The purpose of this report is to estimate annual sediment delivery in ton/acre/yr from each field to the nearest surface water with current and alternative management practices. Although this calculation of sediment delivery uses RUSLE2, this is not the same as the soil loss calculated for nutrient management planning.
How the report is calculated: First RUSLE2 is run for the representative hillslope for the predominant soil map unit in the field. Hillslope sheet and rill erosion sediment delivery for RUSLE2 is in ton/acre/yr for 5 particle size classes: clay (0.002 mm), silt (0.01) mm, sand (0.2 mm), small aggregates (0.03 mm) and large aggregates (0.3 or greater). Making the assumption that only the smaller particles, silt and clay, will be delivered, silt+clay is multiplied by a field-to-stream delivery ratio derived from mechanistic modeling. Sediment losses from concentrated flow channel or gully erosion within a field are not included in these calculations.
As with the P Trade Report, for this report RUSLE2 is run for each field as a sequence of years, rather than a rotaion. This means that changing data in later years will not change the calculated annual values for earlier years, as happens when soil loss is calculated in a rotation. Also there is no limit on the number of years that can be included, in contrast to rotations which are limited to 8 years. To be able to calculate soil loss accurately with a sequence of years, two "set-up" years are required. That is why this report requires at least two crop years of information before the start year for each field.
How sediment delivery is displayed in the report:
The Sediment Trade report can be run for a farm, subfarm, or group. The report contains a row for each field with the field name, the soil series used for the RUSLE2 calculation (predominant), and the field acres. Then there is a column for every year in the calculation record with the total estimated sediment tons delivered for the field for that year (calculated tons per acre x acres). The sediment delivery for each field will differ from year to year depending on crops, tillage, and fertilizer and manure applications.
How the P Trade report is used:
Planners can compare the Sediment Trade Report for a farm or subfarm under suites of alternative managements to see determine how much they might reduce sediment delivery field-by-field and farm wide. This report was developed to facilitate sediment water quality trading in Wisconsin and more information on how to use it can be found here