Here at PlantCatalyst we’re passionate about agriculture and we love to read articles about a variety of agricultural practices, issues and trends. To that end we’ve begun asking writers to submit blogs that our followers might find interesting. This first blog is by a Bolivian writer named Sebastian Pereira who wrote this blog specifically for us, so you won’t see it anywhere else. We hope you enjoy it!
The Hidden Costs of Chemical Fertilizers
By Sebastian Pereira
The population boom experienced in the years after WWII demanded an equal expansion on the production of food. For crops to increase their yield, chemical fertilizers began to see mass adoption. A chemical fertilizer, also known as inorganic, are synthetically manufactured products that add the necessary nutrients to the soil, so it’s better able to grow crops.
The ease of use, coupled with mass production, have resulted in widespread application of synthetic fertilizers. This has caused an overreliance in agriculture of these products, bringing some unintended effects on the globe’s ecosystems, climate and human quality of life.
First, chemical fertilizers are one of the causes of Climate Change. Soil microbes convert nitrogen-rich fertilizers into nitrous oxide (N2O). This gas is the third most potent greenhouse gas, trapping heat, and causing global warming. Not only this, nitrous oxide destroys atmospheric ozone, which helps protect the planet from harmful ultraviolet rays.
It was long understood that soil microbes belched nitrous oxide, but it was thought to be a linear relation. In the early to mid-2000s results from soil experiments showed that microbes spewed close to one kilogram of greenhouse gas for every 100 Kg of fertilizer. But this result didn’t coincide with increases of nitrous oxide found in the atmosphere.
Since the year 1750 the levels of nitrous oxide have risen twenty percent. From an initial 270 parts per million (ppb) to more than 320 ppb in the most recent survey. The linear relation between the greenhouse gas produced by soil microbes couldn’t account for this increase. This propelled researches from Michigan State University to do more studies on the subject.
The results were alarming. When farmers use more fertilizer than needed for a given field, the microbes produce gas at a higher rate. From 200 kilograms of fertilizer microbes released 4 kg of gas. Further testing showed the conversion relation oscillates between 1.75 to 5 percent, it grows exponentially. The team published the results in the journal Proceedings of the National Academy of Sciences in 2014.
Second, continuous use of chemical fertilizers reduces yield. The most common case of this effect is the alteration of the soil’s pH over time. The constant use of nitrogen heavy fertilizers makes the soil more acidic. This reduces the ability of certain crops to grow on land where they used to thrive.
Macronutrients and micronutrients are not the only elements needed for a crop to grow. Soils microbes and worms are parts of the ecosystem, and play a major part in fertility. The overuse of chemical fertilizers alters this balance, and affect the ability of a soil to produce consistent yields over time. This in turn pushes farmers to pour more fertilizer on the same soil, resulting in a vicious cycle. Also, this compounds with the previous phenomena. More fertilizer means more nitrogen, which, as we saw, results in greater quantities of nitrous oxide.
Another problem caused by the multiplication of microbes in rich nitrogen environments is soil degradation. The microbes consume more organic matter than what is added by the crop’s organic residue, which compacts the soil over time. As the volume of organic matter falls, the soil’s physical structure changes, losing its sponge-like capacity to hold water, air and organic nitrogen. Water flows with ease through this compacted soil, contributing to our next side effect.
Our third cost of synthetic fertilizers is water pollution. As this article has shown, not all the fertilizer is used by the plant, a great deal is processed by microbes and another portion is washed off by irrigation water and rain. But where does it go?
First a large portion of the nitrogen in a fertilizer turns into nitrates. These can easily travel through soil and reach underwater reservoirs, which become contaminated. In fact, these fresh water reserves are no longer safe for human consumption. Furthermore, the pH is modified to such an extent that they become useless for irrigation without extensive treatment.
Next, the nitrates travel using the streams, creeks and rivers accumulating in lakes and lastly the ocean. In those bodies of water where they end up being deposited algae blooms. This drops the levels of oxygen to such an extent as to create what researchers call “Dead Zones.” In this areas plant life, and fish disappear, unable to survive in the low oxygen environment.
The disturbance the phenomena causes on the ecosystem cannot be understated. Whole food chains are disrupted and animal populations, both aquatic and terrestrial, are threatened. As the planting season begins “Dead Zones” grow, endangering even larger areas. The loss of biodiversity in the oceans reduces their ability to sequestrate carbon, accelerating climate change.
The various negative effects of synthetic fertilizers have on the planet reinforce their contribution towards climate change. The microbes which convert nitrogen to nitrous oxide are also changing the soil and reducing its capability to sequestrate carbon. The nitrates that travel through the compacted soil, end up polluting underground water sources, as well as, lakes, rivers and finally the ocean. This is a vicious self-reinforcing cycle.
Steps towards reducing the dependency agriculture has for chemical fertilizers is crucial. The human population keeps growing and thus we must once again raise food production. But this time we must look beyond chemical fertilizers and find a sustainable solution.