 |
|||||||||
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
RESEARCH – NITROGEN – BMPs
Best Management Practices (BMPs) are effective, practical, structural or nonstructural methods which prevent or reduce the movement of sediment, nutrients, pesticides, and other pollutants from the land to surface or ground water, or which otherwise protect water quality from potential adverse effects of agricultural activities. These practices are developed to achieve a balance between water quality protection and agricultural production within natural and economic limitations. BMPs for nitrogen include on-field improvements, new drainage management systems, and edge-of-the-field and in-stream N sinks. An essential element of BMP research includes BMP monitoring and effectiveness. This website highlights some of the efforts to develop and improve BMPs for nitrogen (N) within the Land Grant University System, often with CSREES funding.
North Carolina State University created a manual - Selected Agricultural Best Management Practices to Control Nitrogen in the Neuse River Basin 
that provides an excellent overview and review of BMPs that resulted from scientist working group in the Neuse River Basin.
At the 2006 CSREES National Water Conference, a symposium entitled Advances and Challenges in Reducing Nitrogen Export from Rural Watersheds highlighted recent advances in understanding and managing nitrogen losses from rural and agricultural lands – and offered suggestions to meet the research and extension challenges to reduce the risk of watershed nitrogen export
On-field improvements
Researchers are evaluating the performance of various on-field BMPs aimed at minimizing N loss from the field.
Cover Cropping: Cover crops are important soil-improving and pollution-preventing tools. Legumes can add substantial amounts of available nitrogen to the soil – minimizing the need for fertilizer application. Non-legume cover crops can be used to take up excess nitrogen from previous crops and recycle the nitrogen also minimizing fertilizer additions – and N loss from the field. Researchers are evaluating different cover crops in each region of the United States.
Researchers at Washington State University are developing underseeded cover crop guidelines for humid Northwest environments and also are investigating seeding ratios to improve N contributions by mixed cover crops without losing too many benefits of ground cover and weed suppression.
A field study was carried out by Florida A&M University and the University of Florida to determine the effectiveness of ground cover in removing residual nitrates following crop harvest. 
Cover crops reduced soil nitrate-N by up to 15 mg/L in the soil profile.
Researchers at the University of Maryland and other universities in the northeast are investigating the special properties of Brassica cover crops and their potential for alleviating problems with soil compaction, parasitic nematodes, weed competition, nitrogen leaching or tie-up. If effective, these cover crops should increase crop yields and quality while saving significant dollars that otherwise would be spent on deep tillage, soil fumigation/solarization, nutrient purchases and the like.
Irrigation Strategies: Irrigation method and timing can influence the amount of nutrients that runoff from a field. Research through CSREES and the Land Grant System is being conducted to develop more efficient irrigation strategies that reduce nitrogen loss from fields.
Researchers at the University of Mississippi found that using multiple inlet plus intermittent rice irrigation, producers were able to capture more rainfall and reduce irrigation inputs by 30% as compared to continuously-flooded rice fields thereby reducing the potential for non-point source runoff of agrochemicals from rice fields.
At the University of Idaho, control technology for center pivot irrigation systems 
allowing both water and nitrogen to be independently applied was developed and evaluated. Results demonstrated that this system is feasible and can lead to increased gross return and reduced N leaching.
New drainage management systems
Subsurface drains, common in Midwest agriculture, have been found
in numerous studies to increase losses of nitrate-N through the
enhanced leaching of the soil profile. New
drainage management systems, including
drainage water management, sub-irrigation, bioreactors, and improved
ditch management, have recently been developed to reduce nitrate
loss due to agricultural drainage. Researchers
are continuing to develop and evaluate these improved drainage
management systems.
Flow and nitrate leaching into tile drains have been monitored since 1983 at
Purdue University. Results demonstrated the level of nitrate carried by tile drains and showed how reductions can be achieved when crop management practices are changed.
Ohio State University researchers are trying to quantify the extent that agricultural drainage ditches can help reduce nitrogen loading and identify management practices that increase the removal of excess nitrogen while maintaining economic viability.
