Elaboration and Characterization of Vitreous Fertilizers and Study of Their Impact on the Growth, Photosynthesis, and Yield of Wheat (Triticum durum L.)

Four different phosphate glass formulations (F0, F1, F2, and F3) were developed according o wheat nutrient requirements to be used as controlled-release fertilizers. These glasses contain macro-elements (P2O5-K2O-CaO-MgO), with the addition of microelements (Fe-Mn-Zn-B-Cu-Mo) in each formulation. The effects of these elements’ addition on thermal properties, glass structure, and dissolution behaviors were investigated. Results showed that these glasses are composed essentially of metaphosphate chains and that the addition of micronutrients could change the chemical durability of phosphate glasses. A greenhouse experiment was performed using wheat (Triticum durum L.) to evaluate the efficiency of the four glasses, with or without application of chemical nitrogen (N) (N + VF and VF, respectively). The different formulas were tested using two rates of 0.3 and 1 g per plant. In addition to the vitreous fertilizer formulations, two other treatments were applied: control treatment with no amendment and Nitrogen-Phosphorus-Potassium treatment with the application of the conventional fertilizers on the base of optimal rates. After four months of cultivation, vitreous fertilizers application significantly improved growth (7% to 88%), photosynthetic (8% to 49%) parameters, and yield (29% to 33%) compared to NPK treatment and to the control. It has been found that formulas F1, F2, and F3 may constitute a potential alternative to conventional fertilization due to their positive impact on wheat production and can be used in practice as an environmentally controlled-release fertilizer

Study of the Effect of Calcium Substitution by Magnesium in the Vitreous System 3P2O5-2K2O-(1 − x) CaO-x MgO

Phosphate glasses have potentially interesting properties that can be used in various applications. Recently, different studies are focusing on their dissolution behaviours that can be modified to suit some environmental applications, such as controlled-release fertilisers. In this work, magnesium had been suggested to improve the glass durability of 3P2O5-2K2O-(1 − x)CaO-xMgO glasses (0 ≤ x ≤ 1). Indeed, its effect on glass structure, thermal properties and most important dissolution behaviours were studied, in order to evaluate their suitability of being used as controlled-release fertilisers. Various compositions in which calcium was partially replaced by magnesium were prepared by melting at 800 °C. The samples were characterised by differential scanning calorimetry, density measurements, X-Ray diffraction, FTIR spectroscopy and Raman spectroscopy. The dissolution behaviours were investigated using inductively coupled plasma optical emission spectrometry ICP-OES, pH measurements and SEM. Substitution of calcium by magnesium reduced the glass density, owing to the lower atomic weight of magnesium compared to calcium, and caused an increase in glass transition and crystallisation temperatures. Magnesium substitution significantly improved the chemical durability of the glasses due to more covalent Mg–O bond than the Ca–O bond. This study demonstrated that 3P2O5-2K2O-0.3CaO-0.7MgO (x = 0.7) had a dissolution profile adequate to the criteria of controlled-release fertilisers and could be used to nourish the plants with phosphorus, potassium, calcium and magnesium

Innovative Formulations of Phosphate Glasses as Controlled-Release Fertilizers to Improve Tomato Crop Growth, Yield and Fruit Quality

Three phosphate glass compositions, VF1, VF2, and VF3, containing macro and micronutrients with different [K2O/(CaO+MgO)] ratio, were formulated to be used as controlled release fertilizers for tomato crop, depending on their chemical durability in water and their propriety with respect to the standards of controlled-release fertilizers. This study investigated the influence of [K2O/(CaO+MgO)] ratio variation on glass properties. For this, the elaborated glasses have undergone a chemical characterization using inductively coupled plasma atomic emission spectroscopy, a thermal characterization using differential thermal analysis, a physicochemical characterization based on density and molar volume measurements, and a structural characterization using Raman spectroscopy, Fourier-transform infrared spectroscopy, and X-ray diffraction. In addition, the chemical durability was determined by measuring the percentage of weight loss and the pH. Results revealed that the glass structure and composition have the mean role in controlling the release of nutrients in water. By increasing [K2O/(CaO+MgO)] ratio, the dissolution rates of the glasses increased due to the shrinking in the rate of crosslinking between phosphate chains, accompanied with a diminution in transition and crystallization temperatures, and an increase in the molar volume. An agronomic valorization of VF1 and VF2 glass fertilizers, which showed dissolution profiles adequate to the criteria of controlled-release fertilizers, was carried out to evaluate their efficiency on tomato crops. These glass fertilizers improved soil mineral content and tomato performances in comparison to the control and NPK treatments with the distinction of VF2. The results highlight the effectiveness of these smart fertilizers toward their potential large-scale application to improve crop production and quality for high nutritional value foods