Why Organic Fertilizer Is Important

The organic fertilizer hides a complex product that activates various soil processes. Although remedies are commercially available, everyone should think about making their own. This is neither difficult nor expensive, because plants form the basis of good fertilizer.

What is organic fertilizer?

If fertilizer is of organic origin, then dead organisms and their excrement provide the fertilizing components. They are made from waste from agriculture or private horticulture. The nutrients are not available in pure form but are mostly bound to carbon-containing compounds.

These are organic fertilizers:

  • Slurry, liquid manure, or stable manure
  • sewage sludge
  • green manure
  • compost and straw

How does organic fertilizer work?

The composition of the material determines how quickly the organic fertilizer works. The C/N ratio is the ratio between carbon and nitrogen and provides an orientation for the rate of action. The more organically bound nitrogen it contains, the slower the fertilizer works. This must be mineralized in the soil, which first releases ammonium compounds and finally nitrate.

Plants can absorb nitrate. Conversely, this means that the fertilizer works faster the more nitrate and ammonium nitrogen it contains. Manure is an example of a particularly fast-acting organic fertilizer. It resembles a dissolved mineral fertilizer.

Ammoniacal nitrogen content in:

  • Slurry: about 50 percent
  • Stable manure: ten to 20 percent
  • Compost: around five percent

Influencing Factors

The implementation of organic fertilizer depends on the weather because active soil organisms are strongly influenced by their environment. A moist environment with warm temperatures and a good oxygen supply promotes the conversion of the material. Cold, wet, and lack of oxygen inhibit the activity of the soil fauna.

Organic NPK fertilizer

Organic fertilizers can also be industrially processed to contain natural substances and synthetic nutrients. They are less concentrated than mineral NPK fertilizers and can be applied in liquid form or as granules. With regular use, the soil is improved because organic commercial fertilizers build up the humus layer. On the one hand, they contain nutrients that act immediately and components that release nutrients over a longer period of time.

This is what organic commercial fertilizers contain:

  • animal origin: flours made from animal skeleton parts such as meat bones and horn; hair meal pellets, feather meal
  • vegetable origin: water and concentrates from potato plants, leftovers from corn processing, vinasse, malt germ
  • other organic NPK fertilizers: bio sol, legume fertilizers, hydrolysates


Organic fertilizers need to be incorporated lightly into the top layer of soil in order to have their full effect. Microorganisms attack the components from all sides and decompose them so that the nutrients are made available to plants. In the case of a superficial distribution, it is mainly the nitrogen content that is broken down. The material should also not be worked in too deeply, as the absence of air will lead to rotting processes.

Organic fertilizer for lawns

The nutrient supply via organic fertilizers can not only be used for herbs in the bed. They also provide the lawn with vital substances so that it thrives magnificently. However, a solid substrate is not suitable for fertilizing an existing lawn. In this case, liquid alternatives are necessary because compost can no longer be worked into the soil. Organic commercial fertilizers in liquid form are still better than mineral fertilizers.

Buy organic fertilizer – what to look out for?

Laboratory tests have found heavy metals, pollutants, and pesticides in organic fertilizers from various price ranges. A sample from the magazine “Öko-Test” (read the July 2017 issue) states that even most organic products are not perfect. If you want to buy organic fertilizer, you should know exactly where it comes from.

Organic fertilizer – advantages and disadvantages

Natural fertilizers based on plant or animal residues improve the structure of the soil and promote humus formation. Due to their slower action time, the nutrients in organic fertilizers are not washed out as quickly as in mineral alternatives. They provide the crops with nutrients over a long period of time without over-fertilizing the soil. Plants receive sufficient nutrients during their main growth phase because the soil organisms are more active during this time than in the cold months.

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Written by Emma Miller

I am a registered dietitian nutritionist and own a private nutrition practice, where I provide one-on-one nutritional counseling to patients. I specialize in chronic disease prevention/ management, vegan/ vegetarian nutrition, pre-natal/ postpartum nutrition, wellness coaching, medical nutrition therapy, and weight management.

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