You’re standing in the fertilizer isle of your favorite gardening store, and you have a decision to make. Your tomato plants are looking a little worse for wear, and could use a pick-me-up. So, my friend, which fertilizer are you going to buy?
Just as you’re about to answer, you feel your phone vibrating in your pocket: 📳. It’s a text from your daughter. Her practice is done, and she needs you to pick her up. Now the clock is ticking. Once again, how do you know which fertilizer to buy?
There are three letter-number pairs each and every gardener instinctively looks for when considering which fertilizer to buy. You don’t have to be a gardener for very long to know which letters I’m referring to: it’s NPK.
NPK stands for nitrogen, phosphorus, and potassium. Any fertilizer you see represents NPK as a ratio of the percentage by weight for each element. Want more leafy growth, go for the higher N. Want to strengthen those roots? A fertilizer with some extra P will do the trick. Did you just find out your soil needs more potassium? Get a fertilizer with more K.
Simple enough. But where did all this come from?
Last night I was reading about plant cell biology 🤓 when I came across a name I had not seen before: Justus Von Liebig - pronounced “Eustus.”
Justus was a clever guy, often cited as the “Father of Agriculture” or the “Father of Organic Chemistry.” In 1863, after extensive field tests, he popularized an idea called the “Law of the Minimum.” This idea boils down to the notion that if one single nutrient doesn’t reach the minimum amount required by the plant, the plant will not survive.
As part of this new insight, Justus also identified nitrogen, phosphorus, and potassium as the three most important nutrients for plants. The prevailing theory at the time was that plants needed nutrients in an organic form. The critical question for Justus, though, was to see if there was a way to provide nutrients chemically.
Surprise, surprise - you can, and the implications of Justus’ discovery were massive.
In the 19th century, landowners used the urine and manure from their livestock to fertilize their crops. Now that artificial nutrients were on the market, landowners could just buy the nutrients instead. Initial results were quite impressive; you’d often get the same or better yields than if you used “organics.” Plus you didn’t have to tend to your livestock anymore.
Where is the irony in all of this? 🧐
Like many of you, Justus had a vegetable garden at home. Probably unlike you, he fertilized his garden using the pee and poop he collected from his livestock until, that is, he discovered the chemical theory of agriculture. That’s when he switched to using artificial fertilizers in his garden, and it didn’t take long for him to notice some concerning changes in his soil.
Specifically, Justus’ soil had no more life in it! 😔
This caused him to have great misgivings about the industry he helped create. But Justus’ misgivings weren’t just from his own anecdotal experience. He had profound respect for the amount of importance Asian cultures placed on what today we’d call composting. In fact, he highlighted the Chinese in particular as “the most admirable gardeners and trainers of plants.”
All this is to say, soil is complicated.
Our plants are part of a complex ecosystem in the soil, and as convenient as it is, we can’t just reduce their needs down to three individual numbers. When we neglect the microbial life in the soil, when we neglect the need for adding carbon to the soil, we’re missing out on the bigger picture just as much as we’re missing out on better tasting and healthier food from our garden.
Your time is valuable. Thank you so much for reading! What would you like to know more about?