The principle of Occam's Razor states: “the simplest solution is almost always the best.” Sheet mulching proves this to be true when it comes to removing a lawn or weedy area in the garden while at the same time aiding in conserving water.
Sheet Mulching is the name given to the process of using cardboard as a temporary barrier to kill lawns or existing weeds and prevent the next generation from sprouting. Two or three layers of cardboard covered by three inches of compost and then three inches of wood chip mulch can keep an area weed free for years. Fabric or plastic weed barriers restrict the natural flow of air, the delivery of nutrients, and the migration of beneficial organisms into the soil while within a year the cardboard will break down into nutrients leaving no restrictive barrier. Sheet mulching also reduces the use of fossil fuel since no plant debris needs to be hauled away. It is also a safer alternative for people and the environment since no herbicides are used in the process.
The compost used for sheet mulching can retain 30% of its weight in water which is equally
important, especially in water conservation areas. Put differently, only a 5% increase in organic material (compost) quadruples the soil's water-holding capacity. Compost can reduce plants' water needs around their root zones and reduce the overall water a plant requires. Compost aids in reducing rain and irrigation runoff because of its ability to absorb water and because of the spaces it creates in the soil.
A layer of wood chip mulch on top of the compost will help prevent weeds from sprouting and stop weed seeds blown in from making contact with the soil which is necessary for germination. However, mulch as also plays an important role in water conservation in the garden. It slows water evaporation by protecting the soil from direct sunlight and the wind. The wood chips and other plant debris in mulch can absorb water, which in turn will be released slowly into the soil to help keep it from becoming arid.
Water is an essential resource in the garden. Using gray water, weather-based irrigation
controllers and drip irrigation all go a long way to making the garden water efficient. Plant
choices and tree canopies for shade also aid in using less water in the garden. Sheet mulching is just one more tool that can be utilized to save even more water in the garden, and in times of drought, possibly save the garden itself.
Daniel O Donnell is the co-owner and operator of an organic landscape design/build company in Fremont. www.Chrysalis-Gardens.com