Greener Pastures The Organic Way part of a holistic system to maintain good health for animals and build healthy soil By Nancy Brannon Organic pasture management is an alternative to the use of chemical herbicides to control pasture weeds. It is also part of a holistic system of animal husbandry that provides appropriate living conditions and maintains good health for animals, and uses responsible farm management to build healthy soil, the foundation source for food for all living beings. Healthy Pastures and Healthy Horses The horse is a naturally grazing animal designed for continuous intake of forage. Horses need to consume feed at a rate of 1.5% to 3.0% of their body weight each day, on a dry matter basis. For proper digestive function, at least 70% of this feed should be provided as long stem forage, which can be provided by pastures of good quality hay. A well-managed pasture can provide complete nutrition for most mature, healthy pleasure horses. Forage species selection is dependent upon climate, soil drainage, stocking density, and the class of grazing horse. Forage species are classified as grasses or legumes and must tolerate close grazing because horses are capable of extreme defoliation. Cool-season perennial grasses are planted in spring or late-summer to provide grazing in the spring, summer, and fall, but typically yield less during the hot summer months. Palatability also affects species preference, which varies from horse to horse. Resistance to hoof traffic should factor into species selection if horses are highly active. Cool season perennial grasses include Kentucky Bluegrass, Orchardgrass, Perennial ryegrass, Reed canarygrass. Tall fescue is ideal for grazing horses because it is hardy, nutritious, has high seedling vigor, tolerates close grazing, destructive hoof traffic, pests, wet, and acidic conditions. Under low grazing pressure it will grow as a bunch grass, but under high pressure will appear turf-like. The downside is that the tall fescue endophyte Acremonium coenophialum produces ergot alkaloids responsible for hormonal interference in broodmares. The national percentage of infection of tall fescue is at least 85%. Seed transmission is the only mechanism for endophyte infection, so planting an endophyte-free cultivar in an isolated area should eliminate the potential for infection. Endophyte-free varieties are commercially available but have lower seedling vigor, and less resistance to drought, insect pests, disease, and frequent grazing. Legumes. Grasses require nitrogen fertilization, while legumes form a symbiotic association with soil bacteria to convert atmospheric nitrogen to a plant-available form. Legumes are high in protein, enhance palatability and digestibility of pasture and maintain their forage quality longer than grasses. Legumes are a mainstay of organic rotations because they can supply nitrogen to companion or succeeding crops. Used for hay or pasture, they can supply large amounts of high-quality forage rich in plant proteins, while still offering benefits as a cover crop. Soil Fertility. Maintaining soil fertility is a key to maintaining good pastures for horses. Soil is the foundation, and attention to soil organic matter, and the use of crop rotations, cover crops, soil amendments and compost, will improve the health of the soil. Healthy soil is living soil. Biological activity and diversity are critical benchmarks of healthy soil because each soil organism has its own special functions. These soil organisms digest soil organic matter and convert it into substances used by plants and other soil organisms. Soil is the most complex and diverse ecosystem on earth, with more than a billion microorganisms representing some 10,000 species of life per thimbleful, all interconnected in complex food chains, breaking down organic matter into smaller and smaller "bites" that feed crop plants and act as storehouses for water and nutrients. These living organisms in soil, including microorganisms like algae and fungi and macroorganisms such as worms and beneficial insects, form a "soil food web" that works very much like a spiderweb. The more strands this web contains, the more likely it is to catch food and hold nutrients. The more creatures eating and being eaten in soil, the more nutrients will be cycling in the system and available to plants. Healthy soil means healthier and more productive crops. Organic farming practices improve soil cumulatively over time. Weed control. Weed control in pastures is deemed important because these plants compete for soil nutrients, water and sunlight that desired pasture plants also need. The best weed control is achieved by maintaining a dense healthy stand of grasses and legumes through proper soil fertility management, cutting, and livestock rotation. Most Extension Agencies have a list of herbicides that can be applied to pastures for killing weeds. However, many folks choose not to use chemical herbicides and pesticides on their property because of their real and potential harms to human and animal health, wildlife and pond life impacts, and harm to healthy soil microorganisms. Mowing is an important component of pasture management that minimizes the spread of weeds and maintains high quality forage. Mowing weeds before seedheads are produced limits the spread of weeds by seed. Mowing maintains a pasture