Grow. Bloom. Harvest. Dump all that media. Buy a load more. And start all over again. It’s a cycle that many of us, as indoor gardeners, are all too familiar with. Whether you choose to grow in soil, coco coir, rockwool, clay balls or soilless mix, chances are, when the crop’s been chopped, invariably it’s back to your local grow store to reload with fresh media. However, it turns out that lots of indoor growers (especially those growing short-cycle annuals) choose a different route. They reuse their growing media! And before you think this is just the preserve of pennypinching hippies, it turns out that it’s not all about saving a few dollars – it could increase your yields too! Aha, there we go … increased yields … that’s all we needed to say, wasn’t it? It’s worth pointing out that not all growing media is suitable for re-use. So first, here’s what you should factor into your evaluation: Structure stability
Nutrient retention
Practicality
Now let’s look at coco coir in these three terms. Coco coir, as a soilless growing media, is usually a mix dust and fiber, but some mixes can also contain larger coir chips. 1 Structure Stability Good quality, buffered coco coir, will keep most of its attributes throughout its useable life. However, the structure of steam sterilized coco coir will degrade faster than its un-cooked counterpart. For the purpose of this discussion we will assume that the coco coir is soft water washed, unpasteurized and chemically buffered; this represents the majority of coir available to hydroponic growers. Coco coir’s miniature “sponges” will become misshaped and smaller towards the end of their life, resulting in less air space between particles and an overall higher water holding capacity. Even though this is a slow process, some adaptation in watering may be required. After using coir for short cycle crops, amendments with 10-20% fresh coir or perlite may be required when being reused for the 3rd and 4th cycle. Care must be taken with the irrigation regime and nutrient program to insure the coir has an adequate life span. Principally, good watering practices and monitoring run-off EC (keeping it within optimal range) will permit seamless re-use.
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REUSING MEDIA: COCO COIR About the authors: Robert Hunt is the owner of Rocky Mountain Hydroponics in Golden and Edwards, CO and of Evergreen Garden Center in Portland, ME. Zac Ricciardi is the products trainer for Rocky Mountain Hydroponics in CO.
2 Nutrient Retention Buffered coir remains relatively chemically stable throughout its life, particularly when used with a coco coir specific nutrient; formulated to complement the unique cation exchange properties of the media. Coco coir can be easily EC controlled by monitoring the EC of the run-off. Watering with a low EC nutrient solution will reduce its EC without rinsing off the famous buffer. If plain water is used in excess, the coir may be rendered chemically imbalanced and may create problems in subsequent culture. On the other hand, coir reacts quickly to low EC rinse and thus it requires much less run-off than peat mixes. Unpasteurized coco coir is also a very hospitable substrate for its natural beneficial fungal inhabitant trichoderma, making it a very disease resistant and root protective growing medium.
In the early days when coir was first introduced into the hydroponic market, the pre-treatment process was overlooked. Young non-composted and nonbuffered coir products were sold without instruction and many growers suffered major nutrient issues and lost crops. Although these days are behind us, this initial introduction to coir tarnished its reputation as a quality growing media for many years.