A Brief Overview of Nutrient Cycling in Pastures
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A Brief Overview of Nutrient Cycling in Pastures

A Brief Overview of Nutrient Cycling in Pastures

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    A Brief Overview of Nutrient Cycling in Pastures A Brief Overview of Nutrient Cycling in Pastures Document Transcript

    • Overview A Brief Over view of Pastures Nutrient Cycling in Pastures LIVESTOCK SYSTEMS GUIDEAbstract: Nutrients in a pasture system cycle through soil organisms, pasture plants, and grazing livestock. Appropriatemanagement can enhance the nutrient cycle, increase productivity, and reduce costs. Two practical indicators of soilhealth are the number of earthworms and the percentage of organic matter in the soil. A diversity of pasture plantsgrowing on healthy soils use sunlight and the nutrient resources in the soil to effectively produce animal feed. Paddockdesign and stocking density can also affect the efficiency of nutrient cycling in a pasture system. Supplementation ofnatural fertility, based on soil tests, balances the soil’s mineral composition, resulting in better plant and animal growthand increased soil health.By Alice E. BeetzNCAT Agriculture SpecialistNovember 2002 Photos © www.clipart.com 2002ATTRA is the national sustainable agriculture information service, operated by the National Centerfor Appropriate Technology through a grant from the Rural Business-Cooperative Service, U.S.Department of Agriculture. These organizations do not recommend or endorse products,companies, or individuals. NCAT has offices in Fayetteville, Arkansas (P.O. Box 3657, Fayetteville,AR 72702), Butte, Montana, and Davis, California.
    • Table of Contents and grazing livestock. Each will be discussed separately below. They all work together to produce good-quality soils, which in turn Introduction .......................................... 2 produce good-quality pastures. Good-quality Soil Organisms and Nutrient soils don’t erode, since water flows quickly into Cycling .............................................. 2 the ground and is stored there. Good-quality Organic Matter is Essential pastures are springy underfoot, with deep green to Soil Health .................................. 4 forage that covers the soil and a moderate Pasture Plants Also Cycle amount of dead residue under the canopy. They Nutrients .......................................... 5 produce nutritious forage with balanced mineral Grazing Livestock Affect levels. Livestock find these forages palatable and Pasture Nutrient Cycles ................ 5 thrive on them. Animal manure and plant Nutrient Cycling in Relation to Other residues quickly break down to be used again. Natural Cycles ................................ 7 Producers create this kind of soil through good Supplementing the Nutrient management. They use smart grazing strategies. Cycle ................................................. 8 They test their soils regularly and apply Conclusion ............................................ 9 fertilizers, lime, and organic amendments as References ............................................. 9 needed. They monitor the results of these Further Resources .............................. 10 decisions and make note of their observations for future reference. They understand their forages and adjust stocking rates and paddock restIntroduction periods. They make harvesting and seeding decisions to maintain and improve their soil andWhen nutrients cycle efficiently in a pasture pasture resources.system, they move through various soilorganisms and pasture plants, then through thegrazing animals, and back to the soil again as Soil Organisms and Nutrient Cyclingmanure and urine. This publication provides ageneral outline of the nutrient cycle, and gives The soil is alive with organisms, ranging frompasture managers some guidelines for working visible insects and earthworms to microscopicwith the many elements of these complex bacteria and fungi. These living organisms aresystems. For more detail and more technical working for the grass farmer, to whom they areinformation, refer to the companion ATTRA extremely important. We might even refer topublication, Nutrient Cycling in Pastures. them as soil livestock. In fact, the soil can be viewed as home to a great complexity of life,Pasture managers can effectively increase soil rather than just a medium to support plants. Anfertility by understanding the functions of the acre of living soil may contain 900 pounds ofplants and animals living in and on the soil. Not earthworms, 2400 pounds of fungi, 1500 poundsonly can soil organisms generate mineral of bacteria, 133 pounds of protozoa, 890 poundsnutrients or make them available, but these same of arthropods and algae, and even smallminerals can also be recycled several times in a mammals in some cases (1). An understandinggrowing season, if the soil ecosystem is healthy of underground biological cycling can enable theand plant cover is optimal. With good pasture manager to benefit from this herd of soilmanagement, nutrients can cycle quickly with livestock.minimal losses to air and water. Less fertilizerwill be required, and this means increased Soil bacteria are the most numerous, with everyprofitability for the entire farm. gram of soil containing at least a million of these tiny one-celled organisms. There are manyThree different groups of living organisms drive different species of bacteria, each with its ownthe nutrient cycle: soil organisms, pasture plants, role in the soil environment. One of the majorPAGE 2 //A BRIEF OVERVIEW OF NUTRIENT CYCLING IN PASTURES
