There are many benefits of incorporating organic fertilizers into your agronomic, horticultural or residential landscape fertility program. Increased organic matter, improved soil structure and tilth, greater water holding capacity, slow release of nutrients, i.e. prevent leaching and increased cation exchange capacity. Organic fertilizers stimulate microbial and biological life of the soil and provide essential micronutrients.
There is no question these benefits are wonderful. However, typically the guaranteed analysis of nutrients when compared to inorganic fertilizers is very low. If comparing actual nutrients per dollar purchased, organics can become cost prohibitive, since much larger quantities must be applied per acre.
Typically, organic products have nutrient levels near a 1:1:1 N, P, K ratio. So, it also becomes impossible to supply adequate Nitrogen without over application of Phosphorus.
Furthermore, it becomes problematic if your soil test comes back with other than a 1:1:1 ratio recommendation to supply adequate nutrients. If you need to supply one or two nutrients, due to chlorosis or fruit drop, organic sources cannot do that. More important organic sourced fertilizers must first be broken down into an available form before nutrients can be absorbed. They are not immediately available.
Plants can only absorb nutrients in certain forms. Nitrogen is absorbed by the plant in ammonium (NH4+) or nitrate (NO3−) forms only. Inorganic fertilizers can provide this nutrient form in exact amounts and become immediately available. Organic fertilizers must first be broken down or mineralized before they become available. Plants cannot distinguish between organic and inorganic nutrient sources.
Then there is the question of nutritional value of the plant. Despite consumer perception, there is not consistent scientific data demonstrating organic sources are superior to inorganic ones.
Organic fertilizers offer many benefits. Inorganic fertilizers do as well. The definition of “organic” in mainstream keeps getting wider and wider. It is a huge marketing strategy that often appeals to our humanity and goodwill. Inorganic fertilizer can be just as natural as organic, provide immediate nutrients in the right amounts, economically.
What’s the right program? Like Forrest said to Jenny; “I think maybe it’s both.”