Synthesis and Characterization of Polymeric Coating for Control Release NPK fertilizer

Abstract

The population of the earth is rising every day, which leads to global food shortages. Agricultural framers applied a huge amount of artificial fertilizers to meet the demand and supply gap of food caused by this food scarcity. This overdose of fertilizer will cause many bad impacts on the surroundings including environmental pollution in the form of emission to the atmosphere as well as to soil and water bodies. Encapsulation of fertilizers in polymeric coatings is a method used to reduce fertilizer losses and to minimize environmental pollution. The commercial granular fertilizer NPK (17-17-17) was coated using polyvinyl alcohol (PVA), starch, gelatin, and gum Arabic. The coatings were prepared from the polymer solutions in a fluidized bed granulator. The influence of the polymer concentration in the film-forming solution on the physical properties of the coatings was examined. The coating structure controls the diffusion of the elements from the interior of the fertilizer granule. Scanning Electron Microscope (SEM) was used to check the surface structure of uncoated and polymer coated NPK fertilizer. The more compact structure was observed by coating combination of starch, gum Arabic, molasses, and paraffin wax (PC-4 NPK). Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and crushing strength technique was employed to check the quality and characteristics of uncoated and polymer coated NPK granules. PVA, gelatin, molasses and paraffin wax (PC-3 NPK) coating combination gives best result for FTIR and XRD. The highest value of crushing strength was observed in starch, PVA, molasses, and paraffin wax (PC-6 NPK) is 108.52 N. The physical properties of the coatings influence the release rate of macronutrients which are present in the core of the coated fertilizer. Pot test experiments conducted on maize crops. The effect of coated fertilizer was investigated in terms of plant growth by increasing nutrient availability. No significant change in soil pH was observed after using coated fertilizer. The electrical conductivity (EC) of soil increases after the utilization of NPK fertilizer. The most prominent increase in soil EC was observed in PVA, gum Arabic, molasses and paraffin wax (PC-2 NPK). Soil analysis of total organic carbon (7.4 Mg ha-1) and mineral nitrogen (36.02 kg ha-1) showed that coated combination of PVA, gelatin, molasses and paraffin wax (PC-3 NPK) showed the highest value from its initial value. Furthermore, this coating also showed the maximum plant height, plant fresh matter yield, dry matter yield, leaf area, and leaf area index followed by a coating combination of gum Arabic, gelatin, molasses and paraffin wax (PC-5 NPK). In root analysis, PC-5 NPK represents the highest dry matter yield (5939 kg ha-1) followed by PC-3 NPK (5657 kg ha-1) treatments. From soil and plant analysis, it is concluded that PC-3 NPK is the best fertilizer in terms of nutrient release in water and soil. The good Quality binding agent directly affects the efficiency and reduces the release rate of NPK granules. The coating combinations contain an inorganic substance that is effective for plant growth along with retarding the nutrient release rate