SSooiill QQuuaalliittyy CCoonnssiiddeerraattiioonnss ffoorr OOrrggaanniicc FFaarrmmeerrss by Keith R. Baldwin

rules—that strives to mimic natural eco- n our drive to meet the food and fiber systems in its focus on building health. needs of ever-increasing populations, I In fact, to fulfill the many requirements for we are taxing the resilience of the certification of a farm as organic, a farmer planet’s natural resources. This fevered must establish a plan to improve soil quest to pursue ever-increasing crop yields has had devastating impacts: widespread , atmospheric pollution, over- Figure 1. A soil scientist assesses the problem of soil erosion on a farm. Photo courtesy of USDA. grazed forage areas, over-cultivated fields, salinated water supplies, cleared land that is unsuitable for crops, and desertification—the loss of agricultural land to desert. The serious degradation of our soil resources has motivated some researchers and farmers to investigate management systems that are less input-intensive and generally more sustainable. is one such system, but it entails much more than simply substituting one set of management practices and inputs for another. Organic farming is a methodology—a body of methods and

Contents Defining Soil Quality—Page 2 Assessing Soil Quality—Page 8 Soil Quality Indicators—Page 3 Interpreting Soil Quality Indicator Measurements—Page 11 Qualitative Indicators—Page 7 Recommended Reading—Page 12

quality or health. The details of the plan on Farmers prefer the term because each farm depend somewhat upon how it reflects a judgment of the soil as either a each farmer defines soil quality. A plan’s robust or ailing resource. The term also success or failure is determined by changes portrays the idea of soil as a living, dynamic in measurable soil quality indicators. entity that functions in a holistic way—it depends on the condition or state of its In this publication, we will discuss how soil interacting parts—rather than as an quality can be measured and described. The inanimate entity with a value that depends new organic rule stipulates that measuring on its innate characteristics and intended and managing soil condition is an use (Romig et al., 1995). important component of organic certification. Our discussion, therefore, Soil quality is defined by the interactions of includes the following topics: a particular soil’s measurable chemical, physical, and microbiological properties. • Defining soil quality—Different terms These properties can be managed and are often used to describe a soil’s ability adjusted by farmers. Soil quality, therefore, to support crop growth. should be distinguished from a soil’s • Soil quality indicators—These inherent properties, which cannot be parameters for judging a soil’s managed or adjusted by farmers. Inherent biological, physical, and chemical properties are determined by factors such as properties can be measured as climate, topography, vegetation, parent quantities. We will review the material, and time. From a productivity importance of organic matter as a standpoint, each soil has an innate capacity biological property that contributes to to function, and some will be soil productivity. inherently more productive than others. • Qualitative indicators—The personal descriptions used to describe changes in In organic farming, a high quality soil is soil quality can be subjective or exact. one that provides an environment for opti- • Soil quality assessments—Farmers can mum root growth, thereby enhancing crop use simplified assessments and USDA health and productivity. Optimum root soil kits to measure changes in soil growth, however, will also be influenced by quality. the plant species and its genetic potential, • Interpreting soil quality indicator environmental conditions imposed by measurements—Farmers need to weather, and cultural practices used in the consider other factors when they use farming system. indicator measures to evaluate soil health. A soil that is in balance is said to function

within natural or managed ecosystem DEFINING SOIL QUALITY boundaries, sustain plant and animal productivity, maintain or enhance water and The terms soil quality and soil health are air quality, and support human health and often used interchangeably to describe the habitation. (Doran et al., 1996) soil’s ability to support crop growth without becoming degraded or otherwise harming the environment.

