Journal of Soil and Water Conservation

Online ISSN: 1941-3300
Print ISSN: 0022-4561
Publications
Weighted Probit Results for Adoption of BMPs in Beef Cattle Production, Louisiana.
Continued.
Weighted Probit Results for Willingness to Adopt a Rotational Grazing System
Factors affecting cattle producers' adoption of best management practices (BMPs) are examined using probit analyses. Results show that in situations such as when the farm includes more enterprises, the farmer has had contact with Natural Resources Conservation Service personnel at least once within the past year, the farmer holds a college bachelor's degree, the percentage of income from beef cattle production is higher, or the operation includes hilly land, the likelihood of BMP adoption is greater. Having a greater number of other agricultural enterprises and having a greater percentage of income from the cattle operation were significant factors in the adoption of companion practices. Results of this study suggest changes in formulating future environmental policies associated with pasture-based beef cattle production.
 
The study area and watershed delineations 
Annualized social costs (in million dollars)
Area of practices (existing area not applicable for nutrient management)
Nonpoint source pollution in intensively managed agricultural landscapes is of great concern to the general population, farmers and policymakers, as it impacts local water quality and can have large downstream effects, as in the case of hypoxia in the Gulf of Mexico. In this study, we outline a methodology to simultaneously assess economic costs and water quality benefits associated with the hypothetical placement of a broad set of conservation practices. The study, performed for the Iowa Department of Natural Resources, assesses thirteen major subbasins in Iowa by interfacing economic models with the Soil and Water Assessment Tool model. The conservation practices analyzed include land set-aside, terraces, grassed waterways, contouring, conservation tillage, and a simple nutrient reduction strategy. Annual costs range from $300 to $597 million. Predicted sediment, total phosphorus (P), and nitrate decreases range from six to 65 percent, 28 to 59 percent, and six to 20 percent, respectively, relative to the baseline.
 
The organic C concentration of surface soil can be used in agricultural fields to vary crop production inputs. Organic C is often highly spatially variable, so that maps of soil organic C can be used to vary crop production inputs using precision farming technology. The objective of this research was to demonstrate the feasibility of mapping soil organic C on three fields, using remotely sensed images of the fields with a bare surface. Enough soil samples covering the range in soil organic C must be taken from each field to develop a satisfactory relationship between soil organic C content and image reflectance values. The number of soil samples analyzed in the three fields varied from 22 to 26. The regression equations differed between fields, but gave highly significant relationships with R2 values of 0.93, 0.95, and 0.89 for the three fields. A comparison of predicted and measured values of soil organic C for an independent set of 2 soil samples taken on one of the fields gave highly satisfactory results, with a comparison equation of % organic C measured + 1.02% organic C predicted, with r2 = 0.87.
 
Pay-Offs and Classification of Risk Aversion 
Risk Aversion and Adoption of Soil Conservation  
Frequencies of Farmers' Responses to Risk Preferences 
Descriptive Statistics for the Multinomial Logit Model Variables 
Marginal Effects on Probability of Choice of Soil Conservation 
Soil degradation is one of the most serious environmental problems in the highlands of Ethiopia. The prevalence of traditional agricultural land use and the absence of appropriate resource management often result in the degradation of natural soil fertility. This has important implications for soil productivity, household food security, and poverty. Given the extreme vulnerability of farmers in this area, we hypothesized that farmers’ risk preferences might affect the sustainability of resource use. This study presents experimental results on the willingness of farmers to take risks and relates the subjective risk preferences to actual soil conservation decisions. The study looks at a random sample of 143 households with 597 farming plots. We found that a high degree of risk aversion significantly decreases the probability of adopting soil conservation. This implies that reducing farmers’ risk exposure could promote soil conservation practices and thus more sustainable natural resource management. This might be achieved by improving tenure security, promoting access to extension services and education, and developing off-farm activities that generate income.
 
Annual Economic Budget, Baseline Solution
Estimated Value of the Opportunity Cost of Time Devoted to Managed Drainage with Boards Installation and Removal Allowed During Dec. 6 -April 25
Sensitivity Analyses with Respect to Fuel and Nitrogen Prices
Federal conservation programs included in various farm bills with regard to controlled drainage establish the context for further actions to reduce nutrient pollution in the Gulf of Mexico. This study calibrates the financial incentives presented to farmers regarding the adoption of controlled drainage technology that improves downstream drainage water quality by using a representative farm-planning model. The results show that controlled drainage can be more profitable than free-flowing whole-farm field drainage as long as the minimum yield advantage with controlled drainage is 2% with subsidy and 4% without subsidy respectively. However, even with a 10% yield advantage due to controlled drainage, the lack of labor during key periods may limit adoption of controlled drainage technology.
 
In a recent study, Pope, Bhide, and Heady [10] found that conservation tillage, when combined with contour farming, was the most economical means of reducing erosion on most Iowa soils. They continued by indicating that on some of the more erosive soils, less intensive crop rotations, strip cropping, or terracing may be required if soil loss is to be reduced to tolerable levels. However, the soils where terracing may be a viable alternative and a measure of the costs associated with the adoption of this soil-conserving method were not completely analyzed. As a result, a companion study aimed at determining the break-even costs of installing terracing on Iowa's soils has been conducted. The general purpose of this study is to determine, from a farmer's perspective, the economic profitability of terracing in Iowa compared to other means of controlling soil erosion.
 
Economists have long advocated the use of market mechanisms as a means to improve environmental quality at minimum cost. Voluntary water purchase programs are an example of such a policy. This paper examines the structure and performance of two water right purchase programs operating in Nevada: the Truckee River Water Quality Agreement and the Lahontan Valley purchase program administered by the U.S. Fish and Wildlife Service, the State of Nevada and the Nature Conservancy. Statistical analysis of the latter program indicates that it is performing efficiently. Notably, personal factors prompt water sales, and the least productive rights (e.g., those appurtenant to poor soils) are sold to the government. Concluding comments offer suggestions about ways to improve program performance, including allowing the sale of fractional water rights.
 
