Q: What does it mean to “work your soil”? - David, Kerhonkson

A: “A nation that destroys its soil destroys itself.” – Franklin D. Roosevelt

Optimally, soil is 45 percent mineral (sand, silt, and clay), 25 percent air, 25percent water, and 5 percent organic matter. The organic matter, which gives soil so much of its bulk, contains dead and dying leaves and other plant material, plus thousands of species of microbes and roots. Keeping that balance is the “work.”

The uppermost layer of topsoil, which is the first to be eroded, is where we find most of the soil microbes essential to decomposition, nutrient cycling, and healthy crops, and the highest concentration of plant nutrients. Bacteria, fungi, and other microbes living in healthy soil form a natural defense from pests and disease. Infertile, mismanaged soil has fewer microbes, putting plants at risk.

One of the best methods for growing and keeping healthy soil is to disturb it as little as possible by limiting tillage and keeping stubble on the ground. After several years, no-till fields, fields that are not plowed, will hold soil and water longer than tilled soil. That 5 percent organic matter acts like a sponge, with each 1 percent increase in soil biomass retaining about 13,500 gallons of water per acre that can be used by crops during dry periods or heavy storms. With no-till, roots, earthworms, and other soil inhabitants can create tunnels that become tiny reservoirs for water and air.

There are two basic ideas regarding organic matter. First, you can’t add too much. Second, you should mix it into existing soil. Every type of soil benefits from organic matter. It helps sandy soil retain water and nutrients better, and it helps clay soil to loosen and let water percolate through. Organic matter feeds the soil food web. It consists of three distinctly different parts — living organisms, fresh residues, and well-decomposed residues. These three parts of soil organic matter have been described as the living, the dead, and the very dead. This three-way classification may seem simple and unscientific, but it is very useful.

The “living” part of soil organic matter includes a wide variety of microorganisms, such as bacteria, viruses, fungi, protozoa, and algae. It even includes plant roots and the insects, earthworms, and larger animals, such as moles, woodchucks, and rabbits that spend some of their time in the soil.

The “dead” organic matter, consists of recently deceased microorganisms, insects, earthworms, old plant roots, crop residues, and recently added manures.

The well-decomposed organic material in soil is the “very dead,” and is called humus. Humus has a lot to do with the ability of a soil to retain nutrients and water. Humus also supplies organic chemicals to the soil solution that can serve as bonding agents, which can hang onto trace elements, (metals) and increase their availability to plants.

So “working your soil” is, in some ways, letting the soil work for itself with some educated help from the gardener.

Q: Can I use grass clippings to help the soil? - Allyson, Stone Ridge

A: Yes! Grass clippings can perform a myriad of jobs in the soil, adding nutrients and keeping your yard waste bin empty and out of the landfills. Mulching with grass clippings, either on the lawn or in the garden bed, is a time-honored method which enhances soil, prevents some weeds and preserves moisture.

One way to use the clippings that result from mowing is to let them fall on the sod and compost. Clippings that are less than 1 inch slip down to the root zone of the grass and break down quite quickly into the soil. Longer clippings can be bagged or raked up and mulched elsewhere, as these stay on the surface of the soil and take longer to compost.

Grass clippings contain 4 percent nitrogen, 1 percent phosphorus and 2 percent potassium. Decomposed grass clippings also serve as a food source for bacteria in soil. If you’ve not applied any chemical weedkiller recently on grasses, you can use dried grass clippings for mulching in the garden. Spread a layer 2-3 cm thick near the base of plants.

Grass clipping mulch also limits evaporation and conserves water. If you’re using fresh clippings as mulch, only lay a quarter-inch thick layer. This will allow the grass to break down quickly before it begins to smell or rot. Thicker layers made of fresh grass clippings have a tendency to remain too wet and can invite mold and create smelly decay issues.

Dona M. Crawford is the  Master Gardener coordinator for Cornell Cooperative Extension Ulster County.