Photo by Karen Keb Acevedo

Using kelp meal as a fertilizer is a natural way to get potassium to your plants.

Fertilizer is a source of nutrients for plants. Managing the fertility of your soil will involve adding some nutrients. Here are nutrient supplements that are commonly used in organic farming:

• Rock phosphate: used as a source of phosphorus, calcium and trace minerals
• Greens and/or kelp meal: used for potassium and a wide array of micronutrients
• Limestone: used to add calcium and magnesium as well as to raise soil pH

Some soils need a particular micronutrient that is deficient. If you’re new to a city property, it may be worthwhile to get a soil test. Tell the lab what you’re planning to grow, and they’ll give you an idea of the areas where your soil may be deficient. The results of a soil test are an oversimplified look at your soil, but can still be useful.

Micronutrients are usually present in adequate amounts in soil that’s been well-amended with compost, but you may still have a deficiency. The most-often supplemented nutrient in soil is boron, but there are a number of nutrients that can be lacking. These amending substances are essential, but some can be toxic in excessive amounts, so rely on expert advice when applying them to your soil.

An advantage to natural fertilizers is their slow-release characteristic. Most natural fertilizers require action on the part of microorganisms to make them available to plants. This can be a disadvantage if you’re attempting to quickly correct a nutrient deficiency.

However, organic farming isn’t about quick fixes. A nutrient that’s released slowly to the plant will result in steady, sustained growth rather than a quick flush of new vegetation. The danger of environmental contamination is reduced when fertilizers are in a slow-release form. The pollution of waterways by conventional fertilizer runoff is a significant problem in many places.

For more tips on growing healthy, organic plants, read “Be an Organic Gardening Success.”

About the Author: Alexandra Kicenik Devarenne is an independent olive oil consultant based in Sonoma County, Calif. She is the co-author of two chapters of the Organic Olive Production Manual from University of California Agriculture and Natural Resources Publications.