The C content was not consistently different between tillage treatments below the 15-cm (5.9-in) depth. Improved equipment, management, and soil quality allowed conservation tillage plots to produce greater yields during years 9 to 14. Long-term conservation tillage of row crops appears to be a viable method of increasing the C content of sandy SCP soils even when soybean and cotton are part of the rotation.
 
Beasley Lake Watershed, Mississippi, one of 14 USDA-ARS benchmark watersheds in the national CEAP research effort, is typical of topography and cropping systems in the Mississippi Delta Region of the United States. Beasley Watershed, formerly a component of the Mississippi Delta Management Systems Evaluation Area (MD-MSEA) Project, drains into an oxbow lake that has been monitored since 1995. Environmental assessments in support of CEAP have continued since 2003 with termination of the MD-MSEA project. When evaluations began in 1995, 79% of the 915-ha watershed was in row crop agriculture and the remaining area (21%) included a 25-ha lake and a 135-ha riparian forest. From 1995 to the present, agricultural activities in the watershed have evolved from predominantly cotton and soybean (63.3% and 12.2% of watershed area, respectively) production to a mixture of row crops (66.5% of total watershed area) and Conservation Reserve Program (CRP) (12.4% of total watershed area) in 2005. In contrast to 1995, the 2005 cropped land consists of 243 ha soybeans and 81 ha cotton. This paper reports on CEAP research in Beasley Watershed, including continued monitoring of lake limnology, evaluating runoff from edge-of-field sites with various management practices, quantifying management effects in areas that have shifted to CRP, compiling watershed data from the past years of assessment, and modeling.
 
Agricultural policy implies new future scenarios for agricultural landscapes each time a new federal farm bill or emergency aid to farmers is debated. Future landscape scenario studies can suggest policies that could achieve specific goals or make the implications of proposed policy apparent. This paper compares the 1994 landscape with three alternative future landscape scenarios for two Iowa Corn Belt agricultural watersheds. Each alternative emphasizes different ecological, hydrological, and and crop production goals. USEPA Science to Achieve Results (STAR) program Peer Reviewed http://deepblue.lib.umich.edu/bitstream/2027.42/49342/1/JSWC57_Nassauer.pdf
 
The erosive power of rainfall can be expected to change as climate changes. Such erosive changes are likely to have significant impacts on local and national soil conservation strategies. This study uses results of climate change scenarios from two coupled Atmosphere-Ocean Global Climate Models to investigate the possible levels and patterns of change that might be expected over the 21st century. Results of this study suggest the potential for changes in rainfall erosively across much of the continental United States during the coming century. The magnitude of change (positive or negative) across the country over an 80 year period averaged between 16-58%, depending upon the method used to make the predictions. Some areas of the country showed increases and others showed decreases in erosivity. Spatial distributions of calculated erosivity changes indicated areas of both consistency and inconsistency between the two climate models.
 
River valleys have been influenced by sediment derived from agricultural erosion and channel straightening intended to hasten flood routing. Post-settlement alluvium (PSA) has been little documented in tile-drained areas of the upper Midwest, where agricultural settlement began around 1850, and few soils are highly erodible. This study investigated channel movement and PSA accumulation along the South Fork of the Iowa River. Channels of the South Fork and tributary Tipton Creek were digitized using rectified aerial photographs taken in 1939 and 2002. Soil cores were collected along valley-crossing transects to determine PSA extent and thickness. Within 80 m (262 ft) of the South Fork, PSA averaged 0.78 m (30.7 in) thick and 85% frequency of occurrence. Beyond 80 m, PSA decreased below 50%. Within 43 m (141 ft) of Tipton Creek, PSA averaging 0.58 m thick occurred with 75% frequency. An estimated 9.2 x 10⁶ Mg (10.2 x 10⁶ tn) of PSA is stored along these valleys, representing 156.6 Mg ha-1 (69.8 tn ac-1) of soil eroded from uplands since settlement. The volume of PSA is equivalent to 11 mm (0.44 in) runoff from the watershed. The valley's flood-storage capacity has been reduced by 5.1 x 10⁶ m3 (4,123 ac ft), considering pore space of the PSA. Modern flooding events are accordingly exacerbated by accretion of agricultural sediment, compared to presettlement river conditions. Channels were straightened in response to local flood events, which reduced stream length by 10% and hastened routing to the Iowa River. Design of river restoration projects should take account of fluvial processes and how these processes are responding to historical sedimentation and channel straightening.
 
Spatial variability in crop yield can cause large within-field differences in fertilizer N removal. Cereal winter cover crops can trap the residual N, but their ability to do so partially depends on the soil conditions that determine growth. Our objective was to determine site-specific effects of soil variation on biomass and N accumulation by a wheat (Triticum aestivum L.) cover crop that was grown after a droughted corn (Zea maize L.) crop. In 1993, corn was grown with an applied fertilizer N rate of 129 kg ha-1 on an 8-ha field near Florence, SC. Nitrogen removed by grain at 10 locations (representing six soil types) ranged from 14 to 41 kg N ha-1. Wheat was planted in November without additional fertilizer N. Wheat biomass and N content were measured on 15 March, 15 April, and 14 May. Inorganic soil N to a depth of 90 cm was measured on 22 March 1994 and ranged from 49 to 95 kg ha-1. By mid-March, wheat accumulated 49% of its total N but only 14% of its biomass of that measured in May. After mid-April significant increases in N accumulation occurred at only two sites. Biomass accumulation by mid-May ranged from 2032 to 7914 kg ha-1 and N accumulation ranged from 19 to 52 kg ha-1. The amount of variability among sites for wheat biomass was greater than the amount of variability among sites for N. Variation for wheat biomass and N accumulation within soil map units was similar to the amount of variation among soil map units. Most of the variability was caused by differences in sites within and among soils associated with depression areas. Around these depression areas, site-specific management of N inputs appears more effective than cover crops at reducing N losses to the environment. Away from these areas, cover crops should be predictable and reliable in trapping N and increasing soil organic matter.
 
