• Introduction
• Soil Conservation and Restoration
• Soil Water
• Nutrient Management
• Soil Biology
• Productive and Sustainable Soil Management Systems

Introduction

Soil resource is basic to crop and grassland production and its management strongly influences air and environmental quality.  Soils store nutrients and water for plants.  Soil organisms and their biological activities regulate nutrient cycling and the decomposition of chemicals such as pesticides.  Soils can be degraded by misuse and abuse.  When soils erode, they become an air and water contaminant.  Managing soil within a systems concept can help preserve its functions and quality.  Soil conservation, water storage, nutrient storage, biological activity, and system management are essentially the components of this national program.                               

Significant Accomplishments by Component

Soil Conservation and Restoration

Erosion.  Soil erosion is still a major threat to sustained productivity of agricultural soils.  About 1.5 to 2.0 billion tons of soil in the United States are lost annually by soil erosion.  Soil erosion occurs about 17 times faster than soil formation, and about 90 percent of all U.S. cropland is losing soil above the sustainable rate.  The USDA Natural Resources Conservation Service (NRCS) has a critical need for a computer program for farm planning that can estimate interrill and rill erosion.  ARS at Oxford, Mississippi, sponsored a project, in cooperation with the University of Tennessee, that updated the Revised Universal Soil Loss Equation (RUSLE2) and developed the program for NRCS implementation.  RUSLE2 provides the following improvements over previous versions:  more realistic approach to the time-varying aspects of field erosion processes; more flexibility in conservation planning; and applicability to areas where deposition occurs.  This model was released to NRCS in 2000.

Current soil-erosion prediction models do not work well where winter conditions (soil freezing and thawing and snow melt) dominate the hydrologic processes of a region.  During winter, these are the major causes of erosion on 10 million acres of nonirrigated cropland of the Pacific Northwest.  Scientists in Pullman, Washington, analyzed 13 years of long-term runoff plot and field data to improve prediction accuracy for northwest cropland.  The results indicated that the benefits of crop residue, crop canopy, and surface roughness were greater in the Pacific Northwest than in areas with higher intensity storms.  The relationships developed from the data will help producers and land managers in the Pacific Northwest select the best and lowest cost set of practices to reduce erosion and sediment production. 

The erosive effect from soil translocation by tillage can exceed acceptable soil erosion levels. This is a poorly recognized phenomenon that contributes to an increase in soil variability and overall degradation of the landscape.  Field measurements of soil properties taken on complex landscapes by researchers at Morris, Minnesota, demonstrated erosive action over convex slope positions and deposition in concave slope positions.  Reductions in crop yield were highly correlated with landscape positions subjected to soil removal from tillage erosion.  Soil translocation by tillage needs to be considered by NRCS and farm managers before effective conservation management plans can be implemented.

Compaction.  Equipment traffic, grazing, and natural consolidation can cause soil compaction, thereby restricting root growth and movement of water, air, and chemicals.  Morris, Minnesota, researchers determined that corn yields may be significantly decreased up to 12 years after initial compaction from heavy equipment.  Scientists at St. Paul, Minnesota, evaluated compaction caused by common agricultural equipment, from the standard tractor to a heavily loaded combine.  They found that the usual recommendations to control compaction (reducing axle load, avoiding traffic during wet conditions, and reducing contact pressure under the traction device) must also include controlled, not random, traffic, that is, farmers should drive over the same places in the field.  Researchers at Auburn, Alabama, developed a conservation cropping system that included noninversion fall tillage to alleviate problems of soil compaction and a rye cover crop to reduce soil compaction.  Research at El Reno, Oklahoma, demonstrated that cattle which grazed on lespedeza had a minimal effect on soil compaction, compared to cattle in the traditional wheat-grazing system used in the Southern Great Plains.

