Effects of zeolite amendment on phosphate dynamics in acid and calcareous soils

Kay , Kian Hee (2007) Effects of zeolite amendment on phosphate dynamics in acid and calcareous soils. Masters thesis, Universiti Malaysia Sabah.

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Abstract

Soil phosphorus (P) is an essential nutrient required by plants. However, the inherent characteristics of acid and calcareous soils render the native P present to be lowly available to plants. Consequently, various techniques for enhancing the availability of P in these soils have been practiced, each vary in terms of cost, efficiency and practicality. In this study, a novel approach using zeolite as soil amendment was investigated for it's effect on P dynamics (including P adsorption, P solubility and P availability) in acid and calcareous soils. The soils wre analysed for P fractions, soluble P and available P. Phosphate adsorption characteristics of both soils were investigated according to batch method under varying conditions, namely different shaking time, Initial phosphate concentration, solid - solution ratio and addition of natural zeolite (NZ). The extractability (i.e. H₂O - and NaHCO₃ - extractable) of adsorbed P was determined. Batch experiments were also carried out to study the effect of zeolite amendment of the solubility and availability of native P in both soils. The experimental conditions were different shaking time, type of cation saturation on zeolite, zeolite dosage, zeolite particle size. For comparison, a similar experiment was performed on GRP type rock phosphate (RP). The concentration of P (as phosphate) In all filtrates and extracts was determined according to the Ascorbic Acid Method. The results show that P in both acid and calcareous samples Is dominated by inorganic P (~90 %), with the dominant fractions being AI- P and Fe - P (~64 %) in the acid soil and ca - P (~61 %) in the calcareous soil The proportion of soluble P and available P n both soils with respect to total P is about 3 % and 10 %, respectively. The phosphate adsorption capacity of the acid soil (0.253 mg/g) Is relatively higher than that of the calcareous soil (0.200 mg/g). Percent phosphate adsorption increases with shaking time (attaining equilibrium after 60 min) and solid - solution ratio, but decreases with increase In initial phosphate concentration. The adsorption conforms strongly to pseudo – 2nd order kinetics (R² = 1.000) and langmuir (R²= 0.9948) or Freundlich isotherm (It = 0.9895). At fixed shaking time and solid - solution ratio, addition of natural zeolite (NZ) enhances phosphate adsorption by the calcareous soil while them is no effect in the acid soil The proportion of the adsorbed phosphate that is soluble (H₂O - extractable) and available (NaHCO₃ - extractable) are high (14.9 - 31.2 % and 40.55 - 80.60 %, respectively) and is enhanced in the presence of NZ. Zeolite amendment also affects the solubility and availability of native P in the acid and calcareous Soils. The values of both parameters increase with shaking time (i.e. optimum after 60 min) and zeolite dosage (i.e. most apparent at zeolite - soil ratio of 2:1), but are unaffected by zeolite particle size. The values are also dependent on the type of cation saturation on the zeolite in the following order: H-Z> NH₄-Z > NZ. By contrast, K-Z, Mg-Z and Ca-Z either have no effect or have a suppressing effect on soluble P and available P. Amendment of RP with zeolite (i.e. NZ, NH₄-Z and H-Z) produces a similar trend in soluble P and available P but at higher magnitude compared to those obtained for native P In the soils. The values of both parameters also increase with RP dosage. Overall, amendment with zeolite (in particular H⁺ -saturated zeolite, H-Z) is capable of enhancing the solubility and availability of native P in acid and calcareous soils.

Item Type:Thesis (Masters)
Uncontrolled Keywords:soil Phosphorus, zeolite, Phosphate adsorption, fertilizer
Subjects:S Agriculture > S Agriculture (General)
Divisions:SCHOOL > School of Science and Technology
ID Code:9335
Deposited By:IR Admin
Deposited On:14 Jul 2014 10:08
Last Modified:14 Jul 2014 10:08

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