Soil Management: National Organic Program Regulations


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Soil Management: National Organic Program Regulations

  1. 1. Soil Management: ATTRA National Organic Program Regulations A Publication of ATTRA, the National Sustainable Agriculture Information Service • 1-800-346-9140 • www.attra.ncat.orgBy Barbara C. Bellows The National Organic Program Rule, §205.203, Soil Fertility and Crop Nutrient Management PracticeNCAT Agriculture Standard, does not define specific land practices that producers must use. But it does identify generalSpecialist soil management and environmental protection objectives. From these objectives, producers and the© NCAT 2005 organic certifiers they work with must determine whether specific farming practices meet the NOP criteria. This publication provides management guidelines for meeting, and measurable parameters for monitoring, these objectives. It also discusses why these objectives are essential for maintaining sustainable, organic production systems. T Contents he National Or- ganic ProgramSection 205.203(a) (NOP) Rule, ........................................ 1 Section 205.203, out-Section 205.203(b) lines general goals for ........................................ 5 organic production. This publication doesSection 205.203(c) not intend to interpretand (d) ......................... 9 these regulations in aMonitoring Practices legal sense. Instead,for Section 205.203 it explores ecological .......................................11 interactions that af- fect organic produc-References....................18 tion and points outResources .....................19 how understanding these interactions can help farmers, inspec- tors, and certifiers determine which soil management practic- es meet the National Standard. The first part of this publication examines the three major pro- visions within Sec- tion 205.203 and Conservation tillage helps improve or maintain soil health and minimize erosion. discusses the relation- Photo by Tim McCabe, USDA ARS.ATTRA is the national sustain- ship of each of theable agriculture information provisions to soil ecology. This is followed Section 205.203(a)service operated by the NationalCenter for Appropriate Tech- by a list of management options suggested Select and implement tillage and cul-nology, through a grant from by each provision. The second part of the tivation practices that maintain orthe Rural Business-CooperativeService, U.S. Department of publication discusses interactions among the improve the physical, chemical, andAgriculture. These organizations three provisions and describes how certain biological condition of soil and mini-do not recommend or endorseproducts, companies, or individ- management practices can meet multiple mize soil erosion.uals. NCAT has offices provisions within this section. It also exam-in Fayetteville, Arkansas,Butte,Montana, and ines methods for monitoring compliance This subsection provides guidelines for soilDavis, California. ���� with the provisions of this section. preparation. It requires that producers use
  2. 2. tillage and cultivation practices that protect plants and soil organisms can move against soil erosion, while also maintaining through the soil with relative ease. or improving soil quality.  Water from rainfall or irrigation To better understand this subsection, we seeps into the soil, rather than flow- will first examine soil characteristics associ- ing over the soil surface as runoff. ated with improved physical, chemical, and  Soil organisms involved in decom- biological conditions. Then we will look at position and mineralization of plant how these changes in soil quality affect plant and animal residues are able to growth, health, and production. Finally, we thrive and disperse throughout the will look at management practices that can soil. facilitate these changes. Improve physical condition of soil Improve chemical properties of soil Producers describe soil’s physical condi- tions using terms such as “softness,” “mel- Producers describe soil chemical properties lowness,” “workability,” or “tilth.” Soil in terms of soil fertility, salinity, and acidity scientists measure soil physical conditions or alkalinity (soil pH). Soil fertility can be using the terms “bulk density,” “penetrabil- subdivided into nutrient availability for plantS oil that has ity,” “water infiltration rate,” “water hold- uptake, the soil’s nutrient-holding capac- good physi- ing capacity,” and “erodibility.” Soil that ity, and the balances among plant-available has good physical condition is porous, like nutrients. You can evaluate your soils for cal condition a sponge, rather than tightly packed, like a good chemical conditions by monitoring theis porous, like a following characteristics.sponge, rather than ball of modeling clay. Soil in good physical condition provides several benefits for plant  Soils have a near-neutral pH (unlesstightly packed, like growth. the soil is used to grow acid-lovinga ball of modeling  Plant roots can grow through the soil crops, such as blueberries or cran-clay. berries). without restriction.Photo by Lynn Betts,  Air, water, and nutrients needed by  Sufficient nutrients are available forUSDA NRCS. productive crop growth, but not in excess that causes plant toxicities or contaminates nearby streams or aquifers.  Soil nutrients are in forms available for plant uptake, but they are held suffi- ciently enough not to be easily leached or car- ried away by runoff.  The availability of plant nutrients is sufficiently balanced to promote healthy plant growth and microbial activity. This objec- tive recognizes that a plant is only as healthy as its most limiting nutri- ent allows.  Soils do not contain toxins or heavy metals in concentrations high enough to inhibit plant growth or the growth of beneficial soil organisms.Page 2 ATTRA Soil Management: National Organic Program Regulations
  3. 3.  Soils contain enough moisture to the soil are readily broken down and facilitate nutrient movement to plant decomposed so that plant nutrients roots. become available.  Soils contain sufficient oxygen for  A good soil structure, provided by plant growth and the growth of soil stable organic compounds, remains organisms. following the decomposition of plant and animal materials.  