Friday, March 19, 2010
Spring is here. The weather is warming up. It is time to dig the garden and get it ready for planting, right? Well, not necessarily. There is a school of thought out there, one that I increasingly adhere to, called no-dig gardening. The principle is basically this: soil is a living thing and, generally speaking, living things do their best if they are left alone. On the good side, turning the soil buries weed seeds and mixes fertilizer and organic matter deep into the soil. It also aerates the soil, providing more pores for better air flow to the roots and easier penetration of the roots through the soil. The only thing is that worms do most of that work themselves. They aerate the soil, they consume the organic matter on the surface of the soil, process and distribute it. As for the weed seeds, a good layer of mulch will suffocate most of them and judicious weeding (also called healthy exercise) will get the rest.
But there are many other processes at work in healthy soil. Plant roots push aside soil as they grow. When the plant dies, bacteria and fungus in the soil decompose the root, adding organic matter to the soil and leaving the space the root once occupied as pore space in the soil. Mycorrhizal fungus thrives in the soil, providing water and nutrients to the plants in exchange for sugars. The fungus will live from year to year, helping out this year’s new plant growth just as it did last year. It helps break down old roots as well as organic matter on the surface of the soil. Those nutrients, combined with the sugars it gets from the plants, make more organic, living material in the soil. Those in turn break down when they die. This is the cycle of life in nearly all healthy soil around the world. This is the environment plants evolved to grown and it helps them thrive. Healthy soil makes for healthy plants.
When you till the soil, you kill mycorrhizal fungus. You kill some worms by chopping them up and others by smothering them with soil. Overall, you disturb the web of life that has grown into your soil. Sure, it will recover, but that takes time. The new roots of your plants are coming soon and they do best if they have a thriving ecosystem to connect with.
So is there ever a time to till your garden? Certainly. Observe your soil. If you are creating a new garden bed, it might be a good time to till. Tilling does a very good job of doing what it was originally intended for. It loosens compacted soil and it buries the weed seeds too deep to sprout viably. But when you do till, do what you can to restore the life to the soil. Compost is very important in this process. Mycorrhizal fungus is also important, though, and tilling kills it completely. So you will want to add it back in. Just evaluate your soil again next year, and if you don’t have to till, don’t.