The purpose of this research was to identify trade-offs among soil erosion, soil health, and crop production when using cover crops with manure application.Continuous corn silage cropping systems in Wisconsin leads to overall removal of N from the system unless manure is applied. However, this cropping system allows for the planting of cover crops or a winter silage crop post harvest, which may lead to increases in soil N over time. Cover crops are valuable in these corn-silage based rotations as they also provide ground cover after harvest and can reduce N leaching after fall manure application.
What did we do?
The cropping system investigated was a continuous corn silage system with fall manure application. The experiment was a randomized complete block split-plot design where the whole plot treatments were no cover, rye as a cover (chemically terminated) or as a forage (harvested) crop and the split plot treatment was depth.The objective of this study was to determine the effect of cover cropping on potentially mineralizable nitrogen (PMN) over a growing season using a 7-day anaerobic incubation (2015 and 2016 season), a long-term aerobic incubation (2015 season), and N uptake by corn.
What have we learned?
There were no statistical differences in short-term PMN among cover crop treatments at any time point in 2015 or 2016. However, the cover crop treatments led to a yield reduction compared to no cover crop use in both years. Thus, our study showed significant effects of cover cropping on agronomic factors like corn yield and N uptake but these same differences were not measurable in the soil N.
This work will continue to evaluate the long-term effects of cover crop use on soil health.
This material is based upon work that is supported by the National Institute of Food and Agriculture, U.S. Department of Agriculture, under award number 2013-68002-20525. Any opinions, findings, conclusions or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture.
The authors are solely responsible for the content of these proceedings. The technical information does not necessarily reflect the official position of the sponsoring agencies or institutions represented by planning committee members, and inclusion and distribution herein does not constitute an endorsement of views expressed by the same. Printed materials included herein are not refereed publications. Citations should appear as follows. EXAMPLE: Authors. 2017. Title of presentation. Waste to Worth: Spreading Science and Solutions. Cary, NC. April 18-21, 2017. URL of this page. Accessed on: today’s date.
Farmers and ranchers are becoming increasingly aware of the importance of soil quality/health to the productivity and sustainability of their agricultural system. Research and field observations have demonstrated that carefully managed manure applications can contribute to improved soil quality with limited environmental and social risks. However, a comprehensive assemblage of outputs and conclusions from research studies, field trials, soil labs databases, and other sources has never been developed. Therefore, the purpose of the initiative, Manure & Soil Health: Understanding and Advancing the State of the Science, is to assemble current knowledge on this topic, make it available to those influencing manure and land management decisions, and use it to inform and facilitate future research and service needs. The intent of the roundtables is to improve our understanding of: current knowledge, critical and emerging issues for which there are knowledge gaps, and information needs of farmers and their advisors.
What’s A Roundtable?
The four, hour-long roundtables consisted of a panel discussion with experts who were asked to summarize their current understanding of topics. Each panel also included a practitioner who shared perspectives on critical information needs of farmers and advisors and field experiences relative to use of manure. Panels were moderated to encourage interaction with audience. Roundtable participants were invited to ask questions of panelists and share expertise and experience.
Most farmers and ranchers are acutely aware of weather and how it factors into their risk management planing. Climatologists have indicated that the trend toward more extreme events and greater extremes is going to continue. This has many implications for animal agriculture producers. The farmers featured in this Waste to Worth panel all provided their perspectives on adapting to extreme events through diversity, building resilience, and keeping an eye toward long-term profitability.
Diversity, Resilience and Manure Management with Cover Crops
A former ag teacher, Keith Berns understands that you need to be open to multiple ways of achieving a goal. His desire to build resilience into his farm system led to a business selling cover crop seeds that emphasize diversity. He outlines several scenarios where he uses cover crops on his farm and also several ways his seed customers utilize diverse cover crop and annual forage mixes. High stocking densities naturally incorporate manure, and residue helps conserve and hold valuable moisture during/after extreme rainfall events. [Nebraska/Kansas]
Perspectives On a Changing Climate
Dr. Sandra Matheson, DVM (retired) raises grass-fed beef cattle on her northwestern ranch. Weather extremes have created more dust, mud, and she has seen an increase in disease and health issues with cattle. She utilizes the decision-making process, holistic management, and planned grazing to create a system with the greatest amount of adaptability and resilience for her environment and its potential extremes. Her goals converge around building the soil. [Washington]
Grazing Dairy Finds Plants that Work in Low Water Environments
Michael DeSmet watched his cows when they entered a new paddock and noticed something surprising – they liked weeds. Upon further investigation, he found out that the weeds they were selecting were high-protein, palatable, and could survive on very small amounts of precipitation. Michael was no stranger to making changes; he had already converted the family dairy operation into a grazing-based system selling milk into niche markets. He continues to examine forage options for his pastures that allow the farm to utilize limited water, extend the grazing season, and improve soil quality. [New Mexico]
The authors are solely responsible for the content of these proceedings. The technical information does not necessarily reflect the official position of the sponsoring agencies or institutions represented by planning committee members, and inclusion and distribution herein does not constitute an endorsement of views expressed by the same. Printed materials included herein are not refereed publications. Citations should appear as follows. EXAMPLE: Authors. 2015. Title of presentation. Waste to Worth: Spreading Science and Solutions. Seattle, WA. March 31-April 3, 2015. URL of this page. Accessed on: today’s date.