Soils contain relatively high levels of organic matter, which helps them  Soil is well-aggregated; that is, it hold water and nutrients. is composed of soft clumps held together with fungal threads andImprove biological bacterial of soil  Legumes form healthy nodules andImproving soil physical and chemical prop- fix abundant nitrogen, especially inerties is important for both conventional and nitrogen-depleted production, but improving biologi-  Plants have a relatively high resis-cal properties is particularly important for M tance to soil-borne diseases. inimizingorganic production. Producers describe soilbiological health in terms of “earthy smell,” soil ero-“soil crumbliness,” and “greasy feel.” Soil Minimize soil erosion sion is criti-scientists measure soil biological health in Soil erosion is the loss of surface soil to forces cal for sustainableterms of microbial biomass, microbial com- of wind and water. Soil erosion reduces soil agriculture.munities, and rate of organic matter decom- productivity and can cause water and air pol-position. lution. Minimizing soil erosion is critical for sustainable agricultural production, becauseOrganic production relies on nutrients the top layer of soil has properties—physi-released through the decomposition of cal, chemical, and biological—that are muchplant and animal residues. Decomposition more favorable for crop production than theis a biological process involving a variety of lower layers. The topsoil also contains moresoil organisms, including beetles and other organic matter than the lower layers. Thisinsects, worms, nematodes, fungi, bacteria, native soil organic matter—which representsand algae. You can evaluate your soils for centuries of plant growth, death, and decom-healthy biological properties by monitoring position in the soil—can both protect soilthe following characteristics. against erosion and be easily lost to it. Soil  Plant and animal residues added to aggregates, held together by organic com- pounds, facilitate water infil-Earthworms improve soil tilth by creating aggregates and forming passage- tration and enhance water-ways through the soil. Photo courtesy of USDA ARS. holding capacity. They also are slow to erode because of their size and weight. How- ever, if soil aggregates are broken down—by dry condi- tions, excessive tillage, or by raindrop impact—the result- ing organic matter particles are very lightweight and eas- ily removed by erosion. Tillage prepares land for seeding or transplanting. Cultivation practices—imple- mented either before or after crops are in the ground— ATTRA Page 3
  4. 4. manage weeds and improve soil aeration  Protect soil from the erosive forces and water infiltration. Traditional clean till- of wind and water age disrupts soil organisms, reducing their  Minimally disrupt the habitat of numbers and, often, their diversity. Clean beneficial soil organisms tillage also breaks down soil aggregates and produces a bare soil that is vulnerable to  Return or add plant or animal resi- erosion and more subject to temperature dues to the soil to serve as food and changes than soils that have a mulch or energy sources for soil organisms vegetation cover. Under direct exposure to Practices that you can use to reduce soil dis- sun and high temperatures, soil organisms turbance, provide a residue cover, or oth- break down soil organic matter rapidly. The erwise protect the soil surface from erosion rate of organic matter decomposition further and organic matter loss include increases when tillage breaks soil aggregates into smaller pieces, increasing their surface  Minimum tillage area and exposure to oxygen. While a rapid  Undercutter or roll-chopper tillage breakdown of organic matter can benefit plants by increasing nutrient availability,  Mulch tillage or otherwise mulchingU se care in a substantial decrease in organic matter with organic materials residue reduces aggregate stability, decreases soil  Promoting rapid growth of the crop manage- tilth, and increases the potential for nutrient canopyment. While crop loss through leaching and runoff.  Flame weedingresidues provide Conventional farmers control weeds throughorganic matter and a combination of synthetic herbicides and Choosing the appropriate tillage and cultiva- physical cultivation, including cutting, burn- tion practices and implements for your fieldsprotect against ero- ing, incorporation, or plowing. Herbicides depends on the location of the farm, the soilsion, they can also type, the crop being produced, the time of can harm soil organisms, thereby reducingincrease the risk of year, the climate, and weather conditions in nutrient cycling and aggregate formation.plant diseases. Physical cultivation methods vary in their a particular year. Tillage tools that are most impact on soil ecology and soil susceptibil- damaging to soil structure are those that ity to erosion. For example, plowing under shear soil particles, such as moldboard and weeds or crop residues can disrupt micro- disk plows, while sweeps and chisels cause bial populations and produce a bare soil that less damage. is susceptible to erosion. In contrast, prac- Environmental and management factors tices that cut weeds and leave them on the can interact with particular tillage or cultiva- soil surface can protect the soil against rain- tion practices to increase risks of soil-borne drop impact, the heat of the sun, and drying plant diseases and insect infestations, delay winds, while providing soil organisms with a seed emergence, or inhibit organic matter source of food and energy. (Unfortunately, decomposition and nutrient mineralization. these weeds may also be sources of plant For example, farmers in New England and diseases.) the upper Midwest rarely use no-till prac- As stated in §205.203(a), organic produc- tices, because a thick residue cover does not ers must use tillage and cultivation practices allow the soil to warm up and dry out in that “maintain or improve the physical, the spring. The resulting wet, cool soil con- chemical, and biological properties of soil.” ditions increase the time needed for seed Tillage and cultivation practices that meet germination, while also increasing the risk these criteria will have the following general of seed and seedling diseases. Instead, they characteristics. use modified minimum till practices, such as ridge till, which leaves sufficient residues on  Promote water infiltration the soil surface to reduce erosion but allows  Minimize soil compaction the seedbed to warm up and dry out.  Minimize degradation of soil To further “maintain or improve the physi- aggregates cal, chemical, and biological properties ofPage 4 ATTRA Soil Management: National Organic Program Regulations
  5. 5. soil” you can use practices that replace ferent planting dates, rooting habits, lengthsorganic matter lost to decomposition. These of production, cultivation requirements, andpractices include the use of harvesting requirements.(5) All of these fac- tors affect the ability of plants to compete  Cover crops with weeds.  Green manures Cover crops effectively reduce weed pres-  Compost sure by occupying the space and using the  Mulch light, water, and nutrients that would other- wise be available to weeds. Cover crops can  High residue crops also be cut or lightly incorporated just prior  Perennial crops to planting the main crop. The residues left after this cutting provides a cover over theMore details on these practices are included soil surface that suppresses seed germina-in the next section. tion.(2, 3) Cover crops indirectly affect weed growth by increasing soil organic mat-Related ATTRA Publications ter and soil tilth. Compacted or infertile soils favor the growth of some weeds, while crop C For more information on tillage and cultivation practices appropriate for organic production, see plants compete better in fertile, well aggre- over crops the following ATTRA publications. gated soils.