The following article was featured in the 2023 NLRS Biennial Report.
The Illinois NLRS Science Team follows a formal evaluation procedure to adopt new conservation practices and update practice performance numbers, which can be found at go.illinois.edu/NLRS
In July 2022, partner organizations submitted two new proposals to the NLRS Steering Committee: one for floodplain wetlands and one for water and sediment control basins, WASCOBs. A third proposal was submitted to request an updated phosphorus loss reduction efficiency value to constructed wetlands, a previously adopted NLRS practice in Illinois. This was the first time an NLRS practice performance revision has been proposed.
Per the formal evaluation procedure, the NLRS Steering Committee first evaluated the proposals for completeness. The committee determined that all three proposals contained the information required for a full evaluation by the Science Team. Table 3.7 summarizes the decisions made during a series of virtual meetings in October and November 2022.
Table 3.7. Summary of Illinois NLRS Science Team Proposed Practice Decisions
Practice | Decision | Efficiency Number | Cost |
Water and sediment control basins | Include as an NLRS practice | 60% P loss reduction in non-tiled fields; 0% nitrate-N loss reduction | $64/ac/yr |
Floodplain wetlands | Insufficient information | – | – |
Updated P loss reduction efficiency for constructed wetlands | Insufficient information | – | – |
Water and Sediment Control Basins
A water and sediment control basin, WASCOB, is an earthen embankment across the slope of a minor drainageway constructed to trap sediment. This conservation practice was originally submitted for the 2021 Biennial Report cycle and was recommended for resubmission to allow incorporation of known, active research. The Science Team determined that WASCOBs should be included in the list of NLRS practices due to the inclusion of additional Illinois-based research in the proposal. They decided on a phosphorus loss reduction efficiency value of 60%, which was the mean value found in the literature review provided in the proposal. For reference, Iowa includes WASCOBs as a nutrient reduction practice at 85% phosphorus loss reduction value. The Science Team’s more conservative conclusion was due to concerns over dissolved phosphorus loss from WASCOBs during rain events. Since this is a sediment control practice and evidence is lacking at this time for a nitrate-nitrogen loss reduction efficiency value, a 0% nitrate-nitrogen loss reduction efficiency value was adopted.
A cost estimate for this practice was calculated from Natural Resources Conservation Service, NRCS, data provided in the proposal and adopted at $64 per treated acre per year. This factored in installation costs (averaging $4,700), the expected practice life (10 years), and the average drainage area treated (10 acres). These data were converted into an equivalent annual cost per treated acre by multiplying the installation cost per treated acre by a 6% discount factor, then dividing by (1- (1+6%)^(-life)). Annual operation and maintenance costs were not added although such costs are assumed to exist. A primary tracking source for this practice is USDA NRCS. While NRCS cost-share contracts for WASCOBs stipulate operation and maintenance activities and standards, the payment schedules for these contracts do not allow for specific operation and maintenance payments for this practice.
Floodplain Wetlands
Insufficient information about this practice precluded inclusion at this time.
Updated Phosphorus Loss Reduction Efficiency for Constructed Wetlands
Insufficient information about this practice precluded inclusion at this time.
Updated NLRS Agriculture Conservation Practices List
The NLRS Science Team assessed the list of agriculture conservation practices to assign performance values based on each practice’s ability to reduce nitrogen and/or phosphorus loss. The original science assessment established these approved NLRS practices. The team approved three new practices – saturated buffers, terraces, and water and sediment control basins – in 2021–22 and added them to the list of recommended practices. Table 3.8 is a combination of tables 3.11 and 3.14 from the original 2015 strategy report to display all of the nitrate-nitrogen and phosphorus reduction practices as well as the newly approved practices.
Table 3.8. Agricultural conservation practices that reduce nitrogen and/or phosphorus loss
Practice | N Reduction | P Reduction |
In-field practices |
Cover Crops (grassed based) | 30% | 30% - 50% based on tillage choices |
MRTN | 10% | 0% |
Soil Test P | 0% | 7% |
Conservation Tillage | 0% | 50% based on tillage choices |
N inhibitor | 10% | 0% |
50% Fall N / 50% Spring Preplant N | 7.5% - 10% | 0% |
40% Fall N / 10% Preplant / 50% Sidedress | 15% - 20% | 0% |
Spring only N | 15% - 20% | 0% |
Terraces | 0% | 40% |
WASCOBs | 0% | 60% |
Edge-of-field practices |
Bioreactors | 25% | 0% |
Wetlands | 50% | 0% |
Saturated Buffers | 40% | 0% |
Stream Buffers on all applicable crop land (reduction only for water that interacts with active area) | 90% | 25% - 50% |
Land use change practices |
Perennial/Energy Crops | 90% | 50% - 90% based on tile drainage and tillage type |
In 2021-22, the following researchers from University of Illinois served on the NLRS Science Team: Dennis Bowman, University of Illinois Extension; Laura Christianson, Department of Crop Sciences; Reid Christianson, Department of Crop Sciences; Jonathan Coppess, Department of Agricultural and Consumer Economics; George Czapar, Emeritus Agricultural and Biological Engineering, and Emeritus Associate Dean & Director of Extension College of Agricultural, Consumer and Environmental Sciences; Paul Davidson, Department of Agricultural and Biological Engineering; Andrew Margenot, Department of Crop Sciences; Maria Villamil, Department of Crop Sciences; and Lowell Gentry, Emeritus Department of Natural Resources and Environmental Sciences.
