When you stroll on the lawn and in the garden, you are walking on an interconnected web of life. The top several inches of soil is teeming with all manner of life, from worms to centipedes, from ants to slugs, from bacteria to fungi. There is a lot going on down there.
The topic of soil is incredibly broad; this column will only scratch the surface (so to speak). So, here’s a brief Soil 101.
Gardeners understand plants need to be fed. We sometimes know less about the nutrients involved or how they get to the plants.
Plant growth depends on 17 essential elements, of which 14 come from soil. Nitrogen, phosphorus and potassium are primary macronutrients and very important to plant growth. Calcium, magnesium and sulfur are secondary macronutrients (found in our Eastern Nebraska soil but less likely in sandy or other soil low in organic matter). Micronutrients – required in lesser amounts – include iron, manganese, zinc, copper, boron, chlorine, molybdenum and nickel.
As fruit, seeds and leaves fall and other plant debris decompose and are released into the soil, they become nutrients. This efficient soil food system works well until humans intervene. When we harvest lovely flowers and tasty vegetables, future soil nutrients leave instead of decomposing.
Those nutrients need to be replaced, typically through fertilization.
Fertilization requirements differ depending on plants grown and type of soil. Soil testing will indicate the amount and availability of nutrients already in the soil. For truly accurate fertilizing, soil should be tested.
Chemical fertilizers have three numbers somewhere on the package representing a percentage by weight of Nitrogen (N), Phosphorus (P) and Potassium (K). Some fertilizer packaging makes it difficult to find those numbers, instead displaying a picture. The picture may be of a tomato or a houseplant or a perennial. Their intent is for you to purchase a package with the picture of what you want to fertilize. That could be misleading. Again, soil testing is important. Using too little chemical fertilizer ends up with minimal benefit to plants; too much can reduce plant quality and be damaging to the environment.
Overuse of chemical fertilizers can injure the microbial life that sustains healthy plants.
My annual container pots are fertilized because I use a soilless potting mix. We do not use chemical fertilizer on our perennial beds, trees or fruits.
Choosing to feed soil as nature does involves use of organic matter. Yes, that can include manure. Alternatives for the squeamish include compost and grass mulch, excellent organic fertilizers.
Believe it or not, growing lots of plants is a way to feed the soil. Areas of bare soil or just mulch are not healthy. Having turfgrass helps. Even growing weeds can improve soil health!
Instead of treating soil like dirt, understand more about it and help your plants thrive.