Chemical composition and the agronomical potential of two types of rock phosphate in Sudan

Abstract EN

This investigation was carried out to test the possibility of using two sources of rock phosphate from Sudan as a phosphorus fer-tilizer.

The two types of rock phosphate examined were collected from Uro and Kurun in Nuba Mountains, Western Sudan.

Chemical analysis of rocks indicated that Uro and Kurun rock phosphates con-tained 20.

5 and 25.

9 % P2O5, respectively.

These levels meet the uni-versal requirements to mark the tested rocks as good sources for plant phosphorus.

Soluble phosphorus was found to be 0.

001 and 0.

002 % P2O5 for Uro and Kurun, respectively, and the respective citrate-soluble phosphorus was 3.

5 and 3.

7 % P2O5.

The heavy metals content of the rocks was also recorded.

The effect of treatment, namely, fineness, temperature and calcina-tion on the solubility of the rock was examined for the various grain sizes tested (1.

00, 0.

10 and 0.

01mm).

The solubility was found to be inversely proportional to the grain size.

Calcination was the most ef-fective at temperature ranging from 700-850ºC.

Based on the previous studies and confirmation measurements in this experiment the rock samples from Uro and Kurun had a high con-tent of radionuclides.

An experiment was, therefore, carried out to in-vestigate the radioactivity hazard of using these rocks in agriculture.

A pot experiment, using fodder sorghum (Abu Sabeen) as a test crop, was conducted for three seasons.

The phosphate rock was applied at a level of 20 gm / 4kg soil (0.

5 %) in the first two seasons.

The results showed that the radionuclide plant content in the third season was well below the recommended level of contamination.

It seems that the availability and, hence, the absorption of radioactive heavy elements by plants is low under the prevailing high pH of soil.