The resultant calibration parameter values and simulation accuracy of hydrologic models such as the 2005 Soil and Water Assessment Tool (SWAT2005) depend on how well spatial input parameters describe the characteristics of the study area. The objectives of this study were to (1) investigate the effect of soils dataset resolution (State Soil Geographic Database and Soil Survey Geographic Database) on SWAT2005 streamflow simulation performance and calibration parameters using four precipitation datasets and (2) determine the best combination of soil and precipitation datasets for the Cobb Creek, Lake Creek, and Willow Creek subwatersheds within the Fort Cobb Reservoir Experimental watershed, Oklahoma. SWAT2005 was calibrated and validated for streamflow for the three subwatersheds using the State Soil Geographic Database and the Soil Survey Geographic Database for each of the four available precipitation datasets with different spatial resolutions. The four sources of rainfall data included the National Weather Service's network of Cooperative Observer Program weather stations, statewide Oklahoma Mesonet, USDA Agricultural Research Service's weather station network (MICRONET), and National Weather Service Next Generation Radar (NEXRAD) precipitation estimates. The model performance was assessed using the Nash-Sutcliffe efficiency coefficient and percent bias statistics. During both the calibration and validation periods, there were no significant differences in the model monthly performance statistics between the higher resolution Soil Survey Geographic Database and the lower resolution State Soil Geographic Database across subwatersheds, irrespective of the rainfall dataset used. However, the model performed better when the NEXRAD and MICRONET precipitation datasets were used. There were slight to large differences in the resultant calibration parameter values depending on the calibration parameter, the precipitation data used, and the subwatershed. Large differences in the simulated surface runoff and deep aquifer recharge due to soils dataset resolution could lead to significant differences in the simulated water quality components such as sediments and nutrients. This is important because significant differences in simulated sediments and/or nutrients could lead to significantly different outcomes in terms of the impacts of a given conservation practice for studies like the Conservation Effects Assessment Project. Due to the lack of measured data to validate the simulated water balance components, it was recommended to use both the fine and coarse resolution soil datasets in combination with the finer spatial resolution precipitation datasets and the simulated water balance components of interest reported as a range.
 
Variogram properties for erosion estimates, soil properties, and yield.
Total carbonate content (transformed values) in top 15 cm of soil as a function of field position. Carbonate contents ranged from 0 to 26 percent by weight. Carbonate contents are highest in shoulder slope positions where long-term tillage has exposed calcareous subsoil and lowest in areas of high soil deposition.
Pearson correlation coefficients for erosion estimates and soil properties. Values in bold indicate significance at the 0.0001 level.
Intensive tillage moves large quantities of soil, resulting in a pattern of soil redistribution where topsoil is depleted from convex slope positions and deposited in concave positions. In these experiments, the variation in erosion estimates, properties of the surface soil, and crop yield (four years) were determined in an undulating landscape that is subject to annual moldboard plowing. Results indicated that areas with high tillage erosion (shoulder slope positions) had high inorganic carbon contents in the surface soil due to the incorporation of calcareous subsoil material. Wheat yields in 2000, 2001, and 2003 were lowest in these areas, demonstrating yield reductions of 50 percent or more. Conversely, wheat yields were highest in areas in which soil translocation by tillage and water results in a net deposition of soil (depressions). These areas had a deeper A horizon, and the surface soils had higher organic carbon contents, lower pH and lower inorganic carbon contents. Soybean yields in 2002 did not show a strong dependence on location within the landscape. These results indicate that the observed variation in crop yield in undulating landscapes may be significantly influenced by removal of topsoil through repeated intensive tillage, and point to opportunities for landscape restoration to reduce yield losses.
 
Conservation tillage is a commonly adopted best management practice for improving soil quality and reducing erosion. However, there are currently no methods in place to monitor conservation tillage adoption at the watershed scale. The primary objective of this study was to evaluate the usefulness of Landsat TM data as a tool to depict conservation tillage in a small Coastal Plain watershed. Satellite imagery was used to calculate four commonly used indices: Normalized Difference Vegetation Index, Crop Residue Cover Index, Normalized Difference Tillage Index, and the Simple Tillage Index. Ground truth data consisted of a windshield survey, assigning each site a tillage regime (conventional or conservation tillage) at 138 locations throughout the watershed and surrounding areas. A logistical regression approach was used on two subsets of the data set (n = 20 or n = 44) to determine the influence of the number of ground control points on the success of modeling the occurrence of conservation tillage. The most accurate model was re-applied to the satellite image and evaluated using an independent sample of 94 survey sites. Results indicate that the normalized difference tillage and simple tillage indices performed best, with an overall accuracy of 71% and 78% for models developed using n = 20 and n = 44 sample locations, respectively. Errors were typically in the form of commission. Results are encouraging and suggest that currently available satellite imagery can be used for rapid assessment of conservation tillage adoption using minimal a priori information.
 
C over crops have been defined as crops grown to protect the soil from erosion losses and losses of nutrients via leaching and runoff (Reeves 1994). This definition was expanded in the Encyclopedia of Soil Sciences to those crops that are grown for improving soil, air, and water conservation and quality; nutrient scavenging, cycling and management; in-creasing populations of beneficial insects in integrated pest management; and/or for short-term (e.g., over-winter) animal-cropping grazing systems (Delgado et al. 2006). A detailed review on the use of winter cover crops for weed suppression and integrated pest management was pre-sented by Dabney et al. (2001). Several researchers have reported the benefits of cover crops to reduce sediment off-site transport (Frye et al. 1985; Mutchler and McDowell 1990; Holderbaum et al. 1990; Bilbro 1991; Langdale et al. 1991; Decker et al. 1994; Dabney 1998; Delgado et al. 1999). Additionally, several studies have reported the impacts of cover crops increasing nutrient use efficiencies (Lal et al.
 