Organic Production—Soil Quality Considerations for Organic Farmers 2 Soil Impacts on Local Ecosystems within a data set is likely to change as land A soil’s properties determine how effectively it use changes. Comparisons between data contributes to local ecosystem functions. sets are usually restricted to sites having These functions include: similar conditions. • Retention and release of nutrients and Biological Indicators other chemical constituents. • Partitioning of rainfall at the soil surface Some biological indicators of soil quality into runoff and . that are commonly measured include soil • Retention and release of water from the organic matter, respiration, microbial biomass soil to plants, streams, and (total, bacterial, fungal, or all of these), tables. microbial biomass carbon and nitrogen, and • Resistance to wind and water erosion. mineralizable nitrogen. • Buffering against the concentration of . Soil organic potentially toxic materials. matter is that fraction of the soil composed (Larson and Pierce, 1991; Karlen et al., 1997) of anything that was once alive. It includes plant and animal remains in various stages of decomposition, cells and tissues of soil SOIL QUALITY INDICATORS organisms, and other organic substances. While overall soil health can be measured When the organic substances within the by the soil’s contribution to how well an soil and any organic matter that has been ecosystem functions, soil quality can be added to it, such as compost, decompose, measured by certain parameters or indica- they produce humus—organic matter that is tors. Examples of such indicators are soil stable or relatively resistant to further water-holding capacity, organic carbon decay. Organic matter is an essential content, and microbial respiration. component of soils because it plays such an important role in the physical, chemical, Checklists of physical, chemical, and and biological components of soil. microbial indicators are commonly assembled in a minimum data set (MDS). MDS indicators can be measured quantita- A healthy soil produces a plant that: tively at regular intervals. In other words, • Accumulates nutrients efficiently. these indicators can be defined with • Competes well with weeds. specific units of measure, and the measure- • Resists pests. ments can be judged against some common • Suppresses erosion through an extensive standards or analyzed for improvements root system. over time. The key to such a healthy soil is a sustainable A general minimum data set of quantitative microbial ecology. A high quality soil is indicators is presented in Table 1. Such a biologically active and contains a balanced data set may vary from location to location population of microorganisms. depending on how the land is used, such as for rangeland, wetland, or agricultural land. The relative importance of indicators

Organic Production—Soil Quality Considerations for Organic Farmers 3 Table 1. Proposed minimum data set (MDS) of physical, chemical, and biological indicators for screening soil quality Function and Rationale for Measurement Indicator a. Relationship to soil condition and function b. Rationale for measurement

Biological

Microbial a. Describes microbial catalytic potential and repository for carbon and biomass C and N nitrogen. b. Provides an early warning of management effects on organic matter. Potentially a. Describes soil productivity and nitrogen supplying potential. mineralizable N b. Provides an estimate of biomass. a. Defines a level of microbial activity. b. Provides an estimate of biomass activity.

Chemical

Soil organic a, b. Defines and stability. matter (OM) pH a, b. Defines biological and chemical activity thresholds. Electrical a, b. Defines plant and microbial activity thresholds. conductivity Extractable N, a. Describes plant-available nutrients and potential for N loss. P, and K b. Indicates productivity and environmental quality.

Physical

Soil texture a. Indicates how well water and chemicals are retained and transported. b. Provides an estimate of soil erosion and variability. Soil depth and a. Indicates productivity potential. rooting b. Evens out landscape and geographic variability. Infiltration and soil a. Describes the potential for , productivity, and erosion. bulk density (SBD) b. SBD needed to adjust soil analyses to volumetric basis. Water holding a. Describes water retention, transport, and erosion. capacity b. Available water is used to calculate soil bulk density and organic matter.

Sources: Derived from Doran et al. (1996) and Larson and Pierce (1994)

