Winter cover crops for gardens

If not planting a fall garden, you may want to consider a winter cover crop. A cover crop is specifically planted to: protect the soil from erosion, suppress weeds, maintain soil moisture, increase organic matter in the soil or recycle soil nutrients. Cover crops are not harvested, but rather contribute to soil improvement in the place where they are grown. Most gardens benefit from the use of these when not planted, instead of leaving the garden unplanted. Cover cropping is a valuable component within a crop rotation plan for pest and disease management.

Cover crops are divided into two primary groups: legumes and non-legumes.

Legumes have the ability to “fix” atmospheric nitrogen gas into “soil nitrogen,” which is available to plants. It is advised to inoculate legume seeds at the time of planting with beneficial species-specific bacteria (rhizobacteria) for nitrogen fixation to occur. Rhizobacterium maximize the amount of nitrogen fixed in legume root nodules. Nitrogen fixation will be low without the presence of the rhizobacterium. The fixed nitrogen will be available in the soil after the legume is terminated and starts to decompose. This allows the garden to rely less on added synthetic fertilizer. Cover crops will not supply all of the nitrogen needed for the following year, but over time will improve soil structure and nutrient levels for long-term sustainable growth.

Nonlegumes are planted primarily to provide biomass, i.e. carbon-based plant material that includes stems, roots and leaves. This biomass improves the structure and water holding capacity of the soil while feeding beneficial soil microbes. Nonlegumes consist mostly of grain crops such as oats and rye, but several brassica crops like mustard and daikon radish are valued non-leguminous cover crops.

Before sowing, turn over the garden with a rotary tiller. Clear the area of weeds and any remaining refuse from the vegetables or flowers that were not previously removed from the site. Level the soil with a garden rake. Sow seed by hand for small areas, broadcasting as evenly as possible. Broadcast back and forth over the area several times in an attempt to distribute the seed evenly. Lightly cover seeds by raking to ensure good seed to soil contact. Larger areas may require seeding equipment. Irrigation may be necessary to ensure a good stand.

For maximum benefit, a cover crop should be terminated while in the flowering stage. At this point, the crop will return the greatest amount of biomass and nutrients to the soil. If cover crops are not terminated before seed formation, then their seeds may become weeds in a later crop. Once killed, the crop can either be left on the soil surface to decompose as a mulch, or tilled into the soil where it will decompose below the soil surface.

If the no-till option is used, the crop will need to be mowed or crimped down prior to planting of the vegetable crop. Cover crops that are tilled into the soil will usually need to be mowed or otherwise chopped prior to tilling. Time the cover crop seeding so that the crop is terminated and tilled under about three weeks to a month prior to planting the vegetable crop. This will provide adequate time for the crop residue to break down before planting the vegetable crop.

Soil microbes convert the decomposing cover crop into organic matter for addition to the soil profile. Regular use of cover crops over a period of years will slowly raise the organic matter level in the soil and increase the activity of soil organisms, such as earthworms and fungi, in the soil. As these organisms decompose the organic materials, help improve soil structure and tilth, making the soil a more favorable place for root development. It is important to understand that organic matter is continually decomposing and cannot be built up permanently in the soil.

For more information, call Allen Bates, county extension agent - agriculture, at 623-6841 or email abates@uaex.edu.

Master Gardener

Master Gardener meetings are held on the third Thursday of each month at Lake Valley Community Church, 910 Shady Grove Road. They’re open to the public. For information, call the Extension Office or email Allen Bates.

4-H

There are 4-H clubs for Garland County youths 5 to 19 years old. For information, call Linda Bates at the Extension Office or email lbates@uaex.edu. EHC

Interested in joining an existing Extension Homemakers Club? For information, call Jessica Vincent at 623-684 or email jvincent@uaex.edu.