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Ten years ago, the USDA Agricultural Research Service (ARS) began a series of watershed assessment studies as part of the Conservation Effects Assessment Project (CEAP). In this overview, a decade of research progress in 14 watersheds dominated by rain-fed croplands is reviewed to introduce a special section of this journal issue containing papers describing multiwatershed syntheses. The papers evaluate impacts of agricultural practices on soil quality, stream sediment sources, and the role of climate variability in watershed studies and conservation assessments at the watershed scale. The cross-watershed comparisons help enhance our understanding of emerging conservation technologies in terms of their readiness and suitability for wide-scale adoption. Research from ARS CEAP watershed assessments published during the past 10 years suggests encouraging (1) wider adoption of minimum disturbance technologies to reduce runoff risks associated with applying manure, nutrients, and agrichemicals; (2) adoption of winter cover crops; and (3) a renewed emphasis on riparian corridors to control loads of sediment, phosphorus (P), and other contaminants originating from within (and near) stream channels. The management of agricultural watersheds requires that watershed-scale data can be interpreted and applied in management at the farm scale, and that farm-scale information, including financial and management constraints, can be used to clarify watershed management opportunities and challenges. Substantial research needs remain, including social engagement of agricultural communities, use of multiple conservation practices to account for environmental tradeoffs, improved models to simulate the dynamics of nutrient retention and movement in watersheds, and understanding ecosystem responses to changes in water quality. Moreover, a long-term commitment to understand land use trends, water quality dynamics, climate impacts, and the real effectiveness of precision conservation approaches for improving water quality will help secure agriculture's capacity to provide food, water, and other ecosystem services vital to society. [ABSTRACT FROM AUTHOR]

The MarkTwain Lake/Salt River Basin was selected as one of the USDA Agricultural Research Service benchmark watersheds for the Conservation Effects Assessment Project because of documented soil and water quality problems and broad stakeholder interest. The basin is located in northeastern Missouri within the Central Claypan Region, and it is the source of water to Mark Twain Lake, the major public water supply in the region. At the outlet to Mark Twain Lake, the basin drains 6,417 km² (2,478 m²), including 10 major watersheds that range in area from 271 to 1,579 km² (105 to 609 m²). The basin is characterized by flat to gently rolling topography with a predominance of claypan soils that result in high runoff potential. The claypan soils are especially. vulnerable to soil erosion, which has degraded soil and water quality throughout the ,basin, and to surface transport of herbicides. Results from cropping system best management practice studies showed that no-till cropping systems did not reduce surface runoff compared to tilled systems, and no-till led to increased transport of soil-applied herbicides. A major challenge is the need to develop cropping systems that incorporate herbicides yet maintain sufficient crop residue cover to control soil erosion. Results of the Soil and Water Assessment Tool model simulations showed that the model was capable of simulating observed long-term trends in atrazine concentrations and loads and the impact of grass waterways on atrazine concentrations. Current and future research efforts will continue to focus on best management practice studies, development of needed tools to improve watershed management, and refinements in the calibration and validation of the Soil and Water Assessment Tool model. [ABSTRACT FROM AUTHOR]

Efficient and environmentally acceptable nutrient management requires an understanding of when and at what rates nutrients are accumulated by plants. For graminaceous species, a mathematical procedure involving compound cubic polynomials was previously demonstrated to be useful for evaluating growth and nutrient accumulation patterns. Our objective for this study was to compare dry matter and nutrient accumulation rates for determinate and indeterminate soybean [Glycine max L. (Merr.)] by reanalyzing the original data from five field experiments. Data from a maximum yield research (MYR) experiment that yielded 6.8 Mg ha‐1 provided information for soybean grown with near‐maximum accumulation rates. The high MYR yield resulted from intensive management practices that included high fertilization, high plant population, complete pest control, and timely irrigations to supplement rainfall. The MYR results were compared with rates determined for four non‐MYR studies that yielded from 2.2 to 5.4 Mg ha‐1 in Iowa, South Carolina, and North Carolina. Contrary to patterns found for corn (Zea mays L.) and wheat (Triticum aestivum L.), no consistent, distinct peaks in accumulation rate were observed for soybean. Instead, trends were masked by short‐term variation caused either by responses to environmental variation or by random sampling errors. In addition, computed maximum growth rates for the 6.8 and 5.4 Mg ha‐1 studies were higher than the hypothesized maximum rate of 360 kg ha‐1 d‐1, suggesting either biased sampling or a need to reexamine the theory. These findings lead us to conclude that further research in intraseasonal accumulation patterns for soybean should concentrate on causes for short‐term variation, such as weather patterns, via mechanistic simulation. Further, the data for extremely high yields should be considered cautiously until supporting data are found. [ABSTRACT FROM PUBLISHER]