Organic Production—Soil Quality Considerations for Organic Farmers 4 Soil organic matter improves tilth in the stabilized organic matter, which improves surface horizons of the soil, reduces crust- the soil’s physical properties. ing, increases the rate of water infiltration, helps to control runoff, and facilitates root growth. Generally, organic matter makes Less Crop Residue = Less Organic Carbon soil more friable, less plastic or sticky, and Generally, practices that reduce the amount easier to work. It stabilizes and holds soil of residue left in the field after harvest deplete particles together in aggregates, thereby soil organic carbon. These practices include: reducing the raindrop splash that can lead • Replacing perennial vegetation with short- to erosion. By improving pore size season vegetation. distribution and decreasing bulk density, • Replacing mixed vegetation with organic matter also improves the soil's monoculture crops. ability to store and transmit air and water. • Introducing more aggressive but less Soil organic matter is also critical to plant productive species. growth and soil organisms because it • Using cultivars with high harvest indices provides a reservoir of nitrogen, phos- (ratio of harvested biomass to total phorus, potassium, calcium, magnesium, biomass). sulfur, and various minor elements that • Increasing the use of bare fallow (fallow become available for plant growth as it periods provide little in the way of decomposes. Management practices biomass additions while allowing common in organic farming systems work mineralization of organic matter in soil to to build soil organic matter and humus continue). content over time. These practices include Factors that increase the mineralization rate of regular applications of compost, manure, organic matter also deplete soil organic and other organic materials; inclusion of carbon (such as frequent tillage, drainage of cover crops as green manures in cropping wet soils, and application of fertilizers, systems; rotations that include forage crops; especially nitrogen). and reductions in tillage. Cropping systems and Soil Respiration. Soil respiration is the also profoundly influence the amount of creation of carbon dioxide (CO2) as organic soil organic matter. For instance, dramatic matter decomposes in the soil. It provides a losses in soil organic matter can take place gauge of the activity of living organisms in on farms where soil is inverted or mixed the soil. Microbial respiration and activity annually through tillage. are influenced by such elements as moisture, temperature, availability and As discussed in the composting publication degradability of organic residues, and toxic of this series, compost can be an important effects of various agricultural chemicals. component of organic farming systems. Because of the humified nature of compost, Respiration generally increases as organic it is relatively resistant to further decom- matter is added to the soil, indicating that position. So additions of compost over time increased biological activity is taking place. can increase soil organic matter and humus Decreased respiration rates in times of content. Organic farmers use composts not heavy rains might reflect flooded soils that so much to provide nutrients as to provide have problems with partitioning water as they should. A rise in respiration rates in cases of environmental contamination in

Organic Production—Soil Quality Considerations for Organic Farmers 5 soils might indicate that living microbes are layers, and creating an aeration and drain- at work to decompose pollutants. age system in the soil. Organic Carbon. Soil organic carbon, in particular labile (easily decomposed) How Organisms Help To Build Soil organic carbon, has an overwhelming effect Quality on soil microbial activity (Hajek et al., 1990). Labile organic carbon makes up Soil organisms contribute to the maintenance approximately 10 to 14 percent of total soil of soil quality because they control many of carbon. It is the heterogeneous mix of the key processes that occur in healthy soil, living and dead organic materials that are including these: readily circulated through soil biological • Decomposition of plant residue and pools, groups of interacting organisms. This organic material. carbon is the basis for a major soil nutrient • Mediation of availability of phosphorous reservoir. (P), manganese (Mn), iron (Fe), zinc (Zn), and copper (Cu) via microbial-mediated Microbial Activity. Microbial activity in processes, including symbiotic mycorrhizal the soil can be assessed in a number of associations. ways. Farmers can measure the status of • Production of organic chelating agents. either the total community of micro • Solubilization of phosphate. organisms or specific members of that • Fixation of biological N. community. Of these two assessments, the • Biological control of plant diseases, latter is perhaps the most useful. For nematodes, insects, and weeds. example, populations of predatory • Biodegradation of synthetic pesticides or nematodes are good indicators of soil other contaminants. quality. These microscopic worm-like • Enhancement of a plant’s drought organisms play numerous important roles tolerance. in the soil, with both negative and positive • Improvements in soil particle aggregation. effects. Some act as primary consumers of plants—in other words, they are pests. (Kennedy and Papendick, 1995) Others act as secondary predators of bacterial and fungal feeders—they serve as beneficials Farmers must be cautious in attempting to in the soil. Thus, an analysis of nematode judge soil quality by interpreting biological communities is one way to determine the indicator measurements. For instance, an health and balance of a soil. increase in soil microbial biomass or Earthworms. Earthworms are also good activity cannot automatically be equated bioindicators of soil quality. Earthworm with an increase in soil quality. After a populations can tell a researcher a great farmer incorporates organic matter into the deal about the structural, microclimatic, soil, microbial biomass and respiration nutritive, and toxic status of soils usually increase. This is because the (Christensen, 1988). Large, vertically- increased food supply in the soil will burrowing earthworms play an important support a higher population of decomposer role in conserving and improving soil organisms. Whether or not respiration and structure, recycling soil nutrients, pro- biomass remain elevated will depend on moting the gradual mixing of the soil whether additional organic matter is added or not.