stand that is uniform in maturity and helps promote a nutritionally higher quality pasture. Horses prefer to eat shorter grasses because they have less fiber and are higher in protein. Manure Management and fly control.The organic standard also covers responsible manure management to protect crops, soils and water resources from contamination with nutrients, heavy metals and pathogenic organisms. "The producer of an organic livestock operation must manage manure in a manner that does not contribute to contamination of crops, soil, or water by plant nutrients, heavy metals, or pathogenic organisms and optimizes recycling of nutrients” (section 205.239c). On-farm composting is an effective way to manage livestock wastes while promoting soil health. Manures can be mixed with carbon-rich materials and allowed to heat and decay. Farm-based carbon sources might include bedding or waste hay. Improperly managed manure can increase the risk of E. coli, other pathogenic bacteria, intestinal worms and insect pests. Keeping flies' numbers reduced is an important part of providing comfortable living conditions for your animals. Flies will congregate when manure is present. Fly-control strategies approved for organic management include releasing natural enemies like hister beetles and predatory wasps, keeping barns clean and dry, and using various non-synthetic traps. Green manure is a crop that is incorporated into the soil when it is green, or soon after flowering, for the purpose of improving the soil. Widely used green manure crops include winter rye and the common legumes, such as vetches, clovers and alfalfa. A major benefit of green manures is the addition of organic matter to the soil. Nutrient Cycling in Pastures The following is summarized from “A Brief Overview of Nutrient Cycling in Pastures.” Three groups of living organisms drive the nutrient cycle in pastures: soil organisms, pasture plants, and grazing livestock. They all work together to produce good quality soils, which produce good quality pastures. Good quality pastures don’t erode because water flows into the ground. They feel springy underfoot, with deep green forage that covers the soil and a moderate amount of dead residue under the canopy. They produce nutritious forage with balanced mineral levels, which livestock find palatable and thrive upon. Animal manure and plant residues quickly breakdown to be used again. This kind of soil is created through good management, which includes regular soil testing, applying fertilizers, lime and organic amendments as needed; don’t overgraze by adjusting stock rates through pasture rotation and pasture rest periods. Testing for soil organic matter is a simple way to make sure there is a functioning community of organisms in the soil. Building and maintaining organic matter are the first steps to developing soil humus. Soil Organisms. Healthy soils abound with a great complexity of living organisms ranging from visible insects and earthworms to microscopic bacteria and fungi. An acre of living soil may contain 900 pounds of earthworms, 2400 pounds of fungi, 1500 pounds of bacteria, 133 pounds of protozoa, 890 pounds of arthropods and algae, and small mammals. One of the major benefits bacteria provide for plants is to help them take up nutrients. They do this primarily by releasing nutrients from organic matter and soil minerals. Some species release nitrogen, sulfur, phosphorus, and trace elements from organic matter. Others break down some soil minerals and release potassium, phosphorus, magnesium, calcium and iron. Others make and release plant growth hormones, which stimulate root activity. Some bacteria, either living inside the roots of legumes or free-living in the soil, fix nitrogen. Other species of bacteria improve soil structure, fight root diseases, and detoxify the soil. Many fungi aid plants by breaking down organic matter or by releasing nutrients from soil minerals. Some produce hormones and antibiotics that enhance root growth and provide disease suppression. Some species of fungi trap harmful plant-parasitic nematodes. Mycorrhizae, fungi that live on or in plant roots, extend the reach of root hairs into the soil and thus increase the uptake of water and nutrients, especially in soils with nutrient deficiencies. Various species of algae that live in soils improve soil structure by producing sticky materials that glue soil particles together into water-stable aggregates. Nematodes are abundant in most soils, and only a few species are harmful to plants. The harmless species eat decaying plant litter, bacteria, fungi, algae, protozoa and other nematodes. They speed up the rate of nutrient cycling. Earthworms are good indicators of soil health. There is a demonstrated correlation between worm population and forage production. Forage production nearly doubles when worms are introduced and establish themselves in pastures. Earthworm burrows enhance water infiltration and soil aeration. They pass soil, organic matter, and soil microbes through their digestive systems as they move through the soil, increasing the soil’s soluble nutrient content. They also secrete a material that stimulates plant growth. Pasture Plants Cycle Nutrients. Rhizobium bacteria live in legume root nodules and convert nitrogen from the air into forms the legume can use. But the nitrogen used by the