By Michael Rehm
On April 4th, 2012 the students of the Organic Farm Planning, Growing, and Marketing class transplanted Spinach (Spinacia oleracea) sprouts into one of the hoop houses located on the Cornercopia farm. The crop was separated into plots which would either have a mulch treatment or a bare ground control. This was part of an experiment to determine how beneficial applying mulch can be to crops on an organic farm.
The application of mulch to the soil surrounding crop transplants helps build up the amount of organic matter and can have a multitude of affects depending on the particular mulch used. This fresh organic matter that is decomposing is high in moisture content and helps reduce the amount of water evaporating from the soil, therefore minimizing the need for watering as well as reducing the amount of stress that drought can have on them. If too much is applied though, it can actually lead to excess moisture in the root zone and root rot along with other insect and disease issues. The new layer of mulch is a great environment for microbes and insects that are beneficial to the health of your plants, and the breakdown of organic material provides necessary nutrients and minerals to your soil such as calcium, magnesium, nitrogen, and phosphorus.
Mulch also works to suppress the germination of weeds that will pop up around your plants. These seeds can still be blown on top of your mulch or carried there by animals, but mulching will greatly reduce the amount of time and effort spent pulling weeds. Many plants prefer warmer soil temperatures and tend to be planted later in the season, these plants will benefit from the insulation that mulch can provide. Plants like tomatoes do well in warm soil temperatures, so when mulch is placed on these crops the heat from insulation helps them to thrive. You can run into problems if you place your mulch too soon in the season though, because it will work to contain the cool temperature of the soil, inhibiting plant growth. An application of too much mulch has the possibility of depriving your plants of oxygen and can lead to issues of drainage and excess soil moisture, as well as being prone to slugs.
There are many different varieties of mulch and the key is to understand which type of mulch will be most beneficial, the amount to use, and the time of the season to apply it. If you find what is appropriate for your particular crops, mulch can be a great boost toward a healthy vegetable yield.