Moisture Measurement on Peat-based Substrates vs Peat Alternatives

Peat based substrates have been used for decades since peat is relatively sterile, has good buffering capacity and its properties are easy to predict. New growing media, such as those containing wood fiber, coir or bark, are less easy to predict.

The so-called new substrates have lower buffering capacity for both water and nutrients, require higher N fixation and are more susceptible to pH fluctuations. Therefore, it can be necessary to adjust the nutrient supply and irrigation throughout the growing season to ensure good quality plants. The right measurements and measurement technology can help make decisions on how to adjust.

Moisture Management: Difference between Peat substrates and Peat Alternatives

New growing media are more susceptible to moisture fluctuations compared to peat-based substrates. Whereas peat has a great water holding capacity, peat alternatives such as coir and wood fiber have a much lower water holding capacity and dry up quicker. This is why new growing media often requires more often irrigation with smaller quantities of water. To ensure your crops receive enough water, substrate moisture measurements should be taken.

Available water in the substrate can be measured with tensiometers which are available in different lengths and designs and are uncomplicated in use. They are available for use in nursery goods from 12 up to 100 cm. Tensiometers measure the suction tension, i.e. the force that plants need to extract the necessary water from the substrate in mbar. This can give valuable insight into the moisture levels of a substrate and the need for irrigation.

Crops have different water needs even during different growth cycles. For example, when roots are not developed there’s and higher need of water. A normal range is 0.3-0.5 m³/m³ water/substrate

Other methods of measuring soil moisture are also available. Sensors that measure the percentage volumetric soil moisture (vol.%) or soil moisture in m³/m³ can be used to determine the amount of water in a substrate. This can be measured with handheld sensors or wireless sensors that can be placed in pots all over the nursery to get a real-time insight into soil moisture.

Trials conducted on substrates to measure the optimal moisture condition clearly showed that good re-wetting is crucial for successful cultivation. When using peat-free substrates H2Gro wetting agent has shown to improve the water balance, as explained on this article about H2Gro and Peat Substitutes

Conclusions

Planning regular monitoring of most crucial substrate’s parameters such as EC and salt or pH, as well as moisture level, is particularly important when growing plants on peat-free or peat-reduced substrates because of their different physical and chemical composition. Regular measurements help detect problems at an early stage.

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