A young man’s fancy may turn to thoughts of love in the spring, as the old saying goes, but at this time of the year a gardener’s fancy better be turning to soil building. No soil is perfect. Your garden works hard through the spring and summer, supplying you with all those delectable snow peas, radishes, salads, green beans and tomatoes, and needs to be rejuvenated. Even if you plant a late-year garden to harvest through the winter, fall is a good time to be thinking about giving back to your garden. Your soil needs a nice blanket of winter organic matter, just like you need a warm coat. On bare soils, rain compacts the soil particles, pushing out oxygen and making the soil less able to absorb water. Nitrogen leaches from exposed soils and exposed soils are also more subject to erosion.
Ideally soil building should go on all year. Whenever you harvest a crop, you should apply compost or start a cover crop. In practice, fall is often a good time to obtain soil-building materials like leaves, and the cooler temperatures don’t burn up organic material the way a blistering summer will. You may also have a little more time to concentrate on this aspect of gardening, once the press of late summer harvest and preserving are over.
If you’re cleaning out the chicken house (I usually do it in spring and fall), you can spread that material on your garden beds and let it mellow over the winter. Yes, you’ll lose a bit of nitrogen, but if you think about it, that’s how nature builds soil: leaves drop, grasses are beaten down by snow or rain and both decompose throughout the winter. I’m a big fan of letting nature do the work and of mimicking natural processes whenever possible. I figure Ma Nature knows what she’s doing, and far be it from me to mess up her system.
Nature doesn’t till or double dig, and my back’s not getting any younger, so I try to avoid this thankless labor as well. If I don’t have something planted in a bed, I like to layer on compost materials like leaves, sheep and chicken bedding, horse manure, spoiled hay or straw. I water the bed first, especially if the weather is dry. Soil needs oxygen though, especially for the decomposition process, so you want the soil moist but not waterlogged. I pitch on whatever I have available and let it decompose through the winter.
I also sprinkle on kelp and mineral supplements like Azomite, and — because I’ve been bitten in the past by straw that was supposed to be herbicide free and wasn’t — finely ground activated charcoal to neutralize any herbicide that may have snuck past my guard. If you get your materials from a local landfill, this may be a good idea for you as well, since you never know what people have been spraying on their lawn grass and plants. Come spring, I can just pull the mulch aside and plant transplants. If I’m direct seeding, I make rows in the decomposed mulch or — for fine seeds like carrots — gently rake off the bits that haven’t decomposed and put them in the official compost pile. This is another reason for the charcoal; many herbicides are pre-emergent and will prevent seeds from germinating.
In a bigger garden, cover crops are generally a better way to go. You can plant some — like buckwheat or sorghum — in the summer. Others, like clover, oats, vetch, rye and winter radishes, are best planted in fall and winter. They’ll grow slowly through the cold months and can be turned under about two weeks before you’re ready to plant the next crops. Of course, if you have an abundant source of manure or leaves, those can also be spread on a large garden.
The whole point of feeding the soil is to feed the soil microbes and fungi, which normally eat the carbohydrates excreted through a plant’s roots into the soil. That’s one reason why it’s better to harvest a crop by cutting it off at ground level rather than pulling up the plant; you’re not disrupting the microbes. In the wild, those plants would remain right where they are (if not eaten by a critter) and decompose back into the soil. Ma Nature never leaves soil bare over the winter if she can avoid it and neither should you.