In subtropical and tropical area's variation in soil type, pH and nutrient content is huge. Since a lot of Jatropha is not planted on agriculture land, you may end up with unused or degraded land. fertility and soil structure could become a concern. Below you will find a couple of soil samples in various tropical countries with some common characteristics. (all samples taken by the author and analyzed by BLGG in Oosterbeek, Netherlands)
|Country||Remarks||pH||value||N= kg N/ha||value||P=P-Al, mg P2O5/100gr||value||K= mg K/kg||value|
|Thailand||unused land||4.4||very low||30||low||<3||very low||32||low|
|Indonesia||agriculture land||5.7||low||115||good||14||very low||122||good|
|Indonesia||neglected construction site||4||very low||45||low||<3||very low||27||low|
|Thailand||agricultural land||6||good||20||low||4||very low||97||good|
|Indonesia||neglected construction site||4||very low||49||low||10||very low||20||low|
|Tanzania||cleared bush, suitable for agriculture||7.6||high||251||high||<3||very low||139||good|
|Cambodia||neglected agriculture land||3.8||very low||18||very low||6||very low||20||low|
|Thailand||former agriculture area||4.4||very low||24||low||<3||very low||58||low|
|Cambodia||cleared bush||6.8||rather high||91||rather low||<3||very low||154||good|
All the samples have one characteristic in common : There is a structural lack of Phosphorus. The role of Phosphorus in perennial crops is highly underestimated. In the ornamental horticulture it is very well known that a sufficient supply of Phosphorus guarantees a better root system, more branching and more flowering. In annual oil seeds like sunflower sufficient P increases both yield and oil content. (See literature: Phosphorus requirements for sustainable agriculture in Asia and Oceania (15 MB))
Field observations are showing natural branching of Jatropha on nutrient rich soils and no branching where soil is poor.
Same seeds, same location, same age, different branching depending on soil nutrient level (Laos 2007)
Another important factor is soil pH, which has a great influence on availability of soil nutrients. Unfortunately changing the pH of a large area is completely unrealistic because of costs involved
Many countries do have natural resources of Rock Phosphate. It should become standard practice to plant Jatropha with at least enough phosphate to cover the nutrients for the first year.
Apart from soil nutrient capacity there also is an important influence from soil structure. So called heavy soils (black cotton soils, clay) have the reputation that Jatropha does not do well on these soils. This however is not a function of the soil type but is caused by the fact that heavy soils get waterlogged quit easily.. As long as there is good drainage or run of, Jatropha grows very well on these soils because they usually are quite fertile and they hold water very well. Jatropha also grows very well on sandy soils but needs more water and more added nutrients than on heavy soils.
Jatropha on black cotton soil in Tanzania ( 2008)