By Karla Garcia and Deidre Hughes
Substrates are a key element in hydroponic systems. As growers, we must learn the needs of the hydroponic system and crop. Crops and hydroponic systems demand particular characteristics from growing substrates.
Most importantly, what are the advantages of using soilless substrates? When using substrates in hydroponic production we don’t need arable land, meaning we can work in any space where we can create the ideal conditions for good plant growth and development. Also, good substrates provide you control over the root environment, helping to calculate a more precise irrigation schedule, improve crop uniformity, and limit root diseases.
How can you recognize a good quality substrate?
When you work in the hydroponic industry you will notice there are plenty of options for substrates. In this article we will teach you which characteristics you should look for in substrates in order to provide a better root environment for your plants.
Physical properties in substrates include porosity, water retention and drainage.
Porosity is directly related with root gas exchange and root aeration. Total porosity (%) in your substrates will tell you the sum of all the space in macro and micro pores presented in your substrate. Usually larger particles increase air porosity but decrease water holding capacity which can require frequent irrigation cycles depending on your crop. Substrates should retain about 50 to 65% of moisture as minimum to satisfy water requirements. In hydroponic systems we usually look for porous and well drained substrates.
Chemical properties include cation exchange capacity, pH, nutrient retention and chemical stability. In hydroponic production we look for low cation exchange capacity levels in all substrates. This characteristic will help provide targeted plant nutrition based on your hydroponic fertilizers and also will increase stability over time at the root zone.
Also, pH is very important. pH will help provide the ideal environment for nutrient uptake. A general range of ideal pH in hydroponic substrates is between 5.0 and 6.5. However, this can change depending on your crop requirements.
The use of high quality substrates allows the grower to use more standardized production practices, such as fertilization and irrigation.
At Hort Americas we offer multiple options of high quality substrates.
- Rockwool from Grodan: Rockwool is recognized for its low bulk density, ideal porosity, good aeration and high water holding capacity. It can provide a pH of 7 and stands out from other substrates for its non-cation exchange capacity. Grodan rockwool is available in different plug sizes, in blocks, in bags/slabs and even in sheets for super clean microgreen production. The different slabs have different drainage qualities. For example, if you are an experienced grower you may go with the Master slab that holds more water, so you can use Precision Growing techniques to steer your crop vegetatively or generatively. If you have less experience with irrigation techniques, or lack sensors to let you know what is happening in your root zone, you may choose to go with the Vital Slab for ease of irrigation.
- Coconut coir from Jiffy: When choosing coconut coir as a substrate, it is really important to look for good quality products. Some coco products can contain high amounts of salt which can add difficulty in managing your hydroponic system. However, good quality coconut products can provide great conditions for the rootzone. Coconut coir has good aeration and water holding capacity. It also offers a pH between 5.6 and 6.6. Jiffy is a brand committed to providing high-grade products, all-natural, compostable and biodegradable such as the Jiffy Growblock. These are manufactured from a 100% RHP certified coco substrate derived from pithy tissues of the coconut husk at the Jiffy production sites in Sri Lanka. Jiffy Growblocks offers you a renewable, environmentally friendly substrate with zero disposal issues. This product can be used to grow tomatoes, cucumbers, bell peppers or any other crop. Jiffy Growblocks are a perfect match with the Jiffy Growbag, completing your hydroponic system with a high quality stabilized substrate and favorable air/ water ratio for the crop.
- Hydrokorrels: Hort Americas also offers an expanded clay aggregate. The particle sizes range from 8-16mm giving this substrate excellent drainage. Commonly used in combination with dutch buckets, it is lightweight and reusable with proper cleaning between uses. Be aware that the clay pebbles have a higher CEC than the other substrates mentioned above. Clay pebbles can also be mixed with coco coir or other substrates for added drainage capabilities. At $16 per 40 L bag, you won’t find a better deal on these anywhere.