In the Lensli Academy we regularly inform you about practical situations that we encounter in the sector, we talk about insights gained in practice, we give you cultivation tips and we share our knowledge about other interesting substrate-related matters.
Academy – Packaged Growing Media
Producers pack substrate and potting soil in big bales, small bales and bags. Occasionally, a decomposition process can occur in these packages with fertilized and limed, organic substrates or potting soil. In some cases, this can change the product and cause occasional growth problems in plants.
RHP has set out the first insights of an ongoing RHP study in an extensive factsheet, and we are happy to include this article in our own Academy. (Source: RHP)
Packaged growing media
Growing media (substrates and potting soils) can be compressed and stored and transported in sealed packaging. This makes storage and transport to professional growers and consumers more efficient. These packages, such as big bales, small bales and bags, vary in size. However, anaerobic conditions (no oxygen) can occur in the “airtight” packaging. Liming of substrate mixtures with peat also displaces oxygen. Occasionally, anaerobic conditions in (fertilized and limed, organic) substrates can trigger chemical and biological processes. In some cases, this changes the properties of the substrate. Although this occurs very rarely in practice, it could ultimately result in crop damage. RHP, knowledge center for substrates, conducts extensive research into anaerobic conditions and degradation in packaged growing media to gain more insight into the course of the process, to determine why problems sometimes arise and whether and how they can be prevented. Although not everything is known yet and the research is still in full swing, RHP shares the first insights in this article.
What We Know (and Don't Know) About Packaged Growing Media
Sometimes fertilized and limed organic substrates can change in the packaging. In addition to anaerobic conditions, factors such as basic fertilization, longer storage time, higher temperature, compression ratio and humidity play a role. Conditions can arise that give certain microorganisms that are not dependent on oxygen a better chance to develop. This can trigger a decomposition process, change the substrate and ultimately cause crop damage, such as growth inhibition and growth disorders. White discoloration of the leaves of the crop (Weißblättrigkeit) is an example of such a growth disorder. The nitrogen metabolism in particular is strongly influenced by anaerobic conditions, which leads to nitrogen loss (denitrification), for example. Problems occur in particular in warmer countries, where the packaged substrate is exposed to direct sunlight, for example, and the time between production and use of the substrate is longer.
Furthermore, storage and transport time also have an effect on unpackaged substrate; organic products simply do not have an indefinite shelf life. In addition, favourable warm and humid conditions in (packaged) growing media can promote mould growth. If a substrate clearly smells of rotten eggs or has a strong manure smell when the packaging is opened, this is a clear sign that decomposition has taken place in the substrate. The typical rotten egg smell is caused by the decomposition of sulphur-containing fertilisers into hydrogen sulphide. Certain nutrients, such as nitrate, have probably disappeared and the pH and EC have changed. In many cases, substrate can still be used, after a chemical analysis to determine how to fertilise. Because we do not yet know everything about the processes in the packaging, a cultivation trial with a sensitive crop such as Chinese cabbage can help to assess whether the substrate can be used safely.
What are the guidelines of the RHP quality mark?
All quality requirements of the RHP quality mark are described in the RHP product certification scheme, which is continuously updated based on developments. RHP has been investigating for some time how anaerobic conditions in packaged growing media influence the properties of substrates and thus plant growth. Laboratory analyses and plant response tests show that closed packaging can cause a rapid decrease in oxygen and nutrients within 1 to 7 days at temperatures of 25°C. Much more research is needed and RHP is continuing with this.
Advice for the user
Substrate producers and growers can take into account the storage conditions. Important recommendations for storage of packaged growing media are:
- Store in a cool place away from direct sunlight
- Avoid higher temperatures (above 25°C)
- Protect against rain and extreme humidity
- Limit storage time: substrate always changes over time, whether packaged or in bulk
It is recommended that substrate manufacturers provide clear information on the packaging regarding storage advice (temperature, sunlight, rain and storage time). Following the storage advice is essential. Be extra alert if the substrate has a clear stench of rotten eggs or manure when opening the packaging. Then decomposition has almost certainly taken place. A chemical analysis then provides insight for additional fertilization. It may be wise to perform an additional cultivation test before using the substrate for cultivation.
- Packaged growing media can become anaerobic, which incidentally affects substrate properties
- Biological and chemical processes that cause this can influence pH, EC and nutrients, among other things.
- Storage conditions such as temperature, humidity and duration are crucial Do not produce packaged substrates unnecessarily long before use
- Substrate that has been anaerobic may occasionally cause growth disorders/inhibition
- Does substrate smell like rotten eggs or manure after opening the packaging? Be alert, take action!
- RHP continues its research into packaged growing media
Want to know more about this topic or just expand your own knowledge? Please contact your Lensli account manager or product manager. You can also reach us via sales@lensli.com and +31 (0)88 22 44 800.
We are happy to assist you!
Source: RHP. You can download the RHP factsheet here.