    • benefits bacteria provide for plants is to help crumb of granola. In addition, some species ofthem take up nutrients. One of the primary ways algae (the blue-greens) can fix nitrogen, some ofthey do this is by releasing nutrients from organic which is later released to plant roots.matter and soil minerals. Certain species releasenitrogen, sulfur, phosphorus, and trace elements Protozoa are free-living animals that crawl orfrom organic matter. Other species break down swim in the water between soil particles. Manysome soil minerals and release potassium, soil protozoa species are predatory, eating otherphosphorus, magnesium, calcium, and iron. Still microbes. By consuming bacteria, protozoaother spcies make and release plant growth speed up the release of nitrogen and otherhormones, which stimulate root activity. Some nutrients through their waste products.bacteria, either living inside the roots of legumesor free-living in the soil, fix nitrogen. Other Nematodes are abundant in most soils, and onlyservices provided to plants by various species of a few species are harmful to plants. The harmlessbacteria include improving soil structure, species eat decaying plant litter, bacteria, fungi,fighting root diseases, and detoxifying the soil. algae, protozoa, and other nematodes. Like the other soil predators, nematodes speed the rateActinomycetes are thread-like bacteria that look of nutrient cycling.like fungi. While not as numerous as other bac-teria, they perform vital roles in the soil. Likeother bacteria, they help decompose organic These living organisms are working for thematter into humus, releasing nutrients. They also grass farmer, to whom they are extremelyproduce antibiotics to fight root diseases. And important. We might even refer tothey are responsible for the sweet earthy smell them as soil livestock.of biologically active soil. Earthworms are good indicators of soil health.Fungi come in many different species, sizes, and Research in New Zealand pastures hasshapes in soil. Some species appear as thread- repeatedly shown improved soil qualities wherelike colonies, while others are one-celled yeasts. worms thrive. Studies have also proved thatSlime molds and mushrooms are also fungi. forage production nearly doubles when wormsMany fungi aid plants by breaking down organic are introduced and establish themselves inmatter or by releasing nutrients from soil miner- pastures. This higher production might beals. Some produce hormones and antibiotics that attributed to other related changes, not just theenhance root growth and provide disease sup- direct activity of the worms themselves.pression. There are even species of fungi that Nevertheless, there is a demonstrated correlationtrap harmful plant-parasitic nematodes. Mycor- between worm population and foragerhizae are fungi that live either on or in plant production (2).roots and act to extend the reach of root hairsinto the soil. Mycorrhizae increase the uptake of Earthworm burrows enhance water infiltrationwater and nutrients, especially in soils with nu- and soil aeration. Earthworms pass soil, organictrient deficiencies. The fungi, in turn, benefit by matter, and soil microbes through their digestivetaking nutrients and carbohydrates from the systems as they move through the soil. Thisplant roots they live with. process increases the soil’s soluble nutrient content considerably. Worms eat dead plantMany species of algae also live in the soil. Un- material left on top of the soil and redistributelike most other soil organisms, algae produce the organic matter and plant nutrientstheir own food through photosynthesis. They throughout the soil horizon. Research shows thatappear as a greenish film on the soil surface fol- a thick layer of dead organic material remainslowing a rain. Their primary role is to improve on the surface in pastures without any worms.soil structure by producing sticky materials that Earthworms also secrete a material thatglue soil particles together into water-stable ag- stimulates plant growth. Some increase in plantgregates. A soil aggregate looks like a minature growth, as well as the improved soil quality, can //A BRIEF OVERVIEW OF NUTRIENT CYCLING IN PASTURES PAGE 3
