Wood fibers are a promising basis for completely peat-free potting soil or, as an additive, can reduce the amount of peat. We introduce you to the production, properties, use and sustainability of the wood fiber soils.
Peat-free soils such as wood fiber potting soils have become an important sign of responsibility towards our environment. This creates a high pressure to change on horticultural companies, but also the opportunity to recognize the new customer requirements as a selling point.
While hobby gardeners and horticultural services tend to find it easy to switch to peat-free substrates such as wood fiber soil, commercial horticulture is on homogeneous and substrates that can be controlled "as usual", because these form the basis for a (financially) secure and plannable operational process. A switch to wood fiber substrate is therefore associated with greater risks for them. It is all the more important to be well informed before switching to peat-free or peat-reduced soils.
Tip: Peatless potting soils did not appear with an increasing understanding of the role of bogs. Even before the "discovery" of peat as a culture substrate, peat-free mixtures were known in which plants could be cultivated without being tied to the soil.
Wood fibre: peat substitute with extensive experience
The use of wood fiber substrates has been experiencing a clear upward trend for over three decades. The domestic fiber is increasingly being mixed into peat substrates, is the basis for peat-free soils or is even used as the sole substrate in hydroponics.
In addition to the chemical and physical properties favorable for plant growth, the advantage of the softwood fiber used is of course the sustainability of the product . With increasing environmental education (especially among younger generations), the argument of sustainability is becoming a strong selling point. This gives wood fiber potting soil the chance to be part of the unique selling pointsto become a more sustainable and future-oriented company.
By the way: In addition to the wood fiber substrates that are already widely used today, compost soils are also a popular alternative to peat, which hobby gardeners in particular like to use. They have a comparatively high weight and their qualities are absolutely satisfactory even for more demanding private gardeners. However, they are not biochemically stable. Despite the use of quality-assured RAL composts, there may be major deviations in the compost properties during transport or cultivation. For example, you can change water and air capacity and nutrient availability. Due to this instability of the properties, compost-based substrates have not been practicable for commercial cultivation until now.
Wood fiber substrate: production and properties
Wood fiber as a substrate component has been examined by various horticultural institutes and can also be observed in its practical application. The Weihenstephan-Triesdorf University of Applied Sciences and the Industrieverband Garten e.V. as well as several state research institutes have compiled extensive information on wood fiber as a substrate component.
Manufacture of wood fiber from wood residues
Chemically untreated softwood is used to produce wood fibers. Many deciduous trees contain too many disruptive secondary plant substances, such as tannins (tannins) and phenols, which can impede plant growth. The starting material is coniferous wood, which is left over from the wood processing industry - for example wood chips, sawmill or planed fractions can be used. Thermophysical digestion or the steam explosion process can be used to extract the loose fibers from the compact cell structures of the plant wood body. In both processes, disruptive resins and tannins are largely broken down. Further treatments are then carried out to optimize pH, wettability, degradability and color in order to facilitate or enhance its use. The color in particular has a great influence on private customers, because they expect a dark color from potting soil.
Due to its large C/N ratio, wood fiber has the negative property of immobilizing nitrogen when it is broken down by microbes. In order to prevent the associated lack of nitrogen in the crop in the substrate, the fibers are treated with slowly released nitrogen. This"Impregnation" can also be done with organic nitrogen fertilizers.
Properties of wood fiber
The properties of wood fiber are relatively similar to those of peat, but the water capacity is significantly different. Although the pore volume is very similar to that of peat, the high proportion of coarse pores means a significantly higher air and significantly lower water capacity. The resulting loose structure effectively prevents plant roots from experiencing water stress due to the exclusion of air. However, as with any organic substrate, the loose structure is unfortunately not permanently preserved, but is reduced over time by sagging. The decomposability of wood fiber is very pronounced, but the structural stability can be improved through suitable processes in production or ignored in the case of short cultivation times of up to five months.
The thermal pulping process means that wood fiber is basically free of weeds and pathogens. At 4.7 to 6.0, the pH value is in a very favorable range for most cultivated plants and is well buffered at the lower end, but hardly at all at the higher end. In addition, wood fiber is basically low in s alt and contains hardly any soluble nutrients - apart from potassium, whose content of up to 100 mg per liter of wood fiber can be five times as high as in peat.
By the way: The quality of the substrate raw materials should be checked to ensure the homogeneity of the wood fiber soils. The raw materials can be certified with the RAL quality mark.
Use wood fiber substrate
The physical properties of wood fiber and wood fiber substrates enable it to be used, for example, in perennial cultivation outdoors and in container cultivation of trees and shrubs. Wood fiber can also be used for closed culture methods (watering of dams, mats, channels, bag culture), especially because the high drainage capacity prevents waterlogging and thus also many root diseases. Instead, the good air flow promotes he althy root growth.
Wood fiber is easy to wet, on the one hand, and on the other hand, the surface dries quickly, which prevents weed and moss growth - including liverwort. Even if it is only added to peat substrates, wood fiber improves wettability.
In cultivation, it must be noted that wood fiber soil has a shorter water capacity due to the lower water capacityWatering interval required as a peat substrate. However, tests were able to show that in substrates with wood fiber the loss through transpiration is lower than in pure peat substrates.
Because of the one-sidedly buffered pH value, caution is required, especially with calcareous irrigation water, to ensure the availability of some trace nutrients, such as iron , not to be detracted from.
When fertilizing substrates based on wood fiber, it should be noted that the fiber itself contains hardly any nutrients, which means that the basic fertilizer must contain all the essential nutrients. Wood fiber itself only has a minimal ion exchange capacity, which is why suitable mixing partners are essential to avoid excessive s alt concentrations on the plant roots. In this context, clay has proven to be a suitable mixing partner, as well as small amounts of quality-assured compost.
