Effect of Magnesium Silicate Nanocomposites Coating of Phosphate Fertilizer on the Availability and Plant Uptake of Phosphorus

Abstract

ABSTRACT This study assessed the feasibility of struvite formation as a sustainable alternative for increasing the availability of phosphorus by applying a coated fertilizer. Diammonium phosphate fertilizer granules were coated with sepiolite-chitosan nanocomposites (SCF) to increase the use efficiency of phosphate fertilizer. The phosphorus uses efficiency of SCFs was studied under greenhouse conditions using Zea mays (maize) as the test plant and an efficiency improvement were observed. The phosphorus uptake as the result of available phosphorus increased, when fertilizing with the coated phosphate fertilizers. Suspensions of different-coated fertilizer treatments were prepared in 3 pH levels (6,7,8) and the chemical speciation was assessed by Visual MINTEQ 3.1. Precipitation and dissolution reactions were considered as the struvite formation mechanism. Also, the formation of struvite in a calcareous soil was evaluated in three incubation periods by X-ray diffraction (XRD) technique. The XRD patterns showed the peaks of struvite, while the peak of sepiolite decreased gradually with increasing incubation time that could be explained by the transformation of this mineral to amorphous fibrous silica. Energy Dispersive X-ray (EDX) analyses also showed diffusion of phosphorus into the coating region, probably forming metastable magnesium phosphate that can facilitate the movement of P aside from the fertilizer granule toward the soil matrix.