(3, 4, 5) can be used Pursuing Conservation Tillage Systems for Organic to control Crop Production Section 205.203(b) weed growth. Flame Weeding for Vegetable Crops Manage crop nutrients and soil fertil- ity through rotations, cover crops, and the application of plant and animalUse of crop rotations and cover materials.cropping as cultivation practicesCultivation is any practice used to “improve Practices suggested by thesoil aeration, water infiltration and conserva- requirementtion, and control weeds.” In a well-managed This requirement makes implicit that fer-cropping system, crop rotations and cover tility management in organic systems mustcrops can provide the benefits of cultiva- involve, and rely on, biological processes.tion and compensate for many of its nega- Section 205.203(b) does permit organic pro-tive impacts.(1, 2) This is consistent with ducers to use mined substances of low solu-§205.205 Crop Rotation Standard, which bility, such as rock phosphate and green-states that a “producer must implement a sand.(6) However, this section stipulatescrop rotation including but not limited to sod, that at least some crop nutrients be providedcover crops, green manure crops, and catchcrops that provide the following functions through crop management practices and thethat are applicable to the operation: application of organic residues.(a) Maintain or improve soil organic matter This requirement also states that rotations,content; cover crops, and plant and animal materials(b) Provide for pest management in annual must be used to manage crop nutrients andand perennial crops; soil fertility, not just supply or provide crop nutrients. This provision encourages produc-(c) Manage deficient or excess plant nutri-ents; and ers to protect water quality by growing crops that tie-up or immobilize excess nutrients.(d) Provide erosion control.” This reduces the potential for nutrients to beRotating cold- and warm-weather crops leached beyond the root zone, into ground-can suppress weeds by disrupting their life water, or carried away by runoff or erosioncycles. Alternatively, some crops exude into nearby lakes or streams. For example,chemicals that suppress weeds.(3, 4) Good rye is capable of tying up large amounts ofcrop rotations involve crops that have dif- nitrates. Cover cropping to manage ATTRA Page 5
  6. 6. nutrients is particularly important for pro- fixation, recycling the nutrients from plant ducers who farm soil that is sandy or that and animal wastes, and stabilizing nutrients develops cracks in its profile. The perme- in the soil profile will also help ensure that ability of these soils allows for ready leach- production practices are environmentally ing of excess nutrients. sustainable. Reliance of soil fertility manage- Management of crop nutrients ment on biological processes and soil fertility A major difference between conventional Organic soil fertility management is based on cropping systems and organic systems is the feeding the soil a rich, complex diet of plant role of biological processes in organic sys- residues, animal manures, and compost. In tems. Most synthetic fertilizers are immedi- contrast, conventional agriculture simplifies ately available to plants. They do not require crop nutrient and soil fertility management biological processes to make them available. by feeding the plant soluble nutrients. Thus, And they do not enhance the biological crop nutrition in conventional agriculture health of the soil. In fact, several synthetic can be managed with three pieces of infor-O rganic soil fertilizers degrade soil by drying it out or mation: 1) the amounts of nutrients used by making it acidic or saline. the crop during the growing season, 2) the fertility amount of plant-available nutrients in the manage- In contrast, a primary principle of organic soil, and 3) the amounts of fertilizer nutri-ment relies on feed- farming is to feed the soil so that the soil can ents that need to be added to account foring the soil a rich, feed the plants. A healthy soil has good tilth differences between crop nutrient needs andcomplex diet of and mineralizes organic matter efficiently, to available soil nutrients.plant residues, provide plants with their required nutrients. It also has a diverse population of soil organ- Nutrient management in organic systems isanimal manures, isms that enhance plant growth in various more complex. Organic inputs cannot eas-and compost. ways, such as through symbiotic relation- ily be added to the soil to provide the exact ships with the plant, exuding enzymes into balance of nutrients needed by the plant for the soil, degrading toxins, and competing at least three reasons. First, many organic with pathogenic organisms. inputs (such as cover crops, crop residues, weeds, and compost) are added to the soil for Practices and inputs used by organic pro- reasons other than fertility management, yet ducers (as well as many others in sustain- they contribute to the pool of nutrients in the able agriculture) promote biologically soil. Second, most organic materials, includ- healthy soils that sustain fertility in ways dif- ing compost and manure, have only a small ferent from conventional systems. Organic component of soluble nutrients; most of their systems use legumes and algae to fix atmo- nutrients must be transformed through bio- spheric nitrogen in the soil. They promote logical processes before they become avail- the decomposition of plant and animal resi- able to plants. Thirdly, most manures and dues to make nutrients from them available composts do not have a consistent nutrient to plants. Additionally, soil organisms pro- content (such as the 10%N-10%P-10%K duce bacterial gels and microbial threads found on bags of synthetic fertilizers). They that bind soil into aggregates, form humates also contain a ratio of nutrients different that hold water and nutrients, and develop from that needed for optimal plant growth. symbiotic relationships with plant roots to For example, dairy manure has a nitrogen help them reach and use water and nutri- to phosphorus ratio of approximately 2:1. ents.(7) Recent research indicates that However, hybrid corn requires eight times enzymes formed by soil microorganisms can more nitrogen than phosphorus.(10) enhance the growth and nutritional value of plants.(8, 9) Managing soil fertility with bio- You could try to combine plant and animal logically-created inputs ensures that organic residues to get a nutrient ratio similar to that production is a dynamic biological process. required by your crops. But these residues Fertility management that relies on nitrogen may not provide nutrients in the amountsPage 6 ATTRA Soil Management: National Organic Program Regulations
