FY 2007 Annual Report 

National Program 211 - Water Availability and Watershed Management 

Introduction 

Water is fundamental to life. It is a basic requirement for virtually all of our agricultural, 

industrial, urban, and recreational activities, as well as for the sustained health of our 

natural ecosystems. As Earth’s human population tripled during the last century, demand 

for Earth’s finite supply of available fresh water increased six-fold. The United Nations 

estimates that more than a billion people live without access to clean water, and more 

than 2.4 billion people lack the basic sanitation needed for human health. The U.S. 

Environmental Protection Agency has estimated that it will cost in excess of $150 billion 

to provide clean and safe water to the Nation. Shortages of fresh water—already evident 

in the drought-ridden western United States—cost the Nation in excess of $8 billion per 

year in addition to untold environmental impacts. When only freshwater withdrawals are 

considered, agriculture is clearly the largest user of water in the United States; thus 

agriculture has the greatest opportunity to conserve water supplies and improve water 

quality through scientific discovery. 

The goal of the USDA/ARS Water Availability and Watershed Management National 

Program is to manage water resources effectively and safely, while protecting the 

environment and human and animal health. This goal will be achieved by characterizing 

potential hazards, developing management practices, strategies and systems to alleviate 

problems, and providing practices, technologies and decision support tools for the benefit 

of customers, stakeholders, partners, and product users. Research in this National 

Program addresses six component problem areas: (1) the effectiveness of conservation 

practices; (2) irrigation water management; (3) drainage water management systems; (4) 

integrated soil erosion and sedimentation technologies; (5) watershed management, water 

availability, and ecosystem restoration; and (6) water quality protection systems. 

The mission of this National Program is twofold: (1) to conduct fundamental and applied 

research on the processes that control water availability and quantity for the health and 

economic growth of U.S. citizens; and (2) to develop new and improved technologies for 

managing the Nation’s agricultural and water resources. Advances in knowledge and 

technologies provide producers, action agencies, local communities, and resource 

advisors with the practices, tools, models, and decision support systems they need to 

improve water conservation and water use efficiency in agriculture, enhance water 

quality, protect rural and urban communities from the ravages of drought and floods, 

improve agricultural and urban watersheds, and prevent the degradation of riparian areas, 

wetlands, and stream corridors. 

ARS, in cooperation with the Natural Resources Conservation Service, the Cooperative 

State Research, Extension, and Education Service, the Environmental Protection Agency, 

and other Federal and State agencies, has developed a watershed research program called 

the Conservation Effects Assessment Project (CEAP). The purpose of CEAP is to 

provide a methodology for documenting the national and regional environmental effects 
and benefits obtained from USDA conservation program expenditures, and inform 

choices on how to achieve maximum benefit from those expenditures. During FY2007, 

ARS developed a data storage and management system called STEWARDS (Sustaining 

the Earths Watersheds Agricultural Research Data System) to house data collected as part 

of the CEAP assessment for croplands, drafted a retrospective review describing ARS 

accomplishments related to the CEAP assessment for croplands, to be published in a 

special issue of the Journal of Soil and Water Conservation in 2008, extended the CEAP 

cropland assessment to tropical environments through the establishment of a Special 

Emphasis Watershed in Jobos Bay, Puerto Rico, and expanded CEAP activities to the 

assessment of grazinglands and wetlands. 

The National Program Staff continues to coordinate ARS water resource related activities 

with regional, national, and international partners. A milestone of ARS CEAP activities 

during FY2007 were the sessions held in association with Soil and Water Conservation 

Society’s 2007 Annual Conference, held July 21-25, 2007, in Tampa, FL. The 

conference featured a plenary presentation by ARS Administrator Dr. Edward Knipling 

on the significance of CEAP from an ARS perspective, 63 formal contributed papers 

presenting the results of the ARS-CEAP Watershed Assessment Studies, 23 ARS poster 

presentations, and working group meetings for each of the 6 ARS CEAP management 

teams. The proceedings of this conference are available through the Soil and Water 

Conservation Society’s web site: http://www.swcs.org/. 