Peer Reviewed http://deepblue.lib.umich.edu/bitstream/2027.42/49347/1/JSWC_1989.pdf
 
Agricultural sustainability in China, especially in the North China Plain, is highly dependent on water resource availability. Land management has changed dramatically in this region since the 1970's when a more intensive practice of winter wheat (Triticum aestivum L.) and summer corn (Zea mays L.) in one-year rotation started causing excessive exploitation of groundwater to meet crop water needs for high yield productivity. Over fifty percent of the area in the northwestern region of the North China Plain is irrigated using groundwater. Over ninety percent of Luancheng Xian county is in a groundwater-irrigated winter wheat - - -corn rotation. In addition the irrigation management practices, agricultural management practices, soil textural classes (mostly loam soils) and climate are similar throughout the Northwestern North China Plain and the Luancheng Xian county. Our objectives were to identify whether land use is a factor contributing to groundwater table decline in Luancheng Xian county of the North China Plain and to use long term small plot studies from 1998 to 2002 to evaluate the potential of limited irrigation based on wheat stage of growth as a viable water-saving practice to reduce consumptive use and stabilize the groundwater table. Assessment of groundwater resources for the Luancheng Xian county found that groundwater levels have been dropping at a rate of 0.8 m yr-1 (31.52 in yr-1) (P < 0.001). This occurred during a time of significantly lower precipitation that explained about 91 percent of the groundwater depletion rate (P < 0.001). The drop in groundwater levels was also correlated (r2 = 0.71) with the increased area planted to wheat (P < 0.001). At this current rate of groundwater use, the resource will be depleted within three decades. A more efficient management system that increases water use efficiency or amount of grain produced per unit of water use is needed for sustainability of the cropped areas. We found that irrigation scheduling based on wheat stage of growth can significantly increase water use efficiency when we target application of two key 60 mm (2.36 in) irrigation events at the jointing and heading stages of growth when compared to traditional irrigation management practices that use four irrigation events (240 mm or 9.46 in) (P < 0.05). Although simulated Penman-Monteith evapotranspiration from 1998 to 2002 was significantly correlated with measured values (P < 0.001), Penman-Monteith evapotranspiration values were higher than evapotranspiration measured with weighing lysimeters (P < 0.05). Our 1998 to 2002 studies suggest that there is potential to use stage of growth and water budget models for irrigation scheduling in the Northwestern North China Plain and cut water use by nearly fifty percent without significantly reducing grain yields. It is imperative that these practices tested in small plots now be demonstrated in commercial applications to conserve groundwater resources and maintain agricultural sustainability needed to feed China's increasing population.
 
Agricultural practices that incorporate grazed winter wheat and associated summer management are vital to the rural economy of the southern Great Plains. In regions where high intensity, late summer storms can occur, limited information exists about the impact of these practices, including summer fallow and dual-cropping summer fields, on infiltration. This study was designed to determine the effects of two winter wheat management strategies: winter wheat with summer fallow and winter wheat with summer legumes simultaneously with two grazing treatments (grazed and ungrazed) on steady-state infiltration rates. Four pastures were planted in conservation winter wheat (Triticum aestivum L.) and grazed over winter when possible from November to March and graze-out from March to May from 1998 to 2002. A dual-cropping management strategy that incorporated summer legumes, Korean Lespedeza (Lespedeza stipulacea Maxim) and Soybean (Glycine max), was replicated on two of the pastures, while the other two pastures utilized summer fallow. A rainfall simulator calibrated to represent late summer, high intensity (1.67 mm/min) summer storms was used to determine the parameters: time to achieve steady-state conditions (Tss), steady-state infiltration (SSI) rates, and percent of applied rainfall infiltrated at steady-state conditions (%ss).These parameters were shown to be significantly (P < 0.10) impacted by the grazing practices in all instances and the management practices associated with winter wheat in some cases. Grazed winter wheat utilizing summer fallow had the lowest infiltration rate with 0.91 mm/min along with the shortest Tss (19 min) and the lowest %ss (56%). Grazed summer legumes and ungrazed summer fallow displayed similar infiltration parameters (SSI = 1.47 and 1.33 mm/min, Tss = 28 and 30 min, %ss = 81% and 81%, respectively) and ungrazed summer legumes had the least impact to the infiltration with a SSI rate of 1.59 mm/min, Tss of 37 min and %ss of 88%. Understanding the mechanism of interaction between late summer storms and summer management practices will lead to formulation of larger scale mitigation strategies to reduce erosion and enhance capture of precipitation and runoff.
 
Location of the study area, erosion pin sites and badlands. See text regarding the two raingauge sites 
Rates of erosion from erosion pin monitoring on badland areas. Negative values denote accumulation
To the European eye, the Karoo is an ancient landscape untouched by major climate change or glaciation and evolving through erosional processes since deposition of Jurassic rocks, uplift, and the break up of Gondwana about 180 million years ago (McCarthy and Rubidge 2005). This break up marked the end of ~300 million years of sedimentation, largely under arid conditions, and a ~2 million year episode of violent volcanic eruptions and the outpouring of basaltic lava covering virtually the whole of southern Africa. Since this time, the interior of South Africa has been dominated by erosion (McCarthy and Rubidge 2005). The evidence of relatively recent landscape degradation is ubiquitous and has been noted in reports, diaries, and articles for over 100 years (Hoffman and Ashwell 2001; Hoffman et al. 1999; Beinart 2003). In many respects, the situation is similar to semiarid landscapes in the Midwestern United States and in Australia. Gully systems and, in some cases, badlands have been assigned to the influence of European farming systems and in particular to the introduction of large numbers of domesticated sheep and cattle, thus destabilizing hillslopes and impacting rivers (Patton and Schumm 1975; Fanning 1999)
 
