Updated: Feb 27
Hemp is a highly adaptable plant that can survive in a multitude of climatic conditions. However, if you are growing for CBD or CBG, adequate water is crucial. For optimal vegetative growth, flower production, and overall plant health, hemp needs around 20 to 30 inches of rainfall per season. If your area does not get sufficient rainfall during the growth cycle, we recommend adding a proper irrigation system to your operation.
Know your Soil
Different soil types will require different watering amounts. Light, sandy soils with more drainage will require more water, whereas clay soil has smaller particle sizes and retains the most water. Silt and loam soils have medium particle sizes and have moderate water retention. Sandy loam tends to be the highest-regarded soil type for root structure development, water flow, and a lower risk of soil-borne diseases than heavier soils.
Drip irrigation is a favorite for growing feminized hemp. When used correctly, this irrigation method directly applies water to the root area, meaning minimal water waste. Since drip irrigation runs at the plants’ base, the risk of leaf and flower diseases is lower. Drip irrigation is also highly compatible with plastic or biodegradable mulch, which can be extremely useful for weed control around the hemp plant. The application of water-based fertilizers during the growth cycle is also straightforward with drip irrigation. A downside of drip irrigation is that it has little to no reusability and can be a significant ongoing expense year after year. There is also a labor cost associated with laying it down before planting and ripping it up around harvest, as well as ongoing maintenance and repairs of drip lines that may become damaged and cause leaks.
Overhead irrigation is the most common form of irrigation in the US for rotation crops like soy, corn, wheat, and milo. This rainfall-like system is ideal for densely-grown crops as well as the incorporation of surface-applied fertilizers. Another upside for overhead irrigation is that once the equipment is purchased, there is minimal ongoing cost compared to drip irrigation and plastic mulch, which needs to be re-purchased year after year. While overhead irrigation is beneficial for farmers growing many crops year-round, it is not ideal for feminized hemp production. Frequent leaf-wetting of the hemp plant can lead to mold and mildew, which can quickly spread within a field and be a detrimental crop killer. Additionally, feminized hemp requires a minimum spacing of about 3 feet plant-to-plant, meaning substantial water waste with overhead irrigation. Plastic mulch for weed mitigation will also be rendered impractical as the water will run off and not be absorbed where needed most.
Too Much of a Good Thing?
Just as too little water can cause hemp to become sick, too much water can do the same. Overwatering can lead to a lack of oxygen absorption at the root level, causing the plant to become nutrient deficient, experience yellowing or browning, and eventually die if the problem is not corrected. The timing and growth of the hemp plant, along with weather conditions, can help you plan and adjust your watering schedule accordingly. Hemp plants generally require more water during vegetative growth, less during the early flowering stages, and more water during late flowering.
Sunnyland Kansas used drip irrigation combined with plastic and biodegradable mulch in the 2020 growing season and plans to continue using this method in 2021. The recommendations in this blog are meant for informational purposes only.