If productivity gains can support sustainability, climate, and rural development goals, then more explicit consideration and potential yield-enhancing technologies is needed to design effective policy instruments. Future analyses can benefit from consideration of these factors for a more comprehensive assessment of environmental and health impacts of dietary transitions.As one of the six major air pollutants, nitrous oxide emission is one of the biggest contributors to the greenhouse effect. The sources of Nitrogen oxide emission are diverse. According to the federal and state ambient air quality standards in the United States, 75% of the total statewide Nitrous oxide emissions are from various agricultural soil management activities . Based on the data provided by Environmental Protection Agency , Nitrous oxide is always present in the stratosphere. The impact of 1 pound Nitrous oxide is 300 times more detrimental than 1 pound of carbon dioxide on warming the stratosphere. As figure 1-1 shows, there are 4% of the N2O emission from transportation, 4% from manure management, 5% from industry or chemical production, 5% from stationary combustion, and 6% from wastewater treatment. In contrast, there are more than 74% of the N2O emission comes from agriculture soil management in the state of California,stacking pots which sums up about 160,000 metric tons of N2O emitted per year from the croplands of California. In terms of fertilized croplands, they have higher emissions of N2O from the soils.

As one of the greenhouse gasses, Nitrous oxide is also one of the driving forces to ozone depletion. Nitrous oxide facilities raise the temperature of the troposphere as a ramification of the atmosphere. To be more specific, nitrous oxide enhances the greenhouse effect by capturing infrared radiation that is reflected by the planet’s surface and heating the troposphere as an upshot. Generally, it is released from soils to the atmosphere through the nitrification of ammonium. Nitrification of nitrogen fertilizer produces profuse nitrous oxide, which depletes the stratospheric ozone layer. With an estimate of 9 billion global population by2050 , the demand for food would increase rapidly, which indicates the N2O emission can have an upsurge in the future. As a state that supports 12% of U.S. food production, California has an over fertilization N2O emission factor above 13%. The application of an efficient Nitrous reduction treatment system needs to be widely carried out in the field of agriculture to lower N2O emission. In the next section, viable solutions would be discussed after exploring the factors causing Nitrous oxide emission. According to previous research , fertilizer with higher Nitrogen input results in high emission of N2O in soil. The direct fertilizer-related agricultural N2O emission is related to the amount of nitrogen input. However, it has not been proved that either different environmental factors or nitrogen fertilizer usage in the soil would affect the N2O emission on a greater scale. It has been discovered that the amount of N input in fertilizer/soil affects agricultural Nitrous oxide emission. This statement indicates that low nitrogen fertilizers would not have a zero N2O emission but a much lower N2O emission than fertilizers with an excess of Nitrogen input.

The N2O emission could also be affected by the textures of soil, the categories of crops, various amounts of nitrogen input in fertilizer, and climate conditions including temperature and humidity. To be concise, Environmental parameters determine the mass of produced gas in microbiological processes. With existing problems of the high N2O emission from the agricultural sector, the rationale and process of agricultural nitrous oxide production can be critical to the research. The microbiological basis of N2O is the process of soil nitrification and denitrification. In the process of nitrification and denitrification, different soil properties and environmental conditions are found to have a direct linkage to the amount of N2O emission production. As a result, one of the research topics of this research is, what agricultural factors are affecting Nitrous oxide emission from the soil. Assumptions of this research question are types of crops/plants, different types of soils and fertilizer, and disparate climatic conditions. The second topic towards problem solving: what an effective way is to reduce Nitrogen oxide emission by treating fertigation. In another word, how to reduce the Nitrogen input in fertigation by applying different water treatment methods. To reduce the N2O emission, the first task is to explore the main agricultural factors that cause the excess discharge of Nitrous oxide.There is a high possibility that it is not only related to the soil properties and environmental conditions but also the fertigation system that has been used.

