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The underlying basis of organic lawn care practices is the management of a soil in which the biotic character is preserved. Organic matter provides nutrients, moisture retention, texture, and an environment to sustain high populations of microorganisms. Fertile soil is essential for a healthy lawn. A soil test is a fundamental first step to any organic or conventional lawn care program. The two programs differ mostly in the forms in which nutrients are added. Nitrogen: Sources of nitrogen in organic fertilizers include bone meal, dried blood, vegetable and feather meals, manures and sludge, and may range from 3-10% by weight. In this form, most of the nitrogen is bound to complex organic molecules and is inaccessible to plants until it is slowly released, over time, by the natural activity of soil microorganisms. Organic nitrogen sources permitted include such materials as composted manures, cover crops, and green manures. In contrast to fertilizers which release nitrogen immediately and produce a rapid "green-up," response of grass to organic fertilizers may take months to years. In addition, nutrient availability may be limited during cold periods when microorganism activity is minimal. The typical slow response time and high cost associated with the use of organic products has led to an increase in the sales of fertilizers which contain mixtures of natural/synthetic and natural/inorganic nutrient sources. While use of these products reduces green-up time and cost, they are not in compliance with "natural organic" standards. Other Nutrients: Natural organic fertilizers, as well as composts and manures, are excellent providers of other essential nutrients. Sources of phosphate include bone meal (derived from vertebrate skeletons) and rock phosphate. The first may contain an odor and may be difficult to spread. The latter is effective only if acid treated to break down particles to a more available form, a practice not accepted by organic certifying groups. Low levels of potassium are found in most composts. Potassium may also be provided by wood ash or as potassium sulfate. In addition, humates, or "biostimulants," are sold to provide nutrients for turf. Given a proper pH (approximately 6.5), other nutrients are also available in most sources of composts or can be supplemented in their "natural" form. Cultural Management: Maintenance of a vigorous lawn depends upon cultural practices to increase the diversity and health of beneficial organisms in all levels of the soil. The ecological lawn seed mix should thus be comprised of a variety of grass species and cultivars in order to take advantage of the disease-resistance qualities of each and to reduce susceptibility to damage by pests specific to any one. Endophyte-infected grass mixtures, which are combinations of specific cultivars of tall fescue, perennial ryegrass and fine fescues, are currently being marketed for sustainable, organic lawn care situations. The beneficial symbiotic relationship between the plant and a fungus that lives inside of it results in grasses which tend to be more vigorous than endophyte-free varieties under a range of cultural conditions and when under abiotic stresses such as drought, heat, and low nutrients. Also, endophyte-infected grasses have resistance to foliar feeding insects such as chinch bugs, billbugs and sod webworms. For more information, see GreenShare factsheet on endophyte-enhanced grasses. Integrated Pest Management: The IPM strategy for organic lawn care is prevention. The aim is to use plant selection, establishment and maintenance practices to promote, conserve and enhance natural pest controls. A healthy, well-rooted turf can compete with many species of weeds. Mowing high is another organic strategy aimed at shading out particularly troublesome annual weeds as crabgrass, which require light to germinate. The presence of weeds is used as an indicator of other cultural problems, such as nutrient deficiencies or compaction, which may then be corrected. In addition, organic lawn care endorses the need for education aimed at acceptance of a certain level of "weeds." Disease management also focuses on providing optimal conditions to maintain the health of the grass and soil. Good drainage and proper soil pH contribute to the conservation of organisms antagonistic to pathogens. Practices such as establishment of disease-resistant grasses, increasing air circulation and avoiding watering at times when the grass will remain wet may all be used in attempts to prevent disease. Natural and/or organic supplements may also be used to change an environment which favors the disease organism. Certain composts are disease-suppressive, although the particular organisms involved have yet to be identified. Some specific natural organic fertilizers have also been found to suppress specific diseases such as dollar spot, brown patch and red thread. An organic approach to pest management for insects focuses on "least toxic control strategies." Avoidance of broad spectrum pesticides which affect "nontarget" organisms results in the maintenance of natural pests. Biological controls such as predators and parasites can also be used in addition to natural organic sprays and dusts. As mentioned previously, endophyte-infected grasses are resistant to a number of surface-feeding insects. Entomophagous ("insect-eating") nematodes such as Steinernema carpocapsae parasitize the larvae of sod webworms and cutworms. Bacteria such as B.t. (Bacillus thuringiensis) can be used against the sod webworm and the cutworm as well. Botanical insecticides as rotenone and pyrethrum are also allowed as part of an organic pest control program. Emphasis on scouting and spot treatment reduces costs and overuse of even these more ecologically sound methods of organic pest control. See GreenShare Factsheet on Integrated Pest Mangement for turf for more information.
Adapted from the Unniversity of Massachusetts Extension, 1999
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