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Streekstra’s Tips on Substrate Selection Published by ‘Urban Ag News’


Recently, Grow-Tech’s own Siebe Streekstra was featured in an Urban Ag News article about how to best choose a substrate for hydroponic production. Discussed in the article are tips about assessing the production system, the size of the production space, the manner of harvesting, and the type of crop to best choose a substrate that works for your needs.

As far as the production system goes, the primary consideration needs to be whether the substrate will crumble if it is in a system with recirculating water. In such a system, the crumbled substrate can cause a clog in the lines and the filters. If you are using this type of system, it is recommended that you avoid coir, perlite, and peat substrates.

When considering the size of the production space, holding plants in propagation for an extended time is beneficial and can be done using 1 or 1.5 inch plugs. This way, you don’t have to use up valuable real estate in your final growing space for smaller plants, instead only moving larger seedlings over.

Streekstra spoke on the topics of how your manner of harvesting and the type of crop you’re growing will affect which substrate is optimal for you. He notes that if you are cutting leafy greens, growers can opt for either a thick mat or a plug. While a mat is generally the cheaper option, a plug has more space and is preferred by many growers. Because the plugs are deeper, the roots of the leafy greens grow back more quickly, allowing for as many as eight harvests over a period of four months.

When it comes to microgreens, Streekstra notes the complexity of this seemingly simple plant. Even when grown indoors, he explains, the outside climate must be considered when deciding upon a substrate. He shares the example of a Las Vegas grower who has trouble growing in his greenhouse because the harsh conditions of the desert climate and its propensity for evaporation make growing microgreens difficult. The grower has to use a thick substrate, and Streekstra recommends that any greenhouse grower in a harsh climate do the same to help facilitate a healthy water cycle for their plants.

Though microgreens must be considered carefully, they can be grown without fertilizer inputs. The plants finish growing in only one to two weeks, so in that time they can use nutrients that are available without the addition of fertilizer, making an organic substrate a good choice for microgreen production.

Click here to read the full article at Urban Ag News and see all of the advice that Streekstra and his agricultural colleagues have to offer on the matter of substrate choice.