FERTILIZER MANAGEMENT IN
Many of Idaho's more than 85 crops are intensively fertilized with nitrogen (N), phosphorus (P), and sulfur (S). Nitrogen application rates range from 100 to 480 pounds/acre on irrigated land and from 25 to 140 pounds/acre on rainfed cropland. Phosphorus is applied to roughly 30 percent of Idaho's cropland each year at rates ranging from 20 to 70 pounds/acre. Sulfur is applied to about 35 percent of Idaho's rainfed cropland each year at rates between 10 and 25 pounds/acre. Potassium is annually applied to less than 5 percent of the cropland in the state.
Based on regional and national information, poor N management can impair both surface and groundwaters. Conversely, poor P management primarily impairs surface water. Since soil erosion is the major mechanism by which P enters surface waters, its control will provide environmental protection from P containing fertilizers. Best management practices (BMPs) to control erosion in Idaho have been encouraged for years. Conversely, few practices to discourage N leaching through soils and into groundwater have been utilized to date. Currently, losses of S into surface and groundwater is not an environmental concern.
Nitrogen leaching is a concern in Idaho, particularly in irrigated areas of the state, as locations of prime aquifers and intensively managed farmland often coincide. In many areas water tables are within a few feet of the soil surface. The Idaho Division of Environmental Quality and U.S. Environmental Protection Agency are concerned that agriculture may contaminate aquifers with nutrients, particularly N. Of particular concern are dairy operations and irrigated fields receiving large amounts of commercial N fertilizers.
Nitrogen use efficiency (NUE) is often used as a measure of the efficiency of nutrient management. NUE can be defined as the percent of N applied to the land that actually ends up in the plant. In Idaho, NUE ranges from 10 to 80 percent depending on both the crop grown and the level of management. NUE averages about 50 percent in Idaho. The lower the NUE value, the greater the likelihood that a significant portion of the applied N may end up in the groundwater.
The relatively low NUE values observed across Idaho can be attributed to one or more of the following factors: (1) poor irrigation water management, (2) incorrect rates of N applied to fields [usually too much N], (3) poor environmental conditions [weather], (4) improper agronomic practices, and/or (5) an inadequate research data base resulting in incorrect fertilizer application rates.
In Idaho, nutrient recommendations are research based for major crops. The University of Idaho has published fertilizer guidelines for 34 of the state's 40 most important crops. These fertilizer guidelines are based on soil test correlation research and depend on soil sampling. In addition, tissue analysis for nutrient management can be used throughout the season for some of the most intensively managed crops like potatoes and sugarbeets.
BMPs for N management in Idaho should include one or more of the following practices: (1) soil sampling, (2) fertilizer recommendations based on the soil sample and research data, (3) split applications of N fertilizer, (4) nutrient credits for plow-down residues of legumes and applied manures, (5) use of nitrification inhibitors, (6) manure management, (7) irrigation water management, (8) use of slow release N fertilizers, (9) crop rotation selection to maximize NUE, and (10) variable fertilizer management within a single field.
The University of Idaho has developed publications on N (CIS
962) and P (CIS 963) BMPs to protect water quality. You can
obtain free copies of these publications from your local county
(R. L. Mahler)
DRINKING WATER FOR
You and your family can survive for several days without food, but only a short time without water. Emergencies such as floods, earthquakes, contaminated municipal supplies, backed up sewers, or broken water pipes may cut off supplies of safe water. Storing water now can help you and your family prepare for an emergency.
How much do you need to store? In moderate weather a normally active person requires a minimum of 1/2 gallon of water per day for drinking and cooking. To be safe, store at least six gallons of water per person per week. Additional water will be needed for washing, brushing teeth, and dish washing. Some of the need for liquids can be met by using juices from canned fruits and vegetables. Store at least one week's emergency water supply for each member of your family, NOW!!!