Remediation and restoration.  Poor land management can cause accelerated soil acidification and buildup of excess salts, toxic trace elements, and nutrients.  Recognizing that effective and economically feasible management practices are needed to prevent soil degradation and to remediate degraded soils, considerable progress was made in using plants to remediate toxic-element-contaminated sites.  Scientists at Ithaca, New York, identified plant species to effectively extract radioactive cesium-137 from contaminated soils.  At Beltsville, Maryland, scientists identified plant species and developed management practices to remove nickel, zinc, and cadmium from contaminated sites.  The ashed plant material can be a valuable ore source for nickel recovery.  Knowing that boron buildup in soils can reduce crop growth and productivity, scientists at Riverside, California, developed a model to predict boron adsorption/desorption behavior in soils based on soil chemical properties.  They also developed cost-effective mobile- conductivity measuring equipment capable of inventorying and mapping soil salinity for irrigation management and precision farming applications.

Soil Water 

Infiltration and retention.  Because of harsh climate of the Southern Great Plains region, less than 25 percent of the precipitation is usually stored as soil water.  Dryland crops are strongly influenced by soil water content at planting, because 1 inch of stored soil water produces an additional 450 pounds of grain sorghum per acre.  Any dryland cropping system that is sustainable must improve water storage efficiency and reduce undesirable water losses during the growing season.  ARS at Bushland, Texas, in collaboration with NRCS, found that conservation tillage and no-tillage dryland cropping practices can increase soil water retention and crop yields without causing producers to make additional investments in equipment and supplies.  Scientists at Ames, Iowa, documented that long-term use of ridge-tillage resulted in smaller amounts of runoff, increased baseflow, and increased water use efficiency on deep-loess soil, resulting in more soil water for cover crops and more diversified crop rotations. 

Availability.  Deficits of plant-available soil water significantly reduce crop yields.  ARS scientists are developing tools and practices to allow producers to make management decisions based on soil water availability.  Scientists at El Reno, Oklahoma, developed a simple soil-water budget model that can predict daily values of soil water content from soils information, meteorological measurements, and remotely sensed data from tall grass prairie sites in Oklahoma.  Such a remote sensing/modeling approach could be linked to weather forecasts and climate outlooks to predict future soil water supplies.  This information would allow producers to make economic decisions about management inputs based on crop or forage production estimates.  Scientists at Florence, South Carolina, looked at the cost-benefit aspects of noninversion deep-tillage to increase crop rooting depth and soil water use in compacted soils and found that more frequent deep tillage led to improved soil water use and increased crop yield.

Excess soil water.  Scientists from Ames, Iowa, and their colleagues from Iowa State University found that excess rainfall in the previous growing season influenced the type of tillage practices that should be used the following year.  Corn and soybean production using subsoiling, chisel plowing, and no-tillage practices were compared on silty loam soils that had received 166 to185 percent of the average rainfall the previous year.  No-tillage practices provided a net return for corn that was $54 per acre more than with subsoiling and $42 per acre more than chisel plowing.  These results suggest that the least tillage necessary to produce crops is the best management practice to use on silty clay loam soils that had received excess rainfall the previous year.  

Soil Water Related Properties:  Measurements and Applications.  New soil technologies are needed to overcome the spatial resolution limitations associated with using global and national soil data bases to predict the amount of water that is available for crops and other uses at a variety of scales ranging from individual farmer fields to nationwide.  Soil and topographic data have been assembled and are being analyzed to develop functions for scaling soil properties.  Scientists at Beltsville, Maryland, have shown that topographic features such as slope, curvature, and qualitative soil-profile descriptions can be used to scale soil properties.  This research has an impact on a wide range of projects involving soil moisture dynamics and climate studies conducted by several agencies including NASA and NRCS.

Unsaturated soil hydraulic properties (water retention, hydraulic conductivity) are needed to predict transport of nutrients, trace elements, and organic contaminants from the soil surface to groundwater, but these properties are difficult to measure in the field.  Scientists from Riverside, California, have developed methods to predict unsaturated soil hydraulic properties from readily available soil survey data, such as soil texture and bulk density.  Researchers at Ft. Collins, Colorado, have verified a technique whereby soil water properties can be estimated from remote sensing of soil moisture.  This technique will help extend models to larger areas for precision agriculture and estimating field- and farm-scale environmental impacts of pollutants.

Nutrient Management

Management of nutrients for sustainable production systems.  Improved nutrient management systems were developed for a variety of production systems and soils across the country.  Researchers at Ft. Collins, Colorado, developed a new version of the Nitrogen Leaching Economic Analysis Package (NLEAP) model.  Across 14 cooperator s farms of south central Colorado, the model was calibrated/validated for the effects of management practices on nitrate-nitrogen dynamics on the root zone and below the root zone of irrigated lettuce, potato, barley, spring wheat, and canola.  NLEAP 1.20 was calibrated/validated with winter cover crops (to increase the nitrogen-use efficiency of the entire system) and used to evaluate their potential as scavenger crops.  As a result of ARS cooperation with Colorado State University, the NLEAP model has been listed as one of the best management practices for nitrogen management in south central Colorado.

To improve agricultural sustainability on the Blackland Prairie of Texas, an effort was undertaken to develop nitrogen (N) management in conservation tillage systems.  Temple, Texas, researchers evaluated the effects of tillage systems and fertilizer N application rate and timing in corn production in heavy clay soils of the Blackland Prairie.  Results indicated no N limitations in the no-till system compared to the other tillage systems, but large reductions in corn yields were observed with fall application of fertilizer N in wet years.  The highest yields were seen with the no-till system, indicating that a conservation tillage system can be the most reliable tillage system in heavy clay soils.

Adoption of no-tillage management for row crop production in the upper Midwest has been severely limited by observed yield depressions during the first few years of conversion from conventional tillage to no-tillage management.  Scientists at the National Soil Tilth Lab in Ames, Iowa, completed a comprehensive review for the Advances in Agronomy journal covering the mechanisms of nitrogen cycling in different management systems.  The review includes a recommendation that successful transition from conventional tillage to no-tillage management requires a greater emphasis on early spring-seed-zone nitrogen management.  No-tillage changes the timing of nitrogen mineralization and may result in nitrogen deficiencies during critical early stages of crop growth.  This analysis and synthesis brings new understanding to nitrogen management.

Basic research in soil-plant interactions, nutrient fate and transformations.  ARS researchers developed improved nutrient measurement methods.  Method development studies were coupled with field management research to produce improvements in nutrient use efficiency.  Researchers at Morris, Minnesota, developed a modified procedure for study of soil nitrogen (N) transformation.  The modification enhances the relevancy for field applicability over the traditional laboratory method.  The result is likely to alter the preferred scientific methodology worldwide and increase the usefulness of acquired information on soil nitrogen status, leading to improved nitrogen management.  Researchers at Brookings, South Dakota, mimicked field conditions and developed laboratory incubations that produce realistic estimates of the amount and timing of N release from soil organic matter.  Improved nitrogen management (more nitrogen used by the crop and less lost from the farmer s field) will result from the improved soil nitrogen availability test. 'Quick tests' that can be conducted during the growing season in the field are needed that accurately determine if, when, and how much additional nitrogen is needed for crops grown in manure-amended soils.  In cooperation with ARS at Orono, Maine, the University of Maine Cooperative Extension showed that leaf chlorophyll, petiole nitrate, and soil nitrate levels could all be used for predicting potato crop response to nitrogen.  This gives potato growers a wide selection of tools for managing nitrogen for optimal yield in manure-amended soils. 