The National Program Staff coordinates with other government agencies to leverage 

agency resources through its active participation in a variety of intergovernmental 

committees including: (1) the Committee on Environment and Natural Resources 

(CENR) (the relevant National Science and Technology Council committee for water 

research) Subcommittee on Water Availability and Quality (SWAQ), a subcommittee 

within CENR devoted to water issues that serves as a forum for agency representatives to 

share information about their respective programs; (2) the National Agricultural 

Research, Extension, Education and Economics (NAREEE) Advisory Board, which 

evaluates USDA Research and Development Programs and provides recommendations to 

the Secretary and REE Undersecretaries; (3) the Mississippi River/Gulf of Mexico 

Watershed Nutrient Task Force, charged by Congress with conducting a reassessment of 

(i) nutrient load reductions and the response of the hypoxic zone, (ii) water quality 

throughout the Mississippi River Basin, and (iii) economic and social effects, a draft of 

which is currently being circulated for public comment (4) the Advisory Committee on 

Water Information (ACWI) Subcommittee on Sedimentation; (5) the USDA Drought 

Team and the Working Group on Water Resources; and (6) the Conservation Effects 

Assessment Project Steering Committee, among others. 
Selected Accomplishments: 

Problem Area 1—Effectiveness of Conservation Practices

A new remote sensing technique to estimate nutrient uptake by cover crops. Cover crops have 

been shown to be an effective way to reduce nitrogen losses from agricultural fields, but are 

difficult to monitor at the watershed/landscape scale. ARS researchers in Beltsville, MD, 

developed a remote sensing technique to estimate the amount of N sequestered in cover crop 

biomass on farms enrolled in State cover crop cost share programs. The pilot study was 

conducted in the Choptank River watershed in MD, part of ARS’ watershed research network 

associated with the Conservation Effects Assessment Project (CEAP). The technique will allow 

managers to optimize and efficiently monitor this important best management practice at 

watershed and regional scales with the aid of remote sensing that is non-invasive. 

Improvements in riparian area modeling for water quality assessment. Accurate modeling of 

water movement through riparian buffers is critical for watershed-scale water quality 

assessments. ARS scientists at Beltsville, MD, and Tifton, GA, tested the Riparian Ecosystem 

Management Model (REMM) using a GA riparian database. The sensitivity of REMM nutrient 

and sediment output was quantified with respect to changes in key riparian buffer parameters 

(e.g., vegetation; soil characteristics). Parameters associated with vegetation (e.g., rooting depth; 

plant height) moderately affected nutrient and sediment yields, but outputs were highly sensitive 

to changes in physical parameters (e.g., slope; Manning's surface roughness coefficient). 

Scientists at Beltsville are developing a similar evaluation of REMM for the Choptank SEW. This 

new model will assist farmers and policy makers in quantifying the effectiveness of specific 

riparian buffers in reducing pollutant loads to streams and other surface waters.

A new management practice for reducing nitrate loss in drainage waters. Nitrogen losses from 

agricultural fields are an important contributor to the eutrophication of Chesapeake Bay. Best 

management practices aim to reduce N losses, thereby improving water quality. In the Choptank 

River Special Emphasis Watershed (SEW), MD, excess nutrient transport from agricultural fields 

is primarily through extensive open drainage ditches, where on average, 6% of the nitrate applied 

annually may be transported to streams, rivers, and eventually the Chesapeake Bay. One of the 

best management practices (BMPs) used in these ditches is the installation of water control 

structures at the drainage outlet to reduce water flow and nutrient loss. Preliminary studies 

indicate that increasing water table elevation to just below the root zone during the growing 

season, while lowering it during planting and harvesting operations, can reduce nitrate losses up 

to 40%. These findings provide quantitative efficiencies for both water and nitrate reductions, and 

better management strategies for more efficient use of controlled drainage BMPs. 

Development of a river basin scale water quality model. Simulation models are critical to the 

accurate assessment of water quality concerns and the effects of conservation practices aimed at 

improving water quality. ARS scientists at the Grassland, Soil and Water Research Laboratory, 

Temple, TX, have developed a river basin scale model called SWAT (Soil and Water Assessment 

Tool) that integrates hydrology, soil erosion, plant growth, and nutrient cycling, with off-site 

processes such as channel erosion/deposition, pond and reservoir processes, groundwater flow, 

and climate variability. Numerous interfaces have been developed for the model to assist users 

in obtaining model inputs and interpreting model outputs. The model was calibrated and 

validated, and uncertainty in its output was analyzed, based on observations from the CEAP 

Benchmark Watersheds and other watersheds around the world. In general, the model 

compared well with observed stream flow and sediment and nutrient loads and concentrations. 

The model is being used across the country by US EPA to assess water quality concerns, and by 

USDA to assess the environmental impact of conservation programs on water quality and 

quantity. Scientists around the world are contributing to model development; over 350 scientific 

papers have been published in the open literature on the development and application of SWAT. 
Data and information from ARS Watersheds are assembled to address National research and 

conservation needs. Vast quantities of scientific data are collected annually in the US, but the 

benefits of such data collection activities are not fully realized unless these datasets are stored 

and maintained for integrative analysis and potential future use. ARS researchers and staff from 

El Reno, OK, Columbia, MO, Beltsville, MD, Ames, IA, and Fort Collins, CO, developed a webbased data system—Sustaining the Earth’s Watersheds, Agricultural Research Data System 

(STEWARDS)—that organizes and documents soil, water, climate, land-management, and socioeconomic data from multiple agricultural watersheds across the US, allowing users to search, 

download, visualize, and explore data for research and conservation management purposes. 

