Short-Term Effects of Cover Crops and Minimum Tillage on Nutrient and Sediment Loss from Production Fields
It is widely accepted that both cover crops and minimum tillage will benefit soil health in the long-term. However, nutrient and sediment loading into runoff water from production fields is also a concern because of the resulting pollution effect on streams and rivers that collect the water from those fields.
In a report titled “Transitioning from conventional to cover crop systems with minimum tillage does not alter nutrient loading” by Badon et al., results from research conducted in northwest Miss. provide insight into the short-term effect of these two conservation practices on the nutrient and sediment content of water that leaves production fields that are dedicated to a corn-soybean rotation system. Pertinent points from that article follow.
• Non-point source pollutants such as sediment, nitrogen (N), and phosphorus (P) that are carried in runoff from crop production fields have an unfavorable effect on surface water quality.
• There is limited research at the field scale to scientifically validate the value of conservation management practices to remedy this problem when used in a corn-soybean rotation system that is transitioning to a cover crop minimum tillage (CCMT) system of production from a system of farmer’s best management (FBM). (See publication for cover crop species used and tillage operations performed in both CCMT and FBM).
• Conservation production systems such as CCMT will reduce soil disturbance and increase surface residues, but can also result in an increase in the concentration of nutrients near the surface in soils.
• The specific objective of the research reported in the above article was to quantify the effects of CCMT on the transport of sediment, N, and P to surface waters that receive field runoff from a production site during transitioning of that site from FBM to CCMT.
• Edge-of-field monitoring (EOFM) was used to quantify the effectiveness of CCMT for reducing sediment and nutrient load in surface runoff from the research sites that were in the transition stage.
• This 2-year study was conducted from 2017 to 2019 at six sites in northwest Mississippi using split fields that had soils that are classified as poorly to somewhat poorly drained and with slow to moderately slow permeability.
• The average annual STIR values were 101 and 22 for FBM and CCMT sites, respectively.
• Runoff samples from each site were assessed for N, P, turbidity, and total suspended solids (TSS).
• In this study, CCMT had no significant effect on N, P, and TSS transport in runoff from the research fields to surface waters.
• These results indicate that it is unlikely that a CCMT system will reduce N, P, and sediment loading in water runoff from a production field that is devoted to a corn-soybean rotation while that field is transitioning from an FBM to a CCMT system.
These results support to the following tenets. 1) The benefits resulting from adoption of conservation management practices such as minimum tillage and use of cover crops will not be realized in the short term. Rather, projected benefits from adoption of these practices will likely only be realized when they are applied/used for a longer period–e.g. 10 years or more. 2) Once adopted, conservation management practices such as those used in this research must become the long-term norm in order to see the expected accrual of benefits from their use.
Click Tillage, Cover Crops, and Soil Health to access White Papers on this website that contain detailed information about these subjects.
Composed by Larry G. Heatherly, Jan. 2023, larryh91746@gmail.com