Examines the impact of site-specific crop management with a center pivot irrigation system on water conservation, plant stress reduction and fertilizer loss reduction in the American Coastal Plains. Modifications on conventional center pivot systems; Requirements for site-specific management of crop production; Features of the water application and irrigations systems.

Precision agriculture has mostly emphasized variable-rate nutrients, seeding, and pesticide application, but at several research sites, variable-rate irrigation equipment has been developed to explore the potential for managing irrigation spatially. The modifications to commercial machines are relatively straightforward, but costly; thus economic analyses have not been positive at current grain price: water cost ratios. However, with increased attention to conservation of water during drought, with increased contention for environmental, recreational, municipal, and industry use, or with regulatory constraints, conclusions regarding profitability or desirability of variable-rate irrigation may change. The objectives of this paper are to: 1) define and describe site-specific irrigation, 2) discuss the opportunities for conservation using site-specific irrigation, 3) present case studies from production and research fields that illustrate these opportunities, and 4) discuss critical research needs to fully implement precision irrigation and thus realize these opportunities for conservation. The opportunities for conservation discussed include situations where non-cropped areas exist in a field for which irrigation can be turned completely off, situations where a reduced irrigation amount provides specific benefits, and finally, situations where optimizing irrigation amount to adapt to spatial productivity provides quantitative benefits. Results from the case studies provide estimates of the potential for water conservation using precision irrigation that range from marginal to nearly 50 percent in single years, and average from eight to 20 percent, depending on the previous irrigation management strategy employed. Critical research needs include improved decision support systems and real-time monitoring and feedback to irrigation control. [ABSTRACT FROM AUTHOR]

The Conservation Effects Assessment Project was established to quantify the environmental impacts of USDA conservation programs. The Conservation Effects Assessment Project involve multiple watershed assessment studies designed to provide a scientific basis for a national assessment. The USDA Agricultural Research Service established 14 research sites—benchmark watersheds—to measure regionally specific environmental quality effects of conservation practices and to improve and validate models used by the USDA Natural Resources Conservation Service for their national assessment. Within each watershed, data were collected and continue to be collected to provide insight into the effects of specific conservation practices implemented under programs such as the Environmental Quality Incentives Prof ram and the Conservation Reserve Program. A data storage and management system, sustaining the Earth's Watersheds-Agricultural Research -Data System (STEWARDS), was developed to provide easy accessibility to these data for analysis. Models were validated using data from many of the watersheds and were shown to be valuable tools for extrapolating the results in a national assessment. The physical process models were also combined with economic models to optimize tradeoffs among environmental and economic objectives of conservation practices. The benchmark watershed studies have begun to identify the effects of selected conservation practices, although additional data are required to provide definitive results. A prototype of a new modular modeling system has been developed that will provide a more powerful tool for future analyses. The initial Conservation Effects Assessment Project findings and products demonstrate progress toward the overall goals of quantifying conservation practice effects and providing tools to transfer the knowledge to points where they are applied under future conservation policy. [ABSTRACT FROM AUTHOR]