  7. 7. and at the times needed for optimal plantperformance. Nutrient availability in organicsystems is primarily the result of biologicalprocesses. Soil organisms feed on some ofthe nutrients in the added organic materials,retain some in the soil as humus, and slowlymineralize and release others over time. Inaddition, environmental factors, such as soilmoisture and temperature, affect organicmatter decomposition and mineralization.Consequently, mineralization is slow duringdry periods and in the spring and fall, whenthe soil is cool.While crop and animal residues do notafford precise nutrient management, the Farmers are encouragedintegrated mineralization and humification to test their soils forprocess provides soils with a buffered store- nutrient needs, and tohouse of nutrients. The diverse populations apply only what nutri-of soil organisms involved in decomposi- ents are needed. Photo by Lynn Betts,tion store residue nutrients in their bodies USDA NRCS.(biomass). Biomass nutrients are availablefor plant uptake, but they are protected intent of the standards, nor will they reapfrom runoff, leaching, or volatilization.(11) the multiple benefits of integrated, soil-Microbial processes also make humus from based fertility management.residues that are resistant to decomposition.Humus is responsible for improving soil In summary, plant-available nutrients intilth, water-holding capacity, and nutrient- organic systems include minerals, nutrientsholding capacity. Following mineralization, that have been mineralized from plant andsoil nutrients provided by organic materials animal residues, nutrients held in microbialare subject to the same chemical reactions biomass, and nutrients that are being min-as soluble nutrients from conventional fer- eralized from decomposing residues. As atilizers, such as sorption of phosphorus by good organic producer, you should accountiron oxide or precipitation of calcium with for each of these nutrient sources to deter-sulfate. mine current and future nutrient availability. You should also view nutrient managementThis provision of the standard does per- as but one component of an integrated cropmit fertilizers with high levels of soluble and soil management plan. Cover cropping,nutrients, as long as they are derived from for example, not only produces and con-allowed crop and animal materials (such as serves nutrients but is also used for weedfish and soybeans). These organic fertilizers and pest control and for soil conservation.provide nutrients in standardized amountsthat are immediately available to plants.Ideally, these products are used as a com- Crop rotations, cover crops, andplement to compost or other slow-release green manures as nutrientorganic inputs, in order to provide a bet- management componentster nutrient balance or meet temporary high Crop rotations and cover crops can add,nutrient demands of the plants. Producers deplete, or conserve soil nutrients, depend-can use these soluble products to manage ing on how they are managed. They can alsonutrient availability in a manner that mimics affect nutrient availability through a varietyconventional fertility programs, while legally of processes. They use soil moisture, butcomplying with the materials section of the they enhance water infiltration and aggre-National Organic Standard.(12) However, gate formation. They also influence popula-these producers do not comply with the tions of soil organisms.(13) ATTRA Page 7
  8. 8.  Nutrient additions. Legumes fix occurs, the microorganisms must atmospheric nitrogen through a take nitrogen from the soil as they symbiotic relationship with nitro- proceed with decomposition and gen-fixing bacteria. Although some mineralization. As a result, nitrogen nitrogen is added to the soil while availability is temporarily depressed. these plants are growing, the major- While this process can hinder plant ity of fixed nitrogen becomes avail- growth, it can also conserve nutri- able when they die and decompose. ents for later use, since those same The amount of nitrogen added by microorganisms release nutrients as legumes depends on the type of they die and decompose. legume, the soil conditions, and cropping practices. Alfalfa and clo-  Nutrient conservation and man- ver fix around 175 pounds of nitro- agement. Nutrient management in gen per acre, while soybeans fix only organic systems is not only the addi- around 50 pounds. Most legumes fix tion of plant nutrients but also their more nitrogen when available nitro- conservation. Good nutrient man- gen in the soil is low. Thus, growing agement uses crop rotations andC legumes in nitrogen-depleted soil, cover crops to provide the main crop rop rotations with nutrients when they are needed and cover underseeded with grasses or as com- panion crops with non-legumes, will and to conserve nutrients in the soil crops can between cropping seasons, when stimulate them to fix more nitrogen.add, deplete, or con- they otherwise might be lost throughserve soil nutrients,  Nutrient cycling. Deep-rooted leaching, erosion, or volatilization.depending on how plants can retrieve nutrients that For example, organic matter decom-they are managed. have leached below the root depth position and nutrient mineralization of other plants. Other plants are can continue to release nutrients into hyperaccumulators—they take up the soil following crop harvest. If not higher-than-normal concentrations held in microbial biomass or taken of specific nutrients. While these up by other plants, these mineral- plants do not add nutrients to the ized nutrients, particularly nitrate, soil, their ability to capture or accu- can leach through the soil profile, mulate nutrients can help build soil beyond the root zone, or into the fertility. Nutrients absorbed by these groundwater. In another example, deep-rooted or hyperaccumulating you may apply manure that contains plants are not available until they a ratio of nutrients different from are cut or incorporated and allowed that needed by your crops. This can to decompose. cause excess levels of nutrients, par- ticularly phosphorus, to build up in  Nutrient depletion and tie-up. the soil. Crop rotations remove nutrients from the soil if the crops are harvested Crop rotations can reduce or tie-up excess and portions are removed from the nutrients in the soil. Cover crops take up field. Even when they remain in the plant nutrients as they grow, then release field, cover crops and crop residues these nutrients back to the soil when they can deplete nutrients temporarily, if are cut or incorporated and undergo decom- they do not decompose before the position.(7, 14) Rye and other grasses are nutrients they contain are needed for good scavengers of excess nitrogen; legumes crop production. If the added plant are good for taking up excess phosphorus. materials are woody or dry, they Applying woody residues can help hold may immobilize or tie up nutrients. excess nutrients in the soil. Organisms Immobilization means that plant involved in the decomposition of these car- materials do not contain enough bon-rich and nutrient-poor residues need to nitrogen for microorganisms to effec- use nutrients from the soil to make up for tively decompose them. When this nutrients not available from the residues.Page 8 ATTRA Soil Management: National Organic Program Regulations
