Abstract
Soil infertility is prominent in damp farmlands, causing harm to crop growth. There have been developments attempting to solve this problem, but they stagnate soil health and crop growth. We devised a solution involving a dendrimer-enhanced irrigation system and dendrimer-enhanced ultrafiltration (DEUF). The soil on this farmland receives polyamidoamine (PAMAM) dendrimers bound to water through the irrigation system. The nutrients of the soil would bind to the dendrimers and maximize nutrient nourishment for the crops. When nutrient runoff inevitably happens, the dendrimers will flow into the water. DEUF will take place to remove these nanoparticle complexes from the water altogether. The nanoparticles bind to the ethylenediamine core of the dendrimers, ensuring that the dendrimers are completely removed from the water source. These dendrimers can be reused for this process while clear water is released into waterways. This process preserves soil health and prevents harm to organisms and their environments.










Present Technology
In the present time, there are several advancements that have been made to tackle the prevalent issue of soil degradation and infertility in farm land that is near a body of water. Soil conservation efforts aim to preserve soil’s structure, fertility, and biodiversity. These efforts will help in improving the growing conditions of crops. Crop rotation is growing crops in a particular sequence combined with other soil-conserving crops, grasses, or legumes. It has played an essential role in improving soil health through its influence on reducing the As-contaminated soil. Crop rotation reduces this type of soil by changing the soil pH and the uptaking of the nutrients by a plant root to reduce the bioavailability of the soil (Kama et al., 2025). Crop rotation has been known to maintain good soil health by mitigating the contaminants through these mechanisms. However, crop rotation doesn’t take into account in maintaining a safe amount of fertility. It also increases pest pressure, leaves herbicide residues, and soil compaction. Pest pressure is when plant roots get damaged, which influences the use of chemical pesticides to stop this pressure but ultimately harms soil organisms. The herbicide residues over time will alter the chemical composition of the soil, which could make it more susceptible to erosion. Soil compaction will restrict the movement of nutrients and water, which disrupts the nutrient cycle necessary for soil fertility. A 10-year study in northern Ohio found that continuous corn yielded only 89% as much as corn in a corn-oats-hay rotation, showing a 11% reduction in yield. These issues result in leaving various harms on farm land, which are detrimental to the health of the soil (Bogužas et al., 2022).
Another method to prevent soil infertility is adding animal manure and using microorganisms such as fungi to help expand the land's biodiversity. Since the domestication of animals, livestock dung has been used to help make the land more nutrient-rich. The manure's nutrients are around 70-80% of nitrogen, 60-85% of phosphorus, and 80-90% potassium, depending on the animal's diet. These nutrients are vital to keeping healthy soil and for growing healthy plants, and they indicate that the soil has an elemental balance in ecological interactions and processes (University of Massachusetts Amherst, 2014). Some tested ways of incorporating manure into the soil include but are not limited to composting the manure to remove the harmful pathogens that can coexist inside the soil, fresh manure (semi-liquid or solid) that can be either incorporated into the soil or injected under the soil's surface to reduce runoff and odor, and can also be produced in pellets for convenience sake (US EPA, 2020). Overall, the use of manure as fertilizer decreased and is now 8% over 237.7 million acres planted across seven major U.S. crop fields (Economic Research Service USDA, 2023). Fungi are effective in decomposing organic matter to cycle nutrients throughout the soil. Mycorrhizal fungi are fungi roots known to have a symbiotic relationship with the roots of a plant, extending the roots to allow for an increased absorption area (Viana, C., 2021). Although these methods have been used over vast periods, they are only sometimes effective as the manure can imbalance nutrients, seep into the groundwater, and have pathogens/pests, which can all harm soil fertility. Fungi can also contract diseases that can be spread to plants; an abundance of fungi can cause an imbalance, and sometimes, the fungi favor invasive species over native plants.