In the Manure and Cover Crops roundtable, our goal was to discover whether manure and cover crops have complementary benefits related to soil quality. We debated if certain fields will produce more complementary benefits than others and whether timing of application and sampling affects these benefits. Finally, we’ll discussed whether we can derive an economic value for manure beyond its nutrient value. Field experiences and observations related to the value of manure as well as what farmers still need related to soil building with manure were discussed. This dialogue was the final of a four part series discussing the current state of our knowledge relative to manure’s impact on soil health.
Using the nitrogen reduction planning model involves three steps. The first step is to select a watershed, enter hypothetical adoption rates for each BMP, and compare the effectiveness and cost of the individual BMPs. The second step is to compare suites of the BMPs that would attain any given reduction in the N load at minimum cost. The third step is to “drill down” to the details and assumptions behind the models of effectiveness and costs of any particular BMP and make any adjustments to reflect your particular situation.
Why Develop a Nitrogen Reduction Planning Tool?
A watershed-level nitrogen reduction planning tool (Excel spreadsheet) compares the effectiveness and cost of nine different “best management practices” (BMPs), alone and in combination, for reducing N loads leaving a Minnesota watershed. The Minnesota Pollution Control Agency is developing a new set of standards for nitrate nitrogen in surface waters based on aquatic life toxicity. The tool was developed to assist the agency and local resource managers to better understand the feasibility and cost of various “best management practices” to reduce N loading from Minnesota cropland.
What Did We Do?
The BMPs are: reducing corn N fertilizer rates to extension recommended rates, changing fertilizer application timing, seeding cover crops, installing tile line bioreactors or controlled drainage, planting riparian buffers, or converting some corn and soybean acres to a perennial crop. The spreadsheet does its analysis for a watershed that the user selects. However, the N loadings and crop economic calculations are done first by agroecoregion before aggregating the results into the watershed of interest. Agroecoregions are units having relatively homogeneous climate, soil and landscapes, and land use/land cover. The spreadsheet includes area data for the fifteen high-N HUC8 watersheds that make up roughly the southern half of the state, along with the state as a whole. When the user selects a watershed for analysis, formulas retrieve results as an area-weighted average of the agroecoregions making up that watershed. Each of the fifteen HUC8 watersheds includes between four and nine agroecoregions.
The N loadings from each agroecoregion are calculated in three categories: drainage tile discharges, leaching from cropland, and runoff. Nitrogen loading amounts modeled are “edge-of-field” measures that do not account for denitrification losses that occur beyond the edge of field as groundwater travels towards and is discharged to streams. The BMPs consider only loading from cropland, but loading from forests and impervious urban and suburban land is also included in the totals.
What Have We Learned?
The EPA’s Science Advisory Board has said that a 45% reduction in both N and P is needed in the Mississippi River to reduce the size of the Gulf of Mexico hypoxic zone. This tool suggests that the BMPs considered are not likely to achieve much more than half that reduction even at high adoption rates. Reducing N fertilizer rates on corn down to extension-recommended levels and shifting from fall to spring or sidedressed applications tend to be among the cheaper BMPs to adopt, but the results vary across watersheds and weather scenarios. Various other factors such as crop and fertilizer prices also affect the results, hence the need for a computer tool.
The tool and results of a larger project will be reviewed during the first half of 2013. The tool may then play a role in implementation of the new N state standards in the state.
William F. Lazarus, Professor and Extension Economist, University of Minnesota firstname.lastname@example.org
Geoff Kramer, Research Fellow, Department of Biosystems and Bioproducts Engineering, University of Minnesota
David J. Mulla, Professor, Department of Soil, Water, and Climate, University of Minnesota
David Wall, Senior Hydrologist, Watershed Division, Minnesota Pollution Control Agency
The latest version of the tool and an overview paper are available at the author’s project page.
Davenport, M. A., and B. Olson. “Nitrogen Use and Determinants of Best Management Practices: A Study of Rush River and Elm Creek Agricultural Producers Final Report, submitted to the Minnesota Pollution Control Agency as part of a comprehensive report on nitrogen in Minnesota Surface Waters.” Department of Forest Resources, University of Minnesota, St. Paul, Minnesota, September 2012.
Fabrizzi, K., and D. Mulla. “Effectiveness of Best Management Practices for Reductions in Nitrate Losses to Surface Waters In Midwestern U.S. Agriculture. Report submitted to the Minnesota Pollution Control Agency as part of a comprehensive report on nitrogen in Minnesota Surface Waters.” September 2012.
Lazarus, W. F., et al. “Watershed Nitrogen Reduction Planning Tool (NBMP.xlsm) for Comparing the Economics of Practices to Reduce Watershed Nitrogen Loads.” December 11, 2012, http://wlazarus.cfans.umn.edu/.
Mulla, D. J., et al. “Nonpoint Source Nitrogen Loading, Sources and Pathways for Minnesota Surface Waters. Report submitted to the Minnesota Pollution Control Agency as part of a comprehensive report on nitrogen in Minnesota Surface Waters.” Department of Soil, Water & Climate, University of Minnesota, September 2012.
Partial support for this project was provided by the Minnesota Legislature.
The authors are solely responsible for the content of these proceedings. The technical information does not necessarily reflect the official position of the sponsoring agencies or institutions represented by planning committee members, and inclusion and distribution herein does not constitute an endorsement of views expressed by the same. Printed materials included herein are not refereed publications. Citations should appear as follows. EXAMPLE: Authors. 2013. Title of presentation. Waste to Worth: Spreading Science and Solutions. Denver, CO. April 1-5, 2013. URL of this page. Accessed on: today’s date.