Synthesis and Characterization of Nanocomposites as Slow Release Environment Friendly Fertilizers

Abstract

Agriculture is the back bone of economic development of any agricultural country and it has been transformed into a vast industry fulfilling the primary needs of the masses. Sustainability in agriculture sector is a serious concern specifically in the perspective of environmental conservation as well as maintaining rather improving the crop productivity. This research work was designed to prepare environmentally friendly slow release nano-fertilizer as a substitute for conventional chemical fertilizers that could protect the environment from deleterious effects of conventional chemical fertilizers without compromising agricultural productivity. Two types of nano-composites, based on zeolite (ZNC) and biochar (BNC), with a particle size of 6.05 and 55.6nm, were synthesized by adopting two-step approach and compared with conventional chemical fertilizers. In the first step support materials i.e. nano zeolite (NZ) and biochar of corncob (CB) were synthesized and in the second step support materials were impregnated/ doped with micro and macro nutrients. Physiochemical properties of both the support materials (NZ & CB) and their nanocomposites (ZNC & BNC) were determined using standard methods. While the structure, morphological features, chemical composition, size and thermal stability were determined by fourier transmission infrared spectroscopy (FT-IR), powder x-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive x-ray spectroscopy (EDX), atomic force microscopy (AFM) and thermogravimetric analysis (TGA). Slow release properties of ZNC & BNC carried out in water as well as in soil for 7 and 14 days, respectively, that confirmed the gradual release and long time availability of all the doped nutrients (N, P, K, Ca, Mg, Fe, Zn). Concurrently, the synthesized nano-composites showed excellent water absorbance, salt index and water retention capacities that is good to enhance the soil condition without imparting negative impacts to the crops. The nano-composites’ capability to enhance crop production in comparison to conventional fertilizers was accessed primarily by performing greenhouse experiments on wheat – a major cash crop of Pakistan that is widely grown and serving the purpose of staple food in Pakistan. The completely randomized design with five treatments (control, urea, NPK, ZNC and BNC) was laid ii down, to study the germination parameters; time for 50% germination (T50), mean germination time (days), final germination percentage (%) and germination index. The results indicated early sprouting and germination in ZNC followed by BNC than conventional fertilizers (i.e. urea and NPK). After positive germination results of greenhouse experiment, the field trials were carried on using the same approach i.e. RCBD with three replicates of each treatment to examine the effect of nano-composites on growth and yield parameters for two consecutive years (2014 - 2016). The results were statistically analyzed using one- way ANOVA (LSD at 0.5%) and means were separated by standard errors. The results of field trials demonstrated that nano-composites (ZNC & BNC) positively influenced growth and yield of wheat crop as compared to conventional fertilizers (urea and NPK) and control. In the first year, the highest grain yield was found for ZNC followed by BNC, NPK, urea and lowest for control treatment. While in the second year the scenario was slightly changed and the highest yield was observed in BNC followed by ZNC; the rest of the pattern is same as previous i.e. NPK > urea >control. The proximate, antioxidant and nutritional analysis of wheat grain were performed to determine the comparative effect of nano-composites (ZNC & BNC) with conventional fertilizers. The results demonstrated that nano-composites had marked influence on nutritional quality, antioxidant activity and proximate analysis of wheat grain as compared to urea and NPK. Similarly, comparison of pre and post-cropharvest analysis of soil confirmed that use of nano-composites improve the quality of the soil. Finally, the viability of these nano-composites was quantified through economic analysis for the feasibility of this new approach in field application. The results showed that nano-composites significantly enhanced the gross benefit as compared to conventional fertilizers. Hence, it can be safely concluded that use of these nanocomposites will not only protect the environment but also enhance the yield, nutritional quality of crops and income of farmers by reducing the fertilizer input cost thereby ensuring sustainable agriculture development.