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GAINESVILLE, Fla. — University of Florida scientists have discovered how much water castor needs in order to grow in North Florida, a key finding in their efforts to determine the feasibility of producing castor in Florida for the first time since 1972.
Castor, grown in Florida during World War II and currently being considered as a component for military jet fuel, contains the toxin ricin. So scientists next must develop a ricin-free cultivar, said Diane Rowland, a professor in agronomy and advisor for the lead author, graduate student David Campbell.
Scientists measure what’s known as “evapotranspiration” – or how much water leaves the plant and its surrounding soil – to get what’s called a “crop coefficient.” A crop coefficient tells scientists and growers the relative water use of the crop in comparison to what’s called a “standard crop evapotranspiration.” That standard comes often comes in the form of grass grown under optimal conditions. Florida growers can obtain site-specific standard evapotranspiration from the Florida Automated Weather Network, or FAWN (http://fawn.ifas.ufl.edu/).
“FAWN provides standard evapotranspiration data for more than 40 locations in the state of Florida already. Thus, one thing we need to provide to prospective castor growers is a crop coefficient for castor,” said Chaein Na, a postdoctoral scientist on the study. A grower can determine crop water use by multiplying the appropriate crop coefficient with the standard evapotranspiration to estimate daily, weekly, monthly or seasonal water requirements for the crop.
The crop coefficient is critical because producers want to irrigate efficiently, Rowland said.
“Using the appropriate crop coefficient for castor in North Florida helps insure we are using sustainable production practices if the crop becomes a viable agronomic alternative in the state,” she said.
For the study, Campbell measured the crop coefficient for castor in fields at the UF/IFAS Plant Science Research and Education Unit in Citra, Florida in 2011 and 2012.
To establish a North Florida region-specific crop coefficient for castor, Campbell and his colleagues analyzed daily patterns of sap flow – or the amount of water – going up through a castor plant’s stem during the peak growing season.
Armed with the new data, scientists now know how much irrigation would be required to produce castor north of Interstate 4, said Rowland.
Although castor contains ricin, the toxin can be broken down during the oil extraction and refining process if it involves high temperatures. Castor oil is used in paints, lubricants and deodorants, among other industrial products. It has not been grown in the U.S. since 1972, because the federal government ceased giving price supports.
Campbell conducted the research as part of his master’s thesis, and the study is published in the current issue of Industrial Crops and Products Journal.
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.
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. In a study published last year, Campbell and Rowland set out to see if castor can be cultivated and harvested in Florida.
Because of its many uses, the economic growth potential of castor is immense, according to the 2014 study.
Caption: UF/IFAS agronomy Professor Diane Rowland shows a sap flow sensor used to measure the water flow through the stem of a plant. Rowland and her colleagues used the sensor in a recently published study to quantify transpiration for the estimation of evapotranspiration in castor.
Credit: Brad Buck, UF/IFAS
By: Brad Buck, 352-294-3303, firstname.lastname@example.org
Sources: Diane Rowland, 352-273-3408, email@example.com;
Chaein Na, firstname.lastname@example.org