  9. 9. Planting rotations or mulches that includelegumes, succulent crops, and woody cropsfavor a large and diverse population of soilorganisms. These organisms retain nutri-ents in their biomass, which protects againstnutrient loss through leaching, runoff, orvolatilization.(11) Producers can also usecover crops to control weeds that otherwisewould compete with crop plants for nutri-ents.Related ATTRA Publications For more information on methods for using crop rotations and cover crops to manage soil and plant nutrients, see the following ATTRA publications. Organic Crop Production Overview Intercropping Principles and Production Practices nutrients than the plant needs or to apply Photo by Steve Diver. Diversifying Cropping Systems T them in a way that leaves them vulnerable Rye as a Cover Crop to runoff or erosion. You also need to be he green aware that some composts, manures, or manure Protecting Water Quality on Organic Farms other inputs may contain substances that Crimson Also see the SAN handbook Managing can be harmful to human health or to the Clover provides Cover Crops Profitably (2nd edition).The handbook can be ordered at www.sare. environment. robust growth and org/publications/index.htm#books. The pdf high nitrogen version of this publication is also available Maintain or improve soil organic fixation. at this Web address. matter content Soil organic matter is a central component of soil quality. Composed of relatively sta-Section 205.203(c) and (d) ble, decomposed or humified material, soilManage plant and animal materials to organic matter enhances soil quality bymaintain or improve soil organic matter improvingcontent in a manner that does not con-  Water absorption and water holdingtribute to contamination of crops, soil, ability of soilor water by plant nutrients, pathogenicorganisms, heavy metals, or residues of  The ability of soil to prevent nutrientprohibited substances. (These sections go leachingon to list acceptable and prohibited plant,  Soil tilth and aggregationanimal, and mineral nutrient inputs.)  Plant roots’ ability to grow throughPractices suggested by the the soilrequirement  The ability of nutrients, water, andThis requirement specifies that nutrient air to flow through the soilinputs—plant, animal, or mineral—not only  Soil organisms’ habitat and access tosupply crops with necessary nutrients but nutrientsalso help build soil quality. It also requiresproducers to manage nutrient inputs in a Not all plant and animal residues are equallyway that ensures food safety and protects effective in maintaining or improving soilthe environment. To meet these objectives, organic matter content. Soil organisms read-you need to be careful not to apply more ily decompose fresh manure and very ATTRA Page 9
  10. 10. and fresh plant materials. As they decom- is not covered with growing plants or plant pose these materials, they release plant- residues. available nutrients into the soil. In contrast, fewer soil organisms are able to break down Types of contaminants and mineralize woody or dry materials, such as corn stalks, wheat stubble, or woodchips. Contaminants include excessive levels of As a result, decomposition of these materi- plant nutrients, introduced pathogenic als takes longer than it does for more suc- organisms, heavy metals, and residues of culent ones. In addition, soil organisms are prohibited substances. not able to decompose some of this organic  Plant nutrients are most readily material, and they transform it into soil removed and carried by water when humus instead. Humus gives good quality their concentration in the soil is soil a soft and somewhat greasy feel. It is well in excess of that needed by the also responsible for building soil aggregates plants. This happens when heavy and increasing the capacity of the soil to hold applications of manure are made water and nutrients. Thus, if you add a com- many years in a row. bination of succulent and woody residuesC to a field, you will fulfill a key objective of  Pathogenic organisms are usu- ontaminants sustainable organic soil management—sup- ally associated with the application include ex- of uncomposted manure. Organ- plying crops with necessary nutrients while cessive levels isms of particular concern include building soil organic matter and enhancingof plant nutrients, soil microbial health. E. coli, Salmonella, Giardia, andintroduced patho- Cryptosporidium. The compostgenic organisms, Soil and water contamination practice standard §205.203(c)(2)heavy metals, and was incorporated in the National Soil can become contaminated if harmful or Organic Standard—along with rulesresidues of prohib- prohibited substances are limiting fresh manure application,ited substances. §205.203(c)(1)—to reduce health  Applied as components of otherwise allowed materials, like compost hazards from pathogen contamina- tion. Contaminated irrigation water  Contained in irrigation water can also be a source of pathogens.  Contained on seed coatings Irrigation water may be contami- nated by manure-storage or sewage-  Permitted to leach or flow into certi- treatment facilities. Over time, the fied fields from conventional farms activities of beneficial soil organisms will reduce populations of patho- For agricultural practices to contaminate genic organisms. either groundwater (aquifers) or surface water (lakes, streams, rivers), there must be  Heavy metals. Arsenic is added to a source of contamination, and the contami- broiler poultry feed to reduce dis- nant must be transported into the groundwa- eases and stimulate growth. This ter or the surface water. Contaminants leach heavy metal passes through the into groundwater most readily when the soil birds and is deposited in the poul- is very porous, when the contaminant is not try litter, thereby contaminating this held in the soil either by organisms or by source of plant nutrients. Litter from chemical forces, and when the water table is layer operations may contain copper high. Runoff and erosion can transport con- or zinc that leaches from the cages. taminated soil from fields into rivers, lakes, Composts may include residues of or streams. Runoff dissolves and trans- plants that were treated with pesti- ports weakly-bound contaminants from the cides containing heavy metals. Addi- soil surface and off plant leaves. Erosion tionally, fertilizer pellets made from detaches soil particles from the surface, car- manure or litter may have additives rying with them any adhered contaminants. that contain heavy metals or other Erosion occurs most readily when the soil non-allowed substances.Page 10 ATTRA Soil Management: National Organic Program Regulations
  11. 11.  Residues of prohibited substances. that may be present at toxic levels. Organic Organic producers must be sure that producers and inspectors should use these inputs they use for nutrient manage- tests to ment, pest control, or building soil  Determine levels of nutrient inputs quality do not contain materials to add to achieve productive plant listed as “prohibited substances” growth on the National Organic Program National List.(15)  Identify any excess nutrients (If so, cropping and nutrient managementRelated ATTRA Publications practices should be developed to decrease these nutrient levels and For more information on methods for build- minimize their movement from the ing soil organic matter, selecting organic root zone into groundwater or sur- fertilizers, protecting water quality, and face water.) minimizing risks of contamination, see the  Monitor soil organic matter (Note: following ATTRA publications. This test often is not included in the Sources of Organic Fertilizers and standard soil test, but it is available Amendments at an extra charge. You will need Farm-Scale Composting Resource List to specify that you want this test done.) Protecting Riparian Areas: Farmland Management Strategies  Manage nutrient imbalances (Plant Protecting Water Quality on Organic Farms heath is determined by the avail- ability of the least sufficient nutrient. Arsenic in Poultry Litter: Organic Regulations High levels of sodium can degrade For more information on soil conservation soil tilth and aggregate stability, and methods for protecting against runoff while