NRCS studies show the number of producers using cover crops in several Corn Belt states has doubled over the past 5 years. While national statistics on the practice are difficult to nail down, estimates hold 10 million or more acres of American farmland are currently involved in a cover crop rotation of some kind.
Because of wide variations in geography and farming practices, economic figures are also difficult to catalog on the ROI of cover crop use on a year-to-year basis. However, a recent case study on the value of covers by the Iowa Soybean Assn. (ISA) On-Farm Network show the practice has definite economic returns — even if they aren’t immediately realized in the grain tank.
In Iowa, local top soil values have been estimated in a range from $7-20 per ton, not counting the cost to land value because of erosion or the loss of future productivity due to lost soils and nutrients.
The ISA study examined long term benefits of covers on soil health on a field with slope ranges from 2–15% and managed with a no-till corn and soybean rotation. Using NRCS’s RUSEL2 (Revised Uniform Soil Erosion Loss) model, the annual erosion on the field was estimated at 4.1 tons per acre. By using cover crops on the field, erosion losses were reduced to 1.1 tons per acre for a dollar savings of $21-60 per acre, depending upon the value placed on the lost topsoil.
The study also noted a well managed cover crop is equal to the value of herbicides in the control of winter weeds such as marestail, henbit and field pennycrest. In most cases, small yield increases were shown for crops following use of a cover.
Researchers say part of that yield increase could result because Corn Belt fields under cover crops tend to be drier in the spring, allowing earlier and more favorable planting conditions. Also, ISA’s research shows fields planted to cover crops have more soil moisture during the summer months because of better soil structure — which promotes more efficient water infiltration and reduces runoff. The additional soil moisture in cover cropped fields would improve yields over fields with no cover.
ISA research also shows other benefits of cover crops, such as increasing soil organic matter and reductions in compaction, take time and need multiple years of cover cropping to develop measurable economic benefits.
New Erosion Monitor Tools
Equipment dealers offering precision ag support have a new tool available from Agren to add a soil-loss component to their offerings to help growers accurately predict changes in soil quality based on past, present and future farming practices.
SoilCalculator, developed by Agren of Carroll, Iowa, takes the best of NRCS’s RUSLE2 which calculates a Soil Conditioning Index score for one point in a field and makes it possible to analyze soil erosion and soil health on a 9 meter grid, similar to a yield map.
“This tool allows farmers and ag retailers to quickly correlate soil health with yield,” Tom Buman, Agren CEO, explains.
SCI is generated by running the USDA Ag Research Service’s RUSLE2, which is used by growers for conservation planning. The inputs to RUSLE2 are used to predict the balance of soil organic matter, the effects of tillage/field operations and estimated soil erosion; summing them together for an overall soil condition rating.
Buman says the components of the RUSLE2 construct are weighted, with organic matter at 40%, field operations at 40% and soil erosion at 20%. SCI scores can be negative (indicating a decline in soil condition).
NRCS holds that SCI is the most effective predictive tool for soil health, but until recently using it was cumbersome and, many times, involved several days to obtain results.
“Agren SoilCalculator allows service providers to plug in various crop rotations, tillage systems and conservation practices, and view the resulting erosion predictions for up to 3 scenarios,” Buman explains. “Color-coded maps, similar to a GIS yield map, pinpoint areas of high erosion. Growers can easily evaluate alternatives side by side to maximize profits, conserve soil, preserve yields and reduce nutrient inputs.”
The tool can be used to:
- Compare management alternatives to maximize profits
- Target practices to high soil erosion areas
- Lower input costs and protect land value
- Make decisions based on actual slope steepness instead of book values
- Calculate average soil erosion per acre and total annual soil erosion
- Visualize erosion areas across the field
- Define the most erodible 20% of the field
- Create a GIS layer to share with other precision ag software
Buman says licensing agreements for SoilCalculator are available.