I had a question from a new gardener; she wanted to know if I use fertilizer on my plants. The short answer is yes. The larger answer is, sometimes and in some places. The super-large answer is, mostly we shouldn’t need to use fertilizer. And the ecological answer is, using fertilizer is a tricky business, both in the way they are made and the way they interact with our environment, so less is better.
Let’s start with the easy stuff first: Yes, I do fertilize. Plants in pots must be fertilized, because they can’t form connections with a larger soil community. About once a month, I use a liquid, organic fish emulsion on my potted flowers, fruits, herbs, and vegetables. The product I use is Neptune’s Harvest. It has an NPK of 2-4-1. This is a good, low ratio; the amount of Nitrogen won’t hurt the plant, and it has slightly more Phosphorus which is good for developing roots and fruits (or blooms). The thing you want to look for on the package is, how much of the Nitrogen is soluble? Soluble/insoluble is an important thing to know. If it’s soluble, it’s available to the plant right away; it will enter the soil solution and be taken up by the roots. Whatever is not used immediately will not be stored, it will run out with your water. Generally organic products have a low NPK ratio, most of the nutrients are insoluble, and they take some time to work, as the biology in the soil has to incorporate them into their bodies, then poop them out, before they are available to the plants. In soil biology, this is known as the poop-loop. This is an important cycle and is the best way to feed plants. It’s like micro-manure.
I also fertilize the rest of my garden, but maybe not in the way you’d think. I add organic matter regularly. Good quality compost, two inches on each planting bed, is added every fall. Compost is added to the pollinator gardens when I add seeds. And every time I put a new ornamental plant in the ground, I mulch with compost. This way, organic matter is constantly being returned to the soil, and that is the very best way to fertilize your plants. The roots form connections to everything around via fungi, and there is a constant exchange of nutrients going on. We also add wood chips every year or so to all the paths and around large plants and trees. These break down over time and add nutrients, as well as providing habitat for soil creatures. We also incorporate cover crops, which add different nutrients and soil-aggregating qualities. Having a living root inside the ground at all times is the best way to ensure your soil has plenty of food - the microbiology lives on and near roots; the plant pumps out food for the biology, and the biology in turn feeds the plants. So yes, in these ways we also fertilize.
And, when I plant summer crops in the raised beds, I add a granular organic vegetable fertilizer such as Jobe’s Vegetable Fertilizer which is 2-5-3. This breaks down slowly over the course of the season. I do this for summer crops because they are heavy feeders (meaning they need a lot of nutrition to produce big fruit, like tomatoes, peppers, or melons) and I am planting them very closely spaced.
Another thing to consider is your soil type. I tend to have clay soil, which has the ability to hang on to nutrients (this has to do with its chemical composition, cation exchange of electrons, and the minerals that make up clay, factors too large to get in to here). If you have a sandy soil, you’ll have less nutrients available. If you have ‘fill,’ then you have very little soil life, and you’ll need to feed it in order for it to thrive. The best way to do this is through the addition of organic matter.
All fertilizers have an ecological cost. Rock phosphorus is mined in a horrible system that wreaks havoc on the earth. Peat moss is an element that takes hundreds of thousands of years to form, and we are stripping it far faster than it can be replenished. Synthetic nitrogen is applied at enormous amounts in conventional agriculture because soils are depleted; much of it runs off and has caused all kinds of problems downstream. lt’s easy to add cover crops that have the ability to form associations with bacteria that fix nitrogen - the pea family does this of course. The thing is, you have to cut down the cover crop before the fruit is produced - and don’t pull up the roots, let them rot in the ground. Some large-scale farmers have found ways to supply 90% of their nutrient needs with cover crops alone.
I’d like to refer you, once again, to a great movie called Symphony of the Soil. In it, several scientists and farmers explain how soil is formed and how we can hold on to it, and farm with best practices to retain nutrients. I’d also like to suggest the book Growing a Revolution by David Montgomery. You can also find his lectures online. He and Elaine Ingham are my soil mentors.
I loved getting this question from this new gardener, and I love getting questions and comments generally. I know that leaving a comment here on the blog has been difficult. A while ago, we disabled anonymous comments because we were getting some advertisements for porn (!), but we’ve enabled them again in the hopes that perhaps we will get a community going in the comments section (well, a community that doesn’t involve porn, at least). If you are unable to ask a question here, please feel free to email me using the contact page - I love getting your questions.
It’s heating up here - summer might finally be on the way!