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Accueil du site → Doctorat → États-Unis → 1988 → Mineralogy and potassium availability in soils from the Chaouia and Gharb regions of northwestern Morocco

University of Minnesota (1988)

Mineralogy and potassium availability in soils from the Chaouia and Gharb regions of northwestern Morocco

Badraoui, Mohammed

Titre : Mineralogy and potassium availability in soils from the Chaouia and Gharb regions of northwestern Morocco

Auteur : Badraoui, Mohammed

Université de soutenance : University of Minnesota

Grade : Doctor of Philosophy (PhD) 1988

Résumé
The availability of potassium to plants is strongly influenced by the mineralogical composition of the soil. This study was conducted to characterize the mineralogical composition of soils from two important agricultural regions in Morocco and to establish qualitative and quantitative relationships between clay mineralogy and K+ dynamics in these soils. Swelling of clays, before and after saturation with lithium and heating at 300$\sp\circ$C to reduce octahedral interlayer charge, using ethylene glycol, glycerol, and alkylammonium cations with varying alkyl-chain lengths showed that the clay fractions of Vertisols and Vertic Molisols of both regions are dominated by high charge beidellites. The chemical composition and infrared spectroscopy data demonstrated that the beidellite in high Chaouia soils is high in Fe (III). The Xerochrepts of high Chaouia contained high concentrations of dioctaheral, aluminum rich palygorskite in association with beidellitte. The Xerochrepts and Haploxerolls of the Gharb region had a complicated and heterogeneous mineralogy consisting of illite, vermiculite, smectite, chlorite, kaolinite, mixed layers S/I and V/I, and quartz. Chaouia clay fractions fixed more K+ than those from the Gharb in both wet and dry conditions. Simple linear regression analyses indicated significant positive correlations between K+ fixation and total and tetrahedral charges. The amount of K+ added, drying temperature, the number of wetting and drying cycles, and the composition of the extracting solution all had significant effects on K+ fixation. In a greenhouse experiment, Italian ryegrass showed response to K+ addition in terms of biomass only in the Xeralfs and the Vertisols from Chaouia. The rates of plant K+ uptake were significantly higher for the soils from the Gharb compared to those from Chaouia. The rate of release of nonexchangeable K+ by beidellite in the Vertic soils of Chaouia is very low, but the rate is higher in the illitic soils of the Gharb region. Plant uptake of fixed fertilizer K+ is a significant factor in K+ nutrition in the soils studied. Intensive cropping of the Xeralfs and Vertisols of Chaouia will require additions of K+.

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