STEWARDS is currently being beta-tested by the CEAP research team. When released to the 

public, STEWARDS will help: 1) researchers obtain ARS’ long-term data for hydrological studies; 

2) modelers retrieve data for model calibration and validation; and 3) watershed managers and a 

wide array of partners and stakeholders access long term data to support conservation planning 

and assessment. 

Assessing effectiveness of conservation practices within the Little River watershed. One of the 

benefits of long-term data collection relates to the potential for subsequent integrative and 

comprehensive analyses. ARS scientists have collected stream flow and water quality data on 

the Little River Experimental Watershed (LREW) in South-Central GA for the past 37 years, and 

sediment and agrichemical concentrations in stream flow for the past 20 years. The resulting 

database contains hydrologic and water quality data, combined with terrain, soils, geology, 

vegetation, and conservation practices, for this watershed. The database was published in six 

manuscripts and via a public ftp site, and is being used to closely examine long-term water 

quantity and quality patterns for the watershed. The research illustrates the dramatic importance 

of riparian buffers within the watershed, which remove sediment and nutrients from upland 

agricultural sources, preventing them from entering adjacent streams and causing eutrophication. 

Water quality modeling for large-scale watersheds. Agricultural pollutants in drainage waters 

have the potential to degrade the quality of waters used for municipal water supplies. ARS 

scientists in West Lafayette, IN, successfully calibrated and validated SWAT for modeling stream 

flow and atrazine concentrations in the Cedar Creek Watershed (CCW). This research is 

necessary for further use of SWAT as an assessment tool to evaluate the long-term effects of 

different management practices on chemical transport in large, tile-drained agricultural 

watersheds in the Midwest. The results are significant in that Cedar Creek is the main tributary to 

the St. Joseph River, the source of water supply for Ft. Wayne, IN, where concentrations of 

atrazine and other agricultural pollutants have been a major concern. 

Problem Area 2—Irrigation Water Management

Plants for saline water reuse. High salinity levels prohibit the reuse of irrigation drainage waters 

from agricultural fields in the western US. ARS researchers at Parlier, CA, identified plant 

species and poplar tree clones adapted to these high salinity waters. As an example, oil plants 

adapted to high salinity drainage waters can be used for bio-based products that have economic 

value for the grower (e.g., biofuel and Se-enriched feed products). These findings improve our 

ability to sustain an agronomic-based system for drainage water reuse and encourage 

widespread use of degraded water for non-human consumptive uses, reducing competition for 

high quality water in the western U.S. 

Salt Management Guide helps growers select horticultural crops that thrive in recycled waters. To assist landscape professionals, growers, and home gardeners in managing salinity in recycled 

irrigation waters, ARS scientists at the US Salinity Laboratory, Riverside, CA, in collaboration with 

researchers at the University of California Davis, developed a Salt Management Guide. The 

Guide and accompanying CD include an extensive list of plant species suitable for water reuse 

systems, ranging from relatively non-saline settings to salt-affected problem sites. The product 

provides: 1) information on public health aspects, and regulations on use, of Title 22 waters, and 
their suitability for landscape irrigation relative to plants, soil properties, and irrigation application 

systems; and 2) information to educate the public about safe use of recycled water and its value 

in helping to address current and future shortfalls in potable waters. 

Enhanced nitrogen use efficiency in potato production. Better management of nitrogen fertilizer 

applications provide economic benefits to farmers and improve water quality. ARS scientists at 

Kimberly, ID, developed an alternative potato production system using 12-foot wide beds with five 

or seven rows across each bed. This alternate production system increases N use efficiency, 

increasing gross returns up to $300 per acre over conventional potato production in hilled rows. 

Western Ag Research, Blackfoot, ID, received a Conservation Innovation Grant in 2007 to 

demonstrate and evaluate this technology on 10,000 acres in southern ID. 

