Fertilizer Practices: Natural vs Chemical Fertilizers
As we discussed in our introduction post, all fertilisation aims to provide plants with nutrients. We also walked through how farmers can apply fertiliser to their fields. You may recall that the application method depends on the kind of fertiliser used (granular, liquid and gas). However, fertilisers can additionally be divided into four different categories: natural, human-made, organic and inorganic. Understanding their differences is equally important to keep in mind when planning the annual fertilisation strategy. Let’s take a look at why.
When discussing fertiliser, the correct terminology is key as different terms may describe similar characteristics. In this blog post, we will be defining plant -and/or animal-based fertilisers as ‘natural fertilisers’. Another term that is commonly used to describe fertilisers from a natural process is ‘organic’. However, the term ‘organic’ is also often used to describe that something is ecological, being free from additives such as pesticides. Though things that are ‘organic’ tend to be ‘natural’ inherently, the reverse is not always the case (as we discuss later on in the post).
So what are natural fertilisers?
As mentioned above, natural fertilisers can be based on plant or animal products that contain the specific nutrients that the farmer or grower wishes to add to their crops. A key characteristic that sets natural fertilisers apart from synthetic fertilisers is the process by which they are made. As given by their name, natural fertilisers come about naturally. They are predominantly the result of an independent process. Manure is an excellent example of such as animals produce their droppings autonomously. Leaves collected in the autumn time or food compost are other examples.
The process that defines natural fertilisers also impacts the levels of nutrients they contain. Virtually all nutrients that a plant needs can be derived from natural fertilisers, but a farmer may need greater quantities. Comparatively, natural fertilisers contain lower levels of nutrients than synthetic ones. Additionally, the levels of nutrients also have a greater variation in natural fertilisers than in synthetic. For example, the levels of nitrogen and phosphorous in raw bone meal can vary between 2-6% and 15-27%, respectively. There are numerous causes for such a variation, including how and when the fertiliser has been applied, how old it was at the time of application, even its internal moisture level or exposure to the sun has an impact.
A plant that is nourished with natural fertiliser also needs to wait longer until they reach its cells. This is because plants are not able to directly and independently absorb the nutrition in, e.g. manure. Instead, they rely on bacteria and fungi in the soil to break down the natural anatomy of the fertiliser into a chemical one. Only then can the plants freely take it up from the soil. Therefore natural fertilisers can also be referred to as ‘slow-release’ fertilisers. Depending on other organisms to chew your food takes time. Thus farmers that use natural fertilisers need to be aware of their impact on the timeline of the fertilisation strategy. The weather may also slow down nutrition release. Bacteria and fungi operate best in a warm and moist environment while cold weather slows them down. If a farmer fertilises too early or late, it may take even longer for the fertiliser to be broken down. However, this can be considered an advantage. With slow-release fertilisers, farmers can better avoid so-called nutrient leaching. This is because plants absorb and/or hold all the fertiliser spread. Another advantage of natural fertilisers is that they can improve soil structure by providing an environment for bacteria and fungi to grow, though this process may take a long time. Compared to synthetic fertilisers, the natural ones tend to be more expensive and contain high salts. Manure that has not gone through a composting process may contain too much salt, harming the crops.
Synthetic plant nutrition, especially in a granular format, may be the first to mind when thinking about fertilisers. Similar to natural fertilisers, synthetic ones are readily available for private consumers and farmers alike. However, these kinds of fertilisers are not inherently created through a natural process. Instead, they are made through targeted human effort and according to specific criteria based on their final use case. Therefore, being able to develop and tailor nutrition based on particular requirements gives some key advantages.
Alike the natural ones, any kind of nutrition can be manually synthesised but with greater precision. Synthetic fertilisers not only contain much higher levels of nutrients but also don’t degrade as quickly. Hence, farmers don’t need to worry whether their fertilisers actually contain the required % of nutrition and can buy lower quantities. Another advantage of such fertilisers is their absorption rate. Natural fertilisers depend on the metabolic process of bacteria and fungi to break down the nutrients into chemical components that the plants can absorb. Synthetic fertilisers have been designed to already be in this format and can also be referred to as ‘chemical fertilisers’. This means that as soon the fertiliser is spread, the nutrients it contains are readily available for the plants to consume. This fertilisation process can be a tremendous advantage for farmers who can precisely time when they need specific nutrients to be available in the soil. However, as synthetic fertilisers contain higher levels of nutrition, farmers need to be cautious not to over fertilise which would damage both the crops and the environment. How much fertiliser needs to be applied can be difficult to determine, but this becomes much easier using precision farming technologies. Through, e.g. soil health analysis and prescription files, farmers know exactly how much fertiliser each part of the field requires. Combining this with synthetic fertilisers makes this a precise and rapid process.
Can synthesised fertilisers be natural?
Though natural and synthetic fertilisers are different from one another due to the process in which they are made, they can overlap. As we have established, the nutrients plants need are naturally occurring in the soil and as plants grow, absorbing these nutrients, their levels in the soil decrease. However, over time and with the proper environmental conditions, large deposits of these nutrients can form. These are generally referred to as ‘mineral deposits’ and even include our everyday table salt source. Many fertiliser producers use these naturally occurring mineral deposits as the origin for the components of their fertilisers. Once the minerals have been derived from the deposit, they are processed into the desired format and can even be mixed with other naturally occurring nutrients. To the plant, synthetic fertiliser in the soil is like table salt on our pasta, it may not be derived from manure, but the result is the same.
Organic fertilisers are natural, but the origin and creation process has additional regulations. The regulations vary depending on whether the fertiliser is based on plant or animal products and the state or country in which they will be used. The general goal of these regulations is to keep the fertiliser as ecological as possible. For example: in Oregon in the United States, fertiliser based on plant products such as meals made from cottonseed may not contain any pesticides. This means that the farmer who produces cotton and intends to produce organic fertiliser from the seeds may not spray any pesticides over the cotton plants. Similar rules cover manure. If cattle farmers in Oregon want to use the manure by-product from their animals, it needs to remain raw. That means the manure cannot undergo a composition process, whether it is broken down. Hence, just because the fertiliser in question is natural doesn’t mean it is considered organic.
Innovative solutions and optimising practices is a cornerstone of successful agricultural production. Yet, combining natural and synthetic fertilisers may come as a surprise. The so-called ‘organomineral fertilisers’ have the potential to bring farmers the best of both worlds.
But why combine them in the first place?
Natural and synthetic fertilizers have many pros and cons. One reason why using natural fertilizers is preferred is its active contribution to the wellbeing of microbes in the soil. Synthetic fertilizers generally do not have such abilities. Yet, in some ways, they can be considered more reliable. As mentioned before synthetic fertilizers have a much lower variation in their nutritional levels. They are also cheaper and easier to apply. By combining aspects of both natural and synthetic fertilizers we have the potential to create even better fertilizers. Fertilizers which directly tend to the well-being of plants and soil. Organomineral fertilizers can contain any variation and combination of nutrition needed and are commonly available in a solid format such as pellets. The core of the pellet is made up of the natural aspect of this fertilizer. This core can also be referred to as ‘biosolid’ which is a naturally derived material from plant and/or animal products. The pellet is covered in an outer layer in the synthetic material of choice, for example, a urea and potash mixture.
Determining the correct fertilisation strategy is enormous work. Not only do farmers have a plethora of kinds of fertilisers to choose from, but different crops also have different needs. These needs can, in turn, be affected by current weather conditions to what crop was grown on the field the previous year. Therefore, making it easier for farmers to fertilise and do so correctly is vital. Precision farming makes plant nutrition easier on the farmer and planet.
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