Long-awaited study warns against jatropha hype
It has been promoted in Kenya as a biofuel crop that can grow well almost anywhere, but newly published research into yields from the jatropha tree across the country shows 79 per cent of farmers obtained just 0.1kg of seed per tree and 41 per cent of these obtained no seed at all. This poor yield is lower than the economically viable 4Kg of seed needed to produce 1 litre of fuel.
Published in the scientific journal, Agroforestry Systems, the study concludes that because of its low productivity, jatropha farming by smallholder farmers in Kenya requires further research on how yields can be increased.
“In order for jatropha to be grown successfully by smallholder farmers in Kenya, many of the uncertainties need to be removed,” says lead author Miyuki Iiyama, research scientist at the World Agroforestry Centre.
“Farmers need simple and affordable protocols, especially in relation to what must be done during the establishment phases, as well as proper knowledge on what crops will work best with jatropha.”
Results come from data collected during a baseline survey by Endelevu Energy, the World Agroforestry Centre and Kenya Forestry Research Institute (KEFRI) which was funded by GIZ and conducted in early 2009 just prior to the downswing of the jatropha boom.
“The low yields are partly because improved planting material is not available, farmers’ management practices are suboptimal and the biophysical boundaries of high jatropha yield are poorly defined,” explains Iiyama.
Jatropha (Jatropha curcas) is indigenous to Central America and produces a seed that can be processed into biodiesel suitable for diesel cars or further processed into jet fuel.
In recent years, jatropha has been widely promoted by the private sector and non-government organizations in Kenya for its potential to provide biofuel feedstock. While there were no large-scale plantations involving foreign investors in the country at the time of the survey, stories continued to appear in the media about plans to plant thousands of hectares on semi-arid land owned by the government or large private ranches.
“If jatropha is to be grown for pro-poor bioenergy development, the right management regimes need to be identified that consider the preferences and constraints of farm households,” Iiyama urges.
In the study, scientists visited and surveyed 267 farms across 6 provinces in Kenya and interviewed farmers about the yield/harvest from their trees over the previous 12 months. On each farm, 6 trees were randomly selected and the number of branches and fruits per branch counted to provide partial estimates of yield potential.
On 117 of the farms surveyed, farmers were intercropping jatropha with a range of crops including dwarf maize, beans, peas, groundnuts and vegetables. Some farmers were also growing banana and vanilla and other tree crops such as coconuts, citrus and eucalyptus. On the other 150 farms, jatropha was grown on 70 as a monoculture and on 80 as a fence, hedge or windbreak.
“It is likely that other factors are affecting jatropha yields such as poor planting material, the timing of planting or the intercrops that were chosen,” explains Iiyama.
“Management practices are most important during establishment phases and if they are not properly applied at that time then yields will be affected despite ongoing management.”
According to Iiyama, the choice of planting material is vital. In the study, farmers who used externally sourced materials had lower yields, while locally sourced materials were found to be the best alternative in Kenya in the absence of improved jatropha seeds or seedlings.
The timing of planting is also critical for better yields. The start of the rainy season is considered the best time to plant the tree to ensure sufficient moisture for establishment and subsequent growth. In Kenya, due to its diverse climatic and ecological conditions, the rainy seasons start at different times across different regions. Categorizing the surveyed farmers by climatic zones (for convenience, by province) it was found that only 25 to 36 per cent of farmers recalled planting jatropha during rainy months. The rest had planted during dry months, mostly without irrigation, which had likely exposed the trees to moisture stress.
Some intercrops will work better with jatropha than others. In the study, intercropping with banana and/or vanilla (practices often observed among farmers in humid zones) was shown to have a negative effect on yields, probably due to competition for light.
Where jatropha is planted as a fence, farmers are less likely to apply fertilizers and irrigation than monoculture and intercrop farmers. But these farmers do tend to prune trees more frequently which encourages more lateral branches and these produce more fruits; possibly explaining why some of these farmers received slightly higher yields.
Productivity under smallholder conditions in Kenya is still much lower than has been reported from other areas where jatropha is grown, for example up to 2.0 kg per tree in some parts of India and South Africa.
Kenyan farmers got close to no yield in the first 2 to 3 years and estimates for yields 4 to 6 years were very low (less than 1kg per tree) regardless of plantation types. The trees that tended to yield 0.4kg (fence) to 0.8kg (monoculture) were generally 7 years or older.
For any plantation to succeed, high and stable yields are required. This relies on quality seeds or seedlings, the right management practices and appropriate agro-climatic conditions, or a combination of these factors. “For jatropha,” says Iiyama, “there is still very little knowledge about what factors have the greatest influence on yields which makes planting jatropha extremely risky, especially for subsistence farmers”.
Despite the claims that jatropha is easily managed, the study found that some conventional management techniques such as applying manure, weeding, pruning and irrigation did improve yields. Generally these practices were carried out by intercrop and monoculture famers but did not always give them higher yields.
“More trials are needed on new planting material under different management regimes in new areas outside where jatropha is currently grown to determine the feasibility of the tree for biofuel production,” says Iiyama.
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Iiyama M, Newman D, Munster C, Nyabenge M, Sileshi GW, Moraa V, Onchieku J, Mowo JG, Jamnadass R. (2013). Productivity of Jatropha curcas under smallholder farm conditions in Kenya. Agroforestry Systems 87 (4): 729-746.