soils with high calcium to mag- from manure or compost piles, contact your nesium ratios usually have better local NRCS, Soil and Water Conservation water permeability.) District, or Cooperative Extension office. How often you conduct soil tests depends on your cropping intensity and the nutri- ent inputs you use. Annual or bi-annual soilMonitoring Practices for testing is sufficient for general nutrient man- agement. However, if you are a transitioningSection 205.203 producer, changing your nutrient manage-The remainder of this publication provides ment practices, or testing new managementproducers, organic inspectors, and organic methods, you may want to conduct soil testscertification agencies with a set of observ-able or measurable indicators to monitor Most state soil testing laboratories provide nutrient managementcompliance with this section of the NOP recommendations in terms of pounds of conventional fertilizers perregulations. acre. To determine the appropriate amount of manure, compost, or other organic nutrient input to apply, organic producers must make calculations based on soil test results, crops being grown, and theMonitoring soil nutrient levels nutrient content of any crop residues returned to the soil. ManyA good nutrient management plan involves organic growers prefer working with specialized private soil testingon-going monitoring of soil nutrients. You laboratories that will help them with these calculations. Several ofcan request a standard soil test through your these soil testing laboratories recognize that organic growers are in-Cooperative Extension Service. These tests terested in more than just the chemical characteristics of their soils.provide an assessment of plant-available Thus, they also provide microbial assessments and other analyses of soil biological healthnutrients, as well as soil acidity or alkalin-ity (pH), nutrient holding capacity (CEC, or For an annotated list of private soil testing laboratories, see thecation exchange capacity), and trace sub- ) ATTRA publication Alternative Soil Testing Laboratories.stances such as sodium (Na) and boron ( ATTRA Page 11
  12. 12. more frequently to better understand how released through mineralization during the your practices are affecting nutrient avail- growing season. Unfortunately, there is no ability. As discussed below, sampling at easy or inexpensive test that assesses when, different seasons can provide you with an which, or how many nutrients are released indication of changes in nutrient availability from crop residues or mineralizing organic throughout the year. matter. Instead, you will need to estimate mineralization rates based on the following Timing of soil tests is important. If plant and criteria. animal residues are applied in the fall, con- duct soil tests in the early spring, prior to  For compost, manure, poultry litter, planting, to determine the plant-available or mulches nutrients from these additions. This allows  Nutrient analyses of material time for the organic materials to decompose.  Application rate (pounds per To determine whether you need cover crops square foot or tons per acre) to hold excess nutrients in the soil over win-  Date of application ter, conduct soil tests after harvesting the main crop.  Cover crops and green manuresN itrogen is a Nitrogen is a major plant nutrient and a cen-  Crop grown as a cover crop or green major plant tral component of organic nutrient manage- manure nutrient and ment. However, standard soil tests do not  Whether a legume cover crop was provide an accurate assessment of soil nitro- inoculated with nitrogen-fixing bac-a central component gen levels. (While most standard soil tests teria (Rhizobia species)of organic nutrient provide an assessment of nitrate [NO3 ], the  Growth stage at which it was cut ormanagement. level of this soil nutrient is highly affected incorporated (Cut the cover crop by when the sample was taken and how it when it is at 50% bloom, unless your was handled between then and the analy- farm is in an arid area where this level sis. As a result, this reading provides little of cover crop growth would deplete useful information for nutrient management water needed for your primary crop. practices.) Soil test strips provide a simple This is the prevailing recommenda- indicator of nitrogen availability (or excess). tion for maximum nutrient availabil- Soil testing meters and organic matter min- ity for the next annual crop.) eralization tests (Solvita™ and others) pro-  Yield level vide a more accurate assessment.  Nutrient value of the residues left in the field Tissue tests (i.e., leaf analysis) measure a  Management of the cover crop after plant’s nutrient uptake. These tests are use- its growth was terminated (Was it left ful indicators of available soil nutrient levels on the soil surface as a mulch or was during the cropping season. Tissue testing it incorporated into the soil?) is particularly useful for identifying nutrient imbalances or toxic concentrations of nutri-  Environmental conditions following ents in the soil. Unless it is used in conjunc- application of plant or animal mate- tion with soil tests, it cannot provide a good rials (Mineralization occurs most indication of the availability of nutrients for rapidly under warm, moist condi- the following crop or cropping season. tions. It will slow down considerably during winter or during drought.) Monitoring nutrient  Mineralization over time (Only a por- mineralization tion of the nutrients from organic As mentioned above, you can use stan- matter becomes available during dard soil and nutrient mineralization tests the first year following application. to monitor soil nutrient availability. How- Accurate nutrient management ever, organic nutrient management relies accounts for nutrient mineralization not only on nutrients available at the time over several years, not just during of soil sampling but also on the nutrients the current planting season.)Page 12 ATTRA Soil Management: National Organic Program Regulations
  13. 13.  When a clump of soil is placed in See References for publications and Web a clear glass of water, the clump sites that provide detailed information on retains its shape and soft bubbles how to estimate nutrient availability based form around it. It does not break on these criteria. apart rapidly or explosively. The For information on potential nutrient avail- water remains relatively clear, not ability from various organic inputs, see the turning muddy or silty. ATTRA publication Protecting Water Quality on Organic Farms.  