Best Management Practice: Agriculture
Managing Sedimentation. Sedimentation occurs when wind or water
runoff carries soil particles from an area, such as a farm field, and transports
them to a water body, such as a stream or lake. Excessive sedimentation
clouds the water, which reduces the amount of sunlight reaching aquatic
plants; covers fish spawning areas and food supplies; and clogs the gills
of fish. In addition, other pollutants like phosphorus, pathogens, and
heavy metals are often attached to the soil particles and wind up in the
water bodies with the sediment. Farmers and ranchers can reduce erosion
and sedimentation by 20 to 90 percent by applying management measures to
control the volume and flow rate of runoff water, keep the soil in place,
and reduce soil transport.
Managing Nutrients. Nutrients such as phosphorus, nitrogen, and
potassium in the form of fertilizers, manure, sludge, irrigation water,
legumes, and crop residues are applied to enhance production. When they
are applied in excess of plant needs, nutrients can wash into aquatic ecosystems
where they can cause excessive plant growth, which reduces swimming and
boating opportunities, creates a foul taste and odor in drinking water,
and kills fish. In drinking water, high concentrations of nitrates can cause
methemoglobinemia, a potentially fatal disease in infants also known as
blue baby syndrome. Farmers can implement nutrient management plans which
help maintain high yields and save money on the use of fertilizers while
reducing non-point source pollution.
Managing Confined Animal Facilities. By confining animals to
areas or lots, farmers and ranchers can efficiently feed and maintain livestock.
But these confined areas become major sources of animal waste. Runoff from
poorly managed facilities can carry pathogens (bacteria and viruses), nutrients,
and oxygen-demanding substances that contaminate shellfishing areas and cause
other major water quality problems. Ground water can also be contaminated
by seepage. Discharges can be limited by storing and managing facility
wastewater and runoff with an appropriate waste management system.
Managing Irrigation. Irrigation water is applied to supplement
natural precipitation or to protect crops against freezing or wilting.
Inefficient irrigation can cause water quality problems. In arid areas,
for example, where rainwater does not carry residues deep into the soil,
excessive irrigation can concentrate pesticides, nutrients, disease-carrying
microorganisms, and salts-all of which impact water quality-in the top
layer of soil. Farmers can reduce non-point source pollution from irrigation by improving
water use efficiency. Actual crop needs can be measured with a variety
of types of equipment.
Managing Pesticides. Pesticides, herbicides, and fungicides are
used to kill pests and control the growth of weeds and fungi. These chemicals
can enter and contaminate water through direct application, runoff, wind
transport, and atmospheric deposition. They can kill fish and wildlife,
poison food sources, and destroy the habitat that animals use for protective
cover. To reduce non-point source contamination from pesticides, people can apply Integrated
Pest Management (IPM) techniques based on the specific soils, climate,
pest history, and crop for a particular field. IPM helps limit pesticide
use and manages necessary applications to minimize pesticide movement from
the field.
Managing Livestock Grazing. Overgrazing exposes soils, increases
erosion, encourages invasion by undesirable plants, destroys fish habitat,
and reduces the filtration of sediment necessary for building streambanks,
wet meadows, and floodplains. To reduce the impacts of grazing on water
quality, farmers and ranchers can adjust grazing intensity, keep livestock
out of sensitive areas, provide alternative sources of water and shade,
and revegetate rangeland and pastureland.
From
EPA
Pointer
No. 6
EPA841-F-96-004F
