Put Your Garden Soil to Bed for the Winter
Almost all garden soils can be improved by adding organic matter to make soil more workable. Organic matter loosens tight clay, helps sand hold more water, makes soil easier to dig and adds nutrients.
Green manures, cover crops that are tilled into the soil while still green and living, are a great way to protect your garden from weeds and soil erosion over the winter if you have empty space in your garden that won’t be planted during this time. As well as protecting your soil, cover crops can be dug into the earth before spring, improving the soil ecosystem and feeding your plants with essential nutrients. Winter annual cover crops can be either legumes or cereals. The legumes best adapted to our soil and climatic conditions are crimson clover, hairy vetch, Austrian winter pea, and Cahaba white vetch. Cereals or small grains that are best for our area are rye, wheat, barley, triticale, and oats. Do not add more than a 4-inch layer of organic material.
Which cover crops are right for recharging your garden soil? It depends. The legume type plants like those of the pea and clover family deliver the nitrogen that they capture from the air back into the soil. In collaboration with certain bacteria that live in the soil, that process makes the nutrient available to the next crop of plants. Legumes are a great choice for sowing before nitrogen-hungry plants such as cabbages, collards and other leafy greens. You’ll want to plant legumes by mid-October to get a nice stand to till into the ground in early spring when they’ll just be starting to flower.
Cereal rye has deep, fibrous roots that help to improve the structure of heavy soils by breaking it up. You can plant these through mid-November. They also do a good job of weed suppression when mown down and left on top of the soil rather than tilled in. Erosion caused by wind and water are much greater on bare ground than on a surface protected by a cover crop.
Mustard is quick-growing and produces foliage that can be dug into the soil before winter to help improve its structure. Certain varieties can also reduce soil diseases when tilled in at the right time and help against root knot nematodes that are a problem for our tomatoes, cukes and cantaloupes, among other veggies.
Right about now is the time to get started. Roughly dig your garden spot over, removing all weeds, especially the perennial ones. Then once you’ve smoothed over the soil again, broadcast your cover crop seeds evenly across the soil surface, rake them in for good connection to the soil, and then water gently.
In the spring consider leaving a few cover crop plants to flower to feed early beneficial insects, but dig most of your crop into the soil before it begins to flower. At this stage the stems are still soft and will be easier to cut up and dig in, and quicker to rot down. Dig in cover crops at least a month before sowing or planting spring crops.
Remember that the soil is “a pantry” for elements plants need to grow: nutrients, organic matter, air, and water. Soil also provides structural support for plant roots. When properly prepared and cared for, soil can be improved each year and will continue to grow strong, robust plants. Most heavy clay soils can also benefit from the addition of gypsum. It adds some nutrients but, more importantly, it loosens clay soils and makes it more workable. Spread about 3 to 4 pounds of gypsum per 100 square feet over garden soil after it has been dug in the winter. Work it into the soil or allow it to be washed in by rain. If you’re not already doing it, get in the habit of getting your soil tested periodically. If your garden is made up of sandy soils, it is best to test the soil every two to three years as that soil type does not hold nutrients as long as other types. The nutrient levels in silt and clay loam soils change less rapidly with lime and fertilizer applications. In these soils, testing once every four years is usually adequate.
For more information about cover crop types, varieties, planting times and management techniques, take a look at:
Minda Daughtry is Horticulture Agent for North Carolina Cooperative Extension in Lee County.