Sustainability of Drainage Water Reuse Evaluated. Maintaining adequate supplies of freshwater 

to meet Earth’s human and natural resource needs may be the most important natural resource 

challenge of the 21st Century. Drainage water reuse offers one means of increasing the 

availability of freshwater to support irrigated agriculture, while concomitantly reducing the volume 

of impaired drainage waters. ARS scientists at the U.S. Salinity Laboratory, Riverside, CA, 

evaluated the sustainability of drainage water reuse over a 5 year period (1999-2004), on a 

saline-sodic site on the west side of the San Joaquin Valley (WSJV). The evaluation 

demonstrated the reclamation of marginally productive WSJV saline-sodic soils, while reducing 

drainage volumes and serving as an alternative water resource for salt tolerant forage. At this 

site, rainage water reuse reduced salinity, Mo, B, and SAR from 1999-2004, with associated 

increases in forage yield and quality. The work confirms the short-term viability of drainage water 

reuse as an alternative water source for marginally productive WSJV saline-sodic soils, and as a 

means of reducing drainage volumes, thereby reducing the need for evaporation ponds. The 

unexpected appearance of low levels of Se, and the reappearance of Mo, at shallow soil depths 

suggest that long-term sustainability requires further investigation. 

Water quality in a drainage water disposal facility. Due to elevated concentrations of toxic 

elements such as selenium and arsenic, drainage water disposal continues to be an 

environmental concern. ARS scientists in Parlier, CA examined the salinity, chemical 

characteristics, and biogeochemistry of selenium and arsenic in drainage waters from agricultural 

fields, and in an evaporation basin facility used for the disposal of agricultural drainage in the 

Tulare Lake Drainage District. Water parameters, including redox, dissolved oxygen, dissolved 

Fe and sulfur species, and speciation of selenium and arsenic, were determined in water columns 

as well as spatially in evaporation basins. This information is needed to evaluate the potential 

environmental impacts of agricultural production systems where drainage disposal is required. 

Problem Area 3—Drainage Water Management Systems

A prototype nitrogen management tool for tile drained agriculture. Nitrogen losses from tiledrained agricultural systems in the upper Mississippi River watershed have been identified as a 

major factor contributing to the annual development of the hypoxic zone in the Gulf of Mexico. 

ARS researchers at Ames, IA, and Tucson, AZ, collaborated to develop a prototype spreadsheet 

tool capable of estimating N lost to surface waters from tile-drained agriculture. The tool uses 

statistical relationships from values measured in field experiments combined with a simulation 

model, providing a simple way to calculate the expected reduction in N loading from potential 

management changes. The prototype has the potential to become an operational N management 

tool for use by farmers, growers, and natural resource managers, that will help maintain the 

sustainability of US agricultural practices while enhancing the environment. 

Relative Impacts of Ionic Strength and Nitrate Concentration on Nitrate Movement in Soil. Nitrate 

is a widespread contaminant found in both ground and surface waters. Nitrate in the environment 

typically moves through the soil profile first, especially if introduced via fertilizer application. 

Reducing adverse environmental impacts due to nitrate requires a better understanding of the 
processes that govern nitrate mobility in soil, particularly anion exclusion. In a laboratory 

investigation, ARS scientists in Columbus, OH, found that the ionic strength of the soil solution 

had a much greater influence on the anion exclusion process affecting nitrate mobility than the 

nitrate concentration itself. The results of this study will help improve computer models used to 

predict nitrate movement through the soil profile, leading to improved management of nitrate 

fertilizer application scenarios, reducing nitrate losses from fertilized agricultural fields. A 

manuscript describing these findings has been accepted for publication in the scientific journal, 

Soil Science. 

Management Effects on Nitrogen in Tile Drained Agriculture. Nitrogen losses from agricultural 

lands in the Mississippi River Basin contribute significantly to the annual development of the 

hypoxic zone in the Gulf of Mexico. ARS scientists at the National Soil Tilth Laboratory in Ames, 

IA, in collaboration with scientists from ARS’ Agricultural Systems Research Unit in Fort Collins, 

CO, summarized and quantified the effects of management on nitrogen (N) losses to surface 

waters, based on a rich dataset of observations and an improved, process-based simulation 

model (RZWQM), through a series of papers published as a special issue of Geoderma. Both 

water and N losses from tile drained agricultural systems in the Midwest are addressed, as 

influenced by a variety of management practices. This special issue will be a key resource for 

future efforts to control the magnitude and extent of the hypoxic zone in the Gulf of Mexico, by 

reducing N loadings from tile-drained agriculture in the Mississippi River Basin. 

Farmers Can Save Money and Help the Environment. Nitrogen losses from agricultural lands 

can be reduced more readily if farmers benefit through increased revenues. ARS scientists at the 

Southwest Watershed Research Center, Tucson, AZ, used NRCS’ EconDocs software to develop 

a series of crop budgets for current and reduced N loading management systems in tile-drained 

agriculture. These budgets demonstrate to farmers the economic benefits of management 

systems that reduce N loadings, and could be used to revise conservation programs to 

encourage farmers to adopt management systems that reduce N loadings from tile-drained 

agricultural systems. 

