when i say chemical, i'm talking man (woman) made fertilizers. for example, bat guano is not man made nor is alpaca poop. But since you asked, here's a comparison. I don't care what anyone uses, as long they are happy with their grow results. We prefer organic growing, Our choice.
Organic Fertilizers are materials derived from plant and animal parts or residues. Examples are Blood Meal, Compost, Bat Guano, Manure, Seaweed, and Worm Castings.
Synthetic Fertilizers are “Man made” inorganic compounds - usually derived from by-products of the petroleum industry. Examples are Ammonium Nitrate, Ammonium Phosphate, Superphosphate, and Potassium Sulfate.
Plants require 13 nutrients. There are three primary macronutrients; nitrogen (N), phosphorus (P), and potassium (K). These nutrients are used in significant amounts by growing plants, so they must be replaced periodically to sustain productivity.
The secondary nutrients are; calcium (Ca), magnesium (Mg), and sulfur (S). There are usually enough of these nutrients in the soil, so additional fertilization is not always needed. The micronutrients used in small quantities are; boron (B), copper (Cu), iron (Fe), chloride (Cl), manganese (Mn), molybdenum (Mo) and zinc (Zn).
Plants cannot distinguish between an organic or synthetic fertilizer – the nutrients are processed in exactly the same way. However, the similarity stops there.
Chemical fertilizers add nutrients to the soil, but they don’t add anything else. Plants needs more than just nutrients to survive. They also need organic matter and living organisms.
Synthetic fertilizers do not support microbiological life in the soil. The application of a synthetic fertilizer actually kills a significant percentage of beneficial microorganisms. These tiny creatures are responsible for breaking down organic matter into a stable amendment for improving soil quality and fertility. Some convert nitrogen from the air into a plant useable form.
Compost and organic material introduce beneficial microorganisms into the soil’s complex mix. Microorganisms commonly found in soil and compost convert organic nitrogen into inorganic nitrogen, a process called mineralization. Plants may then take up the nutrients released by this process. Composts contain an astonishing variety of microbes, many of which may be beneficial in controlling pathogens.
Organic matter improves soil structure, resulting in a crumb-like structure that improves water retention, air infiltration and enhances soil fertility. Microorganisms can also break down contaminants in the soil and water to components that pose less of an environmental hazard.
Organic amendments(which include more than nutrients) can be highly variable in composition. They are also a dilute source of nutrients compared to inorganic fertilizers, so the nutritive shock to the growing system isn't as noticeable. Because of this diluted feature, organic materials might be more expensive than petroleum-based synthetic fertilizers and might be difficult to justify economically for large-scale production.
And if you don't like to get your hands dirty, you might shy away from the earthy qualities of organic soil amendments that mimic nature's own highly variable results based on microbiological activity and soil temperature.
Synthetic fertilizers usually do not contain micronutrients and they do not support microbiological life in the soil. Because of their high concentration, they can easily be over-applied and can "burn" plant roots, or create toxic level of salts. When synthetic fertilizers release nutrients too quickly, they can create a great deal of top growth before the roots are able to balance the growth underground. This top-heavy growth often leads to weaker and disease prone plants, with less fruiting.