Organic Production—Soil Quality Considerations for Organic Farmers 6 Tillage also stimulates microbial activity has other benefits as well. It tends and respiration by increasing the amount of to produce favorable conditions for oxygen available to soil microbes. It is microbial activity in soil, with such related important to remember this: The microbial benefits as enhanced nitrogen fixation and, activity that will be stimulated is associated in some cases, improved . with decomposing soil organic matter, a soil quality parameter that we want to Physical Indicators increase. Soils that have been in conven- A soil’s physical properties affect crop tional tillage for many years may have lost performance in many ways. Plant health much of their organic matter content in and growth are heavily influenced by the this manner. Therefore, it takes a dedicated soil’s texture, bulk density (a measure of effort by farmers to increase soil organic compaction), porosity, water-holding capacity, matter content. Conventional tillage and the presence or absence of hard pans. systems require annual additions of organic These properties are all improved through matter. additions of organic matter to soils. Chemical Indicators Soil physical properties also influence soil- water and plant-water relationships. The Farmers who want to achieve the high crop partitioning of water at the soil surface is yields expected of modern agriculture will important because it determines both the have to provide nutrients in large quan- quantity and the quality of surface and tities. Farmers increase and alter the pool of groundwater, as well as the amount of available nutrients by adding fertilizers, water that will be available for plant incorporating cover crops, and using other growth. Water running over the surface, organic materials, such as manures and rather than infiltrating it, can carry composts. The types and proportions of sediment and other pollutants (Karlen et amendments—and how they contribute to al., 1997). This run-off can result in soil quality—largely depend on each negative impacts on water quality in farmer’s management principles and surface waters, such as rivers, ponds, and philosophy. In any case, , lakes. with its influence on the availability of nutrients to plants, plays a key role in soil quality. QUALITATIVE INDICATORS OF SOIL Acidity. Soil acidity (pH) is one of the QUALITY principal factors affecting nutrient Qualitative descriptions of soil quality are availability to plants. The major nutrients usually personal assessments of short-term (nitrogen, potassium and phosphorous) changes in soil quality. For example, a can’t effectively promote high crop yields if farmer using such a description may tell a the soil pH is not correct. Decreasing soil visiting Extension agent, “There seemed to pH increases the solubility of elements such be more earthworm activity this year.” as aluminum, zinc, copper, and iron. At pH values less than approximately 5.5, toxic Alternatively, the personal assessment may levels of these elements may even be be a thoughtful conclusion based on present in the soil. Applying lime will help recollections of how things were “way back to increase soil pH and thus decrease the when” compared to how they are today. solubility of these elements in the soil. We might hear a farmer make a longer-term

Organic Production—Soil Quality Considerations for Organic Farmers 7 assessment by saying, “All that compost I not represent any absolute measure. added since I bought the place 10 years ago Assessing soil in more than one spot per sure has improved my soil; why, the color’s field will provide more accurate results. changed from brick red to burnt sienna.” USDA Soil Quality Kits Unfortunately, these kinds of field observations may be influenced by wishful As its name implies, a soil quality kit can thinking or subjective impressions—observa- help a farmer to assess and manage soil tions that are colored by one’s personal quality. Farmers can inquire about the views, experience, or background. When availability of testing kits at their local making qualitative assessments of soil USDA office. The USDA soil testing kit was quality, it is important to rely upon a set of designed as an instructional tool and data well-defined qualitative indicators (see Table collection device for those interested in 2). Although these qualitative indicators monitoring changes in soil quality. cannot be gauged in units of measure, each Specifically, the handbook and kit are one can be assessed based on the specific designed to do the following: observations noted in Table 2. • Define and demonstrate the use of indicators of soil quality and degradation. ASSESSING SOIL QUALITY • Explain how practices may A Simplified Assessment enhance or degrade soil quality. • Provide simple field tests of soil quality Farmers can use a simple set of qualitative indicators. and quantitative assessments to track • Provide a list of resources for further changes in soil quality over time (see Table exploration of soil quality issues. 3). This simplified assessment includes a guided visual check of crop conditions, The soil quality kit describes a set of surface residue, living organisms, surface measurements, a minimum data set (MDS). structure, and soil erosion using the These measurements can be taken in the qualitative indicators in Table 2. Included field to assess the holistic nature of soil are evaluations of compaction, subsurface health in agricultural systems. By holistic, structure, soil pH, and humic matter we mean that the measurements interweave content. The last two components of this the physical, chemical, and biological assessment are quantitative indicators that components of soil and the resulting require a . interactions. A farmer should use the kits as a screening tool to show the general trend These simplified assessments are relatively or direction of soil quality; for instance, easy to make. To perform the assessment, whether current management systems are first turn over a shovelful of soil about 6 to maintaining, enhancing or degrading the 8 inches deep. On the assessment sheet, soil. rate each indicator by marking an X or shading out the box that best represents the The soil quality kit can also be used to value for that indicator. Assessments are make side-by-side comparisons of different most effective when filled out by the same soil management systems and determine user over time and under similar soil their relative effects on soil quality. It can moisture levels. The assessments are be used to take measurements on the same qualitative; therefore evaluation scores do field at different times, which will help