In recent years, the popularity of vertical farming has surged, specifically in areas faced with spatial limitations. Vertical farming uses advanced technologies like hydroponics, aeroponics, and/or aquaponics to deliver nutrients directly to plants, eliminating the need for soil (Guida, 2024). Without relying on a specific weather, season, and water supply, vertical farming is a sufficient alternative for those who want to grow crops without ample space. However, adequate funds are required to cover initial costs to sustain this vertical farming method and a reliable energy source to power the system. Vertical farms require an estimated 76.55 kWh per month and can cost up to $83.7 million (Weiss, 2017). This is significantly higher than traditional farming methods, and in areas with a high power outage rate, it would hinder dependability and scalability. Oftentimes, power outages are accredited to severe natural disasters such as floods, forest fires, droughts, and heatwaves, and seeing as these events are unpreventable, systems dependent on an electric energy source are left vulnerable (Yoon et al., 2019). In many cases, vertical farming can be unreliable and costly, making it impractical for many traditional farmers to look to it as an alternative for farmlands that have not been producing enough harvest. Due to the flaws in many modern-day farming methods, we aim to introduce a new, more efficient yet effective mechanism for maximizing plant growth, soil fertilization, and land conservation.

History
Irrigation systems have been crucial for society ever since ancient times. In 6000 BC, Ancient Mesopotamia used the Tigris and Euphrates rivers for irrigation. The basin irrigation system used water from the Nile River's flood for irrigation in the Ancient Egyptian civilization. Aqueducts were built to distribute water to different parts of the Ancient Roman civilization. These systems have developed with new technologies to improve water distribution, such as the introduction of mechanical pumps and pipes during the Industrial Revolution. They continue to evolve until what is in the present day, such as aquifers and basins (Dixon, 2024).
Crop rotation was implemented during ancient times to help irrigation and water use efficiency. It stems back to the Ancient Roman civilization, where farmers would plant legumes, such as lentils, in a season and then plant grains, such as wheat, in the following season. The popularization of the Norfolk System by Charles Townshend became prominent in the Agricultural Revolution. It was a four-course rotation of turnips, barley, clover, and wheat, which would reduce soil depletion (Allotment Garden). This practice of crop rotation has continued to evolve, with modern techniques, such as advanced crop sequencing, being implemented to preserve soil structure and health.
Ancient civilizations would not just confine themselves to growing crops on the ground level either, as they would also use their innovative abilities to keep plants healthy even if they were not directly touching the ground and subjected to traditional irrigation systems. The most well-known example of this ingenuity would be the Hanging Gardens of Babylon, built by King Nebuchadnezzar II between 605 and 562 BC (Steinmeyer, 2023). This structure would bear plants in a series of tiers to create the illusion of a mountain full of greenery. The revolutionary aspect of this construction was the process of irrigating the variety of plants housed on each floor of the structure and getting the water from the Euphrates River to the top of each tier. The river water was transported using chain pumps that would carry the water from the bottom of the garden to the top floor. This ancient system is often credited as the predecessor of modern vertical farming.
Manure was a vital aspect of fertilization back 8000 years ago. Researchers had first suspected that they used manure around 2,000-3,000 years ago, but that ideology had changed. They found that the nitrogen (N-15) content in the wheat, barley, and peas from 4,400-7,900 years ago was much higher than if the crops were grown in typical soil (Balter, 2013). However, they believe that the farmers were not aware of the higher nitrogen content; instead, they were aware of the livestock roaming. Where animals naturally accumulate feces, the farmers most likely notice the difference in the plant's growth, actively using manure as a fertilizer/plant enhancer. On the other hand, Mycorrhizal fungi have been present in most soils for around 400 million years. However, the concept of these fungi was more recently discovered in 1881. They are a symbiotic relationship between the fungus and the host, in which the fungus extracts nutrients from the soil and transmits them to the host plant; the host plant, in turn, nourishes the fungus (Campbell, 2015).

