IS THERE A LINK BETWEEN SOIL CONDITIONS AND A RISING NUMBER OF RICKETS-LIKE-DEFORMITIES IN TROPICAL COUNTRIES?

A rising number of rickets-like deformities have been reported from children in tropical countries within the last 30 years. According to medical analyses in several tropical countries such as Nigeria, Bangladesh, Kenya or Gambia, a one-sided and calcium-poor diet is counted as the main reason for this paediatric disease.

However, recent analyses on soil, maize cobs and drinking water samples from an area with endemic cases of CDR in northern Nigeria showed a Ca deficiency of 47.6%, 26.6% and 79.1% respectively, as compared to a CDR low-risk area nearby. These results suggest not only dietary but also environmental conditions to be involved in the aetiology of tropical CDR.

To follow up this hypothesis, environmental analyses were continued in the northern Nigeria area, where over 1000 children have been reported to be affected by CDR in an area of 450 km². Apart from rock identification works, soil types were determined along toposequences and assessed for their potential fertility. It thereby became apparent that the CDR high-risk area in northern Nigeria is mainly built up by heavily altered granites, ferricretes and hill-wash sediments. Around inselbergs, Luvisols and Alisols have developed, while on ferricretes Plinthosols were found. In lower positions and ricer valleys, Gleysols were identified to be the dominant soil type.

Comparisons to reference soils of CDR low-risk areas in the surrounding showed Alisols, Plinthosols and Gleysols in the CDR high-risk area to be strongly acidified (mean pH < 4.5) and significantly deficient in Ca (4.0 vs. 1.3 cmol/kg, p=0.000), P (0.5 vs. 0.09 mg/100g, p=0.003) and K (0.3 vs. 0.04 cmol/kg, p=0.000). Comparisons to critical limits, however, showed only pH values and K amounts (0.1 vs. 0.04 cmol/kg, p=0.005) to be too low to guarantee a healthy crop development.

Analyses on Cd, Pb, F, Sr and B as well as Se and Zn are currently on the way, as well as a literature review on the soil conditions of other CDR affected areas in the tropics. The results of theses studies will be presented on the conference.