Castor, grown in Florida during World War II and currently considered as a component for military jet fuel, can be grown here again, using proper management techniques, a new University of Florida study shows.
Those techniques include spacing plants properly and using harvest aids to defoliate the plant when it matures.
Growers in the U.S. want to mechanically harvest castor, which is typically hand-picked in other parts of the world, the researchers said. Among other things, the UF/IFAS study evaluated whether the plant would grow too tall for mechanical harvesting machines.
Castor oil is used in paints, lubricants and deodorants, among other industrial products, said David Campbell, a former UF agronomy graduate student and lead author of the study. It has not been grown in the U.S. since 1972, because the federal government ceased giving price supports, the study says.
At UF research units in Citra and Jay, scientists tested Brigham and Hale, two types of castor that were bred in an arid part of west Texas near Lubbock in 1970 and 2003, respectively. These cultivars are shorter than castor found in the wild, said Diane Rowland, an associate professor of agronomy at UF’s Institute of Food and Agricultural Sciences, and Campbell’s faculty adviser.
Scientists tried to control the growth of the plants even more by spraying them with a chemical, she said. Even though the crop didn’t respond to the chemicals, it did not grow taller than expected. So it appears these types of castor can be harvested mechanically, she said.
While yields were lower than those reported in Texas research trials in 1993, results are promising for Florida.
“We were concerned that, in this environment, with all the moisture and the good growing conditions, that it would grow too tall. But it didn’t,” Rowland said. “So it shows that shorter genetic types will still work, without the chemical application. That way, you may save money by reducing crop inputs. If it’s too tall ─ if it’s higher than a corn stalk ─ it won’t go through the harvesting machinery.”
The study came about after a few growers in South Florida who wanted to plant castor asked IFAS administrators for technical advice, Rowland said.
Campbell conducted the research as part of his master’s thesis, and the study is published in the February edition of the journal Industrial Crops and Products.
Since 1972, the U.S. has been forced to turn to producers in India, China and Brazil to supply the majority of its needs with India producing about 90 percent of the world’s castor oil.
The toxin ricin comes from castor, but Rowland said UF researchers used a reduced-ricin cultivar as one of the types tested. Texas scientists are developing ricin-free cultivars, she said. In the near future, any industry that uses domestically grown commercial castor would likely be using ricin-free castor, Rowland said. And she noted that ricin can be broken down during the oil extraction and refining process if it involves high temperatures.
Despite the promise of historically high castor yields in the southwestern U.S., recent droughts have prompted growers to look elsewhere for land on which to grow the crop if a commercial castor industry is revived. The plant already grows along many of Florida’s highways. The UF researchers set out to see if castor can be cultivated and harvested on farms.
Because of its many uses, the economic growth potential of castor is immense, the study said.
Growers also still need to develop and start using a machine to crush the oil from the castor plant to make it a viable crop, Rowland said. She said some Florida growers are in the process of doing just that.