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7 facts to consider when choosing substrate for soft fruits

September 11, 2020

There are many options available for soft fruit substrates. Soft fruits grown on substrates are mainly strawberry and raspberry in the Nordics, also the cultivation of blueberries has increased in tunnels. Next, I will share a few things to consider when choosing the substrate for growing soft fruits.

1. Good water holding capacity and adequate airspace

To function effectively, the root system of plants needs optimal air- and water space in the substrate. The pore volume of the substrate must be high. We recommend coarse peat as a substrate for soft fruits. Coarse peat has sufficient airspace between peat particles which ensures healthy root development. Water storage and airspace can also be increased by adding moss and perlite to the substrate mixture. Perlite increases the capillarity of the substrate.

2. Durable structure

The structure of the substrate should last throughout the growing season so that the total pore volume does not deteriorate. Cotton grass and moss can be used in addition to coarse peat to improve the durability and water drainage of the substrate. Additionally, we have had trials together with our grower customers with so-called hard peat. Despite hard peat’s fine structure, it is permeable and durable growing media. The crop results have been excellent.

3. Suitable pH and good nutrient retention- and buffering capacity

The pH of the substrate should be suitable for the plant to be cultivated. The pH of the peat is naturally low, so it is easy to adjust it to suit each plant by adding lime. In limed peat, the pH remains stable, as peat buffers variations in pH. Peat reserves water and nutrients well, which means growers can use less water and fertilizers during the season compared to many other growing media.

4. Free from diseases and harmful microbial activity

Strawberry and raspberry are sensitive to various root diseases caused by fungal pathogens, for example, FusariumPythium, and Phytophthora. Root diseases can be prevented with biological and chemical pesticides and by using disease-free plant material. Also, the growing media used in cultivation must be free from these fungi that cause root diseases. Many fungal diseases in the root system like a damp and low-air substrate, so root diseases can be prevented by using a permeable and airy substrate. Useful microbes of peat and moss improve plant resistance to pathogens.

5. Good availability and standard quality

The availability of the substrate is important to the grower. When changing the substrate that has been used at the farm, it requires learning how to manage irrigation and fertilization, for example. Quality substrate does not contain impurities and should be homogenous year after year. The substrate should be free from weeds.

6. Sustainability aspect

Recyclability and environmental aspects are also important issues for growers nowadays. For example, transportation distances and substrate production methods are important when considering sustainability. The water and nutrient-reserving feature of peat and moss reduce the consumption of water and fertilizers, which is ecological and cost-effective.

7. Suitability for the plant to be cultivated and the farm’s cultivation technique

For example, the pot filling machines and the irrigation system that is used at the farm may influence the substrate choice. Often pot filling machines require that the substrate does not contain too coarse particles. For this purpose, for example, the previously mentioned hard peat is ideal for pot filling machines due to its fine design. If there are challenges in the function of the irrigation systems or the availability of irrigation water, peat and moss will forgive minor irrigation errors. Also, the substrate must be easy to handle at the farm.


Spring is the busiest time in tunnel farms. Kekkilä’s novelty product reduces the working time spent filling strawberries and raspberry pots. Read more about our new products from Container Board and Raspberry Block and other products for the soft fruit growers: 

Would you like to get some beginner’s tips for growing berries in tunnels? Read this article: Beginner’s tips for growing berries in tunnels.


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