Developing an adaptive management framework for promoting agroecosystem services through cover crops

Developing an adaptive management framework for promoting agroecosystem services through cover crops

Summary

Given the environmental impact of conventional agriculture and its vulnerability to increasingly extreme climate variation, it is necessary to explore and develop alternative, more environmentally sensitive and resilient agricultural systems. By relying more heavily on natural agroecosystem processes, or management practices that mimic these processes, we can establish progressively more sustainable production systems. In order to do this, we must better understand the plant-environment feedbacks in agroecosystems and develop a framework for converting this knowledge into effective management practices.

Cover crops are a key tool as we work to manage ecosystem processes with more precision in sustainable agriculture. Cover crops have been used extensively in the past, and are increasingly used today, especially in organic farming. Cover crops serve many purposes in agricultural systems, and promote different ecosystem functions. This project is focusing on three specific desirable outcomes from cover crops; biomass production (productivity), nitrogen fixation, and weed suppression. Based on current ecologic research, this project is testing the hypothesis that increased diversity in cover crop mixtures will promote the targeted outcomes of productivity, N fixation, and weed suppression.

The project went ahead as planned with a preliminary screening experiment planted in fall 2012 with anticipated harvest and data collection in the spring of 2013. Due to a miscommunication with the research farm staff, the experiment was plowed under in April 2013 before any relevant data could be collected (though no grant funds were spent). A larger scale experiment was planted in fall 2013. The goals of the project remain the same, promoting the ecosystem functions of productivity, nitrogen fixation, and weed suppression through cover crop mixtures, though with a slightly different approach than originally proposed. The project had set out to identify specific traits in cover crop species that were connected to these desirable ecosystem function outcomes. In keeping with the current ecologic research, we shifted our focus from specific traits to the overall diversity of the cover crop mixture as the main driver for promoting these desired functions. Ultimately, this approach will still lead to developing a framework that farmers can use to select and optimize cover crop mixtures for their farm and needs. For more details on my work so far, please see my project website at http://blogs.cornell.edu/soho/.

Objectives/Performance Targets

Our original timeline was based on having completed one field season at this point and analyzed the collected data. While that didn’t happen, the fall 2013 experiment was planted on time and the resulting data from that experiment will contribute to achieving the project objectives updated below. The overall goals of the project have not changed, and I am still confident we will achieve these objectives even with this initial setback.

1. 1. Assess the relationship between diversity and the ecosystem functions of productivity, weed suppression and biologic nitrogen fixation (BNF).

1. 1. Rank legumes and non-legumes in terms of complementarity in mixtures on a relative scale.

1. 1. Evaluate the BNF rates of different legumes in monocultures and mixtures.

1. 1. Develop and refine simple plant-based and visual metrics for BNF and biomass production.

Accomplishments/Milestones

As explained above, the fall 2012 experiment was plowed under in April 2013 before any relevant data could be collected. While no one hopes for this to happen, I learned a lot establishing the experiment, like my planting technique which I improved and used this fall. No NE-SARE funds were spent on that experiment. With no samples to process, I had more time to do some reading and catch up on the current literature. I began reading about the growing field of biodiversity and ecosystem function (BEF) research. I realized that the hypothesis of this field -increased diversity increases ecosystem function like productivity- was closely related to my research. Research in natural ecosystems has shown that more diverse plant communities are generally more productive, more stable, and generally support better functioning systems than less diverse communities (Hooper et al. 2005, Cardinale et al. 2013, Cadotte et al. 2013). The goal of this project and my research is to improve cover crop management by farmers to maximize the desired functions and outcomes of nitrogen fixation and weed suppression, both of which are closely linked to the third outcome of biomass (productivity). My hypothesis is that increasing diversity in cover crop mixtures, will be a more effective way to promote these desired ecosystem functions.

Consequently, the experiment I established in the fall of 2013 is designed to directly investigate the effect of diversity in cover crop mixtures on biomass, nitrogen fixation, and weed suppression. The treatments are composed of 6 species of annual, overwintering cover crop species (hairy vetch, crimson clover, winter pea, rye, wheat, and ryegrass). Within those six species, there are multiple cultivars, or varieties. We have each cultivar growing alone, all cultivars of the same species growing alone, and then mixtures of the different species and cultivars. The idea is to have different levels of diversity in each treatment mixture. Diversity can be measured as simply the number of species, but there is also diversity within-species in the form of varieties and cultivars. In this experiment we are growing equal legume and non-legume mixtures with increasing diversity, starting with one species and one cultivar of each all the way up to all the species together and all possible cultivars. While not every combination was planted, the design will allow us to look along the gradient of diversity for its effect on biomass productivity, nitrogen fixation, and weed suppression.

I anticipate preliminary data collection from this current field experiment in April. In May, we will finish the full biomass harvest. I plan to use the results from this experiment to inform the plans for the second field season of fall 2014-spring 2015. In this plan, all the samples will be processed in June and the data analyzed in July to allow for planning in August, and planting in September.

Cadotte, M., C. H. Albert, and S. C. Walker. 2013. The ecology of differences: assessing community assembly with trait and evolutionary distances. Ecology Letters:n/a–n/a.

Cardinale, B. J., K. Gross, K. Fritschie, P. Flombaum, J. W. Fox, C. Rixen, J. van Ruijven, P. B. Reich, M. Scherer-Lorenzen, and B. J. Wilsey. 2013. Biodiversity simultaneously enhances the production and stability of community biomass, but the effects are independent. Ecology.

Hooper, D. U., F. S. Chapin, J. J. Ewel, A. Hector, P. Inchausti, S. Lavorel, J. H. Lawton, D. M. Lodge, M. Loreau, S. Naeem, B. Schmid, H. Setälä, A. J. Symstad, J. Vandermeer, and D. A. Wardle. 2005. EFFECTS OF BIODIVERSITY ON ECOSYSTEM FUNCTIONING: A CONSENSUS OF CURRENT KNOWLEDGE. Ecological Monographs 75:3–35.

Impacts and Contributions/Outcomes

As I’m still waiting on this first completed field season, I don’t have many concrete outcomes yet. However, I have had more time to work on my blog/website for the project (http://blogs.cornell.edu/soho/). This website is included part of my extension/outreach strategy. I think there is a lot of potential as I start to collect data, process samples, and analyze the data to show farmers and other stakeholders all that goes into a project like this. Of course, the end results and conclusions will be very exciting (whatever they might be), but sharing the process and progress of getting to those conclusions is also valuable. I also hope that it makes it easier to share my work with other researchers, leading to collaborations, or just some tips on how I could be doing things better or easier.

Collaborators: