We established our first industrial hemp trial this spring with the objective of examining several production variables for growing hemp for grain purposes. We sourced six varieties from Hemp Genetics International that varied in height and other traits and evaluated seeding rates, N rates, and planting dates. In addition we did a demonstration planting with a no-till drill in both tilled and no-till seedbeds.
The trial has been a learning experience for us and we are developing some ideas about best management practices. One of the biggest challenges in growing hemp is weed control as no herbicides are labeled.& We used a tilled seedbed and worked it several times before planting on June 6. This helped with weed control but we still got pressure from pigweed and lambsquarters. In our drilled demonstration strip, compared to the 15-inch rows in our plots, the hemp appeared to suppress the weeds more.
Our variety test is showing some striking differences in height among the varieties. I would opt for taller varieties in our situation where we are managing without herbicides. In Canada, where herbicides are available, newer varieties are shorter to facilitate harvesting.
The planting date trial had three planting dates that ranged from June 6 to June 21. We had planned to start in late May but our seed delivery was delayed. It appears that hemp can tolerate later planting and ripen but plant height is reduced and yield will likely be reduced as well. The taller varieties are approximately 5 feet tall in the early planting and 3 feet tall in the later planting. I suspect a late May planting would be nearly ideal. This week, approximately 60 days after planting we have seeds in the soft dough stage in most varieties.
Our nitrogen test is showing a dramatic response to N and based on a visual score I would estimate the optimum would be near 150 pounds. The previous crop in this field was soybeans. The seeding rate trial appears to show a benefit to a heavier seeding rate than we anticipated, perhaps 30 pounds per acre. Hemp is susceptible to crusting and we had some in our trials. The heavier seeding rate could help suppress weeds as well. With the rapid development of the hemp plant, there is probably less ability to compensate for reduced stands than we see in full season soybeans.