Organic Production—Soil Quality Considerations for Organic Farmers 8 farmers to monitor trends in soil quality as affected by soil use and management. It is also handy for comparing problem areas in a field to nonproblem areas.

Table 2. Qualitative Soil Quality Indicators Indicator Poor Medium Good Earthworms 0-1 worms in 2-10 in shovelful. Few 10+ in top foot of shovelful of top foot casts, holes, or worms. soil. Lots of casts and of soil. No casts or holes in tilled clods. holes. Birds behind tillage.

Organic matter color similar Surface color closer to Topsoil clearly (OM) color to color defined, darker than subsoil color. subsoil Roots/residue/(OM) No visible residue or Some residue, few Noticeable roots and roots. roots. residue Subsurface Wire breaks or bends Have to push hard, Flag goes in easily compaction when inserting need fist to push flag with fingers to twice surveyor’s flag. in. the depth of plow layer. Soil tilth, Looks dead. Like brick Somewhat cloddy, Soil crumbles well, mellowness, and or concrete, cloddy. balls up, rough pulling can slice through, like friability Either blows apart or seedbed. cutting butter. hard to pull drill Spongy when you through. walk on it. Erosion Large gullies over 2 Few rills or gullies, No gullies or rills. inches deep joined to gullies up to two Clear or no runoff others, thin or no inches deep. Some topsoil, rapid run-off swift runoff, colored the color of the soil. water Water holding Plant stress two days Water stress after a Holds water for a capacity after a good rain. week long period of time without puddling. Drainage, infiltration Water lays for a long Water lays for short No ponding, no time, evaporates period of time, runoff, water moves more than drains, eventually drains through soil steadily. always very wet Soil not too wet, not ground too dry. Crop condition Problem growing Fair growth, spots in Normal, healthy dark throughout season, field different, medium green color, excellent poor growth, yellow green color. growth all season, or purple color. across field. pH Hard to correct for Proper pH for crop. desired crop. Nutrient holding Soil test values Little or slow change Soil tests trending up capacity dropping with more in relation to fertilizer fertilizer applied than applied and crop crops use. harvested. Source: Maryland Quality Assessment Book, Natural Resource Conservation Service

Organic Production—Soil Quality Considerations for Organic Farmers 9

Table 3. Simplified Assessment of Soil Quality ASSESSMENT SHEET Date Crop

Farm / Field ID

Poor Medium Good

Soil Quality indicators 1 2 3 4 5 6 7 8 9 Earthworms

Organic matter color

Organic matter roots/residue

Subsurface compaction

Tilth/friability mellowness

Erosion

Water holding capacity

Drainage infiltration

Crop condition

pH

Nutrient holding capacity

Other (write in)

