Progress 07/01/23 to 06/30/24
Outputs
Target Audience:Crop and vegetable growers, extension educators, ag industry professionals, consumers, undergraduate students, graduate students, post-docs Changes/Problems:This project was approved in the 2021 grant cycle, but funding was not received until 2022. By that time the original PD, Sieglinde Snapp, had taken a leave of absence from Michigan State University. The project was amended to Kim Cassida as PD in 2022, with Dr. Snapp's post-doc Alexia Whitcombe added as a co-PD and Laurie Drinkwater remaining as the Cornell PD. In the 2023-2024 reporting year, Dr. Snapp's leave of absence became retirement and she will not return. Alexia Whitcomb left the project in late 2023 and was not replaced. The delayed funding and staffing changes have created logistical challenges. We describe how we will deal with these in the section on the next reporting period. What opportunities for training and professional development has the project provided?This past year the project has continued to provide training opportunities for two graduate students (one at Cornell, the other based at MSU), and four undergraduates in the Drinkwater lab worked on this project. The graduate students continued to develop a well-rounded skill set for conducting agroecological research including proposal writing, experimental design, data management and statistical analysis. The undergraduates gained hands-on experience carrying out greenhouse experiments, basic laboratory skills and using designated laboratory protocols. How have the results been disseminated to communities of interest?Results were disseminated via presentations to scientists, students, professionals, farmers, and FAO. A poster was presented at the 2023 Tri-Societies meetings in St. Louis Missouri. What do you plan to do during the next reporting period to accomplish the goals?In this second year of this grant. Dr. Snapp's leave from MSU became permanent and her involvement in the project was greatly reduced. This, combined with other consequences of her departure from MSU caused delays in completing the work, we plan to apply for an NCE in early February 2025 so we can continue our progress. Objective 1. 1) Results from the greenhouse experiment comparing P acquisition in seven cover crop species are being analyzed and will be used in preparing a manuscript. 2) A second greenhouse experiment examining the role of VAM in P acquisition in soils that differed in terms of plant-available P was conducted using two common cover crop species. These results have been analyzed, and a manuscript is in preparation. 3) A field experiment comparing ten functionally distinct cover crop species was established in September 2024. T0 soil samples were collected from all plots prior to planting and soil nitrate, ammonium, nitrogen mineralization, nutrients, pH, CEC and enzyme activities were measured during Oct-Dec 2024. Soil and cover crop biomass samples will be collected from the field experiment in May 2025 and in-growth cores will be used to investigate P mobilization from recalcitrant sources in the field. Objective 2. The survey originally planned was revised into a survey aimed at extension program attendees and network contacts. The objective was to explore farmer beliefs regarding soil phosphorus and 21 responses were received in summer 2024. The results are being summarized; however, the farmer responses indicate that most farmers were unaware of the potential for cover crops to significantly improve P supply mechanisms. After discussions with extension educators and farmers we will evaluate the resources that are available to help farmers select cover crops that best meet their soil health and nutrient objectives. Objective 3. Soil samples from long-term experiments will be fully analyzed in the coming year and we will prepare a manuscript from this research.
Impacts
What was accomplished under these goals?
Objective 1. Greenhouse experiment A: Analysis of samples from the greenhouse experiment characterizing the ability of seven cover crop species (buckwheat, chickpea, millet, rye, vetch, mustard and wheat) to access phosphorus from sources that differed in their bioavailability continued. Briefly, this study used a low P media (sand, filtered sand, and gravel, 2:2:1 ratio) with a bolus of field soil to serve as a microbial inoculum from which plants could recruit their root microbiomes to grow plants in the greenhouse. Each plant species was grown in five different P treatments: ferric phosphorus (FP), calcium hydroxyapatite (CP), compost (OP), inositol hexaphosphate (PY), and the control treatment soluble P (PS). With 4 replicates of each plant-phosphorus combination, we had a total of 140 pots (including controls with no plants). This past year, we analyzed the phosphorus content of shoots and roots from the greenhouse study to compare tissue P concentrations, total P acquisition and allocation of P to aboveground versus belowground biomass. Results: Overall, total biomass production showed few significant within species differences across different P treatments. Differences in P acquisition largely corresponded to biomass production with notable exceptions that reflected variation in P concentrations in plant biomass across species and P source. Key findings are as follows: Most cover crop species tested acquired similar amounts of P from the soluble P control and organic P sources except for rye which showed a significant reduction in P acquisition from compost and phytate treatments. Millet and vetch had a greater ability to acquire P from the recalcitrant mineral treatment. For these two species, P uptake in the ferric phosphorus treatment was not significantly different from plants grown in the soluble P control Compared to the soluble P control, chickpea, mustard, and buckwheat preferentially put resources into building root biomass when accessing recalcitrant P sources. Field experiment: Planning for a two-year field experiment to compare functionally distinct cover crop species commonly used by US farmers began and will continue into the summer. We expect to include the following cover crops: Hairy Vetch (Vicia villosa x two cultivars: cv. 