Synthesis of Zincated Urea Using Zinc Nanoparticles with Polymeric Materials

Abstract

Agricultural growths of any country are directly linked with the economic development which continuously fulfills the needs of nations. Sustainable agriculture shows a great potential towards the environmental conservation with improving the crop yield and quality. In the past two decades, nanotechnology has attracted a lot of scientists and researchers for developing sustainable agricultural products. The demand and supply gap of food all around the world is a big challenge which needs to be addressed. This issue is more prevailing in the developing countries. Excessive synthetic fertilizers, especially urea is applied by the farmers to maintain the yield. Poor nitrogen (N) use efficiency from the conventional urea results in environmental and economic losses with decreasing crop yield. Wheat is one of the most important crops grown all around the world to fulfilling the daily needs of humans and animals. The quantity of food along with its quality is also very important for meeting the daily nutrients requirement by living things. Zinc (Zn) is one of the most essential nutrients required by living things for their healthy growth and helps to boost immunity. The poor nutrient use efficiency of conventional urea fertilizer can be addressed by developing slow release fertilizers. This research study was aimed to formulate environmentally friendly slow release fertilizer using nanotechnology with additional features of Zn as a micronutrient. This eco-friendly product protects the environment from losses without affecting the agricultural product quality and yield. Three different types of formulations were prepared using zinc oxide (ZnO), zinc sulfate hepta hydrate (ZnSO4.7H2O) and zinc oxide nanoparticles (ZnO-NPs) in fluidized bed coater with conventional urea prills. In the first two types of formulations, molasses was used as a binding agent along with Zn (nano or bulk). The third type of formulations comprise of biodegradable polymeric material gelatin along with micronutrient Zn (nano or bulk). The structural, morphological, size, and chemical composition of prepared nano particles were determined using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and powder X-ray diffraction (XRD). The physiochemical properties of prepared formulation were tested using crushing strength, iv equilibrium moisture content, swelling ratio, and water absorption capacity. The slow release feature of all the prepared formulations was tested using urea release rate and Zn leaching in water as well as in soil-water system for different time intervals. The urea release rate and Zn leaching test confirmed the slow release of nutrients (N and Zn) with long term availability to plants. The polymeric nano composites displayed excellent water absorption and soil water retention capacities that are advantageous in areas with water scarcity. The slow release nano fertilizers were assessed on Wheat as a test crop in different field and pot experiments. The slow release nano fertilizer ability to enhance plant yield was compared with conventional urea prills. The field trials with ZnO and ZnO-NPs coated urea prills revealed that the 0.5 % ZnO-NPs coated urea boosts the plant growth and yield in comparison to the bulk ZnO coated urea. The plant parameters and soil properties were greatly enhanced due to the application of ZnO-NPs with molasses on prills. The pot study revealed that 0.5 % ZnO-NPs coated urea boosts the plant growth and yield in comparison to the (0.25, 0.5 and 4 %) bulk ZnSO4 coated urea. The polymeric nano composites for slow release urea also enhanced the yield of field grown wheat. The treatment with 0.5 % ZnO-NPs and 1.5 % gelatin results in the highest grain yield with highest income relative to the conventional prills. The coating of urea prills with Zn + molasses and Zn + gelatin significantly increases the plant parameters with Zn accumulation. The soil application of zincated urea enhances the N and Zn content in the soil and plant tissues because of slow release feature which meets the sequential needs of the crop for their optimum growth. In the same manner, the pre and post-harvest soil bio-chemical analysis confirmed the improvement in soil properties after the application of Zn coated prills relative to uncoated urea. The COMSOL multi-physics simulation results displayed a significant drop in the urea diffusion after the application of ZnO coating. After the coating, the urea solubility greatly reduced which can meet the requirement of crops by slowly releasing the N content for growth. The urea kinetics results revealed that the urea release from the Zn coated urea best followed the second order kinetic model. Second order kinetics express v that the nutrient release from Zn coated urea which was controlled by diffusion and several other parameters including soil pH, humidity, and soil moisture content etc. The kinetics results showed coatings with ZnO-NPs show little more potential for increasing the fertilizer efficiency by slowing down the N release more relative to bulk salt coatings. Lastly, the economic feasibility of polymeric nano composites was computed through cost-benefit ratio and investment factor for the practicability of this novel approach to large field application. The economic analysis revealed that polymeric nano composites greatly increase the gross benefit relative to uncoated prills. Therefore, it can be concluded that the large scale field application of polymeric nano composites with the ZnO-NPs shows great potential. These polymeric nano composites not only protect the environment but also enhance the crop yield and quality along with the profits associated with it. Furthermore, the increase in efficiency also minimizes the input cost thus confirming the application of sustainable agriculture.