Soil Fertility: The Foundation to a Successful Organic Garden

The organic garden is a living, breathing ecosystem full of diverse groups of plants, insects and microorganisms. The cornerstone of a successful organic garden lies in soil fertility. There are many soil characteristics ranging from biodiversity, friability, crumb structure, color, depth, etc., that will affect garden yields and overall health.

One of the most important aspects of garden soil should be soil depth. The deeper the garden soil, the more room there is for root zone growth and overall garden yields. Soil depth can be improved by planting your garden in raised beds or furrows. Soil should also be dark in color as color is usually a good indicator of overall soil fertility.

When soil is darker it usually contains more nitrogen or organic material. Healthy soil will be a balance between clay, silt, and sand particles coupled with organic material. The sand, silt, and clay provide mineral exchange with garden biota and the organic material provides macro-nutrients for the plants. Healthy soil will have a crumb-like structure also called friability.

This crumb structure is formed when earthworms consume rotting vegetation and secrete mucus around their humus-rich castings (worm feces.) Soil with a crumb-like structure aids in providing plants with an ideal mixture of 25% water, 25% air, and 50% soil. This type of soil also encourages the growth of beneficial fungi which aid in the delivery of nutrients to the root zone of plants. Friable soils reduce compaction and regulate water better than non-friable soils.

When rain falls on good garden soil it should disappear very shortly after hitting the surface of the garden. If the water puddles, then the soil is too compact. This is usually caused by too much clay or silt and not enough sand and organic material. If rain falls on soil and the soil dries out very quickly after the rain has stopped, then the soil doesn't have enough water retention properties and should be corrected.

To correct this problem, more organic material in the form of compost or leaf mold should be added. The last and final indicator of soil health is earthworm populations. If you dig up a shovel full of soil from your garden you should be able to count a handful of worms in each shovel.

The absence of earthworms from a garden is a direct indicator that there isn't enough rotting organic material present in the soil. Good garden soil isn't created in the first year. New gardens may take years to come into a state of equilibrium whereby little effort is needed to maintain soil health.