Optimizing soil health in season extension environments through innovative cover crop management
Grant cycle: 2014-2017
High tunnels in cold climates, such as Minnesota, are in great demand, in part spurred by a national NRCS cost share program promoting their use. Yet, most sit empty in the winter, providing an opportunity to add soil-enhancing cover crops to the rotation. Most high tunnel producers that utilize carbon-based inputs do so using composts made from animal manures. Anecdotal information combined with recent studies indicate that high tunnels regularly using composted manures suffer from over-application of phosphorus (P) in the manure and are at risk of P runoff into sensitive waterways. This project sought to increase adoption of winter annual legume cover crop use in high tunnels by identifying species of interest to producers and timing requirements, then transfer evidence-based information to growers, including improvements in both soil quality and cash crop productivity. Our aim was to determine ‘best bets’ species or mixtures of cover crops that meet the unique needs of growers utilizing high tunnels in cold environments. Visit West Central Research and Outreach Center (WCROC) - Morris, MN for more information about cover crop managment in high tunnels.
Optimizing establishment of corn in cover crops and living mulches to maintain yield while reducing nitrate losses
Grant cycle: 2014-2017
Full-width tillage is well known to reduce soil carbon stocks and overall soil quality in systems where it is used continuously, stimulating the investigation of alternative tillage options. When combined with reduced tillage, systems that utilize legume cover crops on a regular basis have been shown to contain twice as much soil carbon as systems that do not, and four times as much microbial biomass, an important indicator of soil quality and nutrient mineralization potential. Strip tillage, also known as zone tillage, is a potentially attractive alternative to full-width tillage in which tilled strips are created, typically on 30 inch spacing, while the interrow areas are left untilled. This preserves surface cover for erosion protection while creating bare soil rows into which the row crops are planted. This study investigated the role of strip tillage with living perennial mulches in reducing N losses and improving soils and water quality in row crop production.
This project was a Minnesota Department of Agriculture (MDA) funded project in collaboration with Dr. John Baker in the Department of Soil, Water and Climate at the University of Minnesota ($232,444).
Rhizobia Ecology and Food Security in Malawi
Soil nitrogen limitations are endemic to the smallholder sector of Malawi due to limited access to fertilizers and a cropping system that depends heavily on maize (Zea mays) with very little integration of legumes. This has led to low yields, famine, and chronic malnutrition among large sectors of Malawian society. Local NGO’s and researchers have promoted legume integration for both soil fertility and family nutrition in the Ekwendeni region since the mid 1990’s. Farmer interest in new legumes has been countered by difficulty achieving adequate yields of these new crops. Farmers show keen interest in soybean (Glycine max) for its nutritional value, however yields are consistently low for both local “promiscuous” and improved varieties. Smallholder farmers, due to limited knowledge and access to resources, rarely practice inoculation, and poor nodulation is hypothesized to cause yield reductions. Soils in Malawi are also limited in available phosphorous, a necessary nutrient in the nodulation process. In this project, Mary Parr (now faculty at Berea College) investigated how soil nutrient status affects microbial diversity and rhizobia ecology and how this in turn affected the ability of soybean to nodulate, both with native rhizobia as well as inoculants.
This work was conducted as part of Parr's dissertation research in collaboration with the Legume Best Bets project, funded by the McKnight foundation and the National Science Foundation (NSF-GRF award).
Lighting up the black box:
Improving legume performance on organic farms by optimizing microbially-mediated plant and soil nitrogen cycling processes
Grant cycle: 2010-2013
This project sought to improve legume cover crop management on organic farms by examining key soil microbial processes that regulate nitrogen (N) cycling in cover crop legumes. Organic growers in NC use a diversity of legume cover corps and are experimenting with a wide range of termination techniques, including mowing, incorporation by disking the residue into the soil, and no-till techniques such as rolling and crimping cover crops with a water-filled drum. We investigated how non-chemical legume kill methods (rolling-crimping, flail mowing, or incorporation) impact N availability from decomposing legume residues. Our activities included:
surveying organic growers to determine current rhizobia inoculant handling procedures and legume perceptions;
establishing legume inoculant demonstration plots and using them to determine how inoculation practices impact legume productivity;
determining how non-chemical winter annual legume cover crop kill methods impact indicators of microbial activity and N supply to crop plants;
disseminating results and jointly educating North Carolina organic growers and students about soil microbial N-cycling processes in sustainable agriculture.
How does organic agriculture impact water quality and sediment losses?
Grant cycle: 2009-2012
The goal this project was to measure and model nonpoint source pollution (nitrogen (N), phosphorus (P) and sediment) associated with long-term organic and conventional vegetable farming systems under different tillage practices in the Appalachian Mountains of North Carolina. Water quality and runoff has been shown to be impacted by cropping system, however there is no water quality research that compares the same crop rotations within organic to conventional farming systems under two tillage regimes. In our research we evaluated soil organic matter, cover crop biomass, and soil nitrogen in order to relate changes in soil properties to nutrient and sediment runoff and water quality.
This project was a collaboration with Dr. Deanna Osmond at North Carolina State University and is funded by a USDA-CSREES Integrated Organic and Water Quality award.
Understanding how the Roller-Crimper implement affects N dynamics in no-till organic systems
Grant cycle: 2008-2011
Generally, soils in organic production have shown dramatic increases in organic matter and microbial biomass, in part due to the addition of organic and carbon rich sources of nutrients such as cover crops. The goal of this project was to quantify nitrogen -fixation and N-mineralization potential of 14 different legumes, including 4 hairy vetch cultivars, 4 crimson clover cultivars, 2 Austrian winter pea cultivars, and others. In non-organic systems, terminating cover crops prior to planting is mainly accomplished by the use of herbicides, however organic standards strictly prohibit the use of synthetic inputs. Along with soil nutrient management, weed control is another challenge for organic growers. Organic grain production relies on cultivation for weed control rather than herbicide use. Over the course of a growing season, organic corn and soybeans are typically cultivated 6 to 10 times, raising questions about the impacts of this practice on soil resource sustainability. The roller-crimper is an implement technology that is showing success in allowing organic farmers in the Southeast to develop no-till grain systems that successfully terminating winter legume cover crops and controlling weeds without the aid of synthetic herbicides or cultivation. The tool works by rolling over the cover crop and crimping the stem with blades when the crop is at full bloom-killing it and forming a thick mat on the soil surface that can suppress weeds as well as contribute fixed N to soil pools as legume biomass is decomposed. The cash crop is then no-till planted into the rolled cover crop.
The Role of Soil Organisms in Carbon Cycling in Anthropic Soils of the Brazilian Amazon
In this project we, in close collaboration with Brazilian scientists at the Centro de Energia na Agricultura, looked at how the soil microbial community influences a fascinating tropical soil system known as “Terra Preta” (Anthropogenic Dark Earth). Terra Preta (TP) soils found in the Brazilian Amazon are known for their unusually high soil C contents. It is now widely accepted that these soils were created between 500 and 2,500 years before present by indigenous pre-Colombian Indians for their own agricultural use. Since the existence of Terra Preta soils is a strong piece of evidence supporting the hypothesis of high population densities in the Amazon prior to Spanish conquest, fertility characteristics of TP soils are of great interest to scientists and local farmers as well. However, their biological properties remain a mystery. Because the carbon cycling in TP has been shown to be very different from other soils, we think that soil microbial life in TP soils will also be distinct, and characterized this diversity through our research. We used both traditional and novel molecular techniques to assess microbial abundance and diversity, including Polymerase Chain Reaction (PCR) to amplify target sequences of organism DNA, and Denaturing Gradient Gel Electrophoresis (DGGE).