Developing a castor (Ricinus communis L.) production system in Florida, U.S.: Evaluating crop phenology and response to management

While castor (Ricinus communis L.) oil is an essential component in many industrial products, the U.S. currently imports all castor oil stocks due to the lack of domestic production of the crop since 1972. To reestablish U.S. production of castor, regional agronomic assessments of cultivars and management systems are required to assess the economic sustainability of the crop. A comparison of two castor cultivars (Hale and Brigham) and management systems using plant growth regulators and harvest aids was conducted at two different locations (PSREU and WFREC) within Florida during two years (2011 and 2012) with the goal of assessing yield potential and phenological development of the crop in this semi-tropical climate. Yields were low in comparison to other U.S. regions where the crop has been tested with the highest yields being 1357kgha−1 for Brigham at PSREU in 2011 and the lowest being 686kgha−1 for Brigham at PSREU in 2012. Mold observed on both cultivars and significant rates of shatter could have led to upwards of 60% yield loss, indicating that yield potential in the region may be much higher. Oil percentages on average across sites and years were very consistent between the cultivars, with 45.0 and 45.4% for Brigham and Hale, respectively. Typical growth patterns of height, leaf area index (LAI), reproductive development, and root architecture were characterized for the region. The maximum height recorded for either cultivar did not exceed 115.2cm and the maximum seasonal LAI value was 2.87. Brigham produced between 3 and 8 more racemes than Hale by the end of the season, depending on the site/year. The application of a mepiquat chloride based plant growth regulator (PGR) did not reduce plant height at either location and had no consistent impact on photosynthetic capacity of the crop. The harvest aid paraquat led to over six times more leaf desiccation and leaf defoliation within 11 days after treatment and was more effective overall than the tribufos harvest aid.