It's time for gardeners to prepare beds for planting. Before mounting your charge on the garden center, review a few things about soil and soil fertility.

Soil fertility is so important to good vegetable growth that the two cannot be separated. Healthy growth that can withstand all that nature throws at it is fed by good soil. It contains all that is necessary to grow a plant, and then passes on the best to us in the form of nutrition.

Every time you take something away from the soil, you must give something back. Otherwise, you are literally stunting growth. Garden soils are rarely fertile enough to supply all of the nutrients required for the best growth of plants, but it's also rare that soils are deficient in more than one or two nutrients. California soils contain most of the elements known to be essential to plants, so it is necessary to add only the nutrients that are deficient in a particular soil.

Choosing a fertilizer: Inorganic fertilizers are characteristically fast-acting and relatively low in cost per pound of actual nutrient. Some inorganic fertilizers can acidify the soil (lower the pH) with long-term use. Because inorganic fertilizers are salts, key disadvantages are their potential to leach and burn crops if mismanaged.Manures are composed primarily of animal excrement, plant remains, or mixtures of both. When used correctly manures can be a good organic fertilizer. They supply garden plants with many essential nutrients and can help improve soil structure. Until they decompose, manures supply plants nutrients in their carbon-containing, organic form. Manures are typically more complete than most inorganic fertilizers because they contain many of the essential nutrients required for plant growth and development. Dry chicken manure is the most concentrated animal manure. The principle disadvantages of organic fertilizers are their cost, bulk, odor, potential undesirable weed seeds and relatively high amounts of salts. However, the value of manures and organic concentrates such as bone meal, cottonseed, and fish emulsion does not lie solely on the nutritional value. Organic materials also have beneficial effects on the soil's physical properties, in which case they are classified as soil amendments.

Fertilizer or amendment: Which one is it? Whether a material is considered a soil amendment or a fertilizer is usually determined by its effect on plant growth. Fertilizers influence plant growth directly by improving the supply of nutrients available in the soil. Amendments affect plant growth indirectly by improving the soil's physical condition. This concept is clear when, for example, we compare ammonium nitrate (a fertilizer), and gypsum (an amendment). In evaluating organic or natural products, this distinction can become blurred when the material acts both as a fertilizer and as an amendment. For example, manure can be applied as a source of ready nutrients, but it also contains organic matter which improves soil aeration and water retention.

Try thinking like a worm. Where would you rather live if you were a worm, in hard, dry, unimproved soil or in soil rich in moist, organic materials? Worms can eat their weight in soil each day. Over 1 million worms may be present in one acre of soil, and these worms can produce 700 pounds of castings each day. Two thousand red worms in a worm bin can produce 7 pounds of castings in one month.¹ Building up soil fertility with organic products takes time, but the idea of feeding the soil and then the soil feeding the plants is a great concept...and a lot of worm castings.

What kind of soil do you have? Paste the following link into your browser to UC Davis soil web and discover what kind of soil you have in your neighborhood. http://casoilresource.lawr.ucdavis.edu/gmap/

 

¹Jen Fong and Paula Hewitt
Adapted from Cornell Cooperative Extension