An Introduction to Fertilizers in Plant Research

If you have ever had a home garden, you are probably familiar with the fact that adding a little fertilizer to a plant can really do wonders. This can also be the case in a lab greenhouse! The difference is that instead of adding a bit of the “blue stuff,” we try to be a bit more precise about fertilizers when working in the lab.

Why Do Lab Plants Need Fertilizers?

While it is true that plants don’t have fertilizers out in the real world, the greenhouse is very different. Usually, the soil you are using will contain some nutrients, but usually not enough for a full growing season. For larger plants, it’s also helpful to remember that the amount of soil in a pot and the size of the pot will come nowhere near the amount of soil or space that a plant would utilize in the field. As a result, the nutrients will gradually become depleted as the plant grows.

Another point to consider is the growth conditions of a plant’s native region. A species that is native to clay soils will have different nutrient demands than one that grows in sandy soils. If you are trying to replicate native growth conditions, adding fertilizers can help you achieve the micro- and macronutrient levels that your plant might be craving.

Which Fertilizer Should I Use?

This is the golden question. The key is always to consider what plant you are growing. For instance, I know labs growing Arabidopsis that will simply apply add some general-purpose fertilizer to the soil when they start growing the plants and never add anything else. The plants are small enough, and the pots large enough so that the nutrient demands never exceed what was originally added. Compare this to my situation growing corn plants. I usually add a broad spectrum and a slow-release fertilizer to the soil when I start the plants, and then I water-in iron and more fertilizer every couple of weeks as the plants grow. The demands of each plant determine how much, and how often you need to apply fertilizers. My suggestion would be to research the nutrient requirements of the particular plant species you are attempting to grow to get an idea of what it requires.

The other consideration is the soil that you are using. Most soils purchased for greenhouses will list their nutrientional content, and whether or not they contain any other additives. If they don’t, it is probably worthwhile having the soil tested to see what nutrients it contains, especially if you are going to be using that soil type for a while. Once you have this information, you can better choose the most suitable fertilizer to cover potential deficiencies.

What Does NPK Stand For?

You have probably noticed on general purpose fertilizers three numbers listed like this: 0-0-0. Those are the NPK numbers, or the amount of nitrogen (N), phosphorous (P), and potassium (K) that the fertilizer contains. NPK fertilizers are broad-spectrum fertilizers, because they provide the three major nutritional requirements to the soil. When you are reading the fertilizer bag, bear in mind that the numbers listed are percentages of the total combined amount of N, P, and K. So, a 10-10-10 fertilizer will contain 70% other ingredients upon treatment. These ingredients often include other micronutrients like boron, copper, and zinc, so it is important to understand what they are. You can consider a 20-20-20 fertilizer to be a more concentrated version of a 10-10-10 fertilizer, because it contains double the amounts of each main component. However, remember that there will be other components to consider in any product, so you can’t always just use half a treatment of a 20-20-20 bag and get the same nutrients as a 10-10-10 bag.

The Plant Will Tell You What It Needs

I know plants can’t talk, but they can definitely give you signals. If you monitor your plants closely, you will pretty quickly be able to spot if/when they are low on nutrients. If you aren’t sure what signals to watch out for, the good news is that there are plenty of great guides online that have pictures of plants with a range of deficiencies. I have a chart I found online printed out and pasted near my lab bench to remind me, and this has come in useful many times. Once I observe a symptom of a low nutrient, it is easy for me to then apply the correct fertilizer to correct the problem. The key is spotting the symptoms of nutrient deficiency so that you can take action quickly.

It’s easy to be caught off guard by the sheer number of fertilizers available. Luckily, the large choice out there means that there is probably one for almost any application. Once you have taken the time to research what your favorite plant needs, you will have all the knowledge you need to find the right fertilizer!

Image Credit: SuSanA Secretariat

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