Production approaches to establish effective cultivation methods for Jatropha (Jatropha curcas L.) under cold and semi-arid climate conditions.

Consistently high yield production of Jatropha has not yet been achieved in Africa. Spurred by the international focus on Jatropha as a non-edible biofuel, Jatropha production trials began in Botswana in 2012. Exploration of genetic resources throughout Botswana yielded 97 accessions, with selection still ongoing. Most Jatropha trees in Botswana are concentrated in northern regions, where they are grown as ornamentals and have apparently been introduced from outside the country. The purpose of this study was to establish an economical cultivation method for Jatropha under marginal dry and cold climate conditions. To enhance winter survival in 2012, pruning, followed by covering with non-woven polyester sheets, was used. These practices significantly decreased plant mortality and accelerated new shoot growth in spring. Based on weather data, Jatropha trees were exposed to cold stress caused by several hours of pre-cooling and subsequent freezing temperatures from strong radiational cooling in the morning. Below-freezing winter temperatures were recorded in the field, especially before dawn. A high diurnal temperature range and low dew point intensified radiational cooling, with water-rich Jatropha stem tissues and sprouting leaves damaged by freezing and rapid thawing. Repeated freeze damage also delayed sprouting in spring. Our trial cultivation results suggest practices for overcoming dry and cold conditions, and support the possibility of Jatropha production in African desert climates