101: get to Know the basics
Hemp is a unique cash crop because it can be harvested for multiple uses including grain, fiber, and flower. Agronomic practices will change according to the intended use of the crop. IndHemp is focused on working with farmers who are interested in growing hemp for grain production. This allows producers to utilize existing equipment similar for what is needed to plant and harvest a wheat crop. Hemp grown for grain typically utilizes genetics that result in a shorter stature and produces a more uniform plant that is better suited to being harvested with a combine. Hemp is a dioecious plant, meaning there will be separate male and female plants. It is also daylight sensitive and will initiate flowering once day length reaches 12 hours or less.
The foundation for any fertility program should be focused on creating healthy soils where nutrients are cycled efficiently and effectively within the soil profile. Plants maximize their energy production and usage when they are obtaining their nutrients in the form of microbial metabolites that are released from microorganisms. Green manure/cover crops, organic fertilizers such as hydrolyzed fish, manure applications and reduced chemical usage can result in soils that can support high yielding crops without a large amount of outside inputs. Nutrient recommendations when growing hemp for grain have been related to a wheat fertility program in the past, with crop needs estimated at 100 lb. Nitrogen, 60-70 lb. Phosphorus, 40-80 lb. Potassium & 30 lb. Sulfur per acre. These are only general guidelines and recommendations will vary widely and are based on results from soil testing.
There is a misconception that hemp can grow on marginal soils and still produce viable yields. While hemp can be a very hardy crop with good drought tolerance, it will show remarkable gains when planted into clean fields consisting of healthy soils with adequate fertility levels. Growing a green manure/cover crop in the year prior to planting hemp can provide an organic source of nitrogen as well as increase the nutrient cycling ability of the soil. Currently there are no herbicides listed for use in hemp production so proper field selection with minimal past weed pressure is highly recommended, along with good weed suppression techniques such crop rotation and cover cropping.
Pests and Disease:
Hemp has shown itself to be resilient against many pests and disease, but as with most crops, there are some diseases and pests to watch out for. European corn borer, army worms, and grasshoppers are a few insects to keep a watch for in your fields, along with fungal pathogens such as gray mold and white mold. Proper field scouting and Integrated Pest Management practices can go a long way in preventing issues with insect pressure alongside a good crop rotation.
Hemp’s natural canopied leaves works favorably for weed control but like any crop weed management begins by selecting fields with relatively low weed pressure in past seasons, and planting into those fields with little to no actively growing weeds. You want your hemp plants growing vigorously until complete canopy has been achieved with the goal being to shade out most weeds before they become competition. A great way to control fall weeds is to broadcast a cover crop into standing hemp prior to harvest. When the grain crop comes out of the field, there will already be an actively growing crop established to outcompete weeds that would otherwise germinate and grow in the fall months and can also contribute to increased soil fertility for next years crop.
Like most plants, hemp grows best on fertile loam soils with good structure, a pH of 6-7.5, and organic matter at 3.5% or above. The key to maximizing any crop, including hemp, is having good soil biology and a balance of soil minerals so that the plant receives all the nutrients it requires without being overloaded with excess applications of fertilizer. Soil testing is very important in determining what nutrients your soils contains in adequate amounts, and which nutrients it may be deficient in. By only supplementing the nutrients that are needed, you save money and maximize plant growth. You can utilize composite samples that represent similar soil types in 50-100 acre sections.
Hemp is planted relatively shallow with a recommended seeding depth of about .5-1”. While seed can germinate and grow at temps just above freezing, it is recommended to wait until soil temps have reached 46-52 degrees for good germination and early plant vigor. The typical seeding date in northern climates is mid-May through mid-June. It is important to plant into adequate soil moisture so that you get uniform germination resulting in an even stand. Germination typically occurs within 2-3 days, followed by emergence around day 5. Seeding rate for grain production is around 25-30 lbs/acre but is dependent upon individual hybrids. Hemp can be planted with a regular grain drill or air seeder, similar to what you would use to plant wheat.
Harvesting and storage:
Proper harvesting and storage is crucial and the difference between a successful or failed year. Hemp is best harvested for grain when the moisture content is around 15-20% to allow easier threshing through the combine and minimize seed loss during harvest. Because hemp is nature’s longest and strongest fiber not allowing the stalks or fiber to dry too much, “cutting while it’s still green”, will help your combine. Due to this higher moisture at harvest though, it is critical to begin drying the grain down immediately following combining. Many farmers have even suggested only filling your hopper trucks halfway before taking it to the bin to start aeration. To eliminate the chance for compost heating and molding limit yourself 1-2 hours transport time before grain is transferred to proper storage. It is critical that you have a plan in place to dry incoming grain before it comes time to harvest.
General combine settings as a starting point for harvesting hemp grain:
Cylinder Speed: 450-600 rpm
Concave: 30-50 mm
Wind: 1070 rpm
Sieve: 3 mm
Chaffer: 10 mm
Here are some helpful videos going into much more detail on all your agronomy questions: