To assess the groundwater vulnerability due to leaching of chemicals, the groundwater system in the unsaturated zone is characterized by conceptual models that are further extended and refined with more detailed mathe...To assess the groundwater vulnerability due to leaching of chemicals, the groundwater system in the unsaturated zone is characterized by conceptual models that are further extended and refined with more detailed mathematical models to understand the governing physical processes in detail. However, due to lack of data and uncertainty level, an intermediate transition through index based models is researched. The attenuation factor (AF) approach, which works under the assumption that the chemicals degrade following a first-order kinetics and determines the fraction of the chemicals that goes to groundwater table, is one of the index based models that has been widely used due to its simplicity. Therefore, the objective of this paper is to review the research works done using the AF approach, to outline the future research needs. Furthermore, the mathematical implementation of the AF approach and the associated uncertainty levels is explained through an example and MATLAB source code.展开更多
On tropical soils, liming and balanced nutrient supply are essential to ensure high crop yield and quality. An adequate agronomic nutrient management should be a balanced nutrition and fertilizers are the key factor o...On tropical soils, liming and balanced nutrient supply are essential to ensure high crop yield and quality. An adequate agronomic nutrient management should be a balanced nutrition and fertilizers are the key factor on supplying nutrients. Urea is the most commonly used fertilizer-N source, despite potential losses by NH<sub>3</sub> volatilization. Thus, new fertilizers technologies are needed to support the increasing demand and avoid the low N use efficiency (NUE). The reduction of NH<sub>3</sub>-N volatilization can be achieved by the use of natural aluminosilicates with nitrogenous fertilizer materials. This review consolidates the current status on the subject and the experience with the application of aluminosilicates as a slow release plant-nutrient fertilizer. Volatilization losses of nitrogenous fertilizers on the soil surface could be reduced with addition of natural aluminosilicates. Clay minerals (zeolites) are widely used in many countries to reduce NH<sub>3</sub> volatilization from amide N fertilizers, such as urea, besides several organic forms of nitrogenous sources. The reduction in ammonia losses by volatilization and the increased efficiency of N utilization and slow release nature of urea-zeolite mixtures when urea is used together with aluminosilicates was demonstrated in laboratory, greenhouse and field experiments with different crops and environments. These results indicate that aluminosilicates minerals used with urea mineral fertilizer can enhance the efficiency of this source by improving the nitrogen use through the control of retention of ammonium ion, contributing to increasd N uptake and crop yields.展开更多
文摘To assess the groundwater vulnerability due to leaching of chemicals, the groundwater system in the unsaturated zone is characterized by conceptual models that are further extended and refined with more detailed mathematical models to understand the governing physical processes in detail. However, due to lack of data and uncertainty level, an intermediate transition through index based models is researched. The attenuation factor (AF) approach, which works under the assumption that the chemicals degrade following a first-order kinetics and determines the fraction of the chemicals that goes to groundwater table, is one of the index based models that has been widely used due to its simplicity. Therefore, the objective of this paper is to review the research works done using the AF approach, to outline the future research needs. Furthermore, the mathematical implementation of the AF approach and the associated uncertainty levels is explained through an example and MATLAB source code.
文摘On tropical soils, liming and balanced nutrient supply are essential to ensure high crop yield and quality. An adequate agronomic nutrient management should be a balanced nutrition and fertilizers are the key factor on supplying nutrients. Urea is the most commonly used fertilizer-N source, despite potential losses by NH<sub>3</sub> volatilization. Thus, new fertilizers technologies are needed to support the increasing demand and avoid the low N use efficiency (NUE). The reduction of NH<sub>3</sub>-N volatilization can be achieved by the use of natural aluminosilicates with nitrogenous fertilizer materials. This review consolidates the current status on the subject and the experience with the application of aluminosilicates as a slow release plant-nutrient fertilizer. Volatilization losses of nitrogenous fertilizers on the soil surface could be reduced with addition of natural aluminosilicates. Clay minerals (zeolites) are widely used in many countries to reduce NH<sub>3</sub> volatilization from amide N fertilizers, such as urea, besides several organic forms of nitrogenous sources. The reduction in ammonia losses by volatilization and the increased efficiency of N utilization and slow release nature of urea-zeolite mixtures when urea is used together with aluminosilicates was demonstrated in laboratory, greenhouse and field experiments with different crops and environments. These results indicate that aluminosilicates minerals used with urea mineral fertilizer can enhance the efficiency of this source by improving the nitrogen use through the control of retention of ammonium ion, contributing to increasd N uptake and crop yields.
