Cover Crop Diversity through Evaluation and Increase from Breeder Stocks and Germplasm Repositories

Project Overview

Project Type: Research and Education
Funds awarded in 2016: $201,249.00
Projected End Date: 09/30/2019
Grant Recipient: University of Florida
Region: Southern
State: Florida
Principal Investigator:
Dr. Carlene Chase
University of Florida

Annual Reports


Not commodity specific


  • Crop Production: cover crops
  • Production Systems: general crop production


    The purpose of this project was to increase the diversity and availability of cover crops adapted to the southeastern United States in general and Florida in particular with the potential to improve soil health, serve as green manure, and suppress weeds and nematodes. The project involved seed increase and evaluation of alternative cover crop germplasm lines of the leguminous cover crops Crotalaria juncea (sunn hemp), C. ochroleuca (slenderleaf rattlebox), Vigna unguiculata (cowpea), and Indigofera hirsuta (hairy indigo) that are not currently commercially available but have the potential for overcoming some of the constraints of existing commercial varieties such as hardseededness and the inability to set seed in Florida. 

    The hairy indigo cultivar Flamingo was originally selected for high soft-seededness (low hard-seededness); however, ‘Flamingo’ seed is no longer commercially available. ‘Flamingo’ breeder’s seed is available at the UF-IFAS Forage Breeding and Genetics Lab and at the USDA hairy indigo germplasm collection. Germination tests using these two germplasm sources revealed large genetic variability, i.e. low and high soft-seed levels, present for soft-seededness in the species. The selection and multiplication of those accessions exhibiting high levels of soft-seededness would lead to the development of soft-seeded hairy indigo cultivars. Seed increases are being conducted in the selected soft-seeded lines to allow for field testing (agronomic performance) and nematode resistance in summer 2020.

    The sunn hemp cultivar Tropic Sun is unable to consistently set seed within the continental US; whereas the day neutral cultivar ‘AU Golden’, which can set seed, is considered to have low biomass production that may compromise weed suppression. ‘Iron Clay’ cowpea produces hard seed that can cause volunteer plants to emerge in subsequent cash crops. Accessions of slenderleaf rattlebox were identified as nonhosts or poor hosts of the sting nematode but suitability as a cover crop in the US is poorly documented. Therefore, alternative germplasm of sunn hemp (Sanni) and cowpea (US 1136, US 1137, and US 1138) were compared with commercially available cultivars of sunn hemp Tropic Sun and AU Golden and Iron Clay cowpea.  Trials were conducted at the Plant Science Research and Education Unit in Citra, FL and at three organic farms in Gainesville and Hawthorne, FL. A commercially available slenderleaf rattlebox genotype Red Hemp also was evaluated in summer 2017 and compared with a USDA accession PI 274767 in summer 2018.

    Sanni and the alternative cowpea germplasm lines provided equivalent or better cover crop biomass accumulation and weed suppression than their respective commercial cultivars. The lower shoot biomass accumulation with Red Hemp and PI 274767 slenderleaf rattlebox genotypes provided less effective weed suppression than cowpea and sunn hemp. Sanni sunn hemp and the three cowpea germplasm lines appear to be viable replacements for ‘Tropic Sun’ and ‘Iron Clay’ cowpea, respectively. Data gathered from the Hawthorne location at our research assessment, field day, and from the collaborator assessments were consistent with our research results. Participants indicated that they are very interested in the sunn hemp germplasm line Sanni and the cowpea germplasm lines: US-1138 and US-1136.

    Project objectives:

    1. Multiply seeds of cover crop species and accessions with high potential for utility but are not currently available to obtain sufficient amounts for replicated field evaluation.
    1. Select for the soft-seed trait in ‘Flamingo’ hairy indigo.
    1. Evaluate on-station and on-farm for ecological services in comparison with commonly available species.
    1. Provide recommendations and make seed available for the most promising species/accessions.
    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 or SARE.