Soil management effects controlling on-site retention of nutrients at rarm, watershed, and basin scales.  The relationship between nitrogen (N) fertilizer rate, corn yield, and the resulting nitrate concentrations in tile drainage water is poorly known for much of the upper Midwest Corn Belt.  Scientists with the National Soil Tilth Lab in Ames, Iowa, measured yields and nitrate concentrations in tile water leaving a producer's field in Iowa where three N fertilizer rates (the farmer's typical rate and 2/3 and 1/3 of this rate) were used on corn, in a corn-soybean rotation.  They found that corn could not be raised at any of the N fertilizer rates used without producing nitrate concentrations in the tile drainage that exceeded the 10 parts per million (ppm) maximum contaminant level set by the Environmental Protection Agency for drinking water.  When water quality is included in the definition of sustainability, this result indicates that corn production in these extensively tile-drained soils is not sustainable under current production practices.  To reduce nitrate contamination of surface waters and improve nitrogen use efficiency by crops, scientists are pursuing a dual strategy.  First, the synchronization between availability of N in the soil and N uptake by plants is being improved by a better understanding of how and when different crop residues and soil organic matter fractions decompose in soil.  Second, methods are being developed for removing nitrate from shallow groundwater through denitrification, a process that converts nitrate to harmless dinitrogen gas (the major component of air) before the water flows into tile drains and then into streams.  Using a late-spring nitrate test (LSNT) and adjusting fertilization rates have resulted in a sustained, statistically significant 30-percent reduction in nitrate contamination of surface water from the LSNT watershed, compared to the control watershed.

Research has also been conducted on ways to remediate excess nitrate from soil and shallow groundwater.  Researchers at Ft. Collins, Colorado, demonstrated that vegetable oils are a good carbon substrate for denitrification and that waters denitrified with vegetable oils as a carbon source do not contain toxic compounds.  A dollar s worth of vegetable oil can remove 10 ppm nitrate-N from 8,000 to 10,000 gallons of water.

Management effects on soil carbon related processes.  Soil organic matter provides numerous benefits to soil.  This form of soil carbon increases water holding capacity, is a source of slow-release nutrients for plants, supports soil microorganisms that degrade pesticides and transform other chemicals, and imparts good soil structure and tilth.  In addition, when carbon is present in soil, either in organic or inorganic forms, it serves as a  sink for carbon, helping to prevent its accumulation in the atmosphere as carbon dioxide, a greenhouse gas.  Soil organic matter is the largest terrestrial reservoir of organic carbon.   Increasing soil organic matter or soil carbon sequestration is, therefore, not only a major soil-related activity, but is also important to global change.  Additional information on this topic is reported in the annual report of the Global Change National Program.

At ARS locations from the west (Oregon) to the east (Florida), researchers are studying the effects of various management practices on soil carbon dynamics and are determining the specific effects of management practices suitable for their regions on soil organic matter.  Reduced tillage, cover crops, elimination of fallow, and setting aside land in the Conservation Reserve Program (CRP), all increase soil carbon.  Quantifying the amounts is now the primary focus of this research.  For example, Ft. Collins data indicate that across the 13-State region of historic U.S. grasslands (14 million acres), the average rates of soil organic C sequestration was 560 to 910 pounds per year at sites in CRP.  Scientists in Ames documented the relative contributions of surface residue and roots under simulated no-tillage management to the formation of soil organic matter.  The study shows that after 1 year of incubation, 66 percent of the carbon in surface residue had been respired as carbon dioxide, 11 percent was still on the surface, and 16 percent was in new soil organic matter.  In comparison, 56 percent of the root- derived carbon was respired as carbon dioxide, and 42 percent was in new soil organic matter.  Florence, South Carolina, researchers demonstrated that in Coastal Plain soil, long-term conservation tillage practices will result in a buildup of soil organic carbon.  Soil organic matter levels in the surface 2 inches continue to increase at a rate of 0.1 percent per year in long-term conservation tillage plots that include corn, wheat, and soybean in rotation.