Conventional cultivation of claypan soils leads to soil and water quality degradation because of high runoff and associated soil erosion. The Goodwater Creek Experimental Watershed, which is part of the USDA Agricultural Research Service Benchmark Conservation Effects Assessment Project, Watershed Assessment Studies, was established to address these issues. Plot studies have highlighted trade-offs between erosion control and herbicide or nutrient runoff. There is a need for long-term field-scale evaluation of combined practices that reduce sediment, nutrient, and herbicide losses by runoff. A 36 ha field located in Missouri was under a conventional corn (Zea mays L.)-soybean (Glycine max L.) system from 1993 to 2003 with fertilizer application and tillage prior to planting in the spring. A precision agriculture system defined by two main management zones was implemented from 2004 to 2014: wheat (Triticum aestivum L.) and soybean in 60% of the field, and corn and soybean in the remaining 40%. The system included no-till, cover crops, atrazine split-applications based on weed pressure, variable rates of nitrogen (N), and variable rates of fall-applied phosphorus (P). The objective of this study was to compare runoff water quality from the two management systems, based on flow and load duration curves, cumulative distribution functions, and conclusions from replicated plot studies. The precision agriculture system did not affect annual runoff, but it did increase the frequency of low flows. Sediment losses were reduced by 87% as a result of no-till and cover crops. Atrazine and P losses were lower than expected, despite the lack of incorporation into the soil. Atrazine losses were possibly lower because of the wheat area acting as a buffer, greater atrazine adsorption and retention in the field, and faster decay. Dissolved P losses as a fraction of applied remained the same, likely because of greater adsorption and lower runoff risk when applying P. Finally, nitrate-N (NO3-N) losses decreased and resulted in an overall decrease of N losses despite a slight increase of ammonium-N (NH4-N) losses. Explanations included a greater soil water content, a different timing of N applications, and N uptake by cover crops. Building on these successes, an aspirational management system is proposed to further improve on the performance and practicality of the precision agriculture system. [ABSTRACT FROM AUTHOR]

The Soil Vulnerability Index (SVI) was developed by the USDA Natural Resources Conservation Service (NRCS) to identify inherent vulnerability of cropland to runoff and leaching. It is a simple index that relies on the SSURGO database and can be used with basic knowledge of ArcGIS. The goal of this study was to investigate a relationship between constituent (sediment and nutrient) loadings and fraction of the watershed in each SVI class. The SVI maps were developed for each of the seven subwatersheds of the Mark Twain Lake watershed in Missouri, which were similar in soil conditions and climatic variability. The SVI assessment was performed by investigating if the distribution of the SVI for cropland in each subwatershed could help explain measured 2006 to 2010 sediment and nutrient loads better than crop distribution alone. Regression analyses were performed between annual loads of sediment and nutrients exported from the watersheds and a composite number that included either cropland distribution alone, or cropland distribution combined with the SVI. Coefficients of determination and p-values were compared to assess the ability of land use and SVI distributions to explain stream loads. Integrating the SVI in the land cover variable improved the ability to explain constituent loads in the watersheds for sediment, total nutrients, and dissolved nitrogen (N). Regression results with and without the SVI were identical for dissolved phosphorus (P), potentially indicating that SVI was not indicative of dissolved P transport at the current site. Overall, the application of the SVI at watershed scale was not perfect, but acceptable at correctly identifying cropland of greatest vulnerability and linking with transported constituent loads. [ABSTRACT FROM AUTHOR]

Selected watershed studies of the Conservation Effects Assessment Project (CEAP) are reviewed and findings are interpreted from the perspective of potential conservation outcomes due to climate change scenarios. Primary foci are runoff, soil erosion, sediment transport, and watershed sediment yield. Highlights, successes, and challenges with regards to climate change impacts on soil erosion, runoff, and watershed sediment yield are presented. The covered information adds to the existing knowledge base of climate change impacts and provides another piece of information that may be useful in the planning and management of agricultural watersheds; assessment of conservation needs; and development, funding, and implementation of conservation programs. The selected conservation assessment studies include, among others, a thought experiment on the sensitivity of soil erosion, runoff, and sediment yield to changes in rainfall; a computer-based investigation of potential climate change effects on runoff and soil erosion in a southeastern Arizona rangeland; the complex response of northern Mississippi watersheds to runoff variations and channel stabilization measures; the impact of conservation practices and a persistent pluvial period on watershed runoff and sediment yield in Oklahoma; and stream bank erosion during major flooding in Iowa and river corridor management. A study of rainfall-runoff in an north-central Missouri watershed and a curve number analysis in a northern Appalachian experimental watershed are included herein. Findings showed that climate change scenarios of increased precipitation intensity lead to an exponential increase in soil erosion, runoff, and watershed sediment yield, thereby stressing current conservation practices or future practices designed with present day practice standards. This diminishes conservation practice effectiveness and increases sediment supply to the stream network. The sensitive response of the watershed hydrologic system may lead to renewed soil erosion that is large enough to offset the reduction in soil loss achieved by current conservation practices. However, in alluvial-floodplain environments with noncohesive bed and bank material, watershed sediment yield is controlled by channel discharge and energy slope, neither of which is influenced by traditional in-field conservation practices or channel bank stabilization structures. Thus, control of sediment yield will gradually shift in the downstream direction from sediment supply to sediment transport capacity and blur any existing relation between a climate change signal, in-field conservation outcomes, and sediment yield at watershed outlets. Targeting conservation practices to erosion prone areas, expanding conservation coverage, and adapting agronomic practices may be necessary to prevent excessive soil erosion and downstream sedimentation under climate change scenarios that include intensified precipitation. [ABSTRACT FROM AUTHOR]