    • be attributed to this substance. In addition, a creates an open soil structure into which water,Dutch study revealed that worms reduced the dissolved minerals, and oxygen can move, readytransmission of some parasitic nematodes in cow for plants to use. It provides further nutrientpats (3). storage in the soil and can disable certain plant toxins. In addition, beneficial soil organismsAs Charles Griffith of the Noble Foundation has depend upon organic matter as a source of food.said, you can never have too many earthworms. These countless tiny plants and animals createHe was working toward a goal of 25 per square an ecosystem that releases mineral nutrients,foot, but reports from New Zealand mention 40 increases their availability to plants, and helpsper square foot in soils where worms were protect plant roots from disease.introduced only seven years earlier (4).Earthworms thrive where there is no tillage, Testing for soil organic matter (OM) is a simpleespecially in the spring and fall, their most active way to make sure there is a functioningperiods. They prefer a near-neutral pH, moist community of organisms in the soil. All thesoil, and plenty of plant residue on top. They organisms mentioned above, except algae,are sensitive to some pesticides. Fertilizers depend on organic matter for their food. Theapplied to the soil surface are often beneficial, primary decomposers start with raw plantbut anhydrous ammonia is deadly, and tillage residues and manure. Their by-products aredestroys nightcrawler burrows. Efforts to protect eaten by other species whose wastes feed stilland increase worm populations will be rewarded other microbes. After moving through severalwith healthier, more productive pastures. species, these raw materials become soluble plant nutrients and humus. The humus contributes toIn addition to earthworms, there are many other well-structured soil, which in turn producesspecies of soil organisms visible to the naked eye. high-quality forage. It is clear that when this soilAmong them are dung beetles, sowbugs, ecosystem is working, there are many benefitsmillipedes, centipedes, slugs, snails, and to the pasture system visible above ground. Thespringtails. These are the primary decomposers. complex ecosystem underground would be hardThey start eating the large particles of plant to evaluate, but soil organic matter, as measuredresidue. Some bury residue, bringing it in contact in regular soil tests, is a simplified way to monitorwith other soil organisms, which further the health of this invisible world.decompose it. The springtails eat mostly fungi,and their waste is rich in plant nutrients. All The organic matter test can be requested throughthese organisms—from the tiny bacteria up to the local Extension facilities. This kind of soillarge earthworms and snails—function together analysis measures, by weight, the percentage ofin a whole–soil ecosystem. Because humans soil that is OM. Organic matter includes mineralscannot see most of the critters living in the soil that are part of living organisms, as well as deadand may not take time to observe the visible ones, plant material that has not yet been digested.it is easy to forget about them. They are present Because organic matter levels are harder toin biologically active soils and perform many maintain in warmer, more humid climates, whatuseful functions, if pastures are managed for their constitutes a “high” or “low” percentage willsurvival. vary in different parts of the country. Local Extension agents or soil scientists can help define relative values. A single test will show aOrganic Matter is Essential to Soil beginning point, and subsequent soil tests canHealth indicate whether progress is being made toward a higher level of soil organic matter.Organic matter is critical for storing water andnutrients in the soil. It holds nutrients in plant- Maintaining or building organic matter is the firstavailable forms that don’t easily wash away. It step to developing soil humus. Humus resultsPAGE 4 //A BRIEF OVERVIEW OF NUTRIENT CYCLING IN PASTURES
    • from the final stages of organic matter urine, it could take as little as two weeks beforedecomposition. Favorable biological processes it’s again available in plant tissue. If the cloverwhich decompose the organic matter into humus isn’t eaten directly, the nitrogen that it harvestedcan be limited or even stopped by lack of from the air may naturally become available tonitrogen, lack of oxygen, unfavorable nearby grasses in as little as four months.temperature, or unfavorable pH. Once stable Nitrogen in a leaf that falls on biologically activehumus has accumulated in the soil, it has a host soil can be used again in the same growingof beneficial effects on plants. These positive season.effects are directly related to the presence anddiversity of microbial life. A final way in which nutrients become available to the forage plants (and thus to the grazing animal) is through the