Effects of vermiculite, nanoclay and zeolite on ammonium transport through saturated sandy loam soil: Column experiments and modeling approaches

Abstract

Economic and nature-friendly amendments are needed to increase fertilizer efficiency and crop yield for sustainable agriculture in coarse-textured soil. In this investigation, the effects of different application rates (2%, 4% and 8%) of vermiculite, nanoclay and zeolite amendments on adsorption and transport of ammonium (NH4-N) in sandy loam soil were studied using batch and column experiments. The results of batch experiment indicated that the maximum distribution coefficient (Kd) was obtained in soil amended with zeolite 8%, while minimum Kd was achieved in the control soil. Column experiments revealed that the application of inorganic amendments decreased the leaching of NH4-N from 89.4% in control soil to 77.6%, 70.2%, 52.5%, 85.3%, 60.8%, 38.5%, 12.6% and 2.1% in soil columns amended with vermiculite 2%, 4%, 8%, nanoclay 2%, 4% and zeolite 2%, 4%, 8%, respectively. On the basis of the application rate of inorganic amendments required to retain 40% of injected NH4-N, the effectiveness of zeolite is about 2 and 4 times that of nanoclay and vermiculite, respectively. The HYDRUS-1D program was used to simulate the leaching of NH4-N using the advection–dispersion equation model (ADE) along with batch and fitted Kd. The simulation results indicated that the ADE model with fitted Kd described the behavior of NH4-N transport more suitable than the ADE model using batch Kd (root-mean-square error, RMSE < 0.06 and RMSE < 0.13, respectively). Results of our study indicated that amending sandy loam soil with inorganic amendments can be an effective technique for decreasing NH4-N transport and improving the efficiency of N fertilizer in sustainable agriculture systems.