Grazing lands, which comprise more than 40 percent of the surface area of the continental United States, provide an enormous potential site for sequestration of carbon in soil.  In a cooperative effort between ARS scientists at El Reno, Oklahoma, and the Samuel R. Noble Foundation, scientists determined the effect of 10 years of differential cattle stocking rates on soil carbon content.  Stocking rate affected the amount of carbon stored in the soil differently for a lighter textured soil than for a heavier textured soil.  Temple, Texas, researchers determined the rate of carbon storage after central Texas soils, degraded by agricultural practices, had been returned to grass for periods of 6 to 60 years.  Soil carbon increased at a rate of 447 kilograms per hectare per year (approximately the same as pounds per acre per year) over the time span of the study.  According to research conducted at Watkinsville, Georgia, pasture management affects soil C sequestration potential.  After determining the standing stock of C in surface residue and soil in grazed versus nongrazed systems (i.e., hayed grassland, conservation-tillage cropland, and adjacent forestland), scientists documented the positive impacts of well-managed cattle-grazing systems on soil carbon.

Soil Biology

Soil Ecology.  Soil ecological research studies the relationship between organisms and their soil environment.  These are often basic studies, but most lead to information on how to foster the beneficial activities of soil microorganisms, while negating the activities of harmful ones.  St. Paul, Minnesota, researchers have shown that earthworms are important in the transfer of water and chemicals into and through soils.  If crop residues are kept near or on the soil surface, which is good for erosion control, the earthworm burrows still remain shallow enough to benefit water infiltration but are not so deep as to cause leaching of nutrients and chemicals before they can be utilized by plants or degraded by soil microorganisms.  In addition, crop residues may be sequestered into organic matter via ingestion and partial intestinal digestion by faunal organisms, including the earthworm.  Fecal pellets from earthworm activity may contain twice as much carbon as in surrounding soil. The earthworm pathway more rapidly converts crop residues into stored soil organic matter and stored carbon.

Researchers at Beltsville, Maryland, modified a commercially available system for identification of microbes to increase the sensitivity almost a thousand times.  Using this system, scientists identified single colonies of several different species of soil, rhizosphere (area of soil immediately next to plant roots), and clinically important bacteria.  This will allow soil scientists to identify bacteria much more quickly and efficiently and may also speed up identification of human pathogens in clinical laboratories.

Humic substances (the major components of soil organic matter) can be a source of important trace metals, such as iron, to stimulate plant growth.  Experiments by ARS researchers in St. Paul, Minnesota, and by cooperators in Rehovot, Israel, showed that plants such as melons and turfgrasses increased in leaf green color (chlorophyll) and had enhanced shoot and root weights when organic matter, with beneficial trace metals, was used.

The rhizosphere and spermosphere.  The rhizosphere is the area immediately adjacent to plant roots and the spermosphere is the volume of soil that surrounds a seed.  Both are areas of higher soil microbial populations and enhanced activity because of the nutrients  leaked into the soil by seeds and roots.  When properly infected with rhizobia bacteria, legumes can use atmospheric nitrogen to meet plant growth requirements.  Research at Beaver, West Virginia, has shown a lack of adequate nodulation of white clover because of acidic soil conditions. White clover plants were used to 'trap' rhizobia in an acidic soil where rhizobial populations are extremely low.  Nearly 150 native strains of rhizobia were isolated that were resistant to acidic soil conditions.  Selected strains could significantly increase legume-based forage production in Appalachia and in many areas throughout the world with acid soils.

