Mineralogical considerations in soil fertility management in Morocco
1997
Badraoui, M. | Soudi, B. (IAV Hassan II, Rabat (Morocco)) | Moujahid, Y. (INRA, Meknes (Morocco)) | Bennani, F. | Mikou, M. (University Sidi Mohamed Ben Abdellah, Fes (Morocco)) | Bouhlassa, S. (University Mohamed V, Rabat (Morocco))
In Morocco, as in other Mediterranean countries, the most active part of the soil with respect to nutrients and water supply is made of crystalline layer silicates, humic substances, iron oxides, and clay-sized carbonates. The 2:1 phyllosilicates regulate the dynamics of K+ and NH4+ as a consequence of their high surface area, their charge characteristics, and environmental conditions. The preference of soil smectites for K+ over Ca2+ is controlled by the tetrahedral charge. Recent developments in electron microscopy coupled with energy dispersive detector have shown that smectites may have a great importance on phosphorus adsorption. Phosphate anions are specifically adsorbed by 1:1 layer silicates and iron oxides. Clay-sized CaCO3 reduces the availability of P by its precipitation as P-Ca forms with low solubility. It is demonstrated that humic substances present in soil solution can chelate Ca and Fe and thus prevent the formation of P-Ca and P-Fe compounds. The availability of nitrogen is largely controlled by the amount of organic matter and soil ecological conditions. The pertinence of clay mineralogy needs to be clarified. Although there is evidence that soil mineralogy influences critical nutrient levels to interpret soil fertility analysis, more research is needed to establish quantitative relationships between clay mineralogy and nutrient availability. Detailed characterization of soil clays and reliable quantitative analysis of the clay minerals are necessary to reach this objective
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