Myth-busting: Hemp needs more water than many think

, Myth-busting: Hemp needs more water than many think

Hemp isn’t as immune to drought as supporters claim, according to a Colorado State University soil researcher who analyzed two years of Colorado hemp production.

“There are a lot of myths about this crop, and one of them is that it doesn’t need much water,” said Brian Campbell, a doctoral student in Soil and Crop Sciences who monitored hemp’s water use on two Colorado plots in 2015 and 2016.

Campbell saw his hemp plants – some seed varieties and some fiber varieties – struggle without irrigation.

“It’s not that the plant won’t grow” without much water, Campbell explained.

“But it’s a no-brainer – you should irrigate your hemp plants if you want them to do well in Colorado.”

He presented his findings last month at the Institute of Cannabis Research conference at Colorado State University-Pueblo. He’s awaiting publication in an agronomic journal.

Campbell found that hemp’s reputation as a good dryland crop – meaning a crop grown without irrigation – isn’t deserved in areas without abundant rainfall.

On his northern Colorado plots, for example, Campbell grew one hemp plot with regular irrigation and the other in drought conditions where the plants got only about 8 inches of rain during its life cycle. The irrigated plants yielded a healthy average of 1,100 pounds of seed per acre, with some acres producing more than 2,000 pounds of seed per acre. The nonirrigated hemp plants yielded an average of just 400 pounds of seed per acre.

“I’ve heard a lot of people promoting hemp as a low-water-use crop, and from what I’ve seen, it’s pretty high compared to other crops,” said Campbell, who specializes in specialty oilseed crops. “I wouldn’t suggest dryland cultivation here without irrigation.”

Campbell’s water research is among the first studies to apply modern large-scale farming methods to a crop still shrouded in mystery. Decades of illegality for hemp production has left the crop way behind other commodity crops in terms of what agronomists know about how to grow it profitably.

Purdue University’s Hemp Project reports that most varieties of hemp need about 25-30 inches of rain a year, especially in the early weeks of life. But that’s about as exhaustive as university research into hemp and water use goes.

Purdue’s research also applies only to the American Midwest, and researchers warn that the hemp industry is plagued by “large information gaps that have developed with regards to production, pest management and economic impact.”

Campbell’s work resonated with some Colorado hemp farmers who attended the conference.

“You definitely need to do some irrigation,” said Bridget Gay, who grows and processes 50 acres of CBD-rich hemp in central Colorado for her company, High Country Lab.

Gay has grown hemp since 2015 and has learned through trial and error that her hemp plants need roughly 6 gallons of water per week to thrive.

“It doesn’t grow on its own unless you’re by a stream,” she said.

Campbell noted that he researched seed and fiber varieties, not the flower varieties grown by Gay and most other hemp farmers. Campbell pointed out that much more research needs to be done around growing CBD varieties of hemp.

“Cropping for CBD, there’s nothing out there” to tell farmers how much water they need, Campbell said. “It’s all shooting in the dark right now.”

5 comments on “Myth-busting: Hemp needs more water than many think
  1. William Bliss on

    I think your research is important. I’m farming A 20 acre lot myself this year. I’m doing flood irrigation under special conditions and equipment. I would like to hear more about the fertilization that you used and how often it was distributed to the plants. It would be interesting to see the amounts at specific times that you used water without fertilization and when you started using fertilization and in what levels you used. Thank you

  2. Alan Aragon on

    Im on a water rotation schedule and I flood irrigate . I have the water for 4 days 6 in the morning to 11 at night twice a month / question would I half to get a storage tank ? .And how many acres would that irrigate . I have 15 acres .alan A

    Alan Aragon 575 533 6514 phone Thanks

  3. Prime Kind Farms on

    I find it funny that so many seem to tout quantity, duration and frequency as an umbrella construct for hemp and its yield potential. While water is certainly an important aspect of a successful hemp farm it is in no way remotely a constant standard across the board. In my opinion water use is relative only once you have fully realized your given set of variables:
    1.Soil type and available biological matter.
    2. Ambient Temperature range and soil temp.
    3. Solar exposer duration (your water rate/frequency should not be a straight line but should vary given seedling, growth, flowering)
    4. Irrigation type: drip with plastic ground cover, exposed drip, or flood. All radically different on water consumption rate.
    5. Elevation and other environmental aspects that directly increase or decrease evaporation.
    Having been in small scale agriculture (30acre family farm) my entire life as well as hemp the last few years I think it is important that we keep an open mind to acceptable practices that make sense given the agricultural target for the the given farm but we really need to be mindful of overuse hype without making sure our set and setting have been properly tuned first. If the 5 points above have not been worked through or if you are setting a farming target with hemp in a zone it is not ideally meant for then yes by all means you will need way more water than the plant needs ideally.
    We average out at 1,200 gallons per week per acre on our hemp with a yield rate 1,000 pound of cbd flower to the acre. Again we have have over 45 years of activity farming and building our soil and have really focused on bioavailability of soil based amendments. We have also tried to use alfalfa mulch with clover instead of plastic but this proved to notably increase water consumption. While great in theory and impact it is simply not practical at scale or in our soil. With that said I have helped consult with many new hemp farmers and have found that in some heavier souls bodies the alfalfa mulch with clover had better overall plant health and productivity in yield over the plastic much options. I would also say if you are not using subsurface drip lines you are either misinformed or at a non sustainable scale (if you are concerned with water consumption to yield ratios)

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