Beneficial soil fungi, arbuscular mycorrhizal (AM), form a symbiotic relationship with roots.  They aid roots in taking up nutrients and water from the soil, improve soil aggregation, and have been shown to impart disease resistance to plants.  Though AM fungi are indigenous in most soils, many conventional agricultural practices depress their populations and may select for less beneficial forms.  Widespread application of these fungi is not presently possible due to our inability to grow these organisms in pure culture.  It has been determined which chemicals are shared and important to both the plant and mycorrhizae.  ARS scientists in Wyndmoor, Pennsylvania, are examining each phase of the metabolism in the mycorrhizae life cycle to understand how the AM fungi can complete their life cycle in the absence of a host plant, in order to produce an inoculum.  They have, in collaboration with Rodale Institute Experimental Farm, determined management practices that foster mycorrhizae.  Reduced tillage, cover crop, and crop rotation practices led to greater populations of spores and inocula of AM fungi.  Studies conducted by ARS scientists at Lubbock, Texas, in collaboration with scientists at Texas Tech University, under both controlled environment conditions and in the field, have shown the importance of the interaction of changes in soil moisture, soil temperature, and soil disturbance on the colonization of cotton roots by mycorrhizae.  This research showed that low soil temperatures have a negative effect on mycorrhizal colonization while increasing soil moisture has a positive effect only if soil temperatures were optimum.

Interactions between soil management and soil biota.  ARS researchers at Sidney, Montana, found a saprophytic basidiomycete fungus that promotes soil aggregation.  These organisms can be an early indicator of trends in soil quality to aid in evaluating management practices.  AM fungi produce large amounts of an insoluble glycoprotein, glomalin, that serves like a glue to form stable soil aggregates.  Soil from test plots in transition from plow-till to no-till and under various continuous crop rotations or conventional crop-fallow were analyzed for glomalin and aggregate stability.  Results show that no-­till practices and continuous cropping (i.e., elimination of fallow) contribute to aggregate stability by promoting production of glomalin by arbuscular mycorrhizae fungi.  The impact of this work is worldwide recognition of the influence of soil disturbance on groups of microorganisms critical to soil stability.

Management of diseases, pests, and weeds.  Cultural and other environmentally benign alternatives for methyl bromide are needed because of the impending ban on methyl bromide.  The soil biota can be used to control diseases, pests, and weeds, eliminating or decreasing the use of potentially harmful chemicals.  Scientist at Beltsville, Maryland, showed that a cover crop, in combination with changes in cultural practice (raised beds with plastic mulch, disease-free greenhouse runner-plug plants, and drip irrigation), eliminated red stele disease in strawberries even under environmental conditions that favor the disease.  Root rot in peas is estimated to devastate at least 10 percent of the planted acreage.  There is no genetic or chemical control for the rot, and the disease cannot be avoided by long periods without a pea crop.  Field research in St. Paul, Minnesota, shows that the pathogen can be controlled by planting an oat crop before the pea crop, if the oat crop residue is incorporated in late fall and soil compaction and drainage are controlled.

Biologically based weed management systems are being developed at Columbia, Missouri, that reduce chemical use and enhance soil quality.  Rhizosphere bacteria were cultured and screened for potential biological control activity from soils with different cropping histories.  Soils with high organic matter content and a history of minimal tillage, low agrichemical inputs, and diverse cropping systems supported the highest populations of weed-suppressive rhizosphere bacteria.  In addition, the evaluation of rhizobacteria from several weed species has yielded new information regarding the products of these cultures that are toxic to weed growth.  Based on these findings, strategies were developed for enhancing the production of these toxins by rhizobacteria in soil in proximity to weed seeds and seedling roots.

Beltsville, Maryland, scientists have determined the characteristics of composts that suppress various root rot diseases and the procedure used to make these composts.  Morris, Minnesota, researchers showed that composting dairy manure produced a more stable end product when treated with biodynamic compost preparations.  Irrigated crop responses to compost application are unknown.  ARS researchers at Kimberly, Idaho, in conjunction with the University of Idaho, compared the effect of yearly and accumulative compost applications.  If crop residue and soils are managed properly, a compost application of 2.5 tons per acre combined with a normal or reduced nitrogen fertilizer application resulted in the greatest economic returns.  In addition, the composts would utilize the yearly manure output from about 61,000 dairy cows. These findings are increasing the use and efficiency of composting on farms and thereby increasing farm waste recycling into soil-­enhancing materials.