'AU merit' and 'Vinter'), Red clover (Trifolium pratense planted with Avena sativa nurse crop), Alfalfa (Medicago sativa planted with Avena sativa nurse crop), Orchardgrass (Dactylis glomerata), Perennial ryegrass (Lolium perenne), Winter Wheat (Triticum aestivum L. x two cultivars: cv.'Byrd' and 'Snowmass' ) Forage Kale (Brassica oleraceae L), and Winter Camelina (Camelina sativa) to be planted in September 2024. Greenhouse experiment B: Our original proposal didn't include research on the role of arbuscular mycorrhizal fungi (AMF) on P acquisition. However, one of the graduate students was interested in conducting research in this area and we recruited a collaborator with expertise to support this work. Many important cover crops partner with AMF and there are significant gaps in our understanding of how these mutualists contribute to the enhanced P cycling that can be provided by cover crops. We conducted a greenhouse experiment in the summer of 2023 with the objective of evaluating the relative contribution of soil P distribution, AMF symbiosis, and cover crop species to cover crop P uptake and growth. Soils were sourced from two treatments at the Long-Term Ecological Research site at Kellogg Biological Station with contrasting management histories that have resulted in distinct soil P profiles. The soil with a history of legume cover crops has two-fold greater organic P content in the active SOM pools. We imposed two AMF treatments (1=no AMF, 2=AMF) and two cover crop species (1=rye, 2=hairy vetch) using these two soils. We found significant differences in the role of AMF between these two cover crop species. Vetch responded positively to AMF with greater biomass and P uptake whereas rye either showed no significant effect or a reduction in growth in response to AMF. The impact of AMF on vetch varied with soil management legacy. A second experiment will be conducted during the Summer/Fall of 2024. Objective 2. Challenges due to the departure of team members and difficulties with farmer recruitment led to delays and changes in this objective. The large survey and subsequent on-farm data collection from selected survey farms that was to be conducted in 2022-23 dropped because farmers are being bombarded by too many surveys and are becoming very difficult to recruit, especially without the expertise of Dr. Snapp who was to have led that work before taking a leave of absence. The focus of our outreach and farmer participation efforts has shifted to reflect these changing conditions and is described under the planned changes section. A smaller survey was designed at Michigan State solely to explore farmer beliefs about soil phosphorus and distributed via extension networks in summer 2024. Objective 3. Composition soil samples were collected from five replicated long-term experiments that compared maize rotations with leguminous cover crops as N sources to conventional maize receiving inorganic fertilizers without cover crops. Fresh soils were analyzed for nitrate, ammonia, and N mineralization potential were carried out on fresh soils. Subsamples were frozen for enzyme activity determinations to be performed at a later date. The remaining soil was air dried.
Publications
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Progress 07/01/22 to 06/30/23
Outputs
Target Audience:Crop and vegetable growers, extension educators, ag industry professionals, consumers, undergraduate students, graduate students, post-docs. Changes/Problems:This project was approved in the 2021 grant cycle, but funding was not received until 2022. By that time the original PD, Sieglinde Snapp, had taken a leave of absence from Michigan State University, which turned into permanent retirement. The project was amended to Kim Cassida as PD in 2022, with post-doc Alexia Whitcombe added as a co-PD and Laurie Drinkwater remaining as the Cornell PD. Delayed funding and staffing changes have created logistical challenges. We describe how we will deal with these in the section on the next reporting period. What opportunities for training and professional development has the project provided?This past year the project has provided training opportunities for two graduate students (one at Cornell, the other based at MSU) and one undergraduate. The students are learning the basics of how to plan and design a greenhouse experiment while gaining hands-on experience in carrying out the laboratory protocols we will be using for this project. They gained experience in researching literature to select functionally distinct cover crop species and analytical methods to be used in our greenhouse experiments. They also learned how to use flow charts to track the progress of complex experiments. How have the results been disseminated to communities of interest?Results were disseminated via presentations to scientists, students, professionals, farmers, and FAO. What do you plan to do during the next reporting period to accomplish the goals?Objective 1. Work in objective 1 will continue in an effort to overcome the difficulties encountered in detecting P mobilization in greenhouse work. These results are needed to inform field treatments for Objective 2. Objective 2. Dr. Snapp's temporary leave of absence turned into retirement from MSU. Since she will not be returning and her graduate student opted to do a terminal MS instead of completing the PhD, we plan to transfer primary responsibility for Objective 2 to the Cornell research group which has a farm network, labor and lab capability to do the required on-farm data collection and P analyses. An amendment application for this change is being prepared. Objective 3. Soil samples from long-term experiments will be analyzed in the laboratory by the Cornell research group as planned and results prepared for publication.