RZWQM Model Evaluation of Cropping System Management Practices. Nitrogen losses from 

agricultural lands represent a serious water quality problem in many areas of the US, including 

the Mississippi River Basin and the Chesapeake Bay. Winter cover crops (e.g., winter rye in 

corn-soybean rotation) are one of the more promising practices to reduce nitrate losses without 

negatively affecting production. ARS scientists in Fort Collins, CO, calibrated the hybrid RZWQMDSSAT model, and tested its ability to simulate the effects of cover crops versus no cover crops 

on nitrate leaching losses in subsurface drainage water under a corn-soybean rotation. Field data 

from Boone County, IA, collected over several years under an application rate of 225 kg N ha-1 in 

corn years, were used for model evaluation. Average observed and RZWQM simulated flowweighted annual nitrate concentrations (FWANC) in subsurface drainage waters for the cover 

crop treatments from 2002 to 2005 were 8.7 and 8.6 mg L-1, compared to 22.1 and 17.2 mg L-1 

for no cover crop (resulting in observed and predicted reductions of 61% and 50%, respectively). 

Simulations based on various N fertilizer application rates showed that annual FWANC in 

subsurface drainage water dramatically increased with increases in N application rate. With a 

cover crop, average FWANC increased from 3.1 mg L-1 at the 0 kg N ha-1 rate to 13.1 mg L-1 at 

250 kg N ha-1 rate. In comparison, a corresponding increase, from 6.1 mg L-1 to 21.1 mg L-1, 

was observed without a cover crop present. Accurate quantification of the nutrient removal 

potential of various cover crops could be linked to nutrient credit trading scenarios, to foster the 

adoption of conservation practices aimed at improving water quality. 

Problem Area 4—Integrated Soil Erosion and Sedimentation Technologies

Starch/Polyacrylamide Soil Erosion Amendment. Water flowing in irrigation furrows can erode 

soil and transport sediment and associated nutrients off the field. A new 

polysaccharide/polyacrylamide amendment was compared against polyacrylamide-treated and 
untreated furrows in a field test at the Northwest Irrigation and Soils Research Laboratory, 

Kimberly, ID. The new amendment, a blend of potato starch and polyacrylamide (PAM), 

increased infiltration by 20%, and reduced soil erosion by 65%, compared to untreated furrows. 

PAM treatment increased infiltration by 13%, and reduced erosion 98%, compared to untreated 

furrows. The new polysaccharide/PAM amendment provides an alternative to PAM for improving 

infiltration on furrow irrigated fields, although greater application rates will be needed to provide 

similar erosion control as PAM. 

Prototype model simulates erosion and sediment deposition patterns due to soil translocation by 

tillage. Accurate quantification of erosion is an important component of developing tillage 

practices that minimize soil and associated nutrient losses from agricultural fields. ARS scientists 

at Oxford, MS, computed the amount of soil translocated following tillage, by taking into account 

slope gradients parallel and perpendicular to the direction of tillage. The prototype model 

operates on a rectangular grid represented by a Digital Elevation Map (DEM) containing initial 

terrain elevations. The model, which has been programmed in Fortran 90 using Compaq’s Visual 

FORTRAN 6.6 compiler for Windows, should provide a valuable future tool for quantifying the 

effects of agricultural practices on soil erosion and sedimentation at the landscape scale.

A physically-based integrated numerical model for flow, sediment, and contaminant transport in 

the surface-subsurface system. Models are useful tools for estimating processes at scales larger 

than can be readily measured through empirical analyses. ARS scientists at Oxford, MS, 

developed a numerical model to estimate flow, sediment, and contaminant transport in surfacesubsurface systems, by combining separate models for surface and subsurface environments. 

Surface flow is calculated using a depth-averaged 2-D diffusion wave model; ground water flow is 

computed using the 3-D mixed-form Richards equation. Coupling of these two component models 

allows assessment of interactions between surface and groundwater flows, which are difficult to 

measure directly, particularly at the landscape scale. 

Sediment yields from cotton drastically reduced. Erosion and associated soil loss are common 

problems associated with cotton cultivation in the southern US, particularly on sloping terrain. 

Standard approaches for growing cotton on sloping lands produce rates of erosion and sediment 

yield several times greater than the 7t/ha tolerance value. ARS scientists at Oxford, MS, 

conducted a four-year study that included measuring water runoff and sediment yield from plots 

cultivated for cotton with conventional approaches, and from plots representing three innovative 

approaches involving combinations of narrow row spacing, no-till, and grass hedges. Sediment 

yield from no-till plots with grass hedges was reduced 94% relative to conventional tillage, and 

yielded an average of 0.2 t/ha of cotton more than conventional tilled plots. Results will be useful 

in guiding future research on field-sized areas, with potential benefits for extension personnel, 

action agencies involved in water quality planning, and farmers.

