Building healthier soils for your garden
Tips for understanding and building a healthier soil in your vegetable or flower garden this fall.
Soil is made up of a combination of different-sized mineral particles, organic matter and living organisms. Sand, silt and clay are the mineral or non-living part of the soil. The largest component of the particles is sand. Sand is big enough to feel or see. On the other hand, silt and clay can be over 100 times smaller than sand. Soil consists of each of these particles mixed with the living or organic components.
Beneficial aspects of healthy soils include a physical composition conducive for plant roots to anchor; a bank or reservoir of essential nutrients and water to promote plant growth; sufficient pore spaces allowing for oxygen movement for healthy roots, nutrient uptake and support for living organisms; organic matter that sustains the living component of soil and releases nutrients as it breaks down; and promoting plant health and resistance to disease and decline.
The organic content is an important key to having healthy soils, whether it is mainly sand or clay. Clay soils with its minute particles have tiny pore spaces that drain slowly, leaving soils saturated with water and reducing space for oxygen. Since oxygen is a key element necessary for growing plants, any soil with poor drainage can lead to damage or death of the plant. When organic matter is added to clay soils, it increases the pore spaces between the small clay particles, allowing the soil to dry out faster.
Organic matter acts as glue, holding soil particles together and creating larger pore spaces needed for oxygen and water exchange. Sandy soils often have too large of pore spaces between particles, reducing the soil’s ability to hold water and nutrients. When organic matter is added to sandy soils, it helps hold moisture and makes nutrients available for plant use.
Organic matter in healthy soils can range anywhere from 5 percent to as high as 15 percent. Soils with less than 5 percent organic matter tend to be less productive, often promoting deficiencies in plant tissues. Organic matter may be added to soils through composting, including well-composted animal manure, chopped up leaves, grass clippings and organic mulches, or by planting cover crops.
Determining your soil’s organic matter content, soil pH, nutrient levels and soil type may be accomplished by obtaining a soil test for the home garden from Michigan State University Extension. Soil test kit self-mailers may be purchased from the MSU Extension Bookstore or from your county MSU Extension office for $25. If soil amendments are needed, instructions will be provided on how to make the necessary adjustments.
The MSU Extension publication “Advanced Soil Organic Matter Management” recommends using a diverse mixture of organic matter residues which will provide some materials that are slow to break down along with others that release nutrients more easily.
Cover crops or green manure crops are plants specifically grown as a ground cover to be tilled under while still in a green, vigorous stage to add organic matter and nutrients back into the soil. Legumes like clover and hairy vetch have nodules on their roots with the ability to fix nitrogen for plant use in the organic form back into the soil for future crops. For more information on gardening with cover crops, read the Cornell University fact sheet, “Improve Your Soil with Cover Crops.”
A tip sheet is available from MSU Extension titled “Smart gardens begin with healthy soil.” For more information on a wide variety of Smart Gardening topics and articles, visit the Gardening in Michigan website at http://migarden.msu.edu/.