Living Soil and Planning Your No-Till Garden
by Melissa, NEW Master Gardener
“Compost is partially decomposed organic matter. It is dark and easily crumbled and has an earthy aroma. It is created by biological processes in which soil-inhabiting organisms break down plant tissue. When decomposition is complete, compost has turned to a dark-brown powdery material called humus. The processes occurring in a compost pile are similar to those that break down organic matter in soil. However, decomposition occurs much more rapidly in the compost pile because the environment can be made ideal for the microbes to do their work.
Once compost is added to the garden, it serves many purposes. Jesse Frost breaks it down into 4 different types, based on the purposes it serves. Inoculating composts are finely textured composts that are very biologically active. These are useful in increasing the number of beneficial microbes in your soil, and even introducing new ones. Vermicompost (worm poop) can be used as an inoculating compost. These composts are typically applied as a tea, a thin layer on the soil or a foliar spray.
Fertilizing compost is a finely textured compost that is high in inorganic nitrogen content. Composted chicken manure is the most commonly available, although manure from rabbits, bats or other small animals may be available for purchase as well. Fresh manure should be allowed to break down for several months before it is used in the garden. It has so much nitrogen that it can “burn” plants or even kill them. If it is not taken up by the plants it can be washed into our water systems, which can cause eutrophication. Read this article to learn more about the nitrogen cycle and eutrophication. What is the Nitrogen cycle and Why is it Key to Life. Fertilizing compost should be used by lightly incorporating a small amount into the top inch of the soil, or by applying on top of the soil and covering with mulch.
Nutritional composts are very balanced composts, providing organic matter, microbiology, nutrients and minerals all at once. This is achieved by incorporating plenty of carbonaceous materials into your compost. “The usual recommended range for Carbon/Nitrogen (C/N) ratios at the start of the composting process is about 30/1... As carbon gets converted to CO2 the C/N ratio decreases during the composting process, with the ratio of finished compost typically close to 10/1.” Cornell Compost Because it is not so nitrogen heavy, several inches can be applied to your gardens to feed your plants over time, and the risk of nitrogen runoff is decreased. Most compost that you purchase or create yourself will fall into this category.
Side note: It seems a lot easier for me as a home gardener to accumulate greens (nitrogen) than browns (carbon). Garden waste, grass trimmings and kitchen scraps are all greens and I have a constant supply. Browns are leaves (I get for one month a year), straw (have to buy), paper and sawdust (have to buy). In order to have enough browns during the summer, I have started saving all my junk mail (non glossy paper only) and shredding it. I currently have 5 grocery bags of shredded paper saved up for building compost piles this season. In order to start out with a ratio of ⅔ browns for every green, I will probably need even more!
The last type of compost is a mulching compost. This type of compost is higher in carbon as compared to other composts. A mulching compost will have a C/N ratio of at least 20/1 at the time it is applied. Often, this is compost that has not completely broken down and will have larger pieces of organic matter, such as wood chips. Leaf mold and partially composted hay/straw are also common mulching composts. Mulching compost can be applied 4-8 inches thick, and be used as you would typically use mulch around plants. It is important, however, not to confuse mulching compost with mulch. Fresh mulch such as woodchips can cause “nitrogen lock up” because the soil organisms are using all the available nitrogen to consume the carbon in the woodchips, thus depriving the plants growing there of nitrogen. This is why you want to use partially decomposed.
One of the common no-till garden systems is a Deep Compost Mulch System. The garden beds are topped with 4-8 inches of mulching compost (or 4 inches of nutritional compost topped with 2-4 inches of mulching compost) and the compost serves not only as the mulch, but also as the growing medium. You plant directly in your layer of compost. Every growing season you add enough compost to have a 4-8 inch layer on top of the bed. This tends to work better when using transplants instead of direct seeding, especially if the compost does have a lot of larger pieces. If you choose to direct seed, it is better to use a finely sifted nutritional compost topped with a 2 inch layer of mulching compost and plant into the nutritional compost layer.
If it seems like there is a lot to know about compost, it's because there is! But the basic thing to remember is that you are trying to feed the microbiome in your soil. Balance is best so when in doubt use a nutritional compost, and monitor how your soil and plants respond. Ultimately, the use of compost should replace all the nutrients in your soil that are used up with growing your plants. This represents a closed loop system, and is also known as sustainable agriculture.