Index for targeting pollution hotspots. Often only a relatively small area is responsible for a 

disproportionate fraction of the fine sediment and associated chemical load leaving a watershed. 

If these ‘hotspots’ can be identified, conservation practices can be targeted to specific locations 

within a watershed where they will provide maximum benefit, reducing the cost of conservation 

management in comparison with implementing practices throughout a watershed. In this study, 

ARS scientists developed a sediment production index using data from the Walnut Gulch 

Experimental Watershed at Tombstone, AZ, that showed that the greatest potential for sediment 

production was on south facing slopes with a steepness of between 13% and 20%. The ability to 

identify primary sediment source areas in watersheds should improve the design of best 

management practices while reducing the cost of their implementation.

Problem Area 5—Watershed Management, Water Availability, and Ecosystem 

Restoration 
New tool for assessing of root zone contaminants. Land application of biosolids can introduce 

persistent, slow moving trace metals and other contaminants to the subsurface environment, 

affecting environmental quality and human health for decades; safe use of biosolids in agriculture 

requires accurate risk assessment of contaminant fate and transport. Researchers at the U.S. 

Salinity Laboratory, in collaboration with scientists in Sweden and Brazil, developed a new 

contaminant transport model suitable for assessing the transport of slow moving contaminants in 

the root zone. The model has relatively modest data requirements, yet is more realistic than 

other root-zone models currently in use or proposed for use in biosolid risk assessment. This 

new modeling tool will benefit both researchers and regulators who are charged with assessing 

the impacts of persistent contaminants in the root zone. 

Stream restoration that works. Over $1 billion are expended annually on stream restoration, but 

few projects are monitored following restoration, and scientists disagree about the most effective 

approaches to achieve various restoration objectives. ARS scientists in Oxford, MS, monitored 

streams for ten years after the surrounding watersheds were treated with standard erosion control 

practices. In addition, two stream reaches were treated with special features to restore fish 

habitat quality. Habitat restoration produced major shifts in the types and sizes of fish present—

shifts that did not occur in non-treated stream sections. The study demonstrates that even 

watershed-scale application of traditional erosion control measures is not adequate to restore 

stream ecological integrity, while identifying effective approaches to specifically address fish 

habitat deficiencies. This research will be beneficial to managers charged with both controlling 

erosion and restoring fish habitat and ecological integrity in streams draining agricultural 

watersheds. 

Rotating crops encourages atrazine degradation. Under ideal conditions, pesticides applied to 

agricultural crops would rapidly degrade after application, but factors that promote such ideal 

behavior are largely unknown. Commonly, some portion of the applied pesticide often ends up in 

associated aquatic ecosystems. ARS scientists in Oxford, MS, compared bacterial populations 

and carbon and nitrogen levels in soils supporting continuous cotton cultivation, continuous corn, 

and a corn-cotton rotation. Continuous corn and a corn-cotton rotation favored the accelerated 

degradation of atrazine, a widely used herbicide, as compared to continuous cotton cultivation. 

This discovery has prompted new studies to ascertain the effect of accelerated atrazine 

degradation on weed control potential. However, the results indicate that replacing continuous 

cotton cultivation with a corn-cotton rotation has the potential to reduce pesticide transport to 

associated aquatic environments. 

Pesticides may leave sediments and harm animals. Agricultural pesticides are often removed 

from streams, lakes and wetlands by becoming attached to sediments and settling to the bottom, 

but the subsequent fate of these pesticides is often unknown. By mixing sediment sampled from 

a wide range of aquatic environments adjacent to cultivated fields with water and then exposing 

aquatic insects to this mixture for 28 days, it was shown that compounds moved from the 

sediments into the animals’ tissues. These findings will guide future studies of the movements 

and fate of such liberated pesticides in aquatic ecosystems. 

Properly managed forage-based livestock operations do not appear to contribute to poor water 

quality. Forage-based livestock systems have been implicated as major contributors to 

deteriorating water quality in many parts of the US. Both fertilizers and manures represent 

sources of phosphorus that can be transported via hydrologic pathways, impacting surface and 

ground water quality. Scientists at the USDA/ARS Subtropical Agricultural Research Station in 

Brooksville, FL, examined historical water quality parameters in three lakes located near beef 

cattle pastures: 1) Lake Lindsey; 2) Spring Lake; and 3) Bystre Lake. Based upon the Florida 

Water Quality Standard, water quality in all three lakes was considered “good” (30-46 TSI). In 

Lake Lindsey, measures of water chemistry from the 1990s were similar to those from the 1960s. 

