Project Overview
Multispecies cover crop mixes are important tools for building functional diversity in a cropping system. Cover crops with different functional traits can be planted together to optimize the ecological benefits provided to subsequent cash crops. Understanding these functional traits is crucial to designing successful multispecies cover crop mixes.
Researchers at the University of Florida set out to understand the ecosystem services provided by several summer cover crop mixes in an annual crop rotation that included a spring and fall vegetable cash crop and a winter cover crop.
Farmer Takeaways
- The three- and five-species summer cover crop mixes increased fall bell pepper crop yields, but these benefits were modest and variable.
- More-diverse summer cover crop mixes may provide greater ecosystem services than less-diverse mixes, increasing pollinator visits, reducing parasitic nematodes, and improving nutrient cycling.
- Buckwheat was the only summer cover crop species to flower during the three-month summer season. Mixes containing buckwheat received significantly more pollinator visits.
- Cover crop mixes provide benefits through traits unique to each constituent species. More research is needed to understand how these benefits present across time and rotation sequences.
Project Objectives and Approach
Evaluate the effects of summer cover crop monocultures and mixtures on fall vegetable crop yields, nutrient cycling, weed abundance, and pest/pollinator populations
Experimental Design:
- A field trial was established in Florida in May 2018. Cover crop monocultures and mixes were grown over the summer, bell peppers were grown in the fall, a winter rye cover crop was grown over the winter, and acorn squash was grown in the spring. All crops were managed organically.
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- Summer cover crop treatments included: (1) a sunn hemp monoculture, (2) a sorghum-sudangrass monoculture, (3) a two-species mix / sunn hemp + sorghum-sudangrass, (4) a three-species mix / sunn hemp + sorghum-sudangrass + buckwheat, and (5) a five-species mix / sunn hemp + sorghum-sudangrass + buckwheat + cowpea + sunflower.
- All cover crop treatments were compared to a fallow control.
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- Cover crops were terminated each year in August with a flail mower. Plots received disking and rototilling at certain times during the crop rotation. Vegetable cash crops were irrigated, but the summer cover crops received no irrigation.
Data Collection:
- Researchers collected whole-plant summer cover crop and bell pepper samples from each treatment, which were analyzed for biomass, carbon accumulation, and P and K uptake. Soil samples were collected at several points throughout the crop rotation – before and after the summer cover crop season, and again after bell pepper harvest – and analyzed.
- Weed biomass was collected and measured at the time of cover crop biomass sampling.
- Cover crop flower density and pollinator abundance were observed through repeated field surveys during the summer cover crop season.
- Marketable bell pepper yields were measured across five weekly harvests around the month of November in each year of the study.
Key Findings
Three- and five-species summer cover crop mixes may increase fall vegetable crop yields slightly, but these benefits are modest and highly variable
- In 2018, peppers grown in the three- and five-species cover crop mix plots had slightly increased yields compared to other cover crop treatments, around 10% higher. Plots that had been fallow over the summer had statistically similar (but more variable) yields compared to the less-diverse cover crop mixes.
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- There were no differences in pepper yield observed in 2019, highlighting the variability of benefits provided by cover crops.
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More-diverse summer cover crop mixes may provide greater ecosystem services than less-diverse mixes, allowing for more pollinator visits, fewer parasitic nematodes, and improved nutrient cycling
- The three- and five-species summer cover crop mixes boosted pollinator visits and reduced parasitic nematode abundance compared to other treatments in this study.
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- Pollinator visits were driven by buckwheat, which was only included in the more diverse mixes and was the only cover crop species in this study to flower. Buckwheat’s ability to flower proved to be a critical functional trait not present in the less-diverse mixes, emphasizing the importance of including functionally/physiologically diverse species in cover crop mixes.
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- All of the cover crop mixes cycled more P, K, and C compared to the fallow control, but these increases in plant nutrient concentrations did not translate into changes in soil organic matter and soil carbon (total carbon and other pools).
Resources
Allar, J., Mallinger, R., Liu, C., Grabau, Z., & Maltais-Landry, G. (2023). Different cover crops have a limited impact on marketable yields and biogeochemical cycling but secondary effects on pollinators and plant-parasitic nematodes in Florida organic vegetable systems. Frontiers in Sustainable Food Systems, 7.
Read MoreLocation
FloridaCollaborators
John Allar, University of Florida
Rachel Mallinger, University of Florida
Chang Liu, University of Florida
Zane Grabau, University of Florida
Region
Southeast
Topic
Soil Health, Crop Nutrient Management, Conservation and Habitat, Insect/Pest Management, Cropping Systems
Category
Vegetables/Fruits
Year Published
2023