The effects of subsurface
drainage depth on hydrology and nitrate-nitrogen loss were
examined over five years in a field experiment at the
University of Minnesota Southern Research and Outreach Center—Waseca,
MN. The shallow (90-cm) drainage depth reduced average
annual drainage volume up to 8-25 percent and annual nitrate-nitrogen
losses -6 (increase) - 30 percent.
Edge-of-field and in-stream nitrogen sinks
The amount of N that enters surface water may be reduced if nitrate-laden groundwater passes through a riparian buffer or filter strip before discharge. Research is ongoing to predict what riparian buffers or filter strips remove N most effectively and to evaluate the effectiveness of various riparian zone restoration and management approaches. Researchers are also assessing the significance of in-stream N removal processes.
Researchers at the University of Rhode Island (URI) Watershed Hydrology Laboratory determined landscape controls of riparian buffer zone groundwater nitrate removal. These insights were translated into methods that can be adapted to available spatial databases and enhance our ability to target high value riparian zones for protection and restoration to improve or maintain water quality. The URI NEMO Program has incorporated these results into their programming with municipal officials and modeling efforts.
Iowa State University researchers have demonstrated that riparian buffers re-established on previously cropped or pastured land have tremendous potential to remediate nonpoint source pollution in agricultural watersheds. Insights from this study are being used to improve buffer performance and placement within watersheds.
Researchers at Colorado State University evaluated the feasibility of using bank stabilization structures that are modified to include a permeable reactive barrier to reduce nitrate in groundwater. The results indicated that reactive stream stabilization structures with sawdust can remove significant amounts of nitrate, up to 60% more than a control structures. These results will provide guidance for design of stream restoration projects.
Researchers at Northwestern University are examining benthic assemblage and engineering them to reliably produce high rates of denitrification. This innovation will enable the construction and operation of artificial wetland systems with minimum area while also achieving maximum nitrate removal.
University
of Notre Dame researchers are measuring
rates of in-stream denitrification (i.e., nitrogen loss) in 7 headwater
agricultural streams in
the Midwest to determine the relative importance of denitrification
in removing N from these water bodies. This
project has identified settings where in-stream
denitrification may not be substantial and
identified management strategies that could maximize denitrification
in Midwest streams thereby reducing in-stream N loads and the adverse
effects of N loading on downstream ecosystems. Data from
this project has also been used to improve and refine models of
N transport in rivers.
The NRI is funding researchers at the University of Rhode Island to conduct a pilot study of in-stream N cycling in streams of the glaciated Northeast. This study provides the basis for future hypothesis-based research that will seek to improve the management of stream riparian zones in agricultural watersheds to enhance in-stream nitrate removal.
BMP monitoring and effectiveness at the watershed scale
Monitoring of water quality throughout a watershed enables researchers to assess the effectiveness of multiple implemented BMPs.
Kansas State University researchers are monitoring the water quality for a paired-watershed study of targeting BMP adoption to the most critical areas of a watershed. In three watersheds, targeted BMP adoption is occurring while in two adjacent watersheds, there is no BMP incentives program.
The Wisconsin Discovery Farms and Water Action Volunteers (an extension volunteer water quality monitoring program) joined forces to work with privately owned farms to identify effective and economical BMPs and to monitor and learn how these BMPs are improving water quality.
Researchers at the University of West Florida are studying the efficacy of BMPs on runoff water quality from row-cropping, silviculture and aquaculture discharge at the field and watershed scale. Results of this project were combined with education and extension activities to disseminate information to the public and encourage BMP implementation.
University of Arkansas researchers are synthesizing
historic watershed BMP, land use, and water quality data in a
GIS-linked database to quantify the impact of BMPs on
water quality.
Visit the Watershed Management Research page to learn more about Evaluating BMPs at the Watershed Scale.
page last modified on
May 21, 2008
all external sites will open in a new browser window