action of deeply rooted Benefits of a humus-rich soil include: plants. Trees, many broadleaf weeds, and forages • Granulation of soil particles into such as alfalfa have taproots that go deep into water-stable aggregates the soil horizon where some grass roots cannot • Decreased crusting reach. The nutrients from these deeper soil levels • Improved internal drainage are used by the plant, but become available at • Better water infiltration the soil surface once the tree leaves fall or the • Fixation of atmospheric nitrogen weeds die, decompose, and release their • Release of bound nutrients nutrients. • Increased water and nutrient storage capacity The roots constitute at least half the weight of a grass plant. Many native warm-season perennial grasses have root systems that reach six feet orPasture Plants Also Cycle Nutrients more into the soil horizon. They occupy a huge underground area and form a network that holds the soil in place. Every year 20–50% of this mass,Rhizobium bacteria live in legume root nodules as well as all of the top growth in temperateand convert nitrogen from the air into forms the climates, dies and becomes organic matter which,legume can use. This nitrogen is used by the in biologically active soil, is broken downplant and generally does not become available quickly. Cool-season grasses also contributeto nearby plants until the legume dies. Some of organic matter through root and shoot dieback.the nitrogen fixed by white clover, however, isavailable as soon as four months into the season.With red clover, the interval is six months, and Grazing Livestock Affect Pasturealfalfa-fixed nitrogen takes 6 to 12 months to Nutrient Cyclesbecome available. Although white clover iscredited with fixing less nitrogen than either redclover or alfalfa, if that nitrogen is available Livestock feeding on pasture use a smallsooner, with efficient nutrient cycling it could be proportion of the minerals they ingest in foragesused more than once in a growing season. It to build bones, meat, and hide. The rest istherefore becomes just as important as other excreted in dung and urine. In general, urinelegumes as a source of new nitrogen in the contains most of the nitrogen (N) and potassiumnutrient cycle. In addition, some nodules (K) wastes, and dung contains most of theseparate naturally from the legume roots during phosphorus (P) the animals don’t use. Refer toa grazing cycle, thus becoming available to other the box on page six to learn about the value ofplants. Some legumes have “leaky” nodules and urine and dung in pastures.share more of their fixed nitrogen than others. Nutrients in urine are soluble and move in theA nitrogen molecule can be fixed by white clover soil solution to the roots. When N and K arein one day. If eaten by a cow and excreted in present at higher levels in the feed, they are //A BRIEF OVERVIEW OF NUTRIENT CYCLING IN PASTURES PAGE 5
    • excreted in manure as well. The liquid forms can Other agents that help to break up manure pilesbe taken up by a plant at once and are then very include ants, birds, and earthworms. Pesticidesquickly available again as food. Sheep, which do that are lethal to these non-target species can thusnot avoid urine spots as cattle do, can have unforeseen negative consequences forimmediately cycle this mineral again. nutrient availability. If dragging or clipping is economical, these operations physically scatter Value Of NPK In Manure And Urine the dung so that smaller organisms can cycle it. The potential of creating a larger area of forage One 1000-pound cow produces 50–60 lbs. rejection, however, is a consideration. Another of manure and urine per day, which negative effect is that more nutrients are lost into contains: the air during mechanical scattering. 0.35 lb. N @ 24¢/lb. = 8¢ N To recapture and evenly distribute these 0.23 lb. P @ 22¢/lb. = 5¢ P nutrients for soil organisms and plants to use 0.28 lb. K @ 14¢/lb. = 4¢ K requires some knowledge about grazing Total NPK = 17¢ behavior. In smaller paddocks, with high stock density, urine and dung are more evenly Therefore: distributed than in large ones. Livestock are less selective in their grazing habits and space 10 cows ⇒ $ 1.70/day themselves more evenly within the area allotted 100 cows ⇒ $17.00/day for a grazing period. They will graze closer to 500 cows ⇒ $85.00/day dung piles and exhibit less avoidance of urine spots so that more forage is used for animal Note: If you add the value of organic matter production. and trace minerals in the manure, the total value of the manure doubles! In large areas, cattle act as a herd and go to water together. When water is available nearby, Source: Salatin, Joel. 1993. One Cow Day of however, animals drink individually and return Manure: What’s It Worth. Stockman Grass to graze in other areas. If they must travel in a Farmer. September. p. 11. lane to the water, manure will concentrate in these non-productive areas en