If the soil is healthy, common sense tells us, so is the plant that grows in it. If you take multivitamins, exercise and sleep well, you are most likely to be healthy. Soil is similar to people. Fertilizers are the vitamins, wind and rain are the exercise, and sun and shade are the rest. Organic fertilizers take a strategic approach aimed at feeding the microorganisms in the soil rather than the plants directly, which is how synthetic fertilizers work. You might ask, "What's the difference if my plants grow?" By fertilizing, or feeding, the soil, you enable it to build nutrient reserves that plant roots can tap into any time as needed. Feeding builds good soil structure, creates pores for roots to extend their reach, helps suppress disease and supports biological diversity. Feeding also helps maintain a neutral pH to support humus formation that adds minerals and micronutrients to a living soil.

Compost and Manure 
A well-made compost functions similarly to a well-made organic fertilizer, except it is not nearly as potent in nutrients. Compost is simply the remains of once living organisms that have been degraded by microorganisms. Compost usually consists of organic materials such as yard wastes, plant trimmings, leaves, grass trimmings, soil with microbes and various wet kitchen scraps other than meat. Applying this composted substance to your soil will help provide great tilth, microorganisms, nutrients and nutrient stores.

Part of the beauty of compost is the nutrients from the organic matter in it are released slowly. Compost is so nutrient rich it often meets the needs of a plant for one year or more, although you do not receive the maximum growth and health potential if you apply compost only once a year. Plants grown with healthy and diverse compost will absorb a slower, steadier and more diverse set of nutrients than if they receive synthetic nutrients. Natural compost leads to healthier, disease-resistant plants packed full of nutrients. Caution: Avoid compost made from bio-solids or sewage sludge. Many organic experts warn against them, because they are linked to heavy metals and human pathogens.

Adding compost to your soil is an excellent way to build it up, especially if the soil was nutrient deprived in the past. Where I grew up in Los Angeles, asphalt lots and industrial yards were redeveloped for residential lots as land values increased. The soil under these new homes had been deprived of organic matter and nutrients for many years. If you live in a similar area, amending the soil with compost is one effective way to prepare your area to support healthy growth. Applying a premium home made or store bought compost benefits a soil in any stage of maturity and helps to establish any edible garden. To get safe, effective compost for your garden, look for a trusted nursery or professional grower who can advise you on how to boost your soil's fertility.

Manure, or animal waste, is another effective but risky way to spread nutrients into your soil. Fresh manure has a substantial effect on soil fertility for agriculture. However, I do not recommend using it in a home garden. Raw manure may release ammonia, which is detrimental to plant health. For this and other reasons, manure needs to be composted for a long time before you use it in your garden. Once composted, though, manure is a nutrient-rich material to mix with your soil. Never use the waste of a carnivore (meat eater) such as a cat or dog, as it can carry harmful pathogens. If you raise rabbits, sheep, chickens, horses or cows, these manures are great. Just remember to compost them before you apply them to the garden.

Organic Fertilizers and Soil Amendments
These materials consist of natural ingredients that the beneficial microbes in a living soil digest as food. Popular ingredients include fish meals, feather meal, alfalfa meal, cottonseed meal, bone meals, kelp meal, seaweed extracts, blood meal and liquid animal manures. The meals and extracts contain organic matter and nutrients, while the bacteria and the symbiotic mycorrhizal fungi convert the nutrient sources into usable forms plants can absorb as needed. Also, fungi extend the reach of plant roots to acquire more nutrients.

Organic fertilizers have a much lower chance of leaching through the soil and contaminating the water table. With organic fertilizers, nutrients are physically bound into larger pieces of organic matter lodged in the soil and available so that microbes can free them up for plant use. There is nothing mysterious or magical about organic fertilizers. They simply give you a way of working with nature rather than against it. The objective in using them is to recycle organic matter back into the soil rather than discarding it and relying on chemicals. In fact, the organic process is much less mysterious than the methods of the chemical grower.

A program of organic fertilizers involves far more than just growing plants without chemical fertilizers and artificial sprays. Using organics is a life choice and commitment that recognizes the complex, successful workings of nature in maintaining life for hundreds of millions of years. Sound organic cultivating principles closely follow processes found in the natural world. Also, do not think that using these principles leads to lower yields or quality. In fact, with organics you are likely to increase both. Organic methods also support habitat for wildlife while insuring the fruits and vegetables you produce in your garden are safe, nutritious and free of chemicals. You also reduce the possibility of the harmful effects of chemicals on infants and children.

