The following is a white paper on a cannabis study using PIP Pulsating irrigation vs convention drip. Please email with questions or concerns.Cannabis Study 2016 - Kendall Ford.docx (984.8 KB)
Interesting! A couple notes: the traditional dripper flow rate was not mentioned, and anything over 1.5 L/H (0.3 GPH) will cause channeling in virtually all hydroponic substrates, including organic soil mixes that don’t have clay content (basically anything but natural soil in the ground). If those were typical 1 GPH or 0.5 GPH emitters, that could definitely be the reason for the channeling.
Pulse fertigation is the go-to method in commercial vegetable and flower production, and the same results seen using these pulsators would likely be seen by using two 1.2 L/H pressure compensated drip stakes per plant and following a 10% draw down of RAW during veg and a 20% drawn down during the generative phase (aka flower). In a 3 gallon pot using top dressed fertilizers and no salt-based nutrients for example, we would be talking a 210 mL pulse given multiple times a day during veg, then a 420 mL pulse given with double the time in between during flower, with no runoff at all. Playing with the time in between during flower will give allow you to really dial it in. The goal is to maintain a WC close to field capacity during veg, then allow a little more dry back and more time before and after the start of irrigation cycles for the day during flower. The total amount of water given will be the same, but larger, less frequent irrigation cycles will lend to a dryer substrate and higher fertilizer concentration overall, steering the plant towards focusing on generative growth.
Just wanted to throw that out there.
Thanks for the study! Love seeing stuff like this starting to be done with cannabis like it is in the rest of the commercial Ag world!
Thanks for the feedback Josh. FYI - the flow of the conventional drip was quite high. If my memory serves me, the grower used 2x8LPH drippers irrigating in 20min increments.
The idea behind using Pulsators was to lower the flow to 4LPH with a wetted surface area covering the entire grow bag (roughly 2’ x 2’). The grower was able to get a consistent wetted area and maintain soil moisture content over an extended period.
We have a different trial ongoing using a Pulsator with a manifold downstream in 2 gallon pots. The flow will be reduced to a fraction of a liter per hour per pot.