Maximizing your crop’s productivity puts more change in your pocket and proper irrigation is a critical factor in getting the best yield from your acres.

Calculating water needs

Irrigation is not a “set it and forget it” proposition. Your crop’s need for water is determined by multiple factors – some of them dynamic, meaning that these are changing and evolving over the course of your growing cycle. Shifting requirements compel us, as crop farmers, to keep an eye on field conditions and adjust flows as needed throughout the season. Hemp is not an especially temperamental crop when it comes to water needs, but you’ll get your best output if you keep your plants from stressing from too much or too little water. Here’s what we’re monitoring:

Plant life stage

Young plants need a bit of extra moisture as they get established. As the plants mature, they become hardier as the roots fan out and they more easily tolerate less-than-ideal conditions. As harvest approaches, proper hydration will help plant THC levels from elevating too much and too quickly.


Goes without saying, really. You know that rainfall – or lack of it – is going to impact how much or little supplemental water you need to deliver to your hemp plants. While hemp is typically pretty drought tolerant, the stress of a drought can have a negative impact on your crop’s productivity. Conversely, hemp plants are not well suited to soggy conditions. Mother Nature can be capricious, so we are likely to be transitioning through periods when rainfall is over- or under-delivered and we’ll have to react accordingly. Since most of us are aiming to achieve bumper-crop status, we know that supplemental water is often going to be essential to get the results we want. Over the course of the growing season, hemp needs between 20 and 30 inches of water. Rain gauges are a good way to track this, but also walk your grow regularly and probe the soil with a moisture meter or your finger to check the moisture level. You’ll no doubt notice that the amount of sun, the average daily temperature, and the level of humidity in your location plays a role in how much you need to irrigate as all these factors impact evaporation rate.


If you read my March blog on Soil Basics, you know that different soils have different drainage rates. If you haven’t done it already, I encourage you to do a percolation test (easy, no cost) to determine how much water your soil holds and for how long. Hemp likes well-drained soil. You can help your plants thrive by staying on top of the moisture level in your field and adjusting your irrigation flow accordingly throughout the season. If you have heavy clay soil, amending your soil over time with organic material will improve drainage.

Additional Tips

Filtering water is a necessity, even if you are connected to a municipal water system. Filtering excess solids will help you control pH levels in your soil and, depending on your source, livestock fecal matter.

Install the correct size of filter and check filters regularly for buildup. Additionally, it is critical to regulate your irrigation water pressure as measured in PSI (pounds per square inch). You need enough force to get the water to flow out to the farthest reach of your system, but not so high that you are risking damage to your equipment or crops. Your best bet is to consult an irrigation professional in your area who can help corroborate your system installation and functional settings.

Final words

Don’t get too locked into the metrics of watering. Knowing your plants is a skill you want to develop so that you can visually recognize signs of plant stress. This is insight we develop over the course of many growing seasons. As you increase your abilities as a grower, there may be times when your rain gauge is telling you “all is well” while you can see with your own eyes that you need to irrigate. Whether you use drip, pivot, or flood irrigation methods, knowing how and when to irrigate will contribute to a successful harvest.

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