Spring Lake contained clear (color < 10 units), medium hard water with low concentrations of total 

N and total P. Bystre Lake was characterized by moderately colored, medium hard waters. 

Findings suggest that properly managed beef cattle operations might not be major contributors to 
excessive nutrient loads (especially of P) in surface waters. Current fertilization 

recommendations for forage-based pastures in central Florida appear to offer little potential for 

negatively impacting water quality, while properly managed livestock operations appear to 

contribute negligible loads of nutrients (especially P) to surface water. Periodic application of 

additional P and other micronutrients may be necessary to sustain agronomic needs and to offset 

the export of nutrients due to animal production. Knowledge gained through this study can be 

used to inform the management of forage-based livestock systems in humid temperate and subtropical environments on similar soils. 

Enhancing water quality from horticultural production. Over the past ten years, the area planted 

in field crops and orchards in South Florida has decreased dramatically, while the area in 

floricultural crops has steadily increased. As a result, ARS scientists in Miami, FL, have begun to 

develop BMPs that reduce or mitigate nutrient leaching from horticultural and floricultural 

production systems, to enhance water quality in South Florida. Scientists are specifically working 

to: 1) develop inexpensive, readily available potting substrates from waste generated by 

commercial nurseries and debris from construction sites; and 2) identify plants of commercial 

value that can serve as biological accumulators of excess nutrients and metals generated during 

nursery operations, for use in border strips to reduce the movement of hazardous materials offsite 

to adjacent riparian areas. When fully developed, this technology will benefit customers in the 

nursery industry, the fertilizer industry, and other commodity associations, by providing guidance 

on management practices that reduce the potential movement of nutrients offsite, and by 

developing growth media that utilize locally generated solid waste to enhance production 

efficiency while simultaneously ameliorating the negative impacts of solid waste collection sites. 

Problem Area 6—Water Quality Protection Systems

Developing sensors and procedures for corn N management. A significant proportion of the 

nitrogen losses from agricultural lands are associated with nitrogen fertilizers added in excess of 

crop nitrogen requirements. ARS scientists in Lincoln, NE, finalized the development of the Crop 

Circle active sensor system for N management through a CRADA with Holland Scientific (Lincoln, 

NE), and developed procedures for its effective use. Sensor readings provided rapid, accurate 

assessments of plant canopy greenness. Use of this sensor system to guide variable rate N 

applications has the potential to improve N use efficiency, enhancing both the environmental and 

economic quality of corn production, while reducing nitrogen losses from agricultural fields that 

contribute to the eutrophication of aquatic ecosystems. 

Vegetative buffers help reduce nutrients in soil and groundwater. Vegetative buffers are often 

used to reduce pollutant exports in waters draining from agricultural fields. Effective vegetative 

buffers require grass species that can capture nutrients before they run off the surface or leach to 

groundwater. ARS scientists at Columbia, MO, in collaboration with scientists at the University of 

Missouri, conducted a field study using five grass treatments (orchardgrass, tall fescue, smooth 

bromegrass, timothy, and switchgrass) compared to a bare ground control, to evaluate the ability 

of the grasses to remove nutrients, preventing their transport to shallow groundwater. All grass 

species except timothy reduced nitrate concentrations in shallow groundwater by ~99% 

compared to the control; switchgrass also reduced phosphate leaching by 60 to 74%. Grass 

treatments reduced soil nitrate levels by 41 to 91%. Overall, switchgrass, smooth bromegrass, 

and tall fescue were the most suitable for use in vegetative buffers because of their superior 

ability to reduce soil nitrate and nutrient leaching. These findings provide important information to 

improve the design of vegetative buffers, increasing their effectiveness in nutrient removal. 

Refining constructed wetland technologies for treating agricultural runoff. Degradation of water 

quality due to agricultural pollution is of global concern. Some treatment strategies use 

constructed, natural, or restored wetlands as buffers between agricultural fields and nearby water 

sources. ARS scientists at Oxford, MS, found that the long-term growth patterns of live, caged 

mussels placed in a constructed wetland were affected by insecticide received in artificial runoff, 
and documented elevated releases of phosphorus during winter die off when a common wetland 

plant species was exposed to elevated levels of nitrogen and phosphorus. These findings will 

help refine technologies that use wetlands to ameliorate agricultural pollution, allowing more 

informed decisions regarding nutrient and insecticide best management practices. 