Organic Production—Soil Quality Considerations for Organic Farmers 10 INTERPRETING SOIL QUALITY Initial measurements of all soil quality INDICATOR MEASUREMENTS indicators should be made in high and low productivity areas to establish a range of Farmers should always remember that field values that are site specific. This allows for conditions vary widely depending on the the assessment of changes occurring landscape, region, climate, and other through time with different management factors. Therefore, the relative importance systems. of soil quality measurements will vary accordingly. Any interpretation of results, A farmer’s ability to interpret changes in particularly comparisons between fields, indicators of soil quality normally improves needs to reflect these differences. It is over time. It takes some experience to know important that each site evaluated is what kind of change and how much characterized by , signs of erosion, change in an indicator is actually management history, landscape position, meaningful. Farmers will need to recognize location of field and sampling site, climatic that local, random changes in field condition, and location of environmentally conditions—caused by such elements as sensitive areas. weather and human activity—can radically influence indicator values at any particular Because soil quality parameters vary widely, point in time. Natural cycles will also sampling at the same site, at sites with influence indicator values. similar management operations (tillage, for example), and at the same time of year is Farmers can expect to see regular changes important. Within a given field, in values that result from seasonal weather consideration should be given to the variations, crop growth stage effects, following: fluctuation of groundwater tables, and other natural cycles. For example, the • row versus inter-row areas amount of plant available nitrogen (PAN) • differences in in the soil depends on the decomposition • differences in management and mineralization of cover crop biomass • tracked versus nontracked areas through microbial activity. Microbial • salt-affected versus non-salt-affected activity is a commonly measured soil areas quality parameter. However, mineralization • eroded versus noneroded areas rates vary with the season and with • drainage management practices. A farmer would Generally, when collecting soil for an need to recognize such variations when assessment, a farmer should select sites making any comparisons of available representative of the field or trouble spots nitrogen. within the field. A minimum of three As a second example, let’s say a farmer samples or measurements should be measures a change in soil pH from 5.9 to collected on any one soil type and 6.0. Is this a meaningful change? A pH management combination. The greater the change of 0.1 units would not normally be variability of the field, the greater the enough to make a difference in crop number of measurements that are needed production, whereas a pH change from 5.0 to get a representative value at the field to 5.8 over a two-year period certainly scale. would be.

Organic Manual—Soil Quality Considerations on Organic Farms 11 New Organic Rule: Managing Soil Fertility enough that management can be altered (if necessary) to influence trends. Regarding soil fertility, the USDA Organic Rule states the following: Another drawback to gauging changes in • Farmers must manage soil fertility, soil quality by trends is that a trend line including tillage and cultivation practices, may essentially be flat. For instance, in a manner that maintains or improves measurement of a quality parameter, such the physical, chemical, and biological as soil microbial biomass, in year 1 may be condition of the soil and minimizes soil equal to the measurement in year 10. A erosion. farmer interpreting this information must consider the possibility that the soil may be • Farmers are responsible for identifying functioning at its highest attainable level measurable indicators that can be used to and cannot improve, or it may be evaluate how well they are achieving the functioning at its lowest level and cannot objectives of the operation. go lower (Seybold et al., 1997). • The specific indicators used to evaluate a

given organic system plan will be determined by the farmer or handler in RECOMMENDED READING consultation with the certifying agent. • If the organic system plan calls for References Cited improvements in soil organic matter Much of the information contained in this content in a particular field, it should section is summarized from The Soil Quality include provisions for analyzing soil Concept, a United States Department of organic matter levels at periodic intervals. Agriculture, Natural Resources Conservation Service publication edited by The Soil Quality Institute.

Changes in measured soil quality Christensen, O. 1988. The direct effects of parameters over an extended period of time earthworms on nitrogen turnover in are referred to as trend changes. Ideally, the cultivated soils. Ecology Bulletin. 39:41- trend is positive. That is, soil quality 44. improves, albeit often slowly, over time. Doran. J.W., M. Sarrantonio, and M.A. Liebig. Note that trend changes can be negative as 1996. Soil health and sustainability. well. For example, soil humus content may Advances in Agronomy. 56:1-54. decrease because of extensive tillage to Hajek, B.F., D.L. Karlen, B. Lowery, J.F. Power, control weeds. This decline would represent T.E. Schumaker, E.L. Skidmore, and R.E. a depletive management system. Trends are Sojka. 1990. Erosion and soil properties. In W.E. Larson, G.R. Foster, R.R. Allmaras, usually gauged over a relatively long period and C.M. Smith (Eds.) Research Issues in of time, such as 10 years. Soil Erosion Productivity. pp. 23-40. Unfortunately, trend changes don’t provide University of Minnesota. St. Paul, MN. an immediate assessment of soil quality. Karlen, D.L., M.J. Mausbach, J.W. Doran, R.G. They require measurements of indicators Cline, R.F. Harris, and G.E. Schuman. over an extended period. Within that 1997. Soil quality: A concept, definition, and framework for evaluation. Soil extended period, farmers should recognize Science Society of America Journal. 61:4- changes between any two points in time 10. that are definitive, important, and rapid