The soil is relatively easy to dig. Soil samples to a depth of at least seven inches have properties as describedBuilding and monitoring above. Plant roots grow throughoutsoil organic matter the soil and do not appear to be inhibited in either their downwardStandard soil organic-matter tests provide a or sideways growth.general guideline for monitoring soil organicmatter levels and should be conducted at  A wire rod (like a straightened,least once every two years. In addition, soil heavy-duty clothes hanger) can be Smanagement should include practices that inserted into the soil with only minor oil manage-add or return organic matter to the soil, as bending. Soil compaction typically ment shouldwell as practices that protect organic matter occurs as a crust on the soil surface include prac-against erosion and excessive mineraliza- or as plow pans beneath the sur- tices that add ortion. These practices include face. return organic  Growing cover crops and green matter to the soil. manures that are cut and left on the Building and maintaining soil surface or incorporated into the soil chemical condition soil Degradation of soil chemical condition is usually visible only when conditions become  Leaving crop residues in the field severe enough to significantly harm crop  Adding manure, compost, or mulch growth and yields. Severely degraded chem- to the soil ical conditions include  Maintaining residues or plant growth  Salinity or high levels of anions (neg- on the soil surface for as many atively charged particles) (This con- months as possible throughout the dition is usually found in arid, irri- year gated environments. Degraded soils have a surface layer with a whitish  Using soil conservation practices coat and a salty odor.) such as contour farming  Sodicity or high concentration ofBuilding and maintaining sodium relative to magnesium (Thissoil physical condition condition is also found in arid, irri- gated environments. Degraded soilsGeneral indicators you can use to monitor have a soil crust, poor aggregation,soil physical conditions: and limited soil pores.)  The soil surface does not have any  Inappropriate pH for crops being visible soil crust. (Microbial crusts, produced (Most crops grow best at found in arid soils, are positive indi- a pH between 6.5 and 7.5. This cators of soil quality, not negative is because chemical reactions at indicators.) this range enhance the availability  When handled, soil feels soft and of plant nutrients. However, some crumbles readily. It does not form plants, such as blueberries and cran- hard blocks or break down into a berries, require a low pH. Plants fine powder. produced on soils with ATTRA Page 13
  14. 14. ate pH grow poorly and often exhibit for their growth and reproduction, you will symptoms of nutrient deficiencies.) also build or maintain soil biological qual- ity.  Low nutrient holding capacity (cat- ion exchange capacity or CEC) Methods for monitoring and assessing soil (The ability of soils to hold nutri- biological quality will differ according to soil ents is affected by both the mineral types, location, and crops being produced. and organic matter components of However, you may find the following assess- soils. Soils with low nutrient hold- ment criteria effective. ing capacity easily lose nutrients to runoff or leaching, resulting in low  Soil smells sweet and “earthy.” fertilizer-use efficiency and high  Legumes form abundant nodules potential for surface or groundwater when nitrogen levels are relatively contamination.) low.  Toxic levels of nutrients or contami-  Crop residues and manure decom- nants (Symptoms exhibited by plants pose relatively rapidly (especially growing on these soils will depend when the temperature is warm andS tandard soil on the toxin or contaminant.) the soil is neither arid nor flooded). tests provide Standard soil tests provide a general assess-  Soil organisms such as earthworms, a general ment of soil chemical conditions. Soil salin- dung beetles, and springtails areassessment of soil ity is measured in terms of electrical con- present.chemical conditions. ductivity or EC. You can assess soil sodicity by calculating the ratio of sodium (Na) to  Soil has good tilth and is well-aggre- magnesium (Mg). Soil pH and CEC are gated. standard assessments on soil tests. Appro- priate pH levels for crop plants are available Controlling runoff and erosion in agronomy, horticulture, or forage guides. Soil conservation practices that control run- Often the seed packet or bag provides this off and erosion minimize the risks of ground- information. Standard soil tests will identify and surface-water contamination. Manage- whether micronutrients are present at toxic ment practices you can use to minimize the levels. If not corrected, they may cause risk of surface water contamination include deformities or changes in plant coloration the following. typical of toxicity symptoms. Soil tests for specific contaminants are available, at an  Provide a vegetative cover over the extra cost, if necessary. soil surface that protects the soil from direct raindrop impact and Building and maintaining promotes water infiltration. soil biological quality  Avoid the surface application of Viable soil organisms are critical for effective manure or compost prior to rainfall. organic matter decomposition and nutrient management. Soil organisms also enhance  Cover compost or manure piles nutrient holding capacity, build soil aggre- or establish water diversion areas gates, and facilitate nutrient uptake. Rhizo- upslope from the piles and nutrient bia, the bacteria that form nodules on the runoff buffer areas downslope from roots of legumes, transform atmospheric the piles. nitrogen into nitrogen available for plant  Do not apply fertilizers or manure in use. Mychorrhizae are fungi that form at the a way that allows nutrient levels in tips of plant roots and effectively extend the the soil to become excessive. root length, giving the plant greater access to nutrients and water. If you use soil manage-  Avoid excess traffic within fields, ment practices that provide soil organisms especially when the soil is wet, to with food, air, water, and other necessities minimize compaction.Page 14 ATTRA Soil Management: National Organic Program Regulations
  15. 15. Very Very Medium Slightly Slightly Medium Strongly Acid Slightly Slightly Strongly Alkaline Acid Acid Alkaline Alkaline Acid Alkaline Related ATTRA Publications For more monitor- ing information and tools, see the following ATTRA publications. National Organic Program Compli- ance Checklist for Producers Organic Field Crops Documentation Forms 4.0 4.5 5.0 5.5 6.0 6.5 7.0 7.5 8.0 8.5 9.0 9.5 10.0The availability of plant nutrients in soils is affected by the soil’s pH.Avoiding the addition of and must not contain sewage sludgecontaminants or other sources of heavy metals or toxins.Use special care when using any manure,compost, mulch, or similar substance for  The organic certifier may requirenutrient management. testing of manure or litter for anti- biotics or heavy metals prior to  Any equipment used in organic approval. In addition, the certifier nutrient management that is also may require that you keep records used to apply prohibited substances on the amount of these contaminants to conventional fields must be ade- applied to fields over time. quately cleaned to prevent contami- nation with prohibited materials  Use mulches that do not contain prior to use in organic fields. contaminating residues. The organic certifier may require testing of the  Compost must be produced in a material to see whether it is accept- manner that meets NOP regulations ATTRA Page 15
