Chen, J., Lü, S., Zhang, Z., Zhao, X., Li, X., Ning, P., & Liu, M. 2018. Environmentally friendly fertilizers: A review of materials used and their effects on the environment. Science of The Total Environment, 613, 829-839.
Too much of a good thing
Producing large amounts of food requires high amounts of fertilizers. Without fertilizer, soils are not as productive and crops do not grow as quickly since fertilizers give more productive soils and faster growing crops. Fertilizer is therefore key to ensuring enough produce is grown to feed populations on a large scale. Any fertilizer that is applied is always intended to stay on the crops it is placed on, but unfortunately, the chemical fertilizers used today often wash out after rain events. Typically, excessive fertilizer is applied and the crop cannot take all of it up. Excess fertilizer can wash away with rain water into habitats where extensive amounts of it cause harmful impacts. It is in fact a major source of pollution in soil and water ways globally. Too much of a good thing, excess fertilizer in soils and waterways can lower oxygen levels and decrease the habitability of these areas for the organisms that live there. Additionally, when fertilizer is washed away, its benefit is lost and is a costly waste. In order to combat the waste and negative environmental impacts of traditional fertilizers, options for environmentally friendly fertilizers (EFFs) are currently being explored.
What are environmentally friendly fertilizers?
EFFs are fertilizers that are designed to remain on crops longer, allowing the crops an extended period of time to absorb them. One way EFFs achieve this is by coating the fertilizer in a natural substance that is broken down over time. This prevents nutrients within the fertilizer from being delivered all at once and from easily washing out of the system. The natural substances used for coating the nutrients come from a variety of sources. Some coatings come from various plant based coatings sourced from plant residues, such as starch and wheat. Another source is chitosan, which is a substance found in the exoskeleton of hard-bodied water animals like crabs and shrimp.
Benefits of using environmentally friendly fertilizers
Using EFFs can have several benefits. The first is that they help to greatly reduce environmental pollution by retaining the fertilizers on crops. Ideally, EFFs are applied once, and then slowly are taken up as the growing season progresses, ultimately releasing the nutrients within. Since coastal waters are increasingly becoming polluted with nutrients from agriculture, any amount that can be reduced is beneficial. Additionally, some of the materials used in EFFs can help take up the greenhouse gas of carbon dioxide from the atmosphere and convert it into organic matter. This helps make the soil healthier and can restore degraded land. Healthier soils retain more water and an optimal pH for crop growth. EFFs can even help lower emissions of nitrogen oxide (NOx), which can contribute to air pollution. The breakdown of nutrients and fertilizers typically produces this gas, so if less fertilizer is applied, there is less opportunity for the gas to be produced.
What is next?
While the use of EFFs has several benefits over traditional fertilizer application, each method of developing EFFs comes with associated pros and cons. Some of the cons include negative impacts to the environment from the way that some coatings for the EFFs are generated, including increased emissions of gases during production. Additionally, EFFs are 2.5-8 times more expensive, which currently limits their use to specialty crops. Although EFFs are only applied once and slowly release over time, this release time may not match when the plants need it most. Currently most EFFs release in the earliest stages of plant growth. More research is needed on ideal release conditions to match release times to peak plant growth. The pros and cons associated with each type of EFF need to be weighed against each other to determine which method has the overall greatest advantages, with the lowest negative side effects. While EFFs hold promise for more environmentally friendly fertilizer applications, they have to be optimized further to make them useable on large scales.