Effects of organic amendment on early growth performance of Jatropha curcas L. on a severely degraded site in the Sub-Sahel of Burkina Faso

摘要

The aim of this study was to evaluate the effect of organic amendment on the germination and growth patterns of Jatropha curcas L. on completely barren and degraded land in the Sahelian area of Burkina Faso. Prior to the field trials, laboratory germination tests were undertaken to explore the impact of different pre-treatments on germination of Jatropha seeds. Seeds soaked in water for 24 h had the highest mean rate of germination (86%) while seeds that were pre-treated with sulphuric acid did not germinate. The results of the field experiment showed that plant growth and biomass development were significantly enhanced by organic amendment compared to the control. With direct seeding, 20% of the plants treated with organic manure survived after 2 years, while all seedlings of the control plot perished. In the plantations, 30% of the untreated seedlings remained alive whereas only 5% of the plants survived with amendment. The trials in unfenced plots were decimated by livestock grazing and trampling 2 months after the beginning of the experiment. This emphasizes the need to protect Jatropha plants at an early stage of their development from roaming animals. Organic amendment attracted humivorous termites, which were destructive to the seedlings. The use of pesticides may be necessary to control this problem. When directly seeded, plants of the control plots demonstrated poor growth and became rapidly diseased, further accelerating their decline. The low survival rates (5–30%) and meagre seedling performance, even for the amended plots, may be an indication that Jatropha is unsuited to severely degraded lands like the zippelé, and cannot be expected to give good yields and the claimed environmental and socio-economic benefits. However, we recommend that the performance of Jatropha on the zippelé should be further tested with other soil and water conservation techniques (half-moon, tillage, etc.) that have been shown to enhance crop production and yield on degraded lands in the Sahelo-Sudanian zone of West Africa. The impact of seed provenance on the outcome of this study is unknown. Therefore, further experiments should embrace seeds from different sources, including genotypes that are more adapted to dry conditions and might therefore show improved performance.