Targetin g critical management areas (CMAs) within cropped fields is essential to maximize production while implementing alternative management practices that will minimize impacts on water quality. The obj ective of this study was to develop physically based indi ces to identify CMAs in a 35 ha (88 ac) fi eld characterized by a restrictive clay layer occurring within the upper 15 to 100 em (6 to 40 in) and under a corn (Z ea mays L.)-soybean (Glycine max L.) crop rotation since 1991. Thirty-five subareas were defin ed based on slope, depth to claypan (CD), and soil mapping units. The Agricultural Policy/ Environmental eXtender (APEX) model was calibrated and validated from 1993 to 2002 using measured runoff, sediment, and atrazine loads, and crop yields. CMAs were delineated based on simulated subarea runoff, sediment, and atrazine loads. Correlation analysis was performed between simulated output by subarea and physical parameters, including CD, surface satu ra ted hydraulic conductivity (Ksat), and subarea slope (SL). Two indices were developed, the Conductivity Claypan Index (CCI; CD XKsat -7-SL) and th e Claypan Index (CPI; CD -7- SL), to correlate with simulated crop yields, runoff, atrazine, and sediment loads. Together, these indices captured 100% of CMAs for simulated runoff and sediment yield and 60% of CMAs for simulated atrazine in surface runoff, as predicted by APEX. These critical areas also matched lower corn productivity areas . Management scenarios were simulated that differentiated the management of the CMAs from the rest of the field. Indices, such as these, for identifying areas of higher environmental risk and lower productivity could provide obj ective criteria for effective targeting of best management practi ces. [ABSTRACT FROM AUTHOR]

Various land management decisions are based on local soil properties. These soil properties. include average values from soil characterization for each soil series. In reality, these properties might be variable due to substantially different management, even for similar soil series. This study was conducted to test the hypothesis that for claypan soils, hydraulic properties can be significantly affected by long-term soil and crop management. Sampling was conducted during the summer of 2008 from two fields with Mexico silt loam (Vertic Epiaqualfs). One field has been under continuous row crop cultivation for over 100 years (Field), while the other field is a native prairie that has never been tilled (Tucker Prairie). Soil cores (76 × 76 mm [3.0 × 3.0 in]) from six replicate locations from each field were sampled to a 60 cm (24 in) depth at 10 cm (3.9 in) intervals. Samples were analyzed for bulk density, saturated hydraulic conductivity (Ksat), soil water retention, and pore-size distributions. Values of coarse (60 to 1,000 μm [0.0024 to 0.039 in] effective diameter) and fine mesoporosity (10 to 60 μm [0.00039 to 0.0024 in] effective diameter) for the Field site (0.044 and 0.053 m3 m-3 [0.044 and 0.053 in3 in-3]) were almost half those values from the Tucker Prairie site (0.081 and 0.086 m3 m-3 [0.081 and 0.086 in3 in-3]).The geometric mean value of Ksat was 57 times higher in the native prairie site (316 mm h-1 [12.4 in hr-1]) than in the cropped field (5.55 mm h-1 [0.219 in hr-1]) for the first 10 cm (3.9 in) interval. Differences in Ksat values were partly explained by the significant differences in pore-size distributions. The bulk density of the surface layer at the Tucker Prairie site (0.81 g cm-3 [50.6 lb fr-3]) was two-thirds of the value at the Field site (1 .44 g cm-3 [89.9 lb ft-3]), and was significantly different throughout the soil profile, except for the 20 to 30 cm (7.9 to 12 in) depth. These results show that row crop management and its effect on soil loss have significantly altered the hydraulic properties for this soil. Results from this study increase our understanding of the effects of long-term soil management on soil hydraulic properties. [ABSTRACT FROM AUTHOR]

