Cover Crop Effects: Farmer Observations and Researcher Measurements
We all know that cover crops [CC] are being promoted to improve soil health on U.S. cropland. Results from myriad research studies have shown that CC use can improve certain soil health parameters, but just how do these results compare to the perceived soil health benefits that producers observe following CC use on their crop fields?
This is the subject of results reported in an article titled “Cover crop management practices to promote soil health and climate adaptation: Grappling with varied success from farmer and researcher observations” by Gutknecht et al. in the Journal of Environmental Quality [2022:1-17]. Pertinent points from that article follow.
• Objectives of the study were to 1) measure the response of several NRCS-recommended field and lab metrics of soil health where various CC’s had been grown for a short period [1-3 years] on working farms, and 2) assess CC performance and improvements to soil health.
• The assessed data were those from 27 farmer surveys and field and lab assessments of soil collected from 15 paired fields that represented a range of soil types and management practices across southern Minnesota.
• The 15 paired fields [CC and no CC] spanned much of the corn-soybean growing area of the state. Fields with no CC were used for comparison.
• CC’s included at least two species, and fall tillage was not performed on any site.
• Surveyed farmers reported better CC performance following drill vs. broadcast or aerial seeding of CC’s. A majority of surveyed farmers used chemical vs. winter kill or mechanical termination of CC’s.
• The effect of the short-term cover cropping was significant for 4 of 42 assessed metrics. The 4 were microbial enzyme activity [cellobiohydrolase], earthworm counts, visual evaluation of soil structure [VESS], and a decrease in percentage of bare ground. The authors suggested that these metrics could signal the early improvement in soil health where CC’s are used, and recommend using them along with farmer input and observations to determine the effectiveness of incentive programs such as the NRCS EQIP [Environmental Quality Incentives Program].
• A high percentage of participating farmers reported improvements in soil attributes and/or productivity following CC use that did not necessarily align with the accepted field and lab measurements of soil quality improvements resulting from use of CC’s.
• The results from this research suggest that: 1) A diverse mix of CC species that will increase off-season ground cover can improve characteristics associated with soil health; and 2) There needs to be more cooperation between farmers who use CC’s and researchers who evaluate their effects so that the metrics needed/used to capture improvements of interest to farmers [e.g. field workability, crop productivity and vigor, pest pressure, earlier planting capability] can be developed and/or enhanced. This should result in field evaluations that more closely align with visible soil improvements reported by farmers.
• Overall, the data presented in this report showcase the need to acknowledge that management decisions [e.g. tillage practices, crop rotation, species of CC, timing of CC planting] involved with implementing a CC system will interact with site-specific soil factors to affect soil health improvements that are expected to result from using CC’s.
Detailed information about using CC’s in Midsouth crop production systems is contained in a Cover Crops White Paper on this website.
Composed by Larry G. Heatherly, Dec. 2022, larryh91746@gmail.com