Irrigation is a difficult topic and can be made even more complicated when switching between medias. Special considerations need to be taken with specific media. Grodan’s Improved Hugo blocks are a popular choice for cannabis and come in 6x6x6” cubes of rockwool. These are most commonly used in greenhouses or indoor production. Understanding how to best irrigate these blocks from beginning of production to the end will set growers up for success.
Water holding capacity and moisture monitoring
“Field capacity” is the amount of water a substrate holds after a complete initial irrigation once excess water has drained away. A properly saturated Improved Hugo block has roughly 83% water content, weighing about 2650 grams. Keeping Improved Hugo blocks well irrigated means allowing them to try back to approximately 60% water content between irrigations. After transplant moisture meters can be used to monitor moisture levels inside the blocks. Without the use of meters, estimating or directly measuring block weight is a very traditional method of monitoring water content. Growers have historically used either the “pick-up” estimation method or a portable scale to get an idea of water content of media. As plants get larger, however, this method becomes less feasible. Grodan’s GroSens moisture meters are one tool growers can utilize regardless of plant size. GroSens meters can monitor individual blocks for moisture content over time, allowing growers to get an idea of how quickly water is being lost or taken up.
Why proper irrigation is important in the veg stage for cannabis cultivation
Especially just after transplant, the tops of blocks need to be well irrigated to prevent media dry down and to support newly developed roots from transplants. If the tops of blocks are not properly irrigated during this time, hydrophobic conditions may develop that can cause irrigation issues further down the line. Additionally, roots need time to extend down into the Improved Hugo block from transplant plugs – improperly placed emitters can lead to underwatered transplants.
Improved Hugo blocks benefit from the use of two or more emitters per block. Using multiple emitters helps ensure uniformity of irrigation as well as spreading out the total volume of water across multiple drip points. Emitters should be placed at opposite corners, or a drip ring emitter could be used. When drip stakes are used, care needs to be taken to avoid pushing stakes too deep, as this can lead to irrigation water running straight past rootzones and out of the block.
Contact your Griffin sales rep to learn about Improved Hugo blocks and the rest of the Grodan Improved line, GroSens, and the types of drip irrigation options.
For more tips on using Hugo blocks, download the full Grodan 101: Huge Blocks Best Practices document here!