AnnAGNPS simulation of current condition of the watershed (average annual results from 1996 to 2003).
The Annualized Agricultural Non-Point Source (AnnAGNPS) model has been developed to quantify watershed response to agricultural management practices. The objective of this study was to identify critical areas where conservation practices could be implemented and to predict their impact on Beasley Lake water quality in the Mississippi Delta using AnnAGNPS. Model evaluation was first performed by comparing the observed runoff and sediment from a US Geological Survey gauging station draining 7 ha (17 ac) of Beasley Lake watershed with the AnnAGNPS simulated runoff and sediment. The model demonstrated satisfactory capability in simulating runoff and sediment at an event scale. Without calibration, the Nash-Sutcliffe coefficient of efficiency was 0.81 for runoff and 0.54 for sediment; the relative error was 0.1 for runoff and 0.18 for sediment, and the Willmott index of agreement was 0.94 for runoff and 0.80 for sediment. The quantity of water and sediment produced from each field within the Beasley Lake watershed, quantity of water and sediment reaching Beasley Lake, and the potential impact of various USDA Natural Resources Conservation Service conservation programs on water quality were then simulated. High sediment-producing areas for nonpoint source pollution control were identified where sediment loads could be reduced by 15% to 77% using conservation practices. Simulations predicted that converting all cropland to no-till soybeans (Glycine max [L.] Merr.) would reduce sediment load by 77% whereas no-till cotton (Gossypium hirsutum L.) would reduce it 64%. The approach taken in this study could be used elsewhere in applying AnnAGNPS to ungauged watersheds or watersheds with limited field observations for conservation program planning or evaluation.
 
Now, more than ever, we need solutions to the complex challenges of meeting the nation’s food, fiber, feed, and fuel needs while simultaneously enhancing the environment. As agriculture strives to meet future production goals including new demands for bioenergy, both our agricultural ecosystems and our natural resources are likely to face unprecedented pressures and levels of intensity. The challenge of protecting and enhancing envi
 
In artificially drained agricultural areas, dredging of drainage ditches is often necessary to ensure adequate field drainage. Stream-simulator (fluvarium) experiments were performed to evaluate the potential of associated bed material changes to impact water column concentrations of atrazine, metolachlor, and glyphosate. In the first experiments, water having high herbicide concentrations flowed across bed sediment collected from a ditch immediately before or after dredging. Afterward, water having initially zero herbicide concentrations flowed across these sediments. Results indicate that the bed sediments remaining after dredging, which had coarser texture and lower organic matter, may contribute to overall higher water herbicide levels in the short term by removing significantly less glyphosate from contaminated water and contributing marginally higher sustained levels of herbicide to uncontaminated water, applicable where sediments exhibit similar dredging characteristic effects. In this case, dredging when herbicide levels are expected to be lowest can help minimize increased transport of some herbicides.
 
Excerpt The National Oceanic and Atmospheric Administration (NOAA) National Weather Service (NWS) forecast offices discontinued issuing their locally tailored agricultural weather forecasts in 1996 as a result of reduced budgets and mounting political pressure to avoid competing with private industry in provision of application-specific forecasts (NOAA NWS 1995). Commercial forecast services did and do exist, but two obstacles preclude widespread use by many agricultural and natural resource managers in the United States: the expense, and a lack of confidence that they offer good value for the expense. At the same time, with the exception of the few rural radio stations that cater to agricultural interests, commercial media tend to concentrate on weather and climate issues important to their metropolitan markets. This situation has left many resource managers and agricultural producers underserved when it comes to forecasts appropriate to their decision support needs. However, the political tides have turned relative to commercial forecasts, and NOAA has gone through a cultural sea change. For more than a decade, NOAA has funded a range of exploratory research and focused workshops, originally to determine why their climate forecasts were not more widely used, and how they could or should be used. These efforts have grown…
 
Excerpt Reducing concentrations of carbon dioxide (CO2) and other greenhouse gases (GHG) in Earth's atmosphere is identified as one of the most pressing modern-day environmental issues (IPCC 2007). As a signatory country to the United Nations Framework Convention on Climate Change (UNFCCC), the United States is actively engaged in a critical international effort to find solutions to the problems posed by climate change. Agriculture, in addition to being affected by the climate, contributes to climate change through its exchanges of GHG with the atmosphere. Thus, the management of agricultural systems to sequester atmospheric CO2 as soil organic carbon (SOC) and to minimize GHG emissions has been proposed as a partial solution to the climate change problem. In this paper, we discuss the potential role of agriculture in the United States to mitigate climate change through sequestration of carbon (C). We also identify critical knowledge gaps where further research is needed. Carbon enters terrestrial ecosystems, including agriculture, through photosynthesis by green plants that assimilate CO2 and fix it into organic forms (figure 1). Some C eventually enters the soil, where its subsequent cycling and storage among SOC and soil inorganic carbon (SIC) pools determine its residence time and ultimately its return back…
 
Phosphorus (P) is an important input for economic crop and livestock production systems. Excessive losses of P from agricultural systems to surface waters can accelerate eutrophication and degrade water quality. This paper reviews the behavior of P in agricultural soils and discusses the transport of P from land to water. The forms, measurement, and sorption processes of P in both soil and water are discussed. Soil test P, the most common soil P analysis, is described relative to other forms of soil P and its use for agricultural and environmental purposes is explained. Loss of soil P to water can occur in particulate forms with eroded surface soil and in soluble forms in runoff, soil interflow, and deep leaching. This paper discusses the relative importance of each transport pathway as affected by soil type and management. Soil P dynamics and water quality risks associated with fertilizer and manure application are illustrated with several examples. Finally, the paper reviews management practices that can effectively reduce the loss of agricultural P to surface waters.
 
