D. Caplan, M. Dixon, Y. Zheng
Nov 1, 2019
Coir-based growing substrates for indoor cannabis production
This study investigated how different soilless growing mixes—particularly those based on coconut coir—affect cannabis plant growth and yield in an indoor setting. The goal was to determine which substrates perform best from early growth through to flowering and harvest.
The researchers tested several substrate mixes:
Some were coir-based blends with different properties for water retention and drainage.
One peat-based mix served as a commercial control.
All plants were grown under tightly controlled conditions for lighting, temperature, and irrigation, using a standardized fertigation program.
Key Findings:
Vegetative Stage: All substrates performed well during the early vegetative phase. The plants showed a good degree of adaptability to both wetter and drier conditions. This suggests that cannabis is fairly tolerant of variation in water-holding properties during early growth.
Flowering Stage: The differences became more significant during flowering. Plants grown in a drier coir-based substrate (referred to as U2-HP) produced approximately 29% higher floral yield compared to those in a wetter coir-based mix (U2). The drier substrate likely improved root oxygen levels and reduced risks of common problems like root disease.
Why This Matters for Growers:
Coir-based media can not only match the performance of peat-based mixes, but in some cases outperform them—especially when managed correctly during flowering.
Using a drier substrate mix may help increase yields and improve root health.
Coir also has environmental advantages over peat, which is less sustainable and increasingly scrutinized in horticulture.
Conclusion:
For indoor cannabis cultivation, carefully selected coir-based substrates—especially those with improved drainage—can offer both agronomic and environmental benefits. Growers aiming to boost yield and improve plant health should consider optimizing their media and irrigation strategies, particularly during the flowering phase.