It is not necessary to treat water for storage, providing the water comes from a public water supply. All public water supplies are already treated and should be free of harmful germs. If stored properly, this water should have an indefinite shelf life. But you may want to rotate and replace this water every 6 to 12 months with fresh safe water. If you do not have access to a public water supply you may need to treat water.
Water from untested and untreated water supplies, such as a farm pond
or private well, should be purified and treated before storage. After
an emergency situation you may need to resort to different measures to
assure the safety of the water before storage. To treat water, consider
Boiling -- Boil vigorously for 10 minutes.
Iodine -- Household iodine from the medicine chest or first aid kit will purify water. The iodine should be 2 percent United States Pharmacopoeia (U.S.P.) strength. Add 1/8 teaspoon per gallon of clear water or 1/4 teaspoon per gallon of cloudy water. Mix water and iodine thoroughly by stirring or shaking water in the container. Allow to stand for at least 30 minutes after which time the water will be safe to use.
Purification tablets -- Available at any drug store. Follow directions on package.
Bleach purification -- Liquid household bleach can also be used. It must contain hypochlorite, preferably 5.25 percent; add according to the table below. Then stir and mix. Do not use scented bleaches. They are not safe for purification.
|Amount of water||Clear water||Cloudy water|
|2 liters||4 drops||1/8 teaspoon|
|1 gallon||1/8 teaspoon||1/4 teaspoon|
|5 gallons||1/2 teaspoon||1 teaspoon|
Mix the bleach completely into the water. Let it stand for 30 minutes. The water should have a slight chlorine odor. If it does not, add the same amount again, and let the water stand for an additional 15 minutes.
Caution: If your water supply has come in contact with flood water, you must purify it and the container again before using it for drinking, cooking, brushing teeth, or dish washing. Farm pond or private well water that is to be stored for use to make formula for a baby should be purified using the tablet or bleach purification method.
Additional information on drinking water for emergencies is contained
in a new University of Idaho publication, "Storing and Treating Water
for an Emergency" (Current Information Series No. 1004). This
new publication will be available in early November and can be obtained
free of charge from your local county Extension office.
(Ernestine Porter and Marilyn Swanson)
FARMERS IMPROVE SOIL
Farmers are now using crop residue management to protect a record 57 percent of U.S. cropland from erosion. Farm acreage under this soil-conserving system has increased by nearly 20 million acres in 3 years. In 1992, U.S. farmers used some form of residue management on a record 161.7 million acres, while in 1989, only 142.4 million acres were under residue management. The encouraging statistics are the result of the Conservation Technology Information Center's (CTIC) national crop residue management survey of the nation's 283 million planted acres. According to CTIC, the trend demonstrates the growing popularity of this environmentally sound and economical practice.
Under the most protective form of residue management, conservation tillage, farmers last year left the soil surface covered with stalks or stubble from their previous crops when they planted 88.7 million acres. An additional 73 million acres were farmed with a more limited form of residue management, according to CTIC Executive Director Jerry Hytry.
CTIC said that farmers who practice crop residue management save on fuel and labor costs. "It's obvious that an increasing number of U.S. growers are recognizing the economic value of leaving plant residue from the previous crop on the soil surface," said Hytry. However, residue management makes environmental sense as well; it contributes to water quality by reducing sediment loading to waterbodies.
Crop residue management is a system that leaves the stalks and stubble from harvest on the soil to protect it from being eroded by rainfall, snowmelt, or irrigation.
Conservation tillage is a highly protective form of crop residue management that maintains at least 30 percent of the soil surface covered by residue after planting to reduce soil erosion by water.
A limited system of crop residue management that leaves 15 to 30 percent residue after planting does not meet the Soil Conservation Service (SCS) requirements for conservation tillage, although it does provide a level of erosion control and water quality benefits.