Agriculture in the Upper Washita River Basin represents mixed crop-livestock systems of the Southern Plains. Research in the Little Washita River Experimental Watershed and the Fort Cobb Reservoir Experimental Watershed addresses interactive effects of variable climate, land use, and management on environmental quality. The Little Washita River watershed provides opportunities to explore impacts of flood retarding impoundments within a watershed. The Fort Cobb Reservoir watershed provides opportunities to study effects of agricultural conservation on a large eutrophic reservoir. Analysis of 1940 to 2005 data from the Fort Cobb Reservoir watershed showed that precipitation increased 33%, corresponding runoff increased 101%, and sediment yield increased 183% when comparing multi-year wet periods to multi-year dry periods. Depth to groundwater exhibited seasonal and interannual variation. A rapid geomorphic assessment indicated that unstable stream channels dominate the stream networks. Phosphorus concentration in streams was correlated to multiple attributes of the contributing areas, including contributing area, slope, stream density, and channel stability. Anticipated outcomes are improved understanding of environmental effects of conservation, new approaches to mitigation of water quality problems, and tools to support strategic placement of conservation practices on the landscape to achieve environmental goals.
 
Agricultural runoff is a major contaminant source threatening water quality in streams, lakes, and public drinking water reservoirs. Agricultural pollution control practices and programs are traditionally based on the assumption that overland flow is only generated when rainfall intensities exceed soil infiltration capacity. This paper challenges this assumption, noting that overland flow associated with agricultural pollutant transport is often physically consistent with the variable source area hydrology concept, for which overland flow is generated in parts of the landscape where the soil saturates to the surface. Incorporation of variable source area hydrology into watershed management practices reconceptualizes nonpoint source pollution as "variable source pollution," in which pollution control efforts can be focused on relatively small hydrologically sensitive areas recognizing that the extent of these areas will vary throughout the year. There are substantial technical, economic, social, and institutional barriers to implementing strategies for managing variable source pollution partially because of massive institutional inertia of existing agroenvironmental policies and programs and best management practices. Substantial research is needed to quantify the water quality risks associated with variable source pollution, expand the capacity to identify the critical management areas, and eliminate the institutional barriers for managing variable source pollution in agricultural watersheds.
 
Nitrate-N concentrations in the Raccoon River have increased beginning in the early 1970s. Since this river is the predominant water supply for the City of Des Moines in Iowa, there is concern about the potential long-term impacts of these trends. Improvements in water quality from agricultural watersheds are critical to protect the water supply, and understanding the factors affecting water quality will lead to potential changes in agricultural management to improve water quality. The historical database of nitrate-nitrogen (NO₃-N) concentrations sampled at the Des Moines Water Works were combined with observations on N fertilizer use, animal production, crop yields, land-use changes, and precipitation patterns to evaluate these interrelationships. Mean annual NO₃-N concentrations in the Raccoon River watershed have been increasing since 1970 in spite of no significant change in N fertilizer use for the past 15 years. There have been three years with maximum NO₃-N concentrations above 18 mg L⁻¹. However, these spikes occurred throughout the past 30 years and are not isolated to the last 10 years of record. Nitrate-N loads from the Raccoon River watershed have shown a slight decrease in the past ten years because of the increased crop yields and increased removal of N in the corn (Zea mays L.) and soybean (Gylcine max [L.] Merr.) grains. Production numbers for cattle have decreased by 63% since the early 1980s, while hogs have shown a 20% decrease over the same time period. Therefore, N available for application into the basin has decreased by 25%. Annual variations in NO₃N loads are significantly related to precipitation in the first five months of the year. A significant correlation was found between the land area within the watershed cropped to small grains and hay crops and the increase of NO₃-N since 1970 (r = -0.76). This relationship was caused by alteration in the seasonal water-use patterns and loss of N during the fall or early spring in the water movement in contrast to corn or soybean, which have a limited N uptake pattern concentrated between June and early September. Changes in the water-use patterns caused by shifts in cropping patterns provide an explanation for the positive correlation between precipitation and flow during the early part of the year. Development of agricultural management practices that can potentially affect water quality will have to be more inclusive of all components in agricultural systems, rather than only changing fertilizer rate or timing.
 
The impact on water quality by agricultural activity in karst terrain is an important consideration for resource management within the Appalachian Region. Three USDA Natural Resource Conservation Service-designed sinkhole filters for removing contaminants from manure-impacted infiltrating water were assessed for removal efficiency of indicator bacteria and nitrate. Geometric mean fecal coliform bacteria concentrations decreased 85% to 96%. Mean nitrate concentrations increased 130% at two of the filter locations. The sinkhole filters probably filtered out sediment and associated contaminants, such as fecal coliform bacteria, but had no filtering effect on solutes like nitrate. Nitrate concentrations might have increased because of nitrification in the filter media between runoff events.The sinkhole filter appears to be an effective management tool in order to reduce inputs of pathogens to karst groundwater aquifers.
 
Excerpt ENERGY CONSERVATION IN THE FARM BILL As energy becomes a larger portion of a farmer's operating costs, farmers and ranchers can cut input costs, maintain production, protect soil and water resources, reduce the nation's dependence on fossil fuels, and save money by implementing conservation practices that promote energy conservation and efficiency. Since 1935, the USDA Natural Resources Conservation Service (NRCS) has provided leadership in a partnership effort to help America's private landowners and managers conserve their soil, water, and other natural resources. Energy conservation and energy efficiency are becoming important aspects of how NRCS delivers technical and financial assistance. The 2002 Farm Bill expanded NRCS's role to directly address energy through the Conservation Security Program (CSP). Among the seven energy enhancements offered to CSP participants was an Energy Audit of Agricultural Operations. Unfortunately, locating local agricultural energy audit providers proved to be difficult and the low enhancement payment of $500 made offering the enhancement to farmers challenging. States such as Maryland were successful in providing on-farm energy audits to qualified CSP program participants by forming a unique partnership between federal, state, private, and nonprofit organizations. The Maryland Energy Administration, NRCS, the private farm energy efficiency consultants EnSave…
 
The USDA Agricultural Research Service has supported watershed research since the 1930s. Data from USDA Agricultural Research Service watersheds have been disseminated independently at each location, hindering multi-site analyses. A virtual team spanning diverse organizational units developed a web-based system, Sustaining the Earth's Watersheds-Agricultural Research Data System (STEWARDS) that allows users to search, visualize, and download soil, water, climate, management, and economic data from Conservation Effects Assessment Project benchmark watersheds. The objective of this paper is to provide an overview of STEWARDS and discuss challenges that were met to deliver STEWARDS on time, according to requirements, and within available resources. The information technology specialists had to understand that vague and changing requirements are reasonable for a system to support loosely coupled research across diverse watersheds. Researchers and data managers had to learn to communicate clearly about their data. Open communication, respect for perspectives and constraints of others, and a shared commitment to the goal provided the basis for trust. Anticipated benefits of STEWARDS include data preservation, increased data use, and facilitation of hydrological research.
 
