This year we all experienced some form of ‘coronacation’ that gave us more time at home. Did your involuntary home-bound hiatus lead you to the garden? Whether this was your maiden voyage in gardening or if you are seasoned sailor of the soil, next year can be even better.
The shortest garden guide that could ever be written would consist of two words: organic matter. This does not refer to the relatively new connotation the term organic has come to symbolize. I refer instead to the traditional definition in soil science. Organic matter is anything that comes from a living plant or animal. At the molecular level, its base building block is carbon. Leaves, grass clippings, manure, compost, straw, wood shavings; all are organic matter. The addition of which will leave your garden more productive for years to come. Is your soil sandy? Add organic matter. Do you have a clay soil? Add organic matter. Is it hard? Does it drain slowly? High pH (probably yes for us)? Tomatoes get blossom end rot? Add organic matter.
Many problems with home vegetable gardens, fruit trees, shrubs, and flower gardens are caused not by pests, diseases, or a lack of nutrients, but by poor soil physical conditions. A productive soil provides physical support, water, air, and nutrients to plants. In a good soil, between 40 and 60 percent of the soil volume is pores. The pores may be filled with water or air, making both available to plants. Clay soils are commonly deficient in pore space. Sandy soils are often nutrient-poor and lack water-holding capacity. Amending the soil with organic matter benefits both textures.
Carbon from organic matter is the base commodity in the soil ecosystem. Microbes that break down mineral soil (derived from inorganic rock) feed on it. As these microbes live and die, minerals and nutrients are released back into the soil and become available to plants. Other microbes, that also utilize carbon, form cooperative associations with roots. Plants provide energy to the microbes in exchange for nutrients that the plant needs. Your soil improves with every addition of organic matter. You are building up a reservoir of slow-release nutrients that increase your garden’s productivity over time.
While all organic matter is beneficial eventually, not all forms are equal. Sources like wood shavings and straw are nitrogen poor. Microbes will rob the soil of available nitrogen to break these down and plants may suffer in the short run. The addition of commercial nitrogen fertilizer can speed breakdown and limit short-term effects. Livestock and poultry manure (and compost derived from these) are often high in soluble salts. These can eventually break down or leach from the soil but too much at once may cause short term damage.
There isn’t an exact recipe, but by and large organic matter addition will benefit your garden soil. Fall is the best time for these additions. This gives soil microbes time to start their work and allows for salts and excess nutrients to be broken down or leach from the soil. Your garden next year will feed you better if you feed your garden soil now.
For more on this topic, see: https://catalog.extension.oregonstate.edu/sites/catalog/files/project/pdf/ec1561.pdf