Q. Why is the nursery recommending a winter rye or barley for a winter cover crop in my vegetable garden?

A. Many of us have limited space for vegetable gardens, which means that soil is pretty depleted each season by the time we pick our last tomato. Cover crops add organic matter that feeds the soil nutrients, which it needs to enrich vegetables the next time you plant them.

Cover crops are grasses, legumes or other plants grown to prevent soil erosion and compaction, enhance soil nutrients, reduce weeds and enhance water retention. These benefits will improve your vegetable garden by improving soil health, thus reducing diseases and increasing yields. Healthy soil means healthy vegetable plants!

Cover crops and green manures are used mostly by farmers to help them manage their fields for optimal crop production and weed suppression. Home gardeners can also do this, though you will have to scale down the amount of seed needed to your garden plot size, and choose the best crops for the home or community garden.

An important thing to think about is the biomass of the plants you will be planting, because you will have to cut them down to terminate their growth and incorporate them into the soil to gain their benefits. You need to mow them just before they set seed so they don't use up the nutrients you want from them.

You can start with a small section of your garden to see how well you can manage the biomass of the plants you select. Your local or online nurseries may have varieties that have been proven to work well in home gardens.

Fall is a perfect time to plant cover crops so your soil is healthy in the spring. You want plants that will grow quickly for the season you are planting. Cool season (generally mid-September to the end of the growing season) and warm season (June through mid-August) plants allow you to rotate your cover crops to build soil up between vegetable plantings. Remember to till them under three to six weeks before planting vegetables; do not plant your vegetable garden seeds or transplants into freshly incorporated cover crop.

Some examples of cover crop grasses are winter rye, barley and oats. Legumes that are used are clovers, peas and beans. Grasses help loosen soil compaction and scavenge unused nitrogen in the soil while legumes fix nitrogen from the atmosphere. As these plants decompose, that nitrogen goes into your soil. You can use both a grass and a legume simultaneously to get the benefits of both.

-- Nancy E. Degnan

• Provided by Master Gardeners through the Master Gardener Answer Desk, Friendship Park Conservatory, Des Plaines. For more information, visit web.extension.illinois.edu/mg or call the Master Gardener Answer Desk at (847) 298-3502 on Wednesdays.