CTIC reported that Idaho had made significant progress in the use of
conservation tillage. Conservation tillage was practiced on 1,038,016
of the 3,975,326, or 26 percent, of the crop acres planted in the state
in 1992. Percentagewise, Idaho ranks 24th out of the 50 states in
conservation tillage. An additional 1,158,000 Idaho acres utilize a
limited system of crop residue management that leaves 15 to 30 percent
residue on the soil surface. Surface residue was less than 15 percent
on the remaining 1,778,465 acres planted to crops in 1992.
(Adapted from EPA News-Notes, #31)
BLUE THUMB BLOOPER
Tossing toxics in the trash. How tacky! Consider batteries, a common household throw-away. They contain lead and mercury. Some ordinary household cleaners have other poisons that contaminate water. Here's a tip -- drop them off at a special collection site or purchase rechargeable batteries and environmentally safe cleaners.
COSTS OF GROUNDWATER
(This is the second in a series of articles on the costs of groundwater contamination.)
If groundwater becomes contaminated but the contaminants are not detected, adverse health and ecological effects may result. For example, contamination of surface water by groundwater recharge can damage spawning grounds, upset food chains and affect habitat in many ways that affect biodiversity and other measures of ecosystem health. These costs are difficult to quantify, although they can be severe.
When contamination of a drinking water supply is detected, a response strategy can be fashioned from available options. Detection itself can be costly, due to the need for monitoring wells and laboratory analysis. For example, if a private well is threatened with possible contamination from agricultural chemicals, biannual testing would cost $100 to $300 per year. If larger areas are threatened, the drilling of new monitoring wells may cost several thousand dollars each, and more elaborate sampling may be necessary.
Adverse Health Effects. Although health effects are a principal concern in cases of undetected water contamination, there is significant uncertainty in any attempt to quantify and value such damages. Economic researchers have identified methods for measuring willingness to pay for reduced risk of adverse health effects across large populations. For example, observation of wage premiums paid to workers in risky jobs has allowed inference of the money-risk tradeoff. In addition, a variety of survey methods has assessed the subjective value of changes in such risks. A survey of recent literature on the valuation of small changes in the risk of death due to such accidental causes as pollution suggests that the value of a "statistical life" saved ranges from $1 million to $7 million.
There is less empirical evidence on the value of avoiding nonlethal health effects. A rough but practical approach is to use the cost-of-illness approach for valuing nonlethal effects. Costs include direct medical treatment costs, whether covered by insurance or not; the value of lost work; and the value of lost leisure time. These costs vary according to the nature of the illness, its severity, duration, possibility of recurrence, and other factors.
Containment and Remediation Costs. Source control can mean stopping an activity like agricultural chemical use; removing a source such as an underground storage tank; injecting barrier walls underground around a source; sealing the surface areas above a source to reduce water infiltration and leaching; or controlling water pumping and reinjection to prevent groundwater from flowing out of the area. Costs for containment action can vary widely depending on site characteristics, the type of contaminant, and the extent of the plume.
For example, analysis of containment options at a hypothetical 10-acre landfill included $4 million for sealing the bottom, $1.4 million for installing a grout curtain, and $200,000 for an injection/extraction barrier. The average cost of remedial action at Superfund sites has been estimated to be $8 million. In many cases the cost of providing alternative water supplies until remediation is complete must be added to other costs to determine the total cost of the contamination incident.
Treatment. Effective removal of many contaminants can occur through central treatment technologies in municipal systems or by point-of-entry/point-of-use technologies in rural residences with private wells. Central treatment often is the least-expensive response to a contamination incident. Such treatment can add several hundred dollars per year to the household cost of water supply in very small systems and from $2 to $50 per year to the annual household bill in large systems.