legume generally does not become available to nearby plants until the legume dies. Some of the nitrogen fixed by white clover is available as soon as four months into the season. With red clover, the interval is six months, and alfalfa-fixed nitrogen takes 6 to 12 months to become available. In addition, some nodules separate naturally from the legume roots during a grazing cycle, thus becoming available to other plants. Some legumes have “leaky” nodules and share more of their fixed nitrogen than others. Trees, many broadleaf weeds, and forages have taproots that go deep into the soil horizon where some grass roots cannot reach. The nutrients from these deeper soil levels are used by the plant, but become available at the soil surface when the tree leaves fall or the weeds die, decompose and release their nutrients. Grazing Livestock. The waste products from grazing livestock also contribute to soil fertility. In general, urine contains most of the nitrogen (N) and potassium (K) wastes and dung contains most of the phosphorus (P) the animals don’t use. Nutrients in urine are soluble and move in the soil solution to the roots. When N and K are present at higher levels in the feed, they are excreted in manure as well. The speed of the cycle of breaking down manure is affected by various biological agents and by mechanical means. Dung beetles bury manure in their eggs in burrows. This puts minerals back into the soil so roots can use them and prevents fly eggs from hatching. Some pesticides designed to control livestock parasites unfortunately kill dung beetles, too. Other agents that break up manure piles include ants, birds, and earthworms. Pesticides that are lethal to these non-target species have negative consequences for nutrient availability. Dragging or clipping pastures is a way to physically scatter the dung so smaller organisms can cycle it. Good pasture management helps distribute nutrients that will feed soil microbes and encourage healthy soil ecosystems. Locate water, minerals, shade, and fly-control devices in different parts of the pasture. Relocate high use areas for each gracing cycle. Supplementing the Nutrient Cycle. Soil tests, taken according to recommended procedures, provide a basic analysis of plant nutrient levels in a pasture. The results commonly include recommendations for fertilizer applications. “Fertilizer ratios indicate the percentage of nitrogen, phosphorus, and potassium, by weight, in a particular fertilizer. Ratios are always given as the percent nitrogen (N), phosphorus (P), and potassium (K).” Fertilizer recommendations that accompany test results, however, are typically based on the assumption that forages will be harvested and removed from the area. In a grazing system, this is not necessarily so. A key component of soil analysis is pH, which indicates the acidic level of soil, an important environmental factor that influences plant growth. A pH less than 7.0 indicates an acid soil (7.0 is neutral). For most pastures, the soil pH should be between 6.0 and 7.0. Lime is a particularly important amendment in pasture management. Most aglime materials are calcium and/or magnesium carbonates. In addition to adjusting pH, there is evidence that the amount of calcium has important consequences for plant production and animal health. Allan Nation, editor of The Stockman Grass Farmer, lists reasons to apply agricultural lime annually: -Helps prevent weeds such as dandelion, plantain, chickweed, and buttercup. -Helps with the movement and absorption of phosphorus, nitrogen, and magnesium -Benefits bacteria, fungi, protozoa and other soil life important for nutrient cycling -Releases important trace and growth nutrients by its pH-altering effect. -Helps clover, which requires twice the calcium of grass. Abundant calcium is necessary for clover nodulation. -Creates soil tilth and structure so that air and water can move more freely through soil by causing clay particles to stick together. Soil must be able to breathe to grow good grass. -Improves palatability of grass and clover, makes the pasture softer for animals to graze, and lessens grass pulling in new stands. Supplementing the nutrient cycle with commercial fertilizers, compost, or manure can increase both plant and animal production, which in turn increases soil organic matter. Sole reliance on commercial fertilizer short-circuits the natural mineral cycle. High fertilization coupled with frequent harvesting of hay speeds organic matter decomposition and releases minerals faster than plants growing on the site can absorb them. As a result, nutrients are leached deeper into the soil, out of the reach of plant roots or are lost to runoff. Resources: Rodale Institute http://www.rodaleinstitute.org/ The National Sustainable Agriculture Information Service http://attra.ncat.org/attra-pub/sustpast.html Rutgers University, Agricultural Experiment Station. “Horse Pasture Management” http://njaes.rutgers.edu/horsepastures/index.htm Charles N Merfield. 2000. Organic Weed Control: A Practical Guide http://www.merfield.com/research/organic-weed-management-a-practical-guide.pdf How to Go Organic.com, Pasture Management and Grazing: http://www.howtogoorganic.com/index.php?page=pasture-management Purdue University Organic and Alternative Livestock Production Systems http://www.ansc.purdue.edu/POA/org%20forage.shtml