Soil processes affecting transformation of pesticides and other xenobiotics.  The public is concerned with the potential effect of herbicides on drinking water, air,  food quality, and human and environmental health.  Well-managed soil has a tremendous potential to sequester and detoxify most agrochemicals.  ARS researchers at Urbana, Illinois; Stoneville, Mississippi; Ames, Iowa; and St. Paul, Minnesota, have determined the effects of various soil properties and management practices on pesticide sorption and degradation, which are important to understanding microbiological degradation of herbicides in the environment.  Researchers at Ames and Stoneville discovered that buffer strip soils transfer and degrade pesticides, so they can be managed most effectively to protect water resources.

Productive and Sustainable Soil Management Systems

Developing sustainable soil management systems.  Sustainable soil management is a central concern of the National Program on Integrated Agricultural Systems.  Accomplishments for this component are reported in that program s annual report.

Identifying critical soil information for site-specific management.  Site-specific farm management has been defined as an information- and technology-based agricultural management system to identify, analyze and manage site-soil spatial and temporal variability within fields to maximize profitability, while protecting the environment.  Applying fertilizer to crops, based on field averages, results in over fertilizing or under fertilizing some parts of the field.  Site-specific application of fertilizer was applied to sugar beets based on soil tests for each site (variable rate) by researchers in Sidney, Montana.  The variable rate increased sugar beet yields by 2 tons per acre without a decreased sugar content or an increased nitrate content.  This indicates that precision-applied fertilizer, based on crop needs for various locations in the field, can reduce inputs while maintaining beet quality and increasing crop yields.

Assessing and interpreting the effects of soil management on soil quality.  Understanding how to measure, interpret, and use soil quality as an indicator of sustainability was identified by the  National Academy of Sciences as a high-priority need.  NRCS established a Soil Quality Institute, recognizing that traditional measurements of only soil erosion were not sufficient to fully understand the value of soil as a natural resource.  Farmers, sustainable agriculture groups, and many other public and private organizations throughout the United States and around the world have identified soil-quality assessment as an important need.  However, it is important to emphasize that soil quality is not an end in itself as some have suggested, but rather a tool to help quantify the sustainability of various land-use practices through a consistent and definable process.

Researchers in North Dakota and Nebraska determined the status of soil-quality indicators on organic and conventional farms.  There was an average of 22 percent more organic carbon (11,200 pounds per acre) and 20 percent more total nitrogen (900 pounds per acre) on organic farms than on conventional farms.  These results, along with trends in other soil-quality indicators, suggest that  organic production practices have a capacity to improve soil quality.

Scientists at the National Soil Tilth Laboratory in Ames, Iowa, developed a flexible framework for indexing soil quality.  They used the framework to provide preliminary information to organic and sustainable agriculture farmers in the Central Valley of California regarding how their management practices are affecting the soil resource.  Data from the Sustainable Agricultural Farming Systems and Biologically Integrated Farming Systems projects were used to develop a framework for assessing the effects of various land management practices.  Expert opinion, scoring function, and decision-support methods of computing soil-quality indices gave similar results.  This participatory, on-farm research documented that even in the Central Valley, use of compost, cover crops, and other organic matter amendments could increase soil organic matter and improve several soil-quality indicators, compared to conventional soil management practices.

Soil-quality assessment findings from research sites in Iowa, Mississippi, Nebraska, and Oklahoma demonstrated the utility of no-tillage management in maintaining soil quality and conservation benefits when CRP grasslands are returned to cropland for grain production.  This information was disseminated by ARS scientists at Lincoln, Nebraska, via technical publications, presentations, workshops, and meetings with producers.  Through 2000, this project facilitated distribution of over 85 ARS soil-quality test kits and over 140 soil-quality methods books for evaluation by scientists, ecologists, and educators in the United States and over 20 foreign countries.