Hemp is best suited to well-drained soils with a pH between 6.0 and 7.0. Hemp does not grow well in moist soils or in soils with a high clay content. Hemp is sensitive to crusting and soil compaction, which can occur in these soils. As early as 1943, we knew that hemp should be planted in the best fields.
The Department of Agriculture bulletin said: “Hemp should be planted in the most productive land on the farm (Farmer's Bulletin No. This means that growers can choose to plant hemp in a field where they would otherwise have planted a different crop. We know that hemp grows best in fertile fields that have abundant organic matter greater than 3.5%. The general reference recommendations of the CHTA eGuide state that the production of hemp grain requires inputs of up to 80 to 120 pounds of nitrogen per acre, 40 pounds of phosphorus per acre, 58 pounds of potassium per acre and 13 pounds of sulfur per acre.
In perspective, hemp requires approximately the same fertility inputs as a high-yielding row crop, such as wheat or corn. Soil test results should inform your input decisions for each field. Recommendations will vary based on these results. This is where universities that have done research on hemp can help.
Although seedlings will germinate and survive temperatures just above freezing, soil temperatures of 46 to 50 degrees Fahrenheit are preferred. Just because the seeds can germinate at 35 degrees Fahrenheit doesn't mean it's a good idea. Planting in soil that is too cold could cause it to become damp if it is also very humid, and many soil pathogens, such as cold and damp soils. It also means that hemp will grow even slower, giving way for weeds to compete with the plant if the weather is too cold and hemp can't quickly close the canopy.
Hemp should generally be planted after the danger of severe frost, usually between mid-April and May. Growers who transplant seedlings or clones have a larger window for planting. To account for differences in germination, emergence, disease, and plant competition, plant hemp for grain at 25 to 40 pounds per acre and hemp for fiber at 40 to 80 pounds per acre. Growers should conduct a risk assessment of how they are going to allocate field space to hemp and the possible consequences of doing so, such as losing money on hemp when something less risky could have been planted there.
Hemp grown for fiber should be sown as soon as possible, while hemp for grain should be sown later to minimize stem height. Growing hemp in the same place two years in a row would probably be OK, but hemp consumes a lot of nutrients.
