6. Tillage & Cover Crops
Public Waters (with 50’ avg. buffer standard)
This common alternative practice guidance is for implementation of tillage management and/or cover crops in combination with a perennially vegetated filter strip as an alternative practice to achieve water quality protection comparable to the prescribed buffer under the Minnesota Buffer Law. Sufficient perennial vegetation or other measures should be considered in all instances to protect and provide bank stability.
USDA Agronomy Technical Note #2 or its equivalent “Using RUSLE2 for the Design and Predicted Effectiveness of Vegetative Filter Strips (VFS) for Sediment” may be used for determining benefits and sizing of installed perennially vegetated filter strips.
Note: Alternative practices installed per this guidance within shoreland zoning districts should be coordinated with county or municipal officials responsible for shoreland ordinance provisions.
- In all situations below, perennial vegetation may be installed following NRCS 342 or 327 practice standards.
- Use the most current erosion prediction system supported by NRCS.
- Site-specific diagrams or pictures should be used to document validations.
Situation 1: Landowner is interested in implementing no-till/strip-till following NRCS 329 practice standard on their entire parcel and using a standardized vegetated filter strip. Follow these steps:
- SWCD validates that the no-till/strip-till 329 practice standard(s) are being met for all adjacent tillable land on the parcel.
- SWCD validates the presence of at least 25 ft of adjacent perennial vegetation.
Situation 2: Landowner is interested in implementing no-till/strip-till NRCS 329 practice standard and wants to calculate the size of the vegetated filter strip. Follow these steps:
- Run RUSLE2, following Tech note #2, for the parcel with a baseline condition without tillage management and a 50’ vegetative buffer strip.
- Run RUSLE2, following Tech note #2, and convert tillage to NRCS 329 No-Till/Strip-Till practice standard and reduce the vegetated filter strip width such that it reduces sediment delivery to the water body as identified in Step 1.
A minimum width of perennial vegetation of 16.5’ should also be established to provide bank stability and serve as a tillage setback to prevent sedimentation or direct application of fertilizer or pesticides below the top of bank or normal water level.
Find additional guidance on using RUSLE2 for Design and Predicted Effectiveness.
Landowner is interested in using situation #2 above AND adding a cover crop.
Follow steps for Situation #2 adding implementation of NRCS practice standard 340 Cover Crop when running RUSLE2.
The no-till/strip-till and cover crop practice standards commonly reduce runoff and associated pollutants to the perennially vegetated filter strip by more than fifty percent as compared to full tillage. For example, conservation tillage can reduce soil loss up to 90% when compared to conventional tillage (MDA Ag BMP Handbook). Demonstration of benefits is accomplished using RUSLE2 following the standard accepted methodology provided by USDA/NRCS Agronomy Technical Note #2.
Figure 12: Cross Section view, Tillage & Cover Crops (not to scale)