Organic Production—Soil Quality Considerations for Organic Farmers 12 Larson, W.E., and F.J. Pierce. 1994. The Magdoff, F. 1992. Building Soils for Better dynamics of soil quality as a measure of Crops: Organic Matter Management. sustainable management. In J.W. Doran, University of Nebraska Press. Lincoln. D.C. Coleman, D.F. Bezdicek, and B.A. National Organic Program. 2000. The Final Stewart (Eds.) Defining Soil Quality for a Rule. Online: http://www.ams.usda.gov/ Sustainable Environment. SSSA Spec. Pub. nop/nop2000/nop/finalrulepages/ No. 35. ASA, CSSA, and SSSA, Madison, finalrulemap.htm. WI. NRCS (National Resource Conservation Larson, W.E., and F.J. Pierce. 1991. Service). 1997. Maryland Soil Quality Conservation and enhancement of soil Assessment Book. USDA. Washington, DC. quality. In Evaluation for Sustainable Land Parnes, R. 1990. Fertile Soil: A Grower’s Guide to Management in the Developing World. pp Organic & Inorganic Fertilizers. agAccess. 175-203. Int. Board for Soil Res. and Davis. Management. Bangkok, Thailand. Sanders, D.W. 1992. International activities in Romig, D.E., M.J. Garlynd, R.F. Harris, and K. assessing and monitoring soil McSweeney. 1995. How farmers assess soil degradation. American Journal of health and quality. Journal of Soil and Alternative Agriculture. 7:17-24. Water Conservation. 50:229-236. Sullivan, P.G., D. Doel, and C. Rugen. 1995. Seybold, C.A., M.J. Mausbach, D.L. Karlen, Sustainable Soil Management. Sustainable and H.H. Rogers. 1997. Quantification of Agriculture Fundamental Series. ATTRA. soil quality. In B.A. Stewart and R. Lal Fayetteville, AK. (Eds.) Advances in Agronomy. Proceedings U.S. Department of Agriculture. 1998. Soil from an International Symposium on Carbon Quality Test Kit Guide. United States Sequestration in Soil. Lewis Publishing. Department of Agriculture. Agricultural Research Service. Natural Resources Conservation Service. Soil Quality Additional Reading Institute. Washington, DC. Cavigelli, M.A., S.R. Deming, L.K. Probyn, and U.S. Department of Agriculture. 1980. Report R.R. Harwood (Eds.) 1998. Managing and Recommendations on Organic Farming. U.S. Govt. Printing Office. Washington, biological processes for productivity and environmental quality. Michigan Field DC. Crop Ecology. Michigan State University Extension Bulletin E-2646. Doran, J.W., D.C. Coleman, D.F. Bezdicek, and B.A. Stewart (Eds.) 1994. Defining Soil Quality for a Sustainable Environment. American Society of Agronomy Special Publication No. 35. Madison, WI. Follett, R.F., J.W.B. Stewart, and C.V. Cole. 1987. Soil Fertility and Organic Matter as Critical Components of Production Systems. SSSA Special Publication Number 19. Society of America, Inc. Madison, WI. Gershuny, G., and J. Smillie. 1986. The Soul of Soil: A Guide to Ecological Soil Management. 2nd Ed. 1986. Gaia Services. St. Johnsbury, Quebec.

Organic Production—Soil Quality Considerations for Organic Farmers 13

The Organic Production publication series was developed by the Center for Environmental Farming Systems,

a cooperative effort between North Carolina State University, North Carolina A&T State University, and the North Carolina Department of Agriculture and Consumer Services.

The USDA Southern Region Sustainable Agriculture Research and Education Program and the USDA Initiative for Future Agriculture and Food Systems Program provided funding in support of the Organic Production publication series. David Zodrow and Karen Van Epen of ATTRA contributed to the technical writing, editing, and formatting of these publications.

Prepared by Keith R. Baldwin, Program Leader, ANR/CRD Extension Specialist—Horticulture North Carolina A&T State University

Published by NORTH CAROLINA COOPERATIVE EXTENSION SERVICE

AG-659W-04 07/2006—BS E06-45788

Distributed in furtherance of the acts of Congress of May 8 and June 30, 1914. North Carolina State University and North Carolina A&T State University commit themselves to positive action to secure equal opportunity regardless of race, color, creed, national origin, religion, sex, age, disability or veteran status. In addition, the two Universities welcome all persons without regard to sexual orientation. North Carolina State University, North Carolina A&T State University, U.S. Department of Agriculture, and local governments cooperating.