Current Hemp Agronomy in US

Written By: David Cook

Today, Cannabis Sativa is grown for industrial hemp purposes in the United States and is a strain characterized by reaching branches, long slender fan leaves and low THC content. Hemp production is very comparable to grain production. However, it is distinctly more varied in harvest and processing, which is very dependent on the components of interest such as fiber, grain, terpenes, CBD and more.

Seeding

Hemp is best grown in sandy-loam soils, but can be effectively produced in marginal quality soils. Soil fertility management should be done pre-planting, with similar nutrient requirements as winter wheat. Farmers have found that it is best to seed mid to late May .5”-1.5” deep when soil temperatures are higher than 50 degrees Fahrenheit. Row spacing may be tighter if harvesting occurs early, but typical row spacing should be 8” for weed management. Farmers target to grow 400,000 plants per acre for efficient grain production.

Growing

A growth spurt will occur early June with plants reaching waist to eye level by the first week of July. A positive characteristic of hemp is that this plant does not typically require any weed or pest control, which is beneficial for many reasons. Not requiring pesticide is of particular importance, because applying pesticide without strictly adhering to the label is a federal offense and no pesticides are labeled for use on any cannabis.

Harvesting

Harvesting depends on the harvested component of interest. Harvesting solely for fiber can be done very early in the flowering stage when the plant switches its energy to producing flowers and won’t expand much more in size. However, even with harvesting for grain, it’s best to harvest earlier rather than later, with ideal harvest to occur in late September. Combines can be used to separate large amounts of grain from straw. Larger and newer combines can work without modification, but most equipment will need to be prepped for new conditions. Hemp has indeterminate flowering so there will be mature and immature seeds on the same plant. The crop will die with hard frost and become increasingly difficult to harvest after 4 days. As more grain matures, more will drop to the grown so it’s critical to not delay harvest. Grain will have 20-30% moisture at harvest and needs to be quickly dried and cooled. The small seed and high moisture makes the grain hard to thrash, so field cleaning is often recommended prior to drying. Hemp is a fragile seed with high oil content that can go rancid quickly, therefore it needs to be dried to 8 percent moisture as soon as possible. Another import aspect of hemp production is the monitoring of the crop in their bins, as it may need aerating until bins can be frozen at earliest opportunity.

Field clean up

Tillage will be easiest within 4 days of grain harvest, where the cutting of fiber and bailing can be done with some discbine mower models. Bailing can begin at 15% moisture content, and in hemp growing, bail density is typically less than a hay bail. Heavy disking can be used to incorporate residue.