This paper presents farm economic tools to support the design and selection of cost effective best management practices (BMPs) and the computation of cost-share payments. Partial budgeting is used to determine the annual costs and receipts associated with optional BMPs. The results serve as input for net present value (NPV) calculations that provide the net profitability of enrollment in alternative multi-year cost-share options offered for the BMPs. Break-even analyses is helpful when NPV results are mixed because it can indicate conditions for which cost-share and incentive payments would just cover the cost of BMPs. Besides a sensitivity assessment, the break-even analysis provides a relative economic ranking of competing cost-shared BMPs. This particular economic ranking is compared to the order of the BMPs on the basis of their potential N-reduction. For cost-share and incentive programs to be effective, the two rankings have to be identical. The farm economic tools were applied to BMPs mandated for the Neuse River Basin in North Carolina.
 
It is now recognized worldwide that soil erosion on agricultural fields due to ephemeral gullies may be greater than those losses attributed to sheet and rill erosion processes. Yet it is not known whether the common practice of repairing or obliterating these gullies during annual tillage activities exacerbates or mitigates soil losses over long time periods. Here, a numerical model is used to demonstrate the potential effects of annual tillage on cumulative soil losses from four geographic regions plagued by ephemeral gullies as compared to no-till conditions where the gullies are free to grow and evolve over time and space. Historical precipitation data and field measurements were compiled for specific-sites in Belgium, Mississippi, Iowa, and Georgia, and the model simulated ephemeral gully development and evolution during the growing seasons over a continuous 10-year period. When agricultural fields are not tilled annually, the simulations suggest that gullies attain their maximum dimensions during the first few years in response to several relatively large runoff events. During subsequent runoff events, the gullies no longer erode their channels significantly, and soil losses due to gully erosion decrease markedly. When agricultural fields are tilled annually, the ephemeral gully channels are reactivated, thus causing significant soil losses each year in response to runoff events. Over the 10-year simulation, the modeling results suggest that erosion rates in these four geographic regions can be 250% to 450% greater when gullies are tilled and reactivated annually as opposed to the no-till condition. These results reveal that routine filling of ephemeral gully channels during tillage practices may result in markedly higher rates of soil loss as compared to allowing these gullies to persist on the landscape, demonstrating a further advantage of adopting no-till management practices.
 
Abundant algal growth in standing water of a ditch.  
Agricultural drainage ditches are essential for the removal of surface and ground water to allow for crop production in poorly drained agricultural landscapes. Ditches also mediate the flow of pollutants from agroecosystems to downstream water bodies. This paper provides an overview of the science, management, and policy of ditches. Ditches provide a unique opportunity to address nonpoint source pollution problems from agriculture due to the concentration of the contaminants and the engineered nature of ditch systems. A better understanding of the nature of these complex system and the technologies available and under development to improve their management will assist in the design and implementation of water quality protection programs.
 
To support the USDA Agricultural Research Service Conservation Effects Assessment Project, a publicly available Web-based watershed data system, named Sustaining the Earth's Watersheds-Agricultural Research Data System (STEWARDS), was developed to provide data search, viewing, and downloading capabilities. The objectives of this paper are to (1) describe the data within STEWARDS, (2) describe the process of accessing watershed data and (3) provide an overview of the system management. STEWARDS is a data delivery system with a geographic information system interface, using space, time, and topic as key fields for searching an extensive database of soil, water, climate, land management, and socio-economic data from multiple long-term research watersheds. STEWARDS facilitates (1) researchers in obtaining USDA Agricultural Research Service historic watershed data for hydrological studies; (2) modelers in retrieving measured data over extensive time periods for model calibration and validation in watershed assessments to support CEAP; and (3) watershed managers, partners, and stakeholders in accessing long term data to support decision-making for selecting effective conservation practices.
 
Skip to main page content HOME CURRENT ISSUE ARCHIVE FEEDBACK SUBSCRIPTIONS ALERTS HELP Keywords Search Advanced »User Name Password Sign In Modeling phosphorus transport in agricultural watersheds: Processes and possibilities A. N. Sharpley, P. J. A. Kleinman, R. W. McDowell, M. Gitau, and R. B. Bryant ABSTRACT: Modeling phosphorus (P) loss from agricultural watersheds is key to quantifying the long term water quality benefits of alternative best management practices. Scientists engaged in this endeavor struggle to represent processes controlling P transport at scales and time frames that are meaningful to farmers, resource managers, and policy makers. To help overcome these challenges, we reviewed salient issues facing scientists that model P transport, providing a conceptual framework from which process-based P transport models might be evaluated. Recent advances in quantifying the release of soil P to overland and subsurface flow show that extraction coefficients relating soil and flow P are variable but can be represented as a function of land cover or erosion. Existing information on best management effects on P export should be linked to watershed models to better represent changes in P transport. The main needs of P transport models are inclusion of flexible coefficients relating soil and overland flow P, fertilizer and manure management and P loss, stream channel effects on edge-of-field P losses prior to water body input, and linkage of watershed and water-body response models. However, it is essential that the most appropriate model be carefully selected, according to a user's needs in terms of available input data, level of predictive accuracy, and scale of simulation being considered.
 