Future Technology
The main issue with previous solutions was how inefficient the process was in giving the plants the proper nutrients. Although there are many ways of increasing the amount of nutrients in the soil overall (such as manure and fungi) or ways of producing more crops (such as vertical farming and crop rotation), helping the plants, in certain farmlands where the weather was damper, it had made the plants lack the proper nutrients to keep them healthy due to water runoff. However, our solution ensures that the plants have direct access to the nutrients they need to nurture a more vigorous plant. To execute this plan, we need to use dendrimers.
This technology uses Polyamidoamine (PAMAM) dendrimers to preserve the soil's structure and fertility on farmlands. They are highly-branched nanoparticles that are known for having several functional groups. As the water flows into the irrigation system in the facility, the PAMAM dendrimers bind to the water. The dendrimers have high water solubility and are often used in aqueous environments, as their amine groups can form hydrogen bonds with water molecules (Vasile, 2019). Following the irrigation of the land, the dendrimer-concentrated water will soak the soil, migrating deep into the ground where it can interact with materials such as clay, silt, and other organic matter. Once underground, the PAMAM dendrimers will bind to essential nutrients, including nitrogen, phosphorus, and potassium, while still bonded with the water. As the water distributes itself underground, it carries the targeted particles towards crops for efficient nutrient use. This subterranean interaction promotes the facilitation of nutrient cycling and fertility of the soil.
The amine groups of these dendrimers will bind to the nutrients in ionic form. The negatively charged dendrimers would bind to cations, while the positively charged dendrimers would bind to anions. With the dendrimers now binding to the nutrients in the soil, the structure can stay longer. The PAMAM dendrimers are then bioengineered to attach to the roots' ends and the nutrients on the other side. To accomplish this, we need the water to be attracted to the PAMAM dendrimer, which naturally brings the dendrimers to the roots. The H2O would need to bind to the negative charge of the dendrimer. However, the bond between the two would be weak as they have an irregular bond, and H2O does not have extra electrons. It would be effective for us as the two bonds will break over time, allowing the PAMAM dendrimers to be reused.
Inevitably, nutrient runoff will occur. However, it will only happen after a much extended period compared to without the dendrimer-concentrated water going into the soil. The excess nutrients will accumulate with groundwater and flow into the nearby bodies of water. There would need to be a method to specifically filter these nanoparticles attached to the nutrients out of the water. Dendrimer-enhanced ultrafiltration (DEUF) effectively removes Cu(II) nanoparticles from aqueous solutions. The Cu(II) would bind to the PAMAM dendrimers with an ethylenediamine (EDA) core. Since these complexes are larger and more sensitive to pH changes in water compared to Cu(II) as a linear polymer, they could effectively be separated from an aqueous solution (Diallo et al., 2005). Thus, the water will be able to flow into the irrigation facility, as this process will cycle through with water binding to these reusable dendrimers again.
In twenty years, this nanotechnology can advance to the extent that it can be readily used in all irrigation systems connected to all farmlands and bodies of water near it, as the problems of soil degradation and nutrient runoff have especially taken place in farmlands. As technology develops, dendrimers will become more readily available and accessible and be used in this way. This system is highly efficient, as it reuses the dendrimers and preserves the nutrients in the soil.

Breakthroughs
Some breakthroughs must be made in order for this technology to be used on a wide scale. First, we need to design bioengineered dendrimers with fixed binding properties. The PAMAM dendrimers have amine groups to bind to cations, such as calcium (Ca²⁺), as well as negatively charged groups to bind to the anions, such as phosphate (Gosika et al., 2019). However, these dendrimers have the capability to over-binding, which could make these nutrients in the soil unavailable to the plants. Overlooking these binding attractions could lead to the nutrients being lost in transport instead of properly going to the plants. The bioengineered dendrimers need to have their functional groups modified to adjust their attractions for specific ions as well as integrate stimuli-responsive polymers, which can release nutrients under different conditions, such as when the pH changes near the roots of the plants (Rosario & Ma, 2024).
