Your Yard and Water Quality PDF

ID-201 Your Yard and Water Quality By Van Bobbitt, former Cooperative Extension Master Gardener and urban horticulture coordinator; Robert Fox, Cooperative Extension project associate, King County; Holly Kennell, Cooperative Extension agent, King County; Curt Moulton, Cooperative Extension county c...

ID-201 Your Yard and Water Quality By Van Bobbitt, former Cooperative Extension Master Gardener and urban horticulture coordinator; Robert Fox, Cooperative Extension project associate, King County; Holly Kennell, Cooperative Extension agent, King County; Curt Moulton, Cooperative Extension county chair, Pierce County; George Pinyuh, retired Cooperative Extension agent, King and Pierce counties; and Mary Robson, Cooperative Extension agent, King and Pierce counties; all of Washington State University. Adapted for Kentucky by Brad Lee, Extension specialist for water quality, and Richard Durham, consumer horticulture Extension specialist and state Master Gardener coordinator, University of Kentucky. Why Be Concerned? In this chapter: Clean water is essential for human health, wildlife, recre- Why Be Concerned?  01 ation, and industry. Water contamination poses many threats. For example: Environmentally Sound Gardening 01 Pesticides and nitrate can contaminate drinking water sup- Soil and Fertility Management 02 plies. Nitrate levels as low as 10 parts per million (ppm) in Using Garden Wastes 03 drinking water can cause methemoglobinemia (blue-baby syndrome). While humans more than six months old are Watering 04 not seriously affected by nitrate in drinking water, cattle Pest Management 04 and sheep are. Sediments from erosion can destroy aquatic habitats for species that need clear, oxygen-rich water. Nontoxic Pest Control Methods 05 Residues from lawn and garden fertilizers can overstimulate For More Information  06 aquatic plant growth in shallow lakes and bays, making water unsuitable for fish and wildlife. Contamination of water by toxic chemicals can reduce fish and shellfish populations or W e generally view gardening as a wholesome activ- make them unfit for human consumption. These problems ity that enhances our environment. But pesticides, concern not only those who fish for sport but also the com- fertilizers, and erosion from gardens and landscapes mercial fishing industry and consumers. can contaminate lakes, streams, rivers, oceans, and groundwa- Contamination can make lakes, rivers, and beaches unsafe ter. Since the quality of our water resources affects our quality for swimming and other recreational activities. of life, we must learn how gardening practices can contrib- ute to water contamination and how to reduce the threat to water quality. Environmentally Sound Gardening We have long been aware of contamination from point Gardens thrive with good water quality practices. The same sources such as factories and municipal sewage systems. simple, practical techniques that improve soil, beautify land- Recently, we have become more aware of the threat of nonpoint scapes, reduce maintenance, and enhance plant health also can source contamination from many relatively small, widespread protect water quality. sources. Each source by itself may seem insignificant; however, For gardeners, the keys to protecting water quality include when added together, they can pose a serious threat. the following: Hundreds of thousands of homes in Kentucky have gar- Reducing the amount of potentially dangerous substances dens. Each garden may contribute a relatively small amount of introduced to the environment runoff containing soil, chemicals, and fertilizers. This runoff Minimizing the amount of water that runs off the gardener’s flows into surface water such as lakes, rivers, and bays. On property the other hand, nitrate (from fertilizers and manure) and some pesticides can leach through the soil and contaminate Landscape Design groundwater (Figure 12.1). Added up, these small amounts of contamination form An environmentally sound garden begins with proper plan- a sizable problem. Only when individuals take respon- ning and design. Properly selected plants and landscape features sibility and make wise choices can we control nonpoint can reduce runoff and minimize pesticide and fertilizer use. source contamination. Pavements allow much more runoff than a landscape of trees or grass (Table 12.1). On the other hand, maintaining a “perfect” lawn often involves more reliance on chemicals than do other types of landscapes. CHAPTER 12 Your Yard and Water Quality Nitrogen cycle in the soil Nitrogen-rich organic compounds from manure, AMMONIUM compost, blood meal, bound to soil decayed organic matter NITRATE Low-nitrogen organic matter in soil water from straw, dry leaves, sawdust excess nitrate leaches to groundwater Figure 12.1. Nitrogen cycle in the soil. All of the arrows represent biological processes in the soil. These steps proceed more rapidly when the soil is warm and there is adequate moisture, but the soil is not saturated. Note that there are three possible fates of nitrate: (a) Taken up by plants, if they are present (b) Used by microbes to help break down coarse organic matter such as dry leaves (c) Excess nitrate not used by plants or microbes can be carried to the groundwater by heavy rain or excess irrigation. (Note: An alternate schematic of the nitrogen cycle is illustrated in Chapter 4, Soils and Fertility, AGR-204.) What You Can Do Soil and Fertility Management Select plants adapted to the environmental conditions (sun, Soil is the essential foundation of a garden. Proper soil and moisture, soil, and temperature) of your site to ensure healthy fertility management produces a healthier landscape and plants and reduced maintenance. reduces the potential for water contamination from erosion, Replace turf in inappropriate areas (e.g., dense shade; steep fertilizers, and pesticides. slopes; narrow, hard-to-irrigate areas; and heavy-traffic areas Drainage refers to the ability of soil to transmit water through with compacted soil) with plants, mulches, or paving materi- the surface and subsoil. Most landscape plants, fruit trees, and als that require less irrigation, fertilizer, and pesticides. berry bushes require good soil drainage to a depth of at least Use porous paving materials (e.g., wood decking, modular two feet. pavers, porous asphalt, gravel, or wood chips) instead of Drainage also affects the potential for water contamina- impermeable concrete or asphalt. tion. A coarse mineral soil, such as sand, drains rapidly but Allow roof runoff to spread over well-drained soil, where infiltration can occur. Build gravel trenches along paved walkways and driveways Table 12.1. Estimated runoff from different surfaces. to catch runoff. Land Cover Runoff (%) Where runoff is a special problem, create gravel seep- Dense forest 10 age pits or a series of infiltration beds over a gravel or tile Light forest 15 drainage system. Consult an agriculture engineer to ensure Lawns 25 proper design. Gravel areas 80 Pavement and roofs 90 Source: King County, Washington, Surface Water Design Manual (January 1990). 12-2  Your Yard and Water Quality CHAPTER 12 also allows dissolved chemicals to leach into the groundwater. Conditioning can greatly enhance soil productivity. Clay particles bind these chemicals and slow their movement Incorporating organic matter, such as compost, ground bark, through the soil, reducing the likelihood of groundwater con- or sawdust, increases the soil’s ability to store moisture and tamination. But a dense clay soil drains slowly, thus increasing nutrients. In addition, organic matter can buffer the effects surface runoff. of pesticides in the soil and prevent rapid leaching of many Fertility refers to the presence of minerals necessary for chemicals into groundwater. plant life. Unfortunately, the fertility of garden soils often is Organic matter helps both sandy and clayey soils. In sandy less than ideal for plant growth. Gardeners usually compensate soils, it improves moisture retention and reduces leaching of by adding fertilizers, either from synthetic or natural sources. fertilizers and pesticides. In heavy clay soils, it improves water Overapplication of any synthetic or natural nutrient source can infiltration. result in excess nutrients being carried into lakes and streams There are several approaches to reducing erosion. For or leaching into groundwater. Overfertilization also wastes example: money, damages plants, and can encourage weeds. Slow down runoff. Try terracing slopes; creating grassy Rainfall and moving water can carry away soil particles, swales; or building earth, wood, or masonry diversions. organic matter, plant nutrients, and soil contaminants. This Mulch bare soil. Use straw, grass clippings, wood chips, water-soil-chemical runoff can cloud natural waters, stimu- ground bark, or geotextiles (landscape fabrics). late unnatural and ecologically disastrous algal blooms, and Plant vegetation that lends itself to erosion control. contaminate fish. Therefore, it is essential to minimize erosion Buttonbush, rough-leaf dogwood, silky dogwood, deciduous and runoff. holly, and native grasses are a few examples. Protect existing vegetation where high water velocities What You Can Do are expected. E.g., use a concrete splash block at your rain gutter outlet, or place large, rough-edged stones at There are several things you can do to reduce the likelihood drainpipe outlets. of fertilizers contaminating groundwater and surface water. Grow cover crops in your vegetable garden during winter They include the following: to reduce erosion, trap nutrients, and add organic matter to Have your soil tested; testing will detect pH problems that the soil. affect nutrient availability to plants. Tests also reveal defi- ciencies of nutrients such as phosphorus, potassium, and calcium. Kentucky county Extension offices will submit soil Using Garden Wastes samples for testing for a minimal fee and provide a recom- Like many things we do, gardening creates wastes: grass mendation once results are known. See Chapter 4 regarding clippings, prunings, and leaves. Thrown into the garbage, yard information on how to take a soil test. Your county Extension wastes use up scarce landfill space. Landfills themselves can office also can provide names of soil testing labs. contaminate groundwater. Decaying vegetable matter