Replacement. For large public water suppliers facing
contamination of a small part of the total source supply, replacement
of the contaminated supply is often a fairly inexpensive response
strategy. Construction of new wells can provide water ranging in cost
from a few cents per 1,000 gallons in very large systems to $3 per
1,000 gallons in the smallest systems. A new well for a single
household can cost $5,000 to $7,000, depending on diameter, depth, and
other site characteristics. Hookup of a household to a public system
can cost $12,000 or more, depending on distance to the water main, plus
(Adapted from Groundwater and Public Policy. Series No. 4 by W. B. O'Neil and R. S. Raucher)
CHLORINATION FOR WATER
Methods used to improve the quality of water are referred to as "treatment" or "conditioning." What is the difference? Water treatment refers to systems that reduce harmful contaminants in the water; therefore, deal with health and safety of the water. High levels of coliform, nitrates, arsenic, lead, and pesticides are examples of harmful contaminants that must be treated before water is safe to drink. Water "conditioning" refers to water problems that effect water taste, color, odor, hardness, and corrosivity rather than health and safety. The presence of high levels of magnesium, calcium, iron, manganese, and silt are common contaminants that require water conditioning. It is not uncommon to use both treatment and conditioning methods to improve water quality.
Water Treatment Systems
Drinking water should be free of coliform bacteria. The EPA drinking water standards indicate that water should contain less than one coliform organism in 100 milliliters. If your coliform test was reported as contaminated, these steps should be taken:
Water can be treated by three basic methods: chlorination, distillation, or by ultraviolet (UV) exposure. This article examines chlorination options.
Chlorination -- The use of chlorine is the oldest and most common disinfection method for private water supplies. Chlorine is inexpensive and readily available, reliable, easy to use and monitor, and effective against most pathogenic bacteria, virus, and cyst organisms. It also kills non-pathogenic iron, manganese, and sulfur bacteria.
For use in the home, chlorine is readily available as sodium hypochlorite commonly known as household bleach. This product contains 5 percent available chlorine. Chlorine is also available as calcium hypochlorite, which is sold in the form of dry pellets. In this form it is about 70 percent available chlorine. Chlorination may be done in many ways.
Chlorine may be used continuously in the dry or liquid form that is dropped or injected into the well water using a chemical feed pump. For periodic or shock water treatment, chlorine can also be poured in or fed in solution using a hose. For chlorine recommendation and installation details refer to the installation manual or contact your local water treatment professional.
Shock Chlorination -- Shock chlorination is recommended whenever a well is new, repaired, or found to be contaminated. Its use is essential after a flood or entrance of surface water into the well. Shock chlorination involves pouring a strong solution of chlorine, usually in excess of 50 parts per million, into the well and pumping it through the equipment and piping. A good practice is to let the chlorine solution stay in the system overnight. The amount of chlorine needed will depend on the volume of water and the persistence of the problem. If bacteriological problems persist after shock chlorination, a continuous chlorination system may be required.
Continuous Chlorination -- Continuous disinfection requires equipment to add chlorine to all water drawn from the source. The chlorine must be thoroughly mixed with the water and have sufficient contact time to kill all disease-causing and nuisance organisms. The time required for disinfection depends on the concentration of chlorine, temperature, and pH of the water, the amount of organic matter in the water, and the discharge rate of the pump. Disinfection for most waterborne disease-causing organisms occurs after 20 minutes of contact time when the pH is between 6 or 8 and the free available chlorine residual is in the range of 0.2 to 0.4 parts per million.
A dry pellet chlorinator can be used. The pellets are injected into the well at a calculated rate. This type of system uses the well casing as a retention tank, permitting the chlorine to kill bacteria and oxidize iron and manganese. Research findings indicate that suspected carcinogenic compounds, called trihalomethanes, can actually be formed during chlorine disinfection when organic substances are present. To remedy this, activated carbon filtration or reverse osmosis units should become a part of all up-to-date home chlorination systems. To remove chlorine taste, an activated carbon filter can also be used. It should be placed after the contact tank and just before the point of use faucet. Continuous chlorinators range in price from $500 to $1,300.
For additional information on water treatment by distillation and UV
exposure and information on water conditioning, obtain a copy of a new
University of Idaho Extension publication "Treating and Conditioning
Home Water Supplies" (Current Information Series No. 1001). This
new publication will be available in early November and can be obtained
free of charge from your local county Extension office.
