Determining factors to consider are geographic location, soil availability, type and quality, and your business plan in general.
Fiber: Planted at higher concentration, around 50 pounds of seed per acre. Seeds are planted densely. Grow tall and thin, maximizing the quality and yield.
Grain: Planted at 20-30 pounds of seed per acre. Harvested at 3-5ft tall. Height allows for machinery to chop off tops and collect the seeds.
Medical/ Recreational: Planted apart to allow the plants to grow bushy, maximizing the flowers. Will mostly be female plants, unless breeding. Ensure it meets the desired levels of THC/CBD content.