What Suitable Alternatives are there? And is it a better choice, Environmentally?
Lately there is a lot of talk about the environmental impact of using peat in horticulture. As well as there is a lot of talk about sustainability, about products being green and environmentally friendly, but what do these terms really mean? The claim that the use of waste products such as coconut fiber or wood fiber is more environmentally friendly than the use of peat is in fact a debatable issue. It is not so simply as it might seem at first. The full life cycle of the material – production, processing, delivery, use and end of life – needs to be considered in more detail. Impacts on climate change, resources, human health and ecosystem quality need to be assessed. In fact, each raw material has an environmental impact. For example coir, compost, wood fiber, bark are subjected to one or more processing steps before they can be used as a component of growing media, resulting in environmental impacts.
We’re going to take a look at most important aspects must be taken into account when choosing the components of the growing media and the main disadvantages of most common peat alternatives, due to which these components do not meet the quality criteria.
Peat – a Key Component of the Growing Media
Over the years and so far, peat has been a key component of many growing media and the most important stand-alone organic substrate. Peat has excellent physical properties: high free air space and water holding capacity, low bulk density, slow degradation ratio and it generally being weed free. It also has unique chemical properties, such as high cation exchange capacity (CEC) and easily adjustable pH. Due to the above-mentioned properties and the fact that it is available in many important countries in terms of horticultural production, peat is widely used as a stand-alone growing media or as a component of a mixture.
Aspects to be taken into account when choosing a Growing Media
- Availability – the component must be readily available in sufficient quantities
- Physical properties – (WATER HOLDING CAPACITY, WATER UPTAKE, AERATION ) Growing Media must ensure an adequate balance of air and water for the plant roots. In addition, the structure of the substrate must remain stable over time
- Biological properties – Growing Media must be free of plant pathogens and weeds. It must be biologically stable
- Consistency – physical, chemical and biological properties of the components must be consistent from batch to batch and year to year
- Cost effective – the costs of purchase, transport and secondary processing are taken into account
- Chemical properties – NUTRITION (what and how many nutrients do components carry themselves?). CATION EXCHANGE CAPACITY and pH BUFFER
- Environmental requirements
Changing the components of the growing media brings with it a great challenge in horticulture. Growers must adapt their cultivation practices -irrigation, nutrition application etc. in accordance with specific materials being used. Alternatives to peat that meet environmental requirements, as well as growers’ requirements in terms of certain characteristics, availability and price, are being actively sought and developed. Nothing has been found that works as well as peat for potting medium. Some products now offer mixtures of peat and other alternative components. The main reason for this is that however, alternative components cannot completely replace peat.
Main Disadvantages of the Most Common Peat Alternatives
Coir dust comes from the coconut husk. The husk is processed for the fiber industry and the dust released is waste. Coconut dust is also called Cocopeat. Coir products is mainly imported from the Sri Lanka, India, Philippines. Therefore, an additional calculation should be made of the real carbon footprint of transport and shipping.
Given that it is a waste product (from the coconut industry) and not specifically produced for the horticultural sector, its physical, chemical and biological properties are not always favorable and can be highly inconsistent.
Unprocessed coir dust contains large amounts of salt, mainly potassium and sodium chloride. To reduce the content of these elements in the products, materials are washed and rinsed.
In addition to calcium and magnesium, coir dust also binds a lot of potassium and sodium in the adsorption complex. So the material is treated to remove potassium and sodium from this complex. Because if the coconut dust is not treated, these elements are released during the cultivation of crops, during fertilization, therefore, it can exceed the permitted norms and cause damage.
Coir dust may contain viable weed seeds. In some cases, coir dust is steamed to eliminate any weeds. Tropical weeds can transmit plant pathogens, and tropical weeds can spread very quickly.
In terms of water absorption, peat can hold 10 to 20 times its dry weight in water, but coir only holds about 8-9 times its dry weight. Consequently, it may be necessary to water coconut substrates more often than peat.
Returning to environmental aspects , the processing of coir products requires a large amount of water. As a result, water is polluted, which affects the environment. In some areas, including India, lack of drinking water is already a problem.
Coir often manufactured in places that had been rainforests until they were destroyed for growing coconuts. So, compared to responsibly harvested peat, it may not always be a clear choice.
Wood – Based Materials
Increasing the use of wood-based materials in substrates, one of the many questions that growers and society often ask is about the sustainability of the use of wood (one of our most valuable natural resources). It should be borne in mind that some wood products are not by-products but are harvested from trees specifically intended for horticulture, so this is not positive from an environmental point of view.
Wood – based materials such as wood fiber, sawdust or composted bark products naturally contain nutrients. The manganese content is an important factor to consider when using these products in horticulture. Presence of wood based materials in growing media may strongly increase the manganese content.
It should be keep in mind that wood-based products bind a lot of nitrogen, because the material is decomposed by microorganisms. So, using such products requires more nitrogen fertilizer than peat.
Usually the material in different batches is inconsistent and you never know what chemicals the wood waste may contain.
The composting process is the result of biological decomposition of organic materials, conducted by various microorganisms. The chemical and physical properties of compost can be quite variable, making it quite impossible to achieve product consistency from batch to batch. Another aspect that should be considered is the particle size. Compost is obtained by allowing organic matter to decompose. The small particle size of the final product creates a growing media with low air porosity and poor drainage, which means an unfavorable conditions for the plants.
Despite the fact that it is chipped and sorted before composting, it often happens that large pieces are found in the compost. This can cause problems using substrates such as sowing and plugging. In addition, pieces of plastic, stone, metal and glass can often be found in compost.
Nutrient imbalance can also be a problem when using green compost. As mentioned earlier, the nutrient levels in compost can vary significantly, no two batches are the same. Compost contains a lot of nutrients, but it is difficult to predict the release of these nutrients. In addition, if the composting processes are not completed before incorporation into the growing media, this may bind the nitrogen applied, resulting in a lack of nitrogen in the plants.
The microbiological activity of compost changes the level of nutrients in the growing medium over time. Nutrients are released as the compost is broken down, so over time and as the temperature rises, nutrients continue to accumulate in the unused growing media.
It is also important to know that high chloride content can be observed in compost, which may prevent plants from absorbing nitrogen.
In summer, it contains large amounts of grass that may contain herbicide residues that do not decompose and can harm plants.0