Fertigation treatment is one of the most effective ways to reduce the Nitrogen input in the soil since there are more than half of farms use fertigation as the main irrigation solution instead of the traditional fertilization methods in the United States. Fertigation is an irrigation system that is added with fertilization. It is more convenient to target the fertigation nutrient deficiencies compares to traditional fertilization. Water treatment methods can remove the excess nitrogen, potassium, phosphorus, and other deficiencies in irrigated water for direct fertigation. Choosing an efficient water treatment method to produce freshwater for direct fertigation becomes difficult due to the limited amount of energy consumption. Among all the membrane treatment methods, forward osmosis uses the natural energy of osmotic pressure to filter water for higher quality. In another word, forward osmosis is not driven by energy-consuming hydraulic pressure, and it has extremely low energy consumption. Hence, fertilizer-drawn forward osmosis with nanofiltration has been studied to remove various nutrients for direct fertigation. Nanofiltration could be either applied as pre-treatment or post-treatment of FDFO as the hybrid treatment process of fertigation. Research indicates that when nanofiltration serves as post-treatment, it could reduce more than 80% of the Nitrogen input. The same treatment model could also be used for desalination, which can remove brine for the water that contains a lower total dissolved solid than seawater. Equation-4 calculates the equilibrium fractionation factor. It affectsthe number of bonds in Nitrous, and it determines the states of Nitrogen . Since the soil and air temperatures contribute to the change of equilibrium effect,hydroponic fodder system temperature value inputs are collected in the cropland. After data collection and calculations, different N input fertilizer usage and N2O emissions are compared to get the results. The emissions of N2O and NO from the soil are mostly produced by the chemical process of nitrification and denitrification. In this review, denitrification is the focus since it is an abiotic process to produce NO and N2O. In this research, the authors collected soil samples containing various Nitrogen input fertilizers in the field and sent them to the lab for analysis. The authors tested the following properties: 1) soil Nitrogen input 2) soil porosity 3) soil organic carbon content 4) soil oxygen content 5) soil temperature 6) soil PH value. The experiment uses the control variable method to test how each property affects the N2O emission. When a certain property is being tested, the authors remain other variables constant. According to the variables calculated in the empirical model, there could be a positive linear relation between the fertilizer input and N2O from the soil. As Table 2-1 shows, higher usage of Nitrogen fertilizer leads to a higher N2O emission. The soil that has a higher porosity also results in a higher N2O emission indirectly. The porosity of soil is the ability to hold water and air in the soil, the porosity of clay is larger than the porosity of sand. Due to the larger porosity, clay is more likely to produce a larger amount of N2O than sand. Therefore, the amount of water and oxygen are critical factors to N2O emission, and soil water content could be controlled by the soil type and evapotranspiration. Another research shows that Nitrous oxide emission from the soil is higher in spring than that in summer. The total emission of agricultural N2O is larger in regions that have a higher amount of precipitation compared to regions that have a lower amount of precipitation. In table 2-1, the increasing nitrogen input and soil oxygen content may boost the N2O emission, while the increasing organic carbon could decrease the N2O and N2 ratio. Bacteria could be a major effect on the N2O emission while carbon has a considerable limitation on the N2O emission since carbon could interfere with the denitrification process as an electron donor.

Moreover, oxygen availability could be the dominant environmental controller of Nitrous oxide emission. Three of the main soil factors that affect the denitrification rate are the application of oxygen, soil water content, and temperature. The compatible temperature for active nitrification should be from 2 to 50-celsius degrees. PH could have minor effects on N2O emission, increasing the soil acidity and decreasing the bacteria could reduce the Nitrous oxide emission effectively. However, to manage the fertilizer effectively to reduce Nitrous oxide emission, climate and seasonal conditions should be considered as well. Since the increasing sulfide could increase the N2O and N2 production from soil, Nitrogen-free fertilizer and sulfite free fertilizer should be prioritized. The largest amount of NH3 is from either urea applied to any crops/soils, or from ammonium sulfate applied to soil as a fertilizer. Considering the economic choice, replacing urea with ammonium nitrate could also reduce the N2O emission in summer due to the higher temperature and higher humidity. In contrast, the substitution of ammonium nitrate for urea as fertilizer would increase the emission of Nitrous oxides due to the higher humidity. The last section has shown all the potential factors for agricultural Nitrous oxide emission, it is found that the nitrogen input has the most momentous effect on the mounting Nitrous oxide emission. As figure 2-1 shows, the area that has a higher Nitrogen fertilizer input results in a higher Nitrous oxide emission estimation. The estimation of Nitrous oxide from California soils is modified using stable isotopic modeling and the IMAGE model. Reducing nitrogen input in the soil becomes the most crucial part of reducing nitrogen oxide emissions. Different water treatment methods could be applied to the fertigation water removing excess nutrients and reducing nitrogen for N2O emission reduction purposes. Forward osmosis is the process where water flows from the area on the lower concentrated water chemical potential side through the selectively permeable membrane to the higher concentrated water chemical potential side area. The draw solution usually has a higher concentration while the feed solution has a relatively low concentration. Two solutions with different osmotic pressures are placed on both sides of the semi-permeable membrane, one side is a feed solution with a lower osmotic pressure, and the other is a driving solution with higher osmotic pressure . Forward osmosis uses the osmotic pressure difference of the solution on both sides of the membrane as the driving force, so that water can spontaneously pass through the selective permeability membrane from the raw material liquid side to the driving liquid side. When the solution on the side with high osmotic pressure applies pressure that is smaller than the osmotic pressure difference , the water would still flow from the raw material hydraulic pressure to the driving fluid side. This process is called pressure damping osmosis . The driving force of pressure damping penetration is called osmotic pressure, so it belongs to one of the forward osmosis processes. In conclusion, FO uses natural energy in the form of osmotic pressure to transport water through the membrane while retaining the dissolved solutes on the other side. The process of Forward Osmosis could be run with low hydraulic pressure or without any hydraulic pressure. Forward Osmosis could be used for product concentration, waste concentration, and the production of clean water. In most situations, water would be extracted from the feed solution, and the waste/concentration would be left on the surface of the membrane. Since water molecules are passing through a semi-permeable membrane, from the feed solution into the draw solution. A draw recovery system is often necessary for producing clean water and recovering the draw solution for reuse.