Can compost improve sustainability of plant production in growing media?

The importance of soilless cultivation is steadily rising worldwide, leading to questions about its sustainability. In general terms, growing plants in soilless media is a sustainable production manner. This is due to the inherent space, nutrient and water use efficiencies of this production method, which are all higher as compared to soil-grown crops. The use of compost as a component of plant growing media (GM) further improves the sustainability of this methods due to the following positive factors:

1. The use of compost as an ingredient of GM allows to replace part of the energy-consuming substrates such as rockwool or perlite.

2. Compost, acting as a slow-release fertilizer, helps to save energy-consuming nutrients such as Nitrogen and others. The cost of synthetic nitrogen has nearly tripled in the last 10 years, stimulating growers to consider the use of compost as a cost-effective source of slow-release nitrogen and other nutrients.

3. By enabling safe disposal/reuse after its end-of-life. Recycling compost-based media is an environment-friendly approach, frequently possible by applying the used substrates as soil amendments or as ingredients in media for less-demanding crops such as forest tree saplings.

4. By improving plant health, thus reducing pesticides' use due to the suppressiveness capacity of well-prepared composts. In this respect it must be noted that sterilization largely negates compost suppressiveness.

5. By serving as an outlet for various types of organic wastes, that otherwise may pollute the environment.

However, there is a variability among commercial composts, which places a question mark regarding the reproducibility and practicality of their use. Only when commercial producers adhere to clear professional set of recommendations, results of large-scale operations were similar to those of controlled scientific experiments. Examples for all the above points are discussed below including their horticultural and environmental benefits and drawbacks.

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