Dense dendritic stream networks in the Tifton Upland (southeastern U.S. coastal plain) provide an opportunity to determine the effects of land management practices on individual farms on downstream hydrology and water quality. A typical farm will be drained by two or three small streams. The streams may be bordered by riparian forests or impounded into farm ponds. Two adjacent farm-scale basins, both of which were 50 to 60 ha (124 to 148 ac) in size were compared for seven years to determine the effects of upstream agricultural land uses, downstream riparian zones, and small impoundments on stream water quality and hydrology. Stream water quality was sampled at four points on the two basins and at a downstream outlet where the two streams came together in a farm pond. The north basin had more cropland than the south basin and had much more area in plastic-covered beds for vegetable production. The south basin had less land in crop production and much more of the total basin area in farm ponds used to supply irrigation water. The north basin had more surface runoff and higher loads of all nutrients and sediment. The south basin had only 55% of the total runoff of the north basin, probably due to the presence of about 6% of the total watershed area in farm ponds. Up to 26% of the north basin (38% of total cropland) was occupied by wide plastic-covered beds in the last two years of the study. Large quantities of sediment transported in surface runoff from these fields on the north basin led to increases in sediment concentrations and loads of over 100 times compared to both the south basin and to earlier years of the study. Based on reductions in differences in loads and concentrations between upstream and downstream sites, there is less potential to reduce nutrients and sediment once these materials are in stream flow than when water is moving to streams through a riparian buffer. A downstream pond that received inputs from both the north and south basins had significantly lower concentrations of most nutrients and sediments than either of the upstream sampling sites.
 
There are growing concerns regarding the fate of nutrients from land application of animal waste. In recent years, phosphorus (P) indices have been developed to provide information regarding nutrient loss potentials from animal waste application methods and topography. However, in many cases, these P indices have not been fully tested, especially in cultivated agriculture. Three factors commonly utilized in soil P indices for manure management are manure rate, manure incorporation, and slope. Rainfall simulations were conducted to examine the impact of these three factors on runoff losses of P on heavy clay soils under cultivated agriculture. Four manure litter (turkey litter) application rates (0, 4.5, 9.0, and 13.5 Mg ha-1 (0, 2, 4, and 6 tons ac-1)) were applied on two different slopes (5 and 9 percent) on a Heiden clay (fine, smectitic, thermic Udic Haplusterts). The litter was surface applied to a corn (Zea mays L.) production area, with or without incorporation. The four application rates were also applied to a permanent bermudagrass (Cynodon dactylon (L.) Pers.) pasture on a 5 percent slope. A rainfall simulator was used to generate water runoff for 30 minutes from 1.5 by 2.0 m (5 by 6.5 ft) plots. Runoff samples were analyzed for runoff volume, sediment, sediment nitrogen (N) and P, dissolved ammonia nitrogen (NH4-N), nitrate nitrogen (NO3-N), and PO4-P. The results were analyzed using regression analysis techniques based on application rates. The dissolved NO3-N concentration was not affected by either litter incorporation or slope in the cultivated sites, but was greatly increased with increasing litter application rate in the pasture sites. Increased losses of dissolved NH4-N and PO4-P were observed with increasing litter application rate, with a significant reduction in losses observed when litter was incorporated. However, increased slope did not significantly impact the level of runoff losses of dissolved NH4-N and PO4-P.
 
Agricultural nutrient losses contribute to hypoxia in the Gulf of Mexico and eutrophication in the Great Lakes. Our objective was to assess effects of topography, geomorphology, climate, cropping systems and land use and conservation practices on hydrology and nutrient fate and transport in the St. Joseph River watershed. We monitored five sites (298 to 4,300 ha [736 to 10,600 ac]) on two drainage ditches within the St. Joseph River watershed in northeastern Indiana. Row crop agriculture, primarily corn (Zea mays L.) and soybean (Glycine max [L.] Merr.), is the dominant land use (approximately 60%) in this pothole or closed depression landscape. The hydrology is dominated by subsurface tile drainage supplemented with surface drainage of remote potholes. Vegetative buffer strips have been implemented along >60% of the agricultural drainage ditches. The vegetative buffer strips play an invaluable role protecting water quality though by acting as natural setbacks during fertilizer and pesticide applications. Multiple regressions indicated land cropped to corn and areas with direct drainage or potholes are highly sensitive to nutrient losses. Future conservation assessment efforts in this and similar watersheds should focus on management of potholes in cropped fields and the subsequent effect of those practices on tile drainage water.
 
Water quality trading is a market-based alternative to command and control policies for meeting water quality goals. A trading program creates a market for pollution discharge reductions for the purpose of achieving a water quality goal at a lower cost than traditional command-and-control policies. The US Environmental Protection Agency and the USDA are promoting water quality trading in watersheds impaired by both point source and agricultural pollution. This research examines the extent to which water quality impairments have the potential for creating a demand for credits from agriculture. We found that the opportunities for the development of active markets between point sources and agriculture are limited, due primarily to Lick of available demand from point sources. Out of 710 eight-digit HUCs containing waters impaired by nutrients, we identified 142 and 224 where active markets for nitrogen and phosphorus credits, respectively, between regulated Point sources and agriculture have the best opportunity to develop, assuming supply and demand impediments can be addressed through program design and government support. We use program data to account for current conservation measures on farms that could drive LIP the price of credits and reduce demand.
 
At the turn of the century, except for trains and water transport, the transportation and agriculture industries of the US were powered largely by herbaceous biomass, converted into usable energy by draft animals. The haylands and pasturelands now released from herbaceous biomass production were converted to grain production in many cases. This article makes the case for reconverting some of such lands to pasture/grasslands for both land and soil conservation and for use as a sustainable agricultural systems for fuel production from biomass. 21 refs., 4 tabs.
 
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.
 
Top-cited authors
Mark A. Nearing
  • United States Department of Agriculture
T. C. Daniel
  • University of Arkansas
Peter Kleinman
  • Agricultural Research Service
Gerard Govers
  • KU Leuven
Rattan Lal
  • The Ohio State University