Wednesday, November 16, 2011

Ecological Gardening: Improving the Health of Your Garden’s Soil

Sunday's workday at the Goodwin Garden.
At Bountiful Brookline’s workday this past weekend, we put the Goodwin Garden to bed for the season.  With the help of volunteers, we pulled out all of the annual vegetable plants and flowers and added this green matter to our yard waste compost pile to decompose.
Beyond cleaning up the garden, we focused on building the soil.  Healthy soil is essential to growing healthy plants and, in turn, to supporting healthy creatures - like us - who eat those plants!  Healthy soil is dependent upon the abundance of soil life: microorganisms such as bacteria, fungi, and larger organisms such as earthworms, millipedes, and mites. These organisms break down organic matter (food scraps, manure, leaves, dead vegetation, among many others) into nutrient-rich humus, an important component of healthy soil structure.

As organic gardeners, we understand the harm that conventional and industrial agriculture poses to the environment and our food. These methods of agriculture are clearly at odds with nature, using chemical fertilizers and pesticides and planting in monocultures, practices which result in environmental degradation by killing soil life (and other life through chemical contamination) and destroying biodiversity. While organic agriculture moves way beyond industrial practices, recognizing the detrimental effects of chemical inputs, organic farming and gardening often still involve practices that work against nature.

Putting the garden to bed for the season.
Specifically, disturbed and bare soils are two things you will never find in natural ecosystems.  Disturbing the soil by tilling provides a short-term boost of nutrients as oxygen comes into contact with churned soil and dramatically increases soil life activity. However, this burst of nutrients is more than plants can use (the excess of which is washed away) and, in the long run, results in depletion of soil fertility, as well as the destruction of soil structure by constant mechanical disruption.  Likewise, exposed soil (after tilling or between plants) is open territory for weeds and destroys soil structure because it is now subject to erosion, compaction, and nutrient loss.

Even composting (in compost piles) is not ideal for building soil from an ecological standpoint. Turning a compost pile disrupts soil life, killing valuable microorganisms and limiting its potential for biodiversity.  Additionally, many nutrients are lost into the air or soil below.  By no means a bad practice (I still fully support composting!), there are more ecological ways to build soil. We just need to take a look at nature around us.

Ecological gardening moves beyond organic gardening, seeking to create gardens that mimic natural systems.  Such gardens are designed with principles of wild ecosystems in mind and within a holistic framework that understands the interconnectedness of soil, microorganisms, plants, insects, animals, and humans.

In nature, the soil is rarely upturned and never left exposed.  Rather, dead matter falls to the ground and decays in place through the activity of decomposers.  This process of decomposition releases nutrients back into the soil and improves soil structure, thereby increasing water absorption and aeration.

How do we mimic this process in our own gardens?  One method is sheet mulching , also known as sheet composting or lasagna gardening .  Simply put, it is composting in place and entails layering organic matter.  One of these layers is always a weed barrier, like cardboard or newspaper, and the top layer is mulch such as seedless straw, leaves, or wood chips, among others.  For the other layers, really anything goes - manure, compost, hay, yard waste, seaweed, wood shavings, etc. You can layer as much as you want, depending on the amount of materials you have.  It can be as simple as a weed barrier and mulch layer, or multiple layers of whatever organic matter you have.

In the Goodwin Garden, we put down a layer of horse manure, followed by a layer of cardboard on some beds and newspaper on others, topped by a layer of leaves. Keep in mind that if you have material that is not free of weed seeds, it should go below the weed barrier layer.  Sheet mulching can be done anytime of year.  Doing it in the fall allows more time for the organic matter to break down.  This fall was the second time we sheet mulched at the Goodwin Garden - we also used this method (with some different materials) when the garden was started in the spring.

- Marie Benkley, Garden Coordinator

There are a lot of good resources on sheet mulching/lasagna gardening.
For more information check out:

Gaia’s Garden: A Guide to Homescale Permaculture by Toby Hemenway
Lasagna Gardening by Patricia Lanza
The Ruth Stout No-Work Garden Book by Ruth Stout