Mulching

Mulching is a layer of material, organic or inorganic, spread on the ground near plants or in the aisles.  It protects the soil from the effects of the wind, rain, and hot sun.  It is known to keep the soil moist, uniform in temperature and easy to work.  It also keeps the rain from splashing mud on plants, the ground moisture from evaporating and weeds from growing.

Material Used

Any number of materials is used for mulch, grass clippings, paper, straw, sawdust, or polyethylene black plastic film.  The preferred material is organic because they can be incorporated in the soil after the growing season, thus adding valuable nutrients.

Grass clippings are one of the best and most commonly used mulches.  When they decompose they leave nitrogen in the soil.  Clippings must be left to dry for a day or two by spreading them in the sun before they are used.  If they are fresh and moist they will mat and rot, becoming slimy and foul smelling.

Newspaper is great when used under other mulches. Never use newspaper by itself because it acts as a wick and pulls moisture from the soil.  Four sheets of newspaper (black print only: colour has toxins in it) on the area you want to mulch and then spread grass clippings or straw on top, covering the paper completely.  When paper is used, only two or three inches of another material are placed on top.  Newspaper used with a mulch is also good because the paper will block weeds from coming up through the mulch.  Any seeds in the mulch material will not go down into the soil to sprout.

Straw is a good mulch, but weed seed may come with it.  This is why paper under the straw will save a lot of headache.  Avoid hay as mulch this usually brings weed problems.

Sawdust is excellent but must be partially decomposed before applying. Otherwise it will deplete the soil of nutrients as it breaks down.  If fresh sawdust is used, apply extra nitrogen to the soil under the sawdust. 

Black plastic does not build the soil or contribute nutrients but it does deter weeds and conserves moisture.  Rain does not penetrate this material, so drip irrigation must be placed under it.  A problem with black plastic is that it tends to absorb the heat of the sun and raise the soil temperature.  A layer of straw or grass clippings on top will help.

Special benefits of Mulch.

Insect barrier – Some insects including the Colorado potato beetle, striped cucumber beetle and spotted cucumber beetle will avoid a mulch of straw.

Water Conservation – Many times conserving water will be as important as watering the crops.  During July and August dry spells, make sure the garden looses as little water as possible.  Mulching helps protect bare soil from evaporation.

Erosion – A layer of mulch will protect your soil from rain that causes erosion.

Weeding – Mulching prevents weeds from growing. Weeds need light to grow and mulch shades out the light.

Do’s and Don’ts of Mulching

Mulching too early in the spring keeps the soil from warming up and encourages rot during excessively wet periods.

Wait until the soil has warmed up in the late Spring then put mulch on the spring crops.  This will help to delay bolting.

Mulch the summer crops late in June when the soil has warmed and will continue to remain warm.  This prevents the soil from becoming hot and dry.  Mulching will keep the soil at an even temperature around the plant roots.

Leave a gap between the mulch and the plant stem for air to circulate.

The best time to mulch is right after a rain shower.

If the mulch is left on over the winter it will encourage earthworms and beneficial micro-organisms.  They will eventually devour the organic mulch and turn it into good humus.  At the end of the season, when the mulch is turned into the soil it will be broken down and continue to enrich the soil’s humus content.