A hand in a blue rubber glove holds many white pellets of fertilizer over a large paper bag of fertilizer next to the leaves of a plant
(Image credit: Vitalii Petrushenko)

Fertilizers are a very common way to amend soil for better plant growth. In fact, the bulk of the produce we find in our supermarkets has been heavily fertilized to maximize yield. There are two main types of fertilizer, organic and synthetic. Our ancestors used organic means until the advent of synthetically produced fertilizers, which have been the most common method of feeding plants. But recent years have seen an uptick in reverting to organic means. Both have their strengths and weaknesses.

When purchasing plant foods, the gardener may wonder what the differences are between organic vs. inorganic fertilizer. Each is beneficial to plant growth, but there are some very basic differences. While useful, some gardeners may feel the synthetic fertilizer disadvantages outweigh their use. But the same can be said regarding organic plant foods. Alternatives to fertilizer include soil amendments and homemade feeds, as well as other land management practices.

Inorganic Fertilizer

Inorganic or synthetic fertilizer is a man-made product. They are commercially made in a wide scale and readily available at any store that carries gardening supplies. They typically contain items like ammonium sulfate or ammonium phosphate. They are generally found in a concentrated state that requires dilution to avoid damaging plant roots. There are three numbers on the product which indicate the amount of nitrogen, phosphorous, and potassium. These are the macro-nutrients that drive growth, root health, and flower and fruit production.

Plants also need micro-nutrients and minerals, which may not always be present in chemical formulations. The amount applied to plants will depend upon soil health, moisture, and variety of plant. It is very easy to over- fertilize a plant in nutrient rich soil. Such a case causes weak, leggy growth, and may pollute the water table and wild waters. There are high amounts of salts in synthetic fertilizers due to the nitrogen count, which may burn and damage roots. It is sometimes best to consider alternatives to nitrogen fertilizer to prevent such injury.

Organic Fertilizer

Natural or organic feeds come in many forms. Compost is a common way to add nutrients to soil and enhance plant growth. It is easy to make it yourself from kitchen scraps or garden refuse. Other forms of organic fertilizer are worm castings, fish fertilizer, manure, chicken litter, rock phosphate, bone meal, seaweed fertilizer, and diluted urea.

These are by no means the only way to naturally feed plants but are widely available. Organic fertilizers release nutrients slowly into the soil, causing less damage to roots. However, in the case of fresh manure, the high nitrogen has the capacity to harm plants. It is best to use older manures that are not so "hot". Similarly, compost that has not been finished properly could bring injury to the garden. But when used properly, organic fertilizers not only feed plants, but help loosen the soil and attract beneficial insects and organisms.

Alternatives to Nitrogen Fertilizer

Nitrogen is the number one driver of plant growth, which is why it is the first number listed in the ratio of nutrients. It is also usually the highest number. Plants like sod grass need tons of nitrogen. In forms such as synthetics, any excess is carried off by irrigation and rain, contaminating streams and other bodies of water. It may also permanently damage the roots of the grass. Instead of such measures, a compost tea broadcast sprayed over the lawn is effective and gentle.

Other alternatives might be manures, corn gluten meal, and chop and drop mulching. Manures bring in 4-9 percent nitrogen in a slow-release manner and are available to purchase. Regular moisture will help organic compounds break down and release the available nitrogen, while preventing root burn and avoiding excess salt build up.

Bonnie L. Grant

Bonnie Grant is a professional landscaper with a Certification in Urban Gardening. She has been gardening and writing for 15 years. A former professional chef, she has a passion for edible landscaping.