Another breakthrough is to bind the nanoparticles stuck to the nutrients in the water, which can be the dendrimers and metals, such as Cu. It has already been successful in binding the Cu(II) nanoparticles to PAMAM dendrimers with an ethylenediamine (EDA) core. (Diallo et al., 2005) However, these dendrimer compounds' size and pH requirements can vary. There has not been research conducted on this matter before, but knowing this would be crucial regarding the quantity of nanoparticles that would be filtered out at a given time.
This technology does not exist today due to a lack of portability in ultrafiltration systems. Many ultrafiltration systems take up much space. However, smaller ultrafiltration systems have been recently developed with models that are only five feet long (Newterra, 2023). This development shows the potential of making smaller ultrafiltration systems possible. PAMAM dendrimers' ecological impact has not been investigated yet, as they have been primarily used for drug delivery and nanotherapeutics. This issue must be investigated, as their ecological impact is essential for this process to work.
The investigation would utilize soil and water samples from different agricultural regions. There would be a control group of soil and water being treated with untreated water, while the test group would have the soil and water treated with dendrimer-concentrated water. Soil and water samples would be collected at weekly intervals for the six-month duration of this investigation. The dendrimer concentrations would be recorded over time to determine their half-life in the different soil and waters. The Lethal Concentration 50 (LC50) will be measured to determine the toxicity of the dendrimers on the soil and the degradation products. If the dendrimers degrade into environmentally friendly compounds and the soil displays improved health from the nutrient enhancement, then the PAMAM dendrimers would be environmentally safe for large-scale application.

Design Process
We considered many alternative solutions before determining that our technology would best tackle nutrient runoff. One solution was mixing the PAMAM dendrimers into the infertile soil using factories. We would dig up the soil and transfer it to a factory where the machines would effectively mix the dendrimers through the soil. This way, we could have an enormous scope of nutrients used. However, we decided to scrap this idea due to the sheer amount of soil that would need to be transported to the factories. It would be ineffective to transport tons of soil into a factory and could, in the process, damage the ecosystem/environment around the soil and in the soil. Another issue is the cost, the transportation of soil and gas, and the facility to incorporate such dendrimers. The last main issue was the viability and scale of stirring in the dendrimers because our original goal was to make sure that as years went by, our process of dendrimers could be incorporated into many farmlands while still being cost-effective. However, we could not dig too deep into the soil due to its hard labor, defeating the purpose of ensuring that most nutrients are used. Not only that, but having large masses of land missing would not be ideal, therefore cutting down the idea of making it viable for many farmlands. Our new and improved technology tackles all three of these problems as transportation is not an issue; its environmental impact would be minimized due to it staying in the ground, and it would cut costs.
Our second idea was to incorporate groundwater into our dendrimer-water cycle. This interest was sparked by the fact that about two-thirds of all United States agricultural lands depended on groundwater as a source of hydrating crops in 2018 (Wallander et al., 2023). By substituting the need for a nearby body of water with accessible subsurface level water (aquifers), our technology could be applied to more farmlands. Although this proposal granted accessibility to more agricultural sites, it raised the matter of retrieving the dendrimers from the soil and reusing them after one cycle. With a water source underground, there is an increased difficulty in finding and returning the nanoparticles to the surface when considering streams of groundwater flow in multiple directions. Furthermore, a reliance on aquifers heightens the possibility of our PAMAM dendrimers being trapped in an unintended area where they would not be able to contribute to the soil's nutrient cycle and be able to help nurture plant growth. In search of a more efficient and reliable method that indicates a specific location where the dendrimers will be taken, we ultimately decided to limit the areas that could use our innovative system, specifically farming areas with nearby bodies of water.
Our third solution was to attach the dendrimer to the plant's root. We initially saw this idea as viable because instead of continuously feeding the water through the irrigation system, we could attach the dendrimer to the plant. The flaw in this solution is that removing all the plants and adding the dendrimers takes a long and tedious process to remove and regrow the plants. Also, attracting many nutrients would be hard as only the nutrients around the roots would be used instead of the broader scope of available nutrients. Lastly, we do not know the long-term effects of the dendrimer being permanently attached to the roots of the plants. We also would like to see if the dendrimers were multifunctional for many crop species. Our