thrown Use only the amount of fertilizer recommended; more is not into a lake or stream can compete with marine animals for the better. limited oxygen supply. If processed in the garden, however, Fertilize according to what your plants actually need. these wastes can be a valuable resource, contributing to healthy Established trees and shrubs do not need annual applications soil and plants. if they are putting on adequate growth and their leaf color is healthy. Use slow-release fertilizers (organic or synthetic) when pos- What You Can Do sible to reduce the loss of excess nitrogen into groundwater Use leaves and grass clippings as a mulch. This practice or surface water. reduces erosion, irrigation requirements, and weed If you use quick-release synthetic fertilizers, make several problems. small applications over a period of time instead of a large Run prunings and woody brush through a chipper and use amount all at once. Split applications reduce the potential the chips as mulch or to cover pathways. for nitrogen leaching. Compost leaves, needles, grass clippings, and annual Time fertilizer applications correctly. Trees and shrubs make weeds (before flowering) to create a valuable organic soil best use of fertilizer just before or as new growth begins in the amendment. spring. Fertilize herbaceous perennials at the beginning of Cover compost piles with a tarp during the rainy season to the growing season. Fertilize annuals when they are actively help prevent leaching of nutrients. growing. In case nutrients do leach from the compost piles, locate the piles away from bodies of water or places where runoff might occur. 12-3 CHAPTER 12 Your Yard and Water Quality Compost herbicide-treated grass clippings for at least a year What You Can Do to eliminate potential herbicide problems. It’s best to keep these clippings separate from other compost materials. Select plants that need minimal water. Many native plants Compost diseased plant materials, annual weeds that have and other species adapted to dry summers and falls require flowered, or perennial weeds only if your compost pile little, if any, irrigation. is “hot.” Decrease the amount of lawn. Turf generally requires more irrigation than a landscape of established trees, shrubs, and groundcovers. Watering Increase your lawn’s drought tolerance through good cultural practices (soil preparation, aeration, fertilization, and mow- The goals of environmentally sound irrigation are to ing at proper frequency and height). maximize water infiltration and minimize runoff. Reduce the Store runoff from your roof in a rain barrel. Mount a hose potential for runoff by reducing the need for supplemental tap at the bottom so you can use the water in your landscape irrigation. Use mulches to conserve moisture, and choose and garden. drought-resistant plants. Divide your landscape into irrigation zones, grouping plants Overwatering can wash away soil, pesticides, and nutrients, that use a lot of water in one zone and those that use less in which eventually find their way into surface water or ground- another. Built-in irrigation systems should have separate water. Overwatering occurs when water is applied faster than circuits for lawns and planting beds. the ground can absorb it or when you let the water run too long. Avoid frequent, low-intensity irrigations. They tend to By watering efficiently, you will reduce your water bill while encourage shallow rooting and make plants more susceptible protecting water quality. to drought. Hand watering, with either a hose or a watering can, gen- Apply water slowly (generally not more than one-half inch erally is appropriate only for containers or small beds. Hand per hour). watering lawns and planting beds usually does no more than Adjust sprinkler patterns and output to avoid runoff and wet the soil surface, since most people are unwilling to invest application of water to paved surfaces. the time needed for thoroughly watering large beds and lawns. Where possible, use soaker hoses or drip irrigation rather Sprinklers can generate considerable runoff if they apply than sprinklers. water too fast or throw water onto paved surfaces. Soaker hoses If you must water by hand, sink perforated cans into the soil reduce runoff and evaporation losses because they apply water by each plant to apply water directly to the roots. slowly. Trickle or drip irrigation is more efficient, reducing water Water when plants need it, not according to the calendar. use by 50 to 80 percent compared with overhead irrigation. Apply mulches to conserve soil moisture. Do not water according to the calendar, since a plant’s water requirement varies depending on weather, soil, species, age, and size. Never allow seedlings to dry out. Newly established Pest Management plants need frequent watering until their root systems become well established. Established trees and shrubs usually do well A pest-free garden is expensive, impractical, and environ- if you soak them once or twice a month during dry periods. mentally undesirable. Attempts to maintain a pest-free garden Many drought-resistant plants require little or no watering often result in heavy use of pesticides, which in turn increases