route. When therePhosphorus and some other minerals cycle is not enough room at the water tank for all tothrough animals primarily in manure. It can take water at once, those waiting will manure thatfrom six months to two years for manure to break area, concentrating nutrients where they are lessdown and for the phosphorus to cycle back into likely to contribute to plant and animalthe plants. The speed of the cycle is affected by productivity.various biological agents as well as bymechanical means. Dung beetles bury manure Good management helps distribute nutrients thatwith their eggs in burrows. This activity not only will feed soil microbes and encourage healthyplaces the minerals back into t roots can use them soil ecosystems. Locating water, minerals, shade,but it prevents fly eggs from hatching as well. and fly-control devices in different parts of theSome pesticides designed to control livestock paddock also discourages nutrient concentration.parasites unfortunately kill dung beetles as well. It is even more beneficial if these high-use areasThis side effect can deal a serious blow to the can be relocated for each grazing cycle or placedability of the natural ecosystem to function. For in areas that would not otherwise attract livestockmore information on this subject, call and request use. Supplemental feed, likewise, should beDung Beetle Benefits in the Pasture Ecosystem or find placed either where nutrients are needed orit on the ATTRA website (http:// under the fence. The location should vary withwww.attra.ncat.org). each feeding.PAGE 6 //A BRIEF OVERVIEW OF NUTRIENT CYCLING IN PASTURES
    • Nutrient Cycling in Relation to Other Conditions that reduce water intake and percolation are bare ground, surface crusting,Natural Cycles compaction, and soil erosion. These conditions are not usually present in well-managedTwo other cycles—water and energy—interact perennial pastures. Bare ground leads to erosion,with the nutrient cycle. They are separated for crusting, and weeds. Crusting seals the soilpurposes of discussion here, but in reality they surface when the soil aggregates break down.function as a whole system. Excessive trampling—especially in wet conditions—and the impact of falling raindropsWater Cycle on bare soil are two common causes of crusting. Therefore, it is important to move water sources,Water is a nutrient, in one sense, since it is one of feedbunks, and minerals before bare ground andthe raw ingredients used by plants to make crusting develop.carbohydrates. It is also key to nutrient cyclingbecause plant nutrients are soluble and move Energy Cyclewith water. Downward leaching of plantnutrients occurs with water movement. Soil itself The energy cycle is powered by sunlight, whichmoves in water, taking with it insoluble nutrients plants convert into carbohydrates. In order tosuch as phosphorus. The area around roots must capture the most solar energy, the plant canopybe moist, since nutrients are taken up dissolved needs to be very dense. If the pasture has bothin water. broadleaf plants and grasses, the different leaf orientations further increase energyManagement determines how effective the water transformation. Taller plants receive light, evencycle will be in pastures. If rainwater can enter at the extreme angles of sunrise and sunset.the soil easily, runoff losses are less. Maximum Horizontal leaves capture the noon sun betterinfiltration of rainfall keeps groundwater tables than upright grass leaves. Increased efficiencycharged up, wells running year round, and in energy conversion can be achieved if thedrought damage to a minimum. pasture is considered a three-dimensional solar collector. Even trees, if they are trimmed highSoil surface conditions that foster high rainwater and do not make dense shade, contribute to suchintake are abundant ground cover (by living a system.plants and surface litter) and good soilaggregation. The best-aggregated soils are those Energy from plants is also transferred into thethat have been in well-managed perennial grass soil ecosystem through the death and decay of(5). Though aggregation can be maintained plant roots and residue. The plant roots andunder crops, the perennial activity of grass residue are decomposed first by soil-dwellingprovides both aggregate-forming processes and insects and other primary decomposers. Theaggregate-stabilizing humus. waste and by-products from the primary decomposers are broken down still further byA grass sod extends a mass of fine roots secondary decomposers. Finally the componentsthroughout the topsoil. The grass sod also of the residue become humus. At each step ofprovides protection from raindrop impact. A the decomposition process, energy is either beingmoderate amount of thatch continually provides used to create the next generation of decomposerfood for soil microorganisms and earthworms or is lost as heat. The energy cycle and thethat generate the glue-like substances that bind nutrient and water cycles require a biologicallyaggregates into water-stable units. The dead active soil to function.material, as well as the plants themselves, shadethe soil, maintaining a cooler temperature and A thick stand of green plants covering the soilhigher humidity at the soil surface. for as long a time as possible creates high energy //A BRIEF OVERVIEW OF NUTRIENT CYCLING IN PASTURES PAGE 7
