Planting the Seed
The ideal planting season for hemp in South Dakota has been Early May when soil temperature has reached 50 degrees Fahrenheit. When planting hemp seed, it's best not to chase the moisture too deep or you'll risk crusting over. A half inch to 1 inch is plenty, but you will want some good seed to soil contact. Consider rolling your field after planting to help ensure an even emergence of your crop. We recommend using a grain drill because your rows will need to be fairly close for making its canopy. Between 6 to 15 inch wide rows are ideal for weed control. Either an air drill or mechanical drill will work on the sorghum sized setting. The only chemical approved for hemp in South Dakota is a pre-emerge called Sonalan. It helps to keep the weeds down while your crop establishes a canopy. There are two ways to grow industrial hemp. One is for the grain (Seeds) and the other is for fiber (Stalks).
Growing for Grain
When growing for grain, we have found that 30LBS of seed per acre is ideal for getting a more uniform field height. During your growing season, the recommended fertilizer rates are 120/30/20 NPK for grain types of hemp. You will know it is the right time to collect the seed if you can clap your hand a few times with a seed head removing around 40% of the total seed. Another indication for us has been the amount of Mourning Doves that inhabit the field and powerlines. You can use a regular bean head combine to target the upper 2-3 feet of seed head leaving behind the residual stalks. Recently we have changed our head from an auger to a drape for a steadier flow entering the feeder house. Also, we have found that swapping your concaves to have larger openings allows the seed heads to enter without wrapping up. The seed is harvested while it's still 20-25% moisture, which means you will want to get the grain on air immediately. Be sure not to use heat when drying your seed or you will cook out the seed oil. Keep your crop in your bin on air until it reaches 10% moisture. This process could take up to two weeks and could require re-elevation. Basically, just empty your bin into a couple of grain carts and refill it again with the air still on to help clean out some remaining debris.
Growing for Fiber
When growing for fiber, we have found that 22LBS of seed per acre is ideal for getting a more uniform field height. During your growing season, the recommended fertilizer rates are 60/30/20 NPK for fiber types of hemp. This a 100-day crop planted in early May and harvested in September. During the vegetative state the stalks will grow tall and fast, making jumps in height weekly. Once the sunlight gets to a certain number of hours per day your plants will change to a reproductive mode. At that point your field may only get another 1-2 feet taller. You will want to harvest before the seed has reached full maturity. The best way to monitor your field is by looking at your fiber development. Cut a stalk into 18-inch sections paying attention to the air space in the center. As the plant matures the center will fill out with hurd resulting in greater tonnage. You can harvest with a sickle bar or swather (With Crimpers Spread) to cut down the stalks. Be sure to leave 6 inches of stalk to protect your tires and for creating a bed of air for the stalks to rest on. The stalks will need to remain in the field for 2 weeks to begin a process called retting. During this retting process the stalks will get wet at night and dry during the day naturally removing lignin in the outer fiber. After two weeks you can come through with a rake to move the stalks into rows. After Raking you will need to leave the rows in place for another two weeks. Now that the retting process has completed, you can come through with a round or square baler.