When choosing a fertiliser, we are faced with many options: conventional fertiliser, organic fertiliser, salt-based fertilisers… but what is best? What will suit your farm? The lines between these fertilisers can get blurred and the actual meaning can be debated - but let’s stick to what we know….
In science, an organic compound is a compound that contains carbon and commonly originates from living things. Organic fertilisers are derived from natural materials such as mined rock minerals, and natural plant and animal materials e.g. compost, guano, seaweed. In certified organics, organic fertilisers are required to meet certain criteria when it comes to the sourcing, ethicality and contamination of heavy metals and inorganic compounds. Organic fertilisers generally release slower, as they rely on living organisms to break down the organic compounds and utilize the minerals when required. It can be deduced that this results in a higher nutrient utilisation, as it mitigates leaching. But on the other hand, organic compounds may require a more biologically active environment to enhance availability.
Synthetic fertilisers, or conventional fertilisers, are manufactured and purified compounds with high percentages of specific elements. This results in products that are often stable in their nutrient composition and contain a few specific nutrients, versus organic compounds that may contain many different nutrients. Synthetic fertilisers are often more water soluble, so tend to release quicker. This has a great effect for short term results but may be less favorable for long term nutrient supply. Due to their water-soluble traits, these nutrients can be more prone to leaching when over applied.Due to the water solubility, synthetic fertiliser is usually more effective as a plant feeder compared to correcting nutrient levels in the soil.When soil life and mineral balance is neglected, this can enhance dependance on regular nutrient applications to sustain plant growth.
Due to the corrosive characteristics of table salt or sodium chloride, there are many negative connotations with salt-based fertilisers. While table salt is the most thought of substance when we talk about salt, there are many other substances that are also officially salts. What defines a salt according to scientific explanations? “A salt consists of the positive ion (cation) of a base and the negative ion (anion) of an acid.” A good example that many people wouldn’t think of as a salt is lime. Ag lime, also known as calcium carbonate, is a salt where calcium is the cation and the carbonate the anion. But also, copper sulphate or plaster, which is a form of calcium sulphate.However, when people refer to salt-based fertilisers, they are often referring to the synthetic, water-soluble type which, as mentioned above, can result in rapid growth and immediate response.
There are ‘horses for courses’ as they say, but when looking for solutions it is important to first outline short-term and long-term goals of the farming outcome. When it comes to fertilising there are a few key things to be considered, such as what is best from an economical and environmental point of view. Good questions to ask include…
Of the 17 nutrients that are required to grow a plant, there are a few key ones, such as phosphate. We often see the likes of phosphate fertilisers applied at high rates; then, because we have seen a good response after applying a specific mineral in the past, we continue to apply these fertilisers at higher rates -year on year. This can result in overloading the soil with single nutrients and undetected deficiencies in our soil, which then come through in our plant and stock health. Whilst conventional fertilisers can be a quick solution and organic compounds are often slower acting, it is important to understand the goals and what time frame you are working within. Creating a balanced, healthy soil isn’t something that happens overnight, and profitability is something that needs to be respected for sustainable business practice.
SoilMatters take all options into account when choosing the right fertiliser for a farming system. It may seem difficult to change from a trusted way of doing things, but with the help and guidance of our experienced team it is possible to do it right and do it well.When it comes to soil, we can help you identify the lowest hanging fruit to make gains in your farming goals.