Matrix Based Fertilizer Formulations Reduce N and P Losses By More Than 60%. Loss of 

soluble nitrogen (N) and phosphorus (P) from fertilizers to surface and ground water is an 

unfortunate side effect of agricultural, turf, nursery and home fertilizer use. A new fertilizer 

formulation strategy was developed at the Northwest Irrigation and Soil Research Laboratory, 

Kimberly, ID, that employs chemical fixation and ion exchange, rather than encapsulation, to slow 

the release of N and P. In greenhouse studies, these formulations, which are patent pending, 

reduced N and P leaching losses by over 60%. More than thirty industry enquiries for joint 

development and licensing to date attest to the potential for commercial development of matrix 

based fertilizer formulations to help reduce nutrient losses from fertilizer applications. 

Reaction of Chlorine and Isoxaflutole (Balance). Herbicides present in untreated water can react 

with the chlorine used by water treatment plants for disinfection. ARS scientists with the 

Cropping Systems and Water Quality Research Unit, Columbia, MO, in collaboration with the 

University of Missouri, studied the breakdown of DKN, the herbicidal metabolite of the corn 

herbicide isoxaflutole (Balance), by chlorine. DKN has been shown to be both present in the 

surface waters of the major corn-growing states, and to rapidly react with chlorine. Results 

showed that DKN was completely broken down by chlorine during the water treatment process, 

but that two potentially harmful products were formed: cyclopropanecarboxylic acid (CPCA) and 

dichloroacetonitrile (DCAN). Fortunately, levels of CPCA and DCAN formed were below those 

reported to cause toxic effects in humans or animals. This research identifies a potential human 

health issue associated with agricultural production, demonstrating the chlorination results in the 

complete breakdown of DKN, generating potentially harmful breakdown products (CPCA and 

DCAN) that appear to be present only at sub-toxic levels in resulting drinking water supplies. 

Best management practices might suggest routine CPCA and DCAN monitoring of chlorinated 

drinking water, and the development of techniques to remove these products from drinking water 

supplies. 

New Analytical Methods Aid In Identifying Herbicides and Their Metabolites in Soils and Plants. 

Accurately assessing the fate of herbicides and their metabolites in the environment requires the 

development of sensitive analytical techniques. ARS and University of Missouri scientists 

collaborated to develop two new analytical methods: one for the analysis of atrazine and its 

chlorinated metabolites in plants, and the other for the analysis of isoxaflutole (IXF) and its two 

primary metabolites in soils and plants. Both methods employ chromatography to separate the 

compounds of interest. Subsequent detection by mass spectrometry results in sub-part per billion 

detection limits (1 to 2 orders of magnitude more sensitive than previously published methods). 

To demonstrate their utility, these methods were applied to measurements of plants or soils from 

a field experiment. Results showed that in forage grasses, the ratio of metabolites to parent 

compound were good indicators of the detoxification pathways and overall sensitivity to each 

herbicide. Scientists, regulators, and industry will benefit from the availability of these 

appropriately sensitive methods for measuring herbicides and their metabolites in the 

environment, facilitating an improved understanding of their fate in the environmental fate, and 

leading to the implementation of vegetative buffers that more effectively prevent contamination of 

surface and ground waters. 

Pollutants in agricultural drainage waters can negatively affect organisms inhabiting wetlands 

constructed for water quality improvement. Constructed wetlands can be used as buffers 

between agricultural fields and nearby water sources, but the pollutants carried in runoff can harm 

organisms living in the treatment wetland. Live, caged mussels were placed in a constructed 

wetland receiving insecticide in an artificial runoff event. Although all of the mussels survived the 

event, long-term growth effects were observed. These findings will be used to refine the design 

of wetland construction projects for treating agricultural runoff. 
Summer cover crops reduce atrazine leaching to shallow groundwater in southern Florida. South 

Florida's surficial aquifer provides potable water for nearly all of South Florida’s rapidly growing 

population. Agricultural practices, which contribute to water quality impairment, have the potential 

to adversely affect the massive project focused on restoring south Florida’s Everglades 

ecosystem. Investigations were conducted in southern Florida to assess risks to groundwater 

quality from atrazine, used for sweet corn production in the region, and whether maintaining fields 

with a highly vigorous cover crop, Sun Hemp [Crotalaria juncea L.], during summer fallow periods 

would reduce impacts. Results demonstrated that climatic and cropping patterns, and relatively 

high dilution rates in the surficial aquifer, combined with high atrazine degradation rates in soil to 

limit contamination levels compared to other atrazine use sites. Measurements also showed that 

cover crop use leads to significantly lower contaminant levels in groundwater. Atrazine use 

presents a small, although potential significant, risk to groundwater quality in southern Florida, 

and that the use of a cover crop like Sun Hemp during summer months, when fields are fallow, 

may be an effective mitigation measure. As a result of this research, growers are being strongly 

encouraged to plant cover crops, which have many other potential benefits (e.g., reduced nutrient 

leaching and wind erosion; improved soil quality) in addition to reducing herbicide leaching.