once they are established. the potential for water contamination. Watch for signs that indicate your lawn needs watering: Try to keep pest populations below the level at which they gray-green grass, turf that does not spring back when walked cause unacceptable damage. Allowing low levels of pests to on, and blades of grass rolled lengthwise. Lawns generally need survive helps maintain a population of their natural enemies. irrigation at least once a week in dry summers to stay green. The first step to effective pest management is to inspect your Alternatively, you can let your lawn go dormant; it will turn plants often so you can catch problems before they become green again when fall rains begin. serious. If you detect and deal with insect and disease problems Apply no more than one-half inch of water per hour, but early, you can reduce or eliminate the need for pesticides. The adjust this amount according to soil type. Use small cans to objective is to make your garden a healthy place for your plants measure the amount of water your sprinklers apply. Turn off and an inhospitable place for pests. the water at the first sign of soil saturation or runoff. 12-4  Your Yard and Water Quality CHAPTER 12 What You Can Do Nontoxic Pest Control Methods Plant pest-resistant species and varieties of plants. Check Insects with local nurseries, landscapers, Extension agents, or other Master Gardeners to see whether resistance information is Keep your garden free of weeds and debris that provide available for the plants you are considering. a habitat for pests. Rotate vegetables and annual flowers so that the same plant Prune out insect-infested parts of plants and destroy or plant family does not occupy the same space every year. the prunings. For example, tomatoes, potatoes, and petunias are all in the Cover susceptible crops with floating row covers or nightshade (Solonaceae) family. Rotation can reduce insect nylon screen to exclude certain pests. infestations and the buildup of soilborne diseases. Use insect traps where appropriate. (Research indicates Keep your garden clean. Rocks, wood, and debris provide that light traps usually are ineffective.) great hiding places for slugs and insects. Use a stream of water or a brush to dislodge insects. Weed your garden. Weeds can harbor insects and diseases Handpick insects from plants. that attack your plants. Encourage beneficial insects by planting flowers that Time plantings to avoid peak insect infestations. Often the provide nectar and pollen. most destructive phase of an insect’s life is brief and predict- able. Check with your Extension office to see whether this Diseases information is available for specific insect pests. Plant disease-resistant cultivars. Preserve naturally occurring beneficial organisms by mini- Rotate annual plants (both flowers and vegetables). mizing your use of pesticides. Allow adequate space between plants and prune for Properly identify plant problems. If your problem is caused good air circulation. by a pest, proper identification is important in selecting the Time waterings so that foliage dries by nightfall. safest and most effective control strategy. Remember that Prune off and destroy diseased plant parts. Do not most problems are cultural or environmental and do not add them to your compost pile unless you are hot respond to pesticide applications. composting. Determine whether a problem really justifies treatment. Improve soil drainage and aeration. Many pests cause only cosmetic damage and are not life- threatening to plants. Try the least toxic control strategies first. Cultural methods Slugs often are a good place to start. Place beer in containers to attract and kill slugs. Record your observations and the results of your treatments Overturn clay pots or place flat boards next to plants for future reference. to lure slugs. Check frequently and kill collected slugs. If you use pesticides, choose those that pose the least threat to water quality. Examples include pyrethrins, insecticidal Weeds soaps, horticultural oils, and Bacillus thuringiensis (Bt). Hand-pull weeds or cultivate with a hoe where If you decide to use pesticides, apply them when the pest is appropriate. most susceptible, not according to a predetermined calendar Use mulches generously. schedule. Keep lawns healthy and dense to crowd out weeds. If using insecticides, spot treat only those plants or plant parts affected. Compared to cover sprays, spot treatments can drastically reduce insecticide use (by more than 90 percent in some cases) and still achieve good control. Apply preventive fungicides only to plants likely to develop disease problems. Better yet, plant disease-resistant species or cultivars. If you use pesticides, carefully read the label for directions, use restrictions, and health and environmental precautions. 12-5 CHAPTER 12 Your Yard and Water Quality For More Information UK Cooperative Extension Publications Living Along a Kentucky Stream (IP-73) Principles of Home Landscape Fertilization (ID-73) More information on this topic is available from the University of Kentucky Environmental and Natural Resource Issues web page at https://water.ca.uky.edu/ Revised 01-2024