- Animals: bees
- Crop Production: cover crops
- Education and Training: focus group, on-farm/ranch research
- Farm Business Management: feasibility study
- Pest Management: allelopathy, cultural control, weed ecology
- Production Systems: organic agriculture
- Soil Management: green manures, nutrient mineralization, soil chemistry
- Sustainable Communities: sustainability measures
Sunn hemp (<i>Crotalaria juncea</i> L.) is a tropical legume that is grown as a source of fiber. It also is an excellent cover crop and green manure because of its ability to produce a substantial amount of biomass and fix nitrogen. Adoption of sunn hemp in farming systems has been hindered by the high cost and limited availability of seed from the main commercial production sources in Hawaii and South Africa. Production of seed on the US mainland could be a lucrative alternative seed crop for organic growers, provide a source of organic seed as required by the USDA organic regulations, and reduce dependence on seed imports. Currently, the only commercially available variety is ‘Tropic Sun’, a short day plant with a long growing season. Obtaining viable seed prior to frost is possible in the southern US, but incorporating this production within existing cropping systems presents challenges. We propose a interdisciplinary project to explore genetic, physiological, entomological, and cultural factors that influence flowering in sunn hemp. Additionally, because of its potential to provide multiple ecological services, we want to determine how cultural practices aimed at increased seed production such as breaking apical dominance may affect biomass accumulation, nitrogen fixation, and weed suppression. Our objectives are to: (1) evaluate the effect of different geographical locations on biomass accumulation, flowering and seed yield of the USDA’s sunn hemp germplasm collection; (2) identify bee species visiting sunn hemp flowers to determine which are effective pollinators and quantify their visits; (3) assess the phenotypic variability of flowering and characterize the sensitivity to environmental factors; (4) investigate the effects of breaking apical dominance on weed suppression and seed yield, and compare the allelopathic potential of the accessions; (5) determine how cultural practices for sunn hemp seed production influence nitrogen accumulation, decomposition, and plant available soil nitrogen; and (6) evaluate the economic costs and benefits of sunn hemp domestic seed, cover, and fodder crops. Outreach will include: presentation of the research findings to state and county extension faculty at the Florida Extension Symposium; field days for extension faculty and growers in Florida and Puerto Rico; and extension publications for use by county extension faculty and growers. The project will be evaluated by the SARE advisory council for the University of Florida and Florida A&M University. These studies represent a foundation for development of new cultivars with attributes of an outstanding cover crop and green manure and allow a new enterprise for organic growers. This proposal integrates the strengths of an interdisciplinary team consisting of an organic grower and scientists in Georgia, Florida, and Puerto Rico to better understand sunn hemp flowering and seed set and the feasibility for its implementation as a new high-value alternative season seed crop in the Southeastern US.
Project objectives from proposal:
- Evaluate the effect of different geographical locations on biomass accumulation, flowering and seed yield of the USDA's germplasm collection of Crotalaria juncea. Identify bees that are effective pollinators of sunn hemp at the Gainesville, Florida test site, to quantify the effective bee visits to the blossoms, and to estimate whether the observed bee pollination is adequate for substantial seed production. Assess the phenotypic variability of flowering and characterize the sensitivity to environmental factors, such as photoperiod and temperature. Investigate how cutting sunn hemp to break apical dominance affects weed suppression and seed yield, and compare the allelopathic potential of the accessions. Determine if genetic differences and planting location influence plant nitrogen accumulation in USDA accessions, and assess the influence of termination date on residue management, decomposition, and subsequent nitrogen contribution from sunn hemp ‘Tropic Sun’ when grown for seed. Evaluate the economic costs and benefits of sunn hemp domestic seed, cover, and fodder crops.