Soil Fertility and Plant Nutrition


Soil fertility is the foundation of plant health. Complete and balanced plant nutrition enhances the right amount of growth,  resistance to pests and diseases, flower and fruit production, and healthy appearance, color and taste.

Soil mineral nutrients are used by plants in metabolism and production of foliage, flowers, fruits and seeds. There is also a certain amount of loss of nutrients  when minerals are leached by rain, irrigation and coastal fog condensation, and become unavailable to the plants. Replenishment of nutrients is called fertilization.

Many commercial fertilizer products do not provide complete nutrition, and some high NPK and high-salt-index fertilizers can be detrimental to the beneficial soil organisms and to plant health. I advocate for and provide soil testing and Rx mineral and biological amendments.

There are also DIY new generation COFs (complete organic fertilizers) available at garden centers and online suppliers. 

Preventive maintenance for plant health care starts with good growing conditions, soil and water management. With adequate soil volume, root zone protection, compatible plantings, soil fertility and the right watering (not too much or too little), many common plant problems can be avoided.

Native trees in natural settings have adapted over centuries to the local soil and climate conditions, and a supportive ecosystem surrounds them. But many residential and business park landscape trees are not natives and are planted with adverse growing conditions. Exotic trees and native trees in altered landscape environments have to be managed appropriately or they may become susceptible to pests, diseases or detrimental environmental factors.

As a tree and landscape PHC specialist (plant health care), most of the plant problems that I get called for, turn out to be the result of poor landscape design, incompatible plantings and growing conditions and poor management. Soil and water factors are at the top of the list.


In the San Francisco region, native oaks are predominant trees.  People love the oaks and want to live among them and build their homes near them, but many times this creates problems. The soil and root disturbances from construction impacts, trenching, soil compaction, pavement for driveways, walkways and patios, incompatible landscape plantings and irrigation can kill trees, or take years sometimes to show up as tree decline and mortality.

There is a lot of good information on native oak care that has been available for a long time, but somehow is being overlooked or ignored by developers, planners, architects, arborists, landscape professionals and residents. The consequences of poor design and management in relation to tree preservation are the most common causes for tree problems that I see.

California Oaks publications:


I get a lot of calls about home fruit trees where the owners are simply not informed about total tree care and preventive maintenance, and don’t understand the need for creation of good growing conditions, including adequate watering, and the intensive management that exotic fruit trees require.  I get many calls for advanced pest and disease conditions that could have been prevented.

Dormant season spraying is important and can reduce some of the problems that occur during the growing season. Many people wait until advanced problems show up before taking action. By then it's difficult or impossible to get control.

Fruit tree care is more than just spraying. Soil and water management are an integral part of tree health and building resistance to pests and diseases.

Once a week deep watering is better than drip emitters on frequent cycle.

A common mistake is watering only close to the tree trunk, but it's important to water the entire root zone in an area at least as wide as the foliar canopy. Mulching with compost or wood chips helps retain soil moisture.

Fertilize spring and fall with a COF (complete organic fertilizer).

By far the best available is Agricola's 4-8-4.  From Michael Astera, author of The Ideal Soil v2.0, A Handbook for the New Agriculture.


One of the best on the shelf at garden centers is Down To Earth brand:

Down To Earth Distributors Inc. Eugene, Oregon.