242 ENVIRONMENTAL ENGINEEFUNG
Protection Agency (USEPA) and the USDA have developed a training module
for learning agricultural management practices that protect water quality @ttp://
http://www.epa.gov/watertrain/agmodule)..) The USEPA/USDA training module describes
the following eight basic types of agricultural management practices: conservation
tillage, crop nutrient management, pest management, conservation buffers, irrigation
water management, grazing management, animal feeding operations management, and
erosion and sediment control.
Conservation tilZage involves leaving crop residues from previous plantings in
place rather than plowing the field before replanting. This practice not only reduces
soil erosion, it helps hold nutrients and previously applied pesticides in the field and
conserves soil moisture.
Crop nutrient management is designed to increase the efficiency of applying crop
fertilizers by measuring soil nutrient levels (particularly nitrogen), plant chlorophyll
concentrations (this helps determine the nitrogen needs for a particular crop), soil
organic matter concentrations, and irrigation water nutrient concentrations. In addition
to reducing nonpoint pollution, careful crop nutrient management can save money and
improve the overall crop yield.
Pest management incorporates the concept of integratedpest management (PM),
which uses a combination of approaches to control plant pests. Chemical pesticides
are still used in IPM, but only sparingly, and only in conjunction with natural controls
such as selecting resistant crops, timing harvests and rotating crops to upset the pest’s
life cycle, and using biological controls such as natural predators.
Conservation buffers can be as simple as leaving strips of untilled vegetation to
reduce soil erosion in a plowed field, or as advanced as replanting a riparian corridor
with native vegetation to provide shade for the stream and appropriate habitat for local
wildlife. The main purpose of a conservation buffer is to use permanent vegetation to
improve the environment, which may include stabilizing soils, reducing nonpoint pol-
lution to streams, protecting crops and livestock, improving the aesthetic environment,
and providing wildlife habitat.
Zrrigation water management is designed to reduce nonpoint pollution associ-
ated with irrigation practices and reduce the energy costs associated with transport
and application of irrigation water. Most water used for irrigation must be transported
from distant sources or pumped from deep aquifers. Careful timing and efficient use
of irrigation water can reduce costs, as well as reduce nonpoint source pollution.
Irrigation water picks up large amounts of dissolved solids, pesticides, and other
pollutants as it moves through the soil. Subsurface drains are often installed under
irrigated fields to collect the excessively salty drainage water before it contaminates
local aquifers.
Grazing management involves adjusting the number and kinds of animals in a
pasture to limit soil erosion and water pollution problems associated with overgraz-
ing. This practice is closely associated with animal feeding operations management,
which includes a grazing management plan along with exclusion of animals from
sensitive habitats such as stream banks and appropriate animal waste management
practices. Waste management is a particular problem for large feedlots, dairies, poul-
try yards, and other mas with high animal densities. The amount of manure generated