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Accueil du site → Doctorat → États-Unis → 1994 → Nutrient stress in acid soils of the Cinzana Station, Mali

Texas A&M University (1994)

Nutrient stress in acid soils of the Cinzana Station, Mali

Doumbia, Mamadou Diosse

Titre : Nutrient stress in acid soils of the Cinzana Station, Mali

Auteur : Doumbia, Mamadou Diosse

Université de soutenance : Texas A&M University

Grade : Doctor of Philosophy (PhD) 1994

Research was conducted to define soil chemical properties associated with poor early growth of sorghum (Sorghum bicolor) in Paleustalfs of Cinzana. Greenhouse studies indicated that P deficiency and Al toxicity were limiting sorghum growth in these soils. Soil amendment tested for two seasons limited symptoms of poor early growth to few treatments in 1990. However, symptoms were displayed in 1991 at every combination of amendments. Amendments significantly improved soil pH (5.1 to 7.8), Bray-1 P (7.1 to 48.5 mg kg$\sp-1$), exchangeable Al (0.48 to 0 cmol$\sb(+)$ kg$\sp-1),$ and ECEC (1.30 to 3.10 cmol$\sb(+)$ kg$\sp-1).$ However, the facts that dying seedlings had deficient concentrations of P ($<$2 g kg$\sp-1$ shoot) and toxic Al concentrations ($>$900 mg Al kg$\sp-1$ shoot) suggest that these elements may be associated with reduced sorghum growth. Phosphorus sorption was strongly correlated with percent clay (r = 0.86$\sp\*\*$), organic matter (r = 0.87$\sp\*\*$), surface area (r = 0.84$\sp\*\*$), ECEC (r = 0.85$\sp\*\*$), and total and poorly crystalline Fe and Al oxides (r = 0.90$\sp\*\*$, 0.81$\sp\*\*$, 0.75$\sp\*\*$, and 0.73$\sp\*\*$, respectively). Soils of Cinzana sorbed from 37 to 98 mg P kg$\sp-1$. Phosphorus sorption data and Bray-1 P content of fertilized soils suggested that P sorption was not a major factor. Phosphorus concentration in soil solution was significantly higher in 1991 when seedlings failed to grow (0.003 vs. 0.005 mM P). The ionic strength of the soil solution was significantly increased in 1991 (0.0026 to 0.0030). The ionic strength and osmotic potential of the soil solution were further significantly increased as the soil dried and evaporative concentration of the soil solution took place. Yet, the increase in osmotic potential ($\Psi\sb\rm o$ = 0.008 to $\Psi\sb\rm o$ = 0.009 MPa) were below critical values for reduced sorghum growth ($\Psi\sb\rm o$ = 0.27 MPa). Sandy soils of the Cinzana toposequence had deficient P concentrations and high Al concentrations. However, timing of soil sampling did not allow measurements of soil conditions during critical periods of seedling growth and symptom development.

Mots clés : Agronomy, phosphorus deficiency, sorghum bicolor, plant stress, manganese toxicity, Biological sciences

Accès au document : Proquest Dissertations & Theses

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