    • Farm Nutrient Budget important consequences for plant production and animal health. Allan Nation, editor of The Nutrients imported to the farm in: Stockman Grass Farmer and student of grass-based • Purchased livestock livestock systems, listed many reasons to apply • Chemical fertilizers agricultural lime annually. His list is reproduced • Manures from off-farm (credit for multiple below. years) • Livestock feed (grain, hay) Soil tests, taken according to recommended • Wind and water procedures (consult Extension), provide a basic analysis of plant nutrient levels in a pasture. Nutrients generated on the farm: Fertilizer recommendations that accompany test • Atmospheric nitrogen captured by legumes results, however, are typically based on the • Rock minerals dissolved by microbial acids assumption that forages will be harvested and • Subsoil minerals mined by deep roots of removed from the area. In a grazing system this trees and other plants is not necessarily so. • Nutrients made available to the crop by changes in pH Lime Nutrients exported from the farm: • In products sold (crops, livestock) 200–500 lbs. of finely ground, face-powder- • By wind and water (erosion) consistency ag lime applied annually: • By leaching into groundwater • Helps prevent weeds such as dandelion, • Volatilized as gas plantain, chickweed, and buttercup. • Helps with the movement and absorption of phosphorus, nitrogen, andflow. This good-quality forage, provided to magnesium.livestock at the right stage of maturity, is the next • Benefits bacteria, fungi, protozoa andlink in the energy cycle. Livestock convert plant other soil life so important for nutrientmaterial into meat, milk, and fiber. The leftovers cycling.become urine and manure. Livestock products • Releases important trace and growthare sold, and the waste products again cycle nutrients by its pH-altering effect.through the decomposer organisms. Minimal • Helps clover, which requires twice theloss of energy depends on proper stocking rates, calcium of grass. Abundant calcium isgood decisions about when animals are moved, necessary for clover nodulation. Noand how much rest the plants require. lime, little clover. • Creates soil tilth and structure so that air and water can move more freely throughSupplementing the Nutrient Cycle soil by causing clay particles to stick together. Soil must be able to breathe toOne of the first steps in assessing the nutrient grow great grass.cycle on any farm is to consider nutrient inputs • Allows pastures to hang on longer in aand outputs. In what forms do nutrients enter drought.the farm? What nutrients leave and in what • Improves the palatability of grass andform? What nutrients are generated or made clover, makes the pasture softer foravailable on the farm? The box above provides animals to graze, and lessens grass-some examples. pulling in new stands. • Reportedly makes an animal more docileLime is a particularly important amendment in and content.pasture management. While it has always beenconsidered necessary for adjusting pH, there is Source: Nation, Allan. 1995. Quality Pasture—growing evidence that the amount of calcium has Part II. Stockman Grass Farmer. January. p. 13.PAGE 8 //A BRIEF OVERVIEW OF NUTRIENT CYCLING IN PASTURES
    • Supplementing the nutrient cycle with majority move through a series of living beingscommercial fertilizers, compost, or manure can in a continuous cycle. Some nutrients escape toincrease both plant and animal production, the air, some are lost to water erosion, and somewhich will, in turn, increase soil organic matter. leach down past the reach of forage plant roots.In the early years of a pasture improvement plan, The grazier who understands these cycles andadding small amounts of fertilizer several times their interactions can, by making smart dailyduring the growing season is a good way to decisions, retain more nutrients on site.increase the amount of available forage. Withgood grazing management, more forage will The health and growth of the grazing livestocktranslate into more pounds of livestock as well depend on high-quality pastures, which in turnas increased soil organic matter. spring from the soil “livestock” in a balanced underground ecosystem. Soil organic matter andTo back up a fertilization program, forage earthworm numbers are simple indicators thatsamples can be taken to see what effect the producers can use to monitor soil health. Goodfertilizer has had. Strategic forage-tissue testing grazing management, based in part on a basiccan be done by