PESTICIDE BMPs FOR YOUR
Most people intensively manage their backyard flower and/or vegetable gardens. Inputs such as pesticides, fertilizers, and water when used incorrectly may adversely impact surface and/or groundwater quality. To protect the environment and water quality you should use BMPs, which are defined as an implemented strategy that eliminates or minimizes environmental pollution. BMPs are designed to be compatible with garden ecosystems. BMPs can protect the environment without compromising the productivity of large or small gardens.
Why should home gardeners be concerned about pesticides? On a square footage basis, home gardeners often use more pesticides than farmers do in large scale production agriculture.
Adverse effects of pesticide over-use in gardens include:
HOW DO AGRICULTURAL ACTIVITIES IMPACT
(This is the third in a series of articles on the causes of groundwater contamination.)
Contaminants can enter groundwater from more than 30 different generic sources related to human activities. These sources commonly are referred to as either point or nonpoint sources. Point sources are localized in areas of an acre or less, whereas nonpoint sources are dispersed over broad areas.
The most common sources of human induced groundwater contamination can be grouped into four categories: waste disposal practices, storage and handling of materials and wastes, agricultural activities, and saline water intrusion.
Agriculture is one of the most widespread human activities that affects the quality of groundwater. In 1987, about 330 million acres were used for growing crops in the United States, of which 45 million acres were irrigated.
Fertilizers. During the 1960s and 1970s, nitrogen (N), phosphorus (P), and potassium (K) fertilizer use steadily increased to a peak of 23 million tons in 1981. By 1987, however, fertilizer use had declined to 19.2 million tons, reflecting the large number of acres withdrawn from production as part of the Conservation Reserve Program and other government programs.
If N supply exceeds N uptake by crops, excess N can be leached to groundwater. In such areas, local nitrate-nitrogen concentrations may exceed the federal drinking water standard of 10 ppm.
Pesticides. Pesticides have been used since the 1940s to combat a variety of agricultural pests. Between 1964 and 1982, the amount of active ingredients applied to croplands increased 170 percent. Herbicide usage peaked in 1982, and since then has declined from about 500 million pounds of active ingredients per year to about 430 million pounds applied in 1987.
In addition to crop applications, infiltration of spilled pesticides can cause contamination in locations where pesticides are stored, and where sprayers and other equipment used to apply pesticides are loaded and washed.
Pesticides most frequently detected in groundwater are the fumigants ethylene dibromide (EDB) and 1,2-dichloropropane, the insecticides aldicarb, carbofuran, and chlordane; and the herbicides alachlor and atrazine.
Feedlots. Feedlots confine livestock and poultry and create problems of animal-waste disposal. Feedlot wastes often are collected in impoundments from which they might infiltrate to groundwater and raise nitrate concentrations. Runoff from farmyards may also directly enter an aquifer along the outside of a poorly sealed well casing.
Irrigation. Percolation of irrigation water into soils dissolves soil salts and transports them downward. Evapotranspiration of applied water from the root zone concentrates salts in the soil and increases the salt load to the groundwater.
Chemigation, the practice of mixing and distributing pesticides and fertilizers with irrigation water, may cause contamination if more chemicals are applied than crops can use. It may also cause local contamination if chemicals back-siphon from the holding tank directly into the aquifer through an irrigation well.
Saline Water Intrusion. The encroachment of saline water
into the freshwater part of an aquifer is an ever-present threat when
water supplies are developed from the highly productive coastal plain
aquifers of the United States, or from aquifers underlain by saline
water in the interior of the country. Local incidents of saline water
intrusion have occurred on all coasts of the United States.
(Adapted from Groundwater and Public Policy. Series No. 3 by D. W. Moody, USGS)
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All contents copyright © 1997-2003. College of Agricultural and Life Sciences, University of Idaho. All rights reserved. Revised: January 3, 2003