Retained samples – not a nuisance, in fact, valuable!
Taking substrate samples, analysing them and finally storing them in a cool, dark and dry place – it might all sound at first like a lot of extra effort for no clear return. Nevertheless, these steps are important, especially for smaller nurseries who can’t absorb noticeable losses in sales. Shortfalls in receipts can hit you sooner than you think if crop development turns out to be less than ideal.
Gütegemeinschaft Substrate für Pflanzen e.V. strongly recommends that all growers take one representative retained sample of each lot as a standard, whether of purchased soils and growing media or media mixed in the nursery itself. For a chemical analysis, 2-3 litres of sample material are enough. By using retained samples, you can localise potential causes of problems much more accurately. The association also recommends that substrate samples be taken on a regular basis as a matter of good practice, because they reveal any errors in cultivation management (such as plant nutrition) at an early stage.
Evaluating analysis results properly
If the analyses show any abnormal values, you should immediately contact your substrate supplier’s external consultant or sales force. Sometimes, things aren’t as bad as they seem. Since organic substrates are natural products, slight fluctuations in chemical properties are completely normal. As long as they are within the thresholds defined by the producer, they do not reduce the substrate’s quality. Also make sure to allow for a certain measuring tolerance when interpreting your lab results. However, if the analysis results give rise to concern even from the substrate professionals’ point of view, you will need to find the causes. Working together, errors are usually tracked fast and you will be able to initiate appropriate countermeasures quickly. This will help you keep damage at a minimum or avert it altogether.
Convenient: RAL-certified substrates
Whether constituents, additives or ready-to-use soil mixes and growing media: products carrying the RAL quality mark are subject to strict quality control. They are analysed for pH value, nutrient content, structure stability and potential contamination with plant-damaging substances by independent labs on a regular basis. Producers of RAL-certified products are obliged to take retained samples and are repeatedly inspected for correct sampling and sample analysis. Therefore, Gütegemeinschaft Substrate für Pflanzen e.V. strongly recommends that growers exclusively buy quality-certified products.