I hear you out there – those of you not living in the South, “Boohoo, big problem I have to grow my garden all year long!”
I know. It is hard to be us! But if you stop and think about it, vegetables, herbs, and fruits all take nutrients from the soil as they grow. Each year you need to replace those nutrients to insure a healthy harvest. It all begins and ends with the soil. The healthier the soil, the better your vegetables will grow and the fewer problems you'll have. But if you are constantly growing those nutrient devouring plants when do you work on building the soil?
Northern gardeners can use the fall to easily prep the soil for the Spring. Adding your organic matter, humus and manures to the soil in the fall gives it an entire winter and spring to become biologically active. The remnants of this year's crop will have plenty of time to break down. But again, in the South, we are still growing those hungry veggies in the fall so what do we do?
A. Well, Matt, your question has sparked the entire post of Garden Tech Tuesday this week! The bottom line simple answer is to use finished compost in you beds. Ideally, finished compost is dark brown or black (almost like bagged potting soil), crumbly-textured, and has a rich earthy smell. But realistically, there is no exact point at which compost is "finished."
Many gardeners choose to use compost that is not fully decomposed. They don't mind if there are still recognizable bits of leaves, minute twigs, straw, hay, and the like. They know it will finish decaying in the soil in their yard or garden. Generally, try to harvest your compost in the late summer or fall to make room for new leaves in your bin(s).
If you intend to use your compost in seed-starting mixes, houseplants, or to cover seed rows, it's best that it is well-rotted and possibly screened. Otherwise delicate roots can be attacked by microbes if the roots touch any unfinished compost.
Yep, right off the bat I am going to recommend compost again (are we seeing a pattern here?). Whether you are using your own homemade compost, or are purchasing compost in bags or by the truckload, stock up early with as much as you can afford. I’d recommend a couple yards of compost each fall for most gardens. You can stockpile it on a big waterproof tarp, which will allow you to keep things neat and keep the compost covered so it doesn't get soggy.
As you remove spent crops from the vegetable garden, use a garden fork to loosen the soil, and mix in a 3" to 4" layer of compost. While soil temperatures are still warm, the nutrients and organic matter in the compost will stimulate microbes and other beneficial organisms. Tired, end-of-season soil will be refreshed and renewed when spring comes around.
Flower gardens also need compost. As you begin cutting back and cleaning up your perennial beds, keep a good supply of compost at hand. Dig in some compost wherever you've pulled out annuals and whenever you're planting bulbs. Pile on a good 2" to 3" layer around the base of established perennials and shrubs (keeping it back an inch or so from the stems).
Planting new shrubs, trees or other landscape plants? Opinions vary, but I always mix a few shovels of compost with the soil that goes back into the planting hole.
The soil in the unused beds of your vegetable garden will probably be laying fallow over the winter months (although I would suggest growing a cover crop of some sort). To boost the amount of organic matter in your soil— beyond what you can get from finished compost— consider incorporating raw organic matter directly into the soil.
There's just one thing to keep in mind when you're adding raw organic matter to your soil. The beneficial soil organisms that will help decompose this material, require nitrogen to do their work. This means that if you don't add some additional nitrogen along with the organic matter, the microbes will start using up the nitrogen in your soil. To avoid this, you can either add some nitrogen-rich manure along with the raw organic matter, or sprinkle on some granular organic fertilizer.
Shredded leaves are my top choice for raw organic matter. Use a leaf shredder if you have one. If not, just mow over the leaves several times with your lawnmower. Animal manures (but not from dogs or cats) are great for the soil. You can gather it in buckets, plastic trash bags, feed bags, or in the back of a pickup truck.
A good thing about adding animal manures in the fall, is that it doesn't really matter if the manure is fresh or aged. Over the winter months, the caustic ammonia will dissipate, leaving behind valuable nutrients and organic matter.
Most organic fertilizers release their nutrients slowly over many months, so applying them in the fall helps ensure they'll be available to your plants next spring. If you can get your hands on some kelp meal, greensand, rock phosphate, or bone meal, do so. Because it's the end of the season, your local garden center may even have some broken bags they'll be willing to sell you at a discount. You can mix these organic materials right into your garden (or side dress around plants), along with the shredded leaves, manure and compost. Breaking down organic material requires some nitrogen. To facilitate the process, you can add 100% alfalfa pellets that are marketed as rabbit food! Just sprinkle in a cup or so mix in the rest of the amendments.
If you suspect that your soil pH may need adjusting, autumn is the time to correct it. It's best to raise or lower soil pH slowly, over a three- to six-month period. Add lime in the fall to raise the pH level of your soil. Add acidifiers like pine needles, peat moss and elemental sulfur if your soil is too alkaline. Remember that unless you already know that your soil is too acidic or too alkaline, you should always do a soil test to determine the pH level before taking corrective measures. Contact your local Extension Office for help with soil samples.
I believe very strongly that keeping roots in the soil is an important part of any gardening program. My great grand mother told once told me, “God don’t seem to like bare ground too much, if you don’t grow something there He sure will!” In my experience that statement is true and I would add that what He grows there may not be what you were wanting there!
Cover crops are an excellent solution to managing nitrogen in the soil. Nitrogen is a major component of chlorophyll, which plants need to perform photosynthesis in order to grow. Nitrogen is a difficult nutrient to manage in agricultural systems because plants can only use it when it is available in a specific chemical form (NOT the form prevalent in the atmosphere) and it easily leaches out of the soil during heavy rainfalls if it isn’t fixed inside the tissue of a plant.
Legumes (a family of plants that often have pods—beans, peas, etc.) can trap significant amounts of nitrogen that can later be used by other crops. A type of bacteria that lives in the plants’ roots converts atmospheric nitrogen into a form that the legume can use for its own growth. When leguminous cover crops begin to decompose, soil microorganisms convert the nitrogen in their tissue is into a form (nitrate) that subsequent plants can use.
Non-leguminous cover crops (typically grasses), can also help to keep nitrogen available by taking in nitrogen already present in the soil that would otherwise be lost to leaching. The nitrogen is assimilated into the plant tissue and when the cover crop begins to decompose, it is released back into the soil for subsequent crops to use.
Just remember that the soil is the foundation on which we build our gardens and improving that soil makes a huge difference in its ability to retain water, support healthy plant growth, and help your plants fend off diseases, pests and other stresses. Whether you're new to gardening, or a seasoned pro, building better soil is the single most important thing you can do to improve your gardening success. And fall is the best time to do it!