Climate effects: heat and drought are impacting growing conditions in some places

July and August are typically the hottest and often the driest months of the year for most of us in North America. Climate change is starting to create impacts that exacerbate traditional temperate and rainfall extremes in certain regions, as we have seen the past few months in the western states and western Canadian provinces. Staying nimble and prepared for changing conditions is increasingly essential.

Water, of course, is essential to the success of your hemp grow and, given current conditions in some locations, may require extra attention and resources this year. Maybe even for the foreseeable future. Good time for us to review some of the basics of watering!

First, let’s talk metrics. Correct watering is dependent on correct measurements. If you have an overhead sprinkler type irrigation system in place, you should calculate watering weekly by adding together the total inches of “rain” fall from both the sky above and your sprinkler heads. A simple rain gauge or two placed strategically in your field is all you need to get that done.

Those of you using drip irrigation will need to do a bit more math. Your metrics will be in gallons emitted from your irrigation tubes per every linear foot crop row. Here is a terrific model created by Lyndon Kelley and Eric Anderson, in July 2020 in Hemp Grower.

Now that we now how to calculate, what are the correct amounts of water to keep a hemp crop thriving through the hot, dry summer months? Before we answer that, we need to consider some of the factors that play into watering hemp. “Correct” will vary by region and weather patterns. If your area is getting excessive rain or suffering a drought, you will have to adjust your watering schedule accordingly. Likewise, arid growing regions are going to have to water more than those that are more humid due to the difference in evaporation rates. Cloud cover can also impact evaporation. Soil type is plays a role as well – heavy soils that have slow drainage will not need as much water as loamy well-drained soil. And plant maturity is an additional consideration – younger plants need extra TLC (and water) to get established to the point where they can withstand a bit of deprivation.

That said, hemp has a reputation for being a crop that doesn’t need a lot of water. Unfortunately, that’s not true. Throughout the growing season, most varieties will need about 25-30 inches of rain. Here in Colorado, our average annual precipitation (i.e., for the entire year) is roughly half that amount, so here in the arid southwest, we need to considerable irrigation to succeed. And keep in mind as you calculate that you’ll want to water more heavily early in the growing season when the plants are getting started.

We have a great article for you on Hemp Field Irrigation on our web site that does a deep dive into the watering needs of hemp plants and some details about drip irrigation systems. You can access that page here.