The soil teems with millions of microorganisms that release nutrients required for healthy plant growth from organic matter. Rather than feeding plants directly, organic fertilizers feed the soil with natural materials that allow your plants to draw on a humus reservoir of nutrients as they need. Plants grown this way are stronger and more resistant to pests and disease. Organic fertilizers work and persist for many months (unlike the short-term affects of chemical fertilizers) because they become a part of the living soil.

You can find a number of different organic fertilizers and amendments at your local nursery. Some are formulated to support the nutritional needs of particular plant categories such as vegetables, while others take an all-purpose approach good for a variety of plants. Fertilizers are generally tested and proven for a specific application. I recommend choosing a selection specific to your types of plants: vegetable fertilizer for vegetables; fruit fertilizer for your fruit trees. In any case, organic fertilizers and amendments are geared for the slow, controlled release of plant food. They are perfect for preparing the soil for upcoming seasons without having to worry about nutrients being wasted or washed away.

Chemical Fertilizers
Chemical fertilizers feed plants directly and do not address the soil, because they are in a form that plants can absorb immediately. While direct plant feeding sounds attractive, it adds no beneficial attributes to the soil. In fact, over time chemical fertilizers can deplete the soil of nutrients. The gardener treating plants only with chemicals uses the soil simply as an anchor to hold plants in place. While this approach appears to have good short-term results, in the long run it has disastrous consequences. When organic matter is not replaced in the soil, beneficial organisms die out, the soil structure breaks down, and the soil becomes hard, airless and unproductive. Attempts at "force-feeding" plants result in soft, sappy growth, which is prone to attack by a host of pests and diseases.

When plants are forced to grow with chemical fertilizers, they become weak. As plant cell walls develop, they do not have enough time to produce two important compounds, cellulose and lignins. These substances strengthen protective cell walls. As cells are forced to duplicate and grow quickly, the amount of cellulose and lignin decreases, making the plant tissues much softer and more attractive for pests to attack. If you were an insect, would you rather bite into a soft head of butter lettuce or chew on a piece of wood? Insects prefer tender, soft growth.

Chemical pesticides are also often used for short-term pest control. Unfortunately, these pesticides also kill the natural predators of the pests that attack plants. Eventually, the problem gets worse as nothing is left to kill the "bad bugs." Stronger, more toxic pesticides then have to be used, setting in motion a hard-to-break, vicious cycle: Plants and soil weakened by chemicals need more chemicals to protect them from pests they resist naturally when well nourished.

Problems with Chemical Fertilizers
Chemical fertilizers feed plants with nutrients directly. This inhibits, and in some cases, kills off microbes within the soil. In addition to this, nutrients added as soluble fertilizers can be lost inefficiently through leaching away or conversion to an unusable form such as nitrogen gas. Chemicals washed away during rain or irrigation can pollute ground water, streams, lakes and oceans. In addition, commercially synthesized chemical fertilizers do not have the beneficial soil microbes that feed the plants certain bio-chemicals such as vitamins and antibiotics.

When soil becomes unbalanced through chemical alteration, certain micronutrients and heavy metals, such as iron, magnesium and aluminum, become more soluble in the soil and can be toxic to plant tissues. Unbalanced soils also reduce the productivity of bacteria (nitrogen fixers) making nutrients less available. Chemical fertilizers also decrease a soil's ability to hold onto positively charged nutrients, which allows water to more easily wash away nutrients. An imbalance of soils locks up other micronutrients and makes them unavailable to plants while concentrating harmful molecules in the soil. All this can lead to further deterioration of the soil by chemically deteriorating humus and organic matter reserves.

Adding petrochemical synthetic fertilizers drives up the salt concentration in the soil and changes the pH, which can adversely affect plants. More importantly, chemical fertilizers only feed for a short time. Organic fertilizers feed continuously, because the microbes do not digest all of the organic fertilizer immediately. Chemical fertilizers reduce the soil aggregation properties of microbes and sacrifice good tilth. Conversely, organic fertilizers support water retention, reduce runoff and support long-term soil health.

Neglecting living organisms in the soil by treating plants with chemically synthesized fertilizers and pest sprays may eventually lead to the extinction of all living matter in commercial soil. In the future, we may become completely dependent on synthetics to get any yield at all. Many gardeners and consumers regard this cycle as unsustainable over time. They have devoted their lives, farming practices and backyards to restoring and preserving biological diversity in soil.

The Answer: Feed the Soil Not the Plants
Feed the soil, not the plants! When we feed our plants and not our soil, we lose all the benefits from microbes. When we feed the soil, we actually feed the microbes in the soil. Microbes make nutrients available for plants. You feed microbes by adding organic material. If you give plants a synthetic chemical fertilizer, you feed only the plant, not the soil. Soil has supported plants and given them nutrients since long before we invented other fertilizers, so why not feed the soil and preserve the natural biological interactions that support plant survival and growth?