Impacts
What was accomplished under these goals?
Objective 1: We performed a pilot greenhouse study to characterize the ability of seven cover crop species (buckwheat, chickpea, millet, rye, vetch, mustard and wheat) to access phosphorus from sources that differed in their bioavailability. We used a low P media (sand, filtered sand, and gravel, 2:2:1 ratio) with a bolus of field soil to serve as a microbial inoculum from which plants could recruit their root microbiomes to grow plants in the greenhouse. Each plant species was grown in five different P treatments: ferric phosphorus (FP), calcium hydroxyapatite (CP), compost (OP), inositol hexaphosphate (PY), and the control treatment soluble P (PS). With 4 replicates of each plant-phosphorus combination, we had a total of 140 pots (including controls with no plants). We harvested plants when they met one of the following criteria: either 80% of the plants in that species reached anthesis or plants had been growing for ten weeks. Plants were destructively sampled, and shoots and roots collected, cleaned, and dried for biomass and tissue nutrient analysis. At this point, we have data on biomass and are processing samples for tissue P concentration to determine total P uptake of plants. Overall, our biomass data shows few within-species significant differences for different P treatments. For five out of the seven species (buckwheat, millet, rye, vetch, and wheat), the only P source that resulted in a significantly different total biomass from the soluble phosphorus treatment was CP. While not statistically significant, species consistently had lower mean total biomass when grown with FP than with PS. Our results also suggest organic forms of P may often be more accessible than mineral P, as four of the seven species had a significant difference in total biomass between at least one of the organic phosphorus forms (OP or PY) compared to both mineral P forms (FP and CP). Our screening experiment relies on our ability to tease apart whether species are differently able to access less available P forms, yet because most plants are performing similarly regardless of P source, it is difficult to identify plants that standout in their ability to access poorly available P forms. There are two issues with our experimental set up which may contribute to detecting significant differences. First, the pH of our media was around 8.5-9.0. At such a pH, ferric P would mostly be soluble, resulting in a higher mobility in our media compared with under typical field conditions. Second, because all of our media components were large particles (sand or bigger), there were few mineral surfaces competing against plants for P. Plant access to phytic acid, for example, is likely not limited by P mineralization but rather because the compound can form four bonds with mineral surfaces and can thus become physically protected. Without mineral surfaces in our media, phytic acid was likely highly available for plant uptake. In the future, we will modify our media composition to include some clay surfaces to lower the pH and provide mineral binding surfaces. Our original proposal lacked consideration of the important role of arbuscular mycorrhizal fungi (AMF) on P cycles in soil. We planned a greenhouse trial with the objective of evaluating the relative contribution of soil P distribution, AMF symbiosis, and cover crop species to cover crop P uptake and growth. Soils were sourced from two treatments at the Long Term Ecological Research site at Kellogg Biological Station. Treatments will consist of two soils differing in P distribution in POM (1= high P, 2= low P), two AMF treatments (1=no AMF, 2=AMF) and two cover crop species (1=rye, 2=hairy vetch). Plants will be grown in cone-tainers for 8 weeks in a greenhouse using P-free Hoagland's solution, then destructively sampled to determine P concentrations in plant tissue and ANF colonization of roots. Objective. 2. Challenges with researcher availability and farmer recruitment led to delays and changes in this objective. The survey and subsequent on-farm data collection from selected survey farms that was to be conducted in 2022-23 was dropped because farmers are being bombarded by too many surveys and are becoming very difficult to recruit, especially without the expertise of Dr. Snapp who was to have conducted that work before taking a leave of absence. Objective 3. Soil samples were collected from long-term trials in New York and Michigan.
Publications
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2022
Citation:
Drinkwater, L.E. 2022. Using cover crops to optimize nutrient cycling processes and restore soil health. 20th Australian Agronomy Conference, September 2022. Invited plenary presentation.
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2022
Citation:
Drinkwater, L.E. 2022. Alternative Approaches to Chemical Fertilizers - enhancing food security. Fourth NSP seminar on Sound Fertilization for Food Security in the context of the current crisis , FAO, July 2022.
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2023
Citation:
Cassida, K.A. 2023. MSU Forage Research Update. Great Lakes Forage & Grazing Conference, St. Johns, MI. Mar. 9, 2023
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