Streams and drinking water reservoirs throughout the claypan soil region of Missouri and Illinois are particularly vulnerable to herbicide contamination from surface runoff during spring. This study follows a plot-scale study conducted on claypan soils to quantify and compare edge-of-field herbicide losses from a corn-soybean rotation under mulch tillage and no-tillage systems. The objectives of the present study were to confirm at field scale (34.4 ha [85 ac] and 7.8 ha [19.3 ad) the plot-scale findings (0.37 ha [0.92 ad) on the effects of tillage and herbicide incorporation on herbicide transport and to evaluate the applicability of plot-scale exponential models in calculating atrazine and metolachlor concentrations as a function of application rate, runoff volume, and days after application at the field scale. Herbicide transport to surface runoff was studied (1997 to 2001) from two fields with cropping systems similar to those on the plots. Field 1 (F1) was a mulch tillage corn-soybean rotation system with surface-applied herbicides, which are then incorporated. Field 2 (F2) was a no-tillage corn-soybean rotation system with surface-applied herbicides that were not incorporated. During each event, runoff volumes were measured, and water samples were collected and analyzed for atrazine and metolachlor concentrations. The percentages of applied atrazine and metolachlor transported to surface runoff from no-tillage (P2) were 3.2 and 2.0 times those from mulch tifiage (F1), respectively. Throughout the study period, 1.0% and 3.2°/ of total atrazine and 1.0°/ and 2.0% of total metolachlor applied to F1 and F2 were lost to surface runoff, respectively. Similar to the results from the plot study, the model performed well iii calculating field atrazme concentrations from both mulch and no-tillage systems with coefficient of determination ⩾ 0.70 and Nash and Sutciffe efficiency ⩾ 0.64. However; model performance in calculating metolachlor concentrations was poor for both tillage systems (Nash and Sutcliffe efficiency < 0.35). When the model was modified to include cumulative temperature instead of days after application, performance in calculating atrazine and metolachlor concentrations was improved, particularly metolachlor concentrations at the field scale. The coefficient of determination and Nash and Sutciffe efficiency values for metolachlor relative to cumulative temperature and days after application were 0.62 and 0.61 versus 0.41 and -0.13 for F1, and 0.73 and 0.55 versus 0.53 and 0.34 for F2, respectively. Overall, the study confirmed plot-scale results that atrazine concentrations and losses were greater for a no-tillage system than for a mulch-tillage system, in which the herbicide was incorporated. The study also showed that the model developed using plot-scale data was applicable in calculating concentrations at the field scale, particularly for atrazine. [ABSTRACT FROM AUTHOR]

Plant water and nutrient use for claypan soils are restricted by an argillic horizon (clay content > 500 g kg-1) that typically occurs 20 to 40 cm (8 to 16 in) below the soil surface. Identifying water infiltration characteristics for claypan soils under different management provides crucial information needed to optimize crop management and estimate watershed hydrology. The objectives of the study were: 1) to evaluate the influence of long-term annual cropping system (ACS) and perennial cropping system management (PCS) [such as Conservation Reservation Program (CRP) and hay crop] on water infiltration, and 2) to examine relationships between apparent soil electrical conductivity (ECa) and other claypan soil properties with water infiltration parameters. The effects of the ACS and PCS management on water infiltration parameters were evaluated using ponded water infiltration measurements in the field. Water infiltration parameters were estimated using the Green-Ampt infiltration equation. Apparent profile soil electrical conductivity was obtained using an EM38 sensor. Analysis of variance and orthogonal contrasts were used to determine effects of management treatments on water infiltration parameters and associated soil properties. Soil organic carbon and aggregate stability were significantly (P < 0.05) improved after 12 years of CRP management compared to 12 years of ACS management. Antecedent soil water content and ECa were lower and water infiltration was greater for PCS than for the ACS. For a hay crop treatment (PCS), water infiltration was greatly improved when compared to any ACS or other PCS management treatments. Antecedent soil water content and soil organic carbon were significantly correlated with the water infiltration parameters. Soil ECa was significantly correlated with infiltration-estimated saturated hydraulic conductivity (Ks). This relationship may be useful for mapping spatially-variable water infiltration within fields. In summary, PCS contributed to improved water infiltration as well as to increased soil organic carbon and soil aggregate stability. Soil ECa may be useful for characterizing management influence on water infiltration without labor intensive sampling. [ABSTRACT FROM AUTHOR]

