancaster county farmers to build fences to keep livestock from streams and build manure pits to minimize runoff during rain storms; government grants are available to cover most of the cost.
Biomass. Biomass, power generated by burning wood, plants and other organic material, generates 50 percent of US renewable energy. However, burning wood and other organic matter releases carbon dioxide into the atmosphere just as coal does, and the burning generates particulate matter.
Many communities oppose biomass projects, which take advantage of federal and state subsidies and, according to critics, are worse for air quality than coal plants. In May 2010, the Environmental Protection Agency said in plans to regulate greenhouse gases that it would not exempt emissions from "biogenic" sources like biomass power plants. The American Lung Association asked Congress to exclude subsidies for biomass from any new energy bill, citing potentially "severe impacts" on health.
About 75 percent of biomass electricity comes from the paper and pulp companies, which collect their residues and burn them to generate power for themselves. Some are connected to the local grid, selling excess electricity for $1 billion a year.
Tom Zeller Jr, "Net Benefits of Biomass Power Under Scrutiny," New York Times, June 18, 2010. Sindya Bhanoo, "Amish Farming Draws Rare Government Scrutiny," New York Times, June 8, 2010.