About soils.

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)

RESEARCH NEEDED!!!

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)