From site-specific crop and soil information collected from a Missouri claypan soil field for over a decade (1993 to 2003), we implemented a precision agriculture system in 2004 with a goal of using site-specific management practices to improve farming profitability and conserve soil and water resources. The objectives of this study were to: 1) show how precision crop and soil information was used to assess productivity, and 2) document the development of the precision agriculture system plan for implementation on the field, relying on this productivity assessment and conservation opportunities. The study field was uniformly managed from 1991-2003, during which time variability in soil and landscape parameters and yield were measured, and causes of yield variation were determined. Profitability maps were created from yield maps and production records. Because erosion has degraded the topsoil on shoulder and side slope positions of major portions of this field, corn-soybean management practices have rarely been profitable in these shallow topsoil areas. We prioritized these and other results, and developed the precision agriculture system plan. The plan, described in detail, is aimed at increasing profitability while improving water and soil quality. [ABSTRACT FROM AUTHOR]

A comprehensive approach to achieving sustained crop productivity and profitability requires implementation of conservation systems that simultaneously consider soil and water quality. The objectives of this study were to: 1) assess long-term surface and groundwater quality in a conventionally managed field; 2) assess long-term changes in soil quality under a conventional management field; and 3) use this assessment to support development of the precision agriculture system presented in the companion paper. The study site was a 36-ha (89 ac) field in the Central Claypan Area of northeastern Missouri. The field was managed in a corn-soybean rotation using mulch tillage and soil incorporated fertilizer and pre-emergence herbicide inputs for 13 years (1991 to 2003). In general, agrichemical leaching to groundwater was minimal, but the existing management system negatively impacted the quality of surface runoff in five of the nine years reported. Preliminary spatial assessment indicated that the northern half of the field has been the main source of herbicides, nutrients, and sediment transported in surface runoff from this field. Topsoil loss and, therefore, decreased depth to the claypan from historic erosion of the field was a key soil quality indicator related to limitations in crop productivity. Spatial variability in soil loss over the last 150 to 200 years controls the soil quality, water quality, and crop productivity patterns currently observed within this field. Therefore, spatial variability in soil erosion, or a surrogate measure such as depth to claypan, serves as a useful basis for the development of a comprehensive precision agriculture system. [ABSTRACT FROM AUTHOR]

Soils that naturally have a significant runoff component because of low permeability, such as claypans or steep slopes, are especially susceptible to herbicide losses in runoff. For these soils, seasonal losses as impacted by management practices are not well quantified. The objectives of this study were to evaluate the effect of three cropping systems on herbicide loss in surface runoff and develop a model that calculates herbicide concentration. Cropping System 1 (CS1) was a mulch tillage corn-soybean rotation system with herbicides surface applied then incorporated. Cropping System 2 (CS2) was a no-till corn-soybean rotation system with herbicides surface applied and not incorporated. Cropping System 5 (CS5) was a no-till corn-soybean-wheat rotation system with split herbicide application in 1997 and 1999 and no incorporation. The study was conducted on 0.37 ha (0.92 ac) plots equipped with flumes and automated samplers. During each runoff event, runoff volumes were measured, and water samples were collected at equal flow increments and analyzed for atrazine [2-chloro-4-ethylamino-6-isopropylamino-s-triazine] and metolachlor [2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-methoxy-1-methylethy/acetamide]. Averaged over years, atrazine and metolachlor losses from CS2 were 2.2 and 1.6 times those from CS1, respectively. Atrazine loss to surface runoff from CS1, CS2, and CS5 accounted for 1.6, 2.5, and 5.7% of the total atrazine applied, respectively. Metolachlor loss to surface runoff accounted for 1.8, 2.0, and 2.0% of the total applied for the three cropping systems. Herbicide concentrations were extremely high in the first runoff event measured after application, particularly when it occurred within a few days after application. A generalized model was developed to account for the effects of time after application, runoff volume, and application rate on herbicide concentration in runoff. Overall, the study showed that accounting for incorporation, split application, runoff volume, and timing of runoff events relative to the day of application can increase the confidence in calculations of the amount of herbicide transported to surface runoff. [ABSTRACT FROM AUTHOR]