  16. 16.  Check irrigation water to ensure that vary according to location, soil type, crop it does not contain contaminants. being produced, time of year, climate, and The organic certifier may require weather conditions in a particular year. Con- testing of the irrigation water to see sequently, practices that you use to comply whether its use is acceptable. with the regulation may vary from field to field, from crop to crop, and from year to Tailoring to local year. Also, because organic soil nutrient management is an on-going process that conditions operates over time, you should examine the As in selecting tillage and cultivation practices you use to meet the standard over practices, the “correct” soil fertility and the course of a rotation cycle or on some crop nutrient management practice will other multi-year basis.P lanting on the contour and leavingresidues on thesoil helps controlerosion. Photo by Lynn Betts, USDA NRCS.Table 1. Soil management practices that fulfill elements of the NOP Section 205.203 requirements. Soil Management Practice 203a 203b 203c Comments Examine soil test results for any nutrients that are exces- Standard soil test X X X sively high or toxic. Check pH, CEC, and EC. Not part of standard soil test; must make special request, Test for soil organic matter X X requiring an extra cost. See References for alternative organic matter tests. Conduct prior to calculating amount of nutrients to add Nitrate assessments X X to the soil. Also conduct following harvest to determine need for nutrient-conserving cover crop. Conduct on fields prior to initiating organic practices Special tests for contaminants or heavy to determine baseline levels of any suspected contami- X metals nants. Conduct on commercial broiler litter or other or- ganic input that may contain contaminants. Determines nutrient content of plant material that will Plant tissue testing of cover crops X X be returned to the soil. (continued next page)Page 16 ATTRA Soil Management: National Organic Program Regulations
  17. 17. Soil Management Practice 203a 203b 203c Comments Weight of biomass x percent nutrient = weight of nutri- Calculate cover crop biomass yield X X ent in biomass. Compare this amount to the amount of nutrients needed for growth by crop plants. Nutrient tests for manure or compost Determines nutrient content of organic material added X X added to the soil. Weight of compost or manure x percent nutrient = weight of nutrient in the amount of compost added. Record amount of manure or compost Divide this number by the number of acres to which this X X added amount of material was applied to determine nutrients per acre. Compare these numbers to the amount of nu- trients needed for growth by crop plants. These factors determine the rate of nutrient mineraliza- Record time and method of application of X X tion, potential availability for plant uptake, and potential nutrient inputs risk of loss through erosion or runoff. Use to determine the amount of nutrients that need to Calculate nutrient availability over time be added to meet crop requirements. Also alerts pro- X X from each added plant or animal residue ducer to need for conserving nutrients by planting cover crops. Identifies any nutrient deficiencies or toxicities. Special Plant tissue testing of crop plants X X tests may be requested to identify uptake of potential contaminants in the environment. Nutrient additions should be based on the equation: crop nutrient needs – (nutrients available from soil + Know nutrient needs of each crop grown X X nutrients available from prior additions of plant or ani- mal materials) Soil texture and mineralogy affect water infiltration and Know soil texture and mineralogy X X water holding capacity, nutrient holding capacity, and susceptibility of soil to compaction, erosion, and runoff. Carefully check all inputs from off-farm sources for po- Applications of NOP-approved nutrient tential contaminants. Apply nutrients based on the nu- sources based on soil nutrient availability, X X trient needs of crops to be grown and on the amount of crop nutrient needs, and expected miner- nutrients expected to be mineralized from each nutrient alization of previously added residues source applied. Cover crops can be grown to build soil organic matter, Cover crops are grown during the “off X X X conserve soil nutrients, enhance soil tilth, and manage season” weeds. Compost and manure are applied as a source of nutri- Compost or manure added to fields X X ents and to build soil organic matter. Crop residues left on the field X X X Crop residues and mulches cover the soil surface, en- hance water infiltration, protect against runoff and Mulches used to cover soil surface X X X erosion, control weed growth, and build soil tilth and organic matter. Contour cropping controls soil erosion. Good buffer Soil conservation practices used, espe- management around streams and lakes protects against X X cially on sloping fields movement of nutrients or sediment into these water bodies. (continued next page) ATTRA Page 17
  18. 18. Soil Management Practice 203a 203b 203c Comments Using minimum tillage or “one-pass” tillage systems min- Excessive traffic on fields is avoided, espe- imizes tillage traffic; using cover crops to control some X X cially when fields are wet weeds minimizes traffic needed for cultivation. Avoid driving on wet fields during harvest. Compost or manure piles should be built on concrete pads or on soil that is compacted and sealed against Protection measures used to minimize leaching. Diversion trenches built upslope from the pile X X runoff from compost and manure piles protect it from contaminating clean water. A grass buf- fer downslope protects against movement of nutrients into water bodies. Use separate equipment for organic fields or thoroughly clean any equipment used Protect against the introduction of contaminants into in fields with non-approved substances X organic fields. before the equipment is used for organic production Protect against the introduction of contaminants into Check irrigation water to ensure that it X organic fields. Protect exposed edible portions of crops does not contain contaminants from potential microbial contamination. Prominently display “Organic – No Spray” Protect against the introduction of contaminants into X signs around farm boundary organic fields.References 5. Peet, Mary. Weed Management. No date. Sus- tainable Practices for Vegetable Production in1. Liebman, Matt, and Elizabeth Dyck. 1993. Crop the South. North Carolina State University. rotation and intercropping strategies for weed management. Ecological Applications. Vol. 3, c07weeds.html No. 1. p. 92–122. Abstract at: www.sarep. 6. National Organic Standards. Regulatory Text Only.2. Staff. SAN. 1998. Managing Cover Crops Profit- AMS/USDA. ably. Second Edition. Handbook Series Book 3. Sustainable Agriculture Network (SAN). Belts- RegTextOnly.html ville, MD. 7. Magdoff, Fred, and Harold van Es. 2000. Build-3. Ferguson, Charles, and Bala Rathinasabapathi. ing Soils for Better Crops. Second Edition. 2003. Allopathy: How plants suppress other Handbook Series Book 4. Sustainable Agricul- plants. HS944. University of Florida IFAS ture Network (SAN). Beltsville, MD. Extension. Gainesville, FL. 8. Lee, J.J., R.D. Park, Y.W. Kim, J.H. Shim, D.H. Chae, Y.S. Rim, B.K. Sohn, T.H. Kim, and K.Y.4. Merfield, Charles. 2002. Organic Weed Manage- Kim. 2004. Effect of food waste compost on ment: A Practical Guide. 29 p. microbial population, soil enzyme activity and let- tuce growth. Bioresource Technology. Vol. 93, management-a-practical-guide.pdf No. 1. p. 21-28.Page 18 ATTRA Soil Management: National Organic Program Regulations