taking samples between areas of understanding of grazing behavior, combinedpoor and good growth or by making before- and with a knowledge of how animals affect theafter-fertilizer comparisons. County Extension whole pasture system, contributes to lushagents or private consultants can explain how to pastures that livestock need only to harvest.take a forage sample. Because samples are Then, with good marketing, profit is the naturalanalyzed for the purpose of ration balancing or result!to assess actual mineral content, it is necessaryto specify the latter to learn whether fertilizers For more in-depth discussion of the topics raisedare achieving their purpose. More information in this publication, consult the companionon soils is available in the ATTRA publications ATTRA booklet, Nutrient Cycling in Pastures.Sustainable Soil Management, Alternative Soil Some other good resources are listed below.Testing Laboratories and Assessing the Pasture SoilResource. ReferencesSole reliance on commercial fertilizer short-circuits the natural mineral cycle. High 1) Pimentel, David et al. 1995. Environmentalfertilization coupled with frequent harvesting of and economic costs of soil erosion andhay speeds organic matter decomposition and conservation benefits. Science. Vol. 267, No.releases minerals faster than plants growing on 24. p. 1117–1122.the site can absorb them. As a result, nutrientsare leached deeper into the soil, out of the reach 2) Stockdill, S.M.J. 1966. The effect ofof plant roots, or they are lost to run off. The use earthworms on pastures. Proceedings: Newof some commercial fertilizer is always an option Zealand Ecological Society. Volume 13. p.to be exercised when necessary. However, 68–75.continuing to look for ways to use naturalsystems to produce nutritious forage and healthy 3) Gronvold, Jorn. 1987. Field experiment onanimals, while lessening one’s dependence on the ability of earthworms (Lumbrididae) topurchased, non-renewable resources, is reduce the transmission of infective larvae ofworthwhile. Cooperia oncophora (Trichostrongylidae) from cow pats to grass. Journal of Parasitology. Vol. 73, No. 6. p. 1133–1137.Conclusion 4) Stockdill, S.M.J. 1959. Earthworms improveThis publication has described the many paths pasture growth. New Zealand Journal oftravelled by pasture nutrients. While some Agriculture. March. p. 227–233.minerals leave the farm as animal products, the //A BRIEF OVERVIEW OF NUTRIENT CYCLING IN PASTURES PAGE 9
    • 5) Allison, F.E. 1968. Soil aggregation—some Pasture Prophet facts and fallacies as seen by a microbiologist. Grazing Lands Technology Institute Soil Science. Vol. 106, No. 2. p. 136–143. Pasture Systems and Watershed Research Labo- ratoryFurther Resources Building 3702, Curtin Rd. University Park, PA 16802-3702Proceedings: The Stockman Grass Farmer 282 Commerce Park DriveJoost, Richard E. and Craig A. Roberts. 1996. Ridgeland, MS 39157Nutrient Cycling in Forage Systems. (601) 853-1861Proceedings of a Symposium held March 7–8, (601) 853-8087 FAX.1996, Columbia, MO. Potash and Phosphate (800) 748-9808Institute and Foundation for Agronomic http://www.stockmangrassfarmer.comResearch, Manhattan, KS. 243 p. Anyone interested in pursuing this subject further should obtain a copy of this book. It Electronic Listservers: contains many bibliographic references. Available for $15 ppd. from: Graze-L Potash and Phosphate Institute To subscribe send an e-mail to: 772 22nd Ave. S. majordomo@taranaki.ac.nz or Brooking, SD 57006 listserv@taranaki.ac.nz (605) 692-6280 In the body of the e-mail type “subscribe graze- l”Periodicals: The Grazer’s Edge To subscribe send an e-mail to:These carry articles on practical aspects of grazing grazersedge-subscribe@onelist.commanagement, including nutrient cycling. In the body of the e-mail type “subscribe grazersedge”The Forage LeaderAmerican Forage and Grassland Council Web Sites:P.O. Box 891Georgetown, TX 78627 Soil Foodweb, Inc.(800) 944-2342 http://www.soilfoodweb.com/index.html More detail on the underground soilGraze ecosystem and its above-ground interactionsP.O. Box 48 can be found on this website.Belleville, WI 53508(608) 455-3311http://www.grazeonline.com Related ATTRA Publications $30 for 1-year subscription (10 issues) Nutrient Cycling in Pastures Assessing the Pasture Soil ResourceHay and Forage Grower Sustainable Pasture ManagementWebb Division Rotational GrazingIntertec Publishing Corp. Dung Beetle Benefits in the Pasture Ecosystem9800 MetcalfOverland Park, KS 66212-2215(800) 441-0294.PAGE 10 //A BRIEF OVERVIEW OF NUTRIENT CYCLING IN PASTURES
    • By Alice E. BeetzNCAT Agriculture SpecialistEdited by Richard EarlesFormatted by Cynthia ArnoldNovember 2002The electronic version of A Brief Overview ofNutrient Cycling in Pastures is located at:HTMLhttp://www.attra.ncat.org/attra-pub/nutcycle.htmlPDFhttp://www.attra.ncat.org/attra-pub/PDF/nutcycle.pdf //A BRIEF OVERVIEW OF NUTRIENT CYCLING IN PASTURES PAGE 11