More than two years ago I reviewed an exceptional book on gardening in two of these columns. The book is "Teaming with Microbes: The Organic Gardener's Guide to the Soil Food Web," by Jeff Lowenfels and Wayne Lewis (Timber Press, 2010). That book uses readily accessible language to introduce gardeners to the microbial life that sustains healthy plants. It remains today an uncommonly scientific perspective on gardening and a valuable resource for all gardeners.
Now, the principal author of that book has released an equally valuable companion work: "Teaming with Nutrients: The Organic Gardeners Guide to Optimizing Plant Nutrition" (Timber Press, 2013). In this book, Lowenfels provides easily understood explanations of the chemistry, biology and botany involved in how nutrients get to plants, and how they contribute to the plant's health and vigorous growth.
Common knowledge indicates that nitrogen is responsible for strong stem and foliage growth, phosphorus aids in healthy root growth and flower and seed production, and potassium is responsible for improving overall health and disease resistance.
Many gardeners employ a fairly rudimentary approach to plant nutrition, and often adopt one of the following major perspectives on the subject.
· The balanced fertilizer group doses all plants with a chemical fertilizer with equal parts of nitrogen, phosphorus and potassium, represented by the symbols N, P and K, e.g., a fertilizer labeled "10-10-10."
· The customized fertilizer group uses chemical fertilizers that have varying percentages of these most important nutrients, depending on the cultivation objectives. For example, Osmocote's Indoor/Outdoor Fertilizer, labeled 19-6-12, focuses on strong top growth and overall health, and less on root growth.
Both of these groups use more nitrogen than their plants really need, while unintentionally delivering excess nutrients that wash into waterways and harm aquatic ecosystems.
· The Organic Fertilizer Group relies on fertilizers composed of organic plant or animal matter. These fertilizers include commercial products, manures and plant materials that a gardener composts in his/her own garden. These fertilizers also could be described in terms of N-P-K ratios, but compared to chemical fertilizers they act more slowly and over longer periods, and are friendlier to the environment.
· The no-fertilizer group includes gardeners who add nothing to their gardens in the belief that plants will grow in the same soil year after year without depleting the nutrients. This is an error, as the garden's declining performance demonstrates eventually.
In this book, Lowenfels offers a deeper understanding of the major and minor plant nutrients and delivers the necessary science in a conversational style that most gardeners will appreciate.
Next week's column will review "Teaming with Nutrients" in more detail and (no surprise) I recommend reading this book as an investment in your long-term success in gardening.
Tom Karwin is a Santa Cruz resident, a UC Master Gardener, a member of several garden groups, and vice president of the UCSC Arboretum Associates. Contact him at firstname.lastname@example.org.