Part I stated that seed crops in wet humid climates should be planted further apart. This helps disease management and plant development. The other thing seed growers worry about is how does that affect seed yield?
Crop Spacing and Yield
A plant usually produces an amount of seed in function of its size. A small plant produces less seed than a larger plant. But, you can fit more small plants in a given area than large plants. Does this all balance out?
Sometimes it does:
If I plant arugula 30 seeds in one rowfoot and they all bolt, I will probably get less seed from all these stunted little plants than if I had 1-2 plants per rowfoot.
Sometimes it doesn’t:
I’ve grown beans at both one plant per rowft and at 2 plants per rowft. Both densities produced about the same yield per area. Wider spacing means more space between plants. This helps reduce disease pressure. You also have less actual plants to handle when threshing and harvesting. Smaller spacing means more plants in the same area. You get a larger genetic population (more on that in future posts) and smaller easier to manage plants.
Sometimes it’s hard to tell without a well-designed trial with multiple replicates.
What spacing should you use?
You can consult the seed books and see what numbers they recommend. Be aware that they might not be targeted to your climate.
Try one plant density this season. If it works, do more of the same next year, or even tighten your spacing if you’re feeling cocky. If you’re not happy with the results, give your plants more space in the future.
Of course crop spacing is only one of the management decisions you can make to get a crop to maturity. Soon on going to seed I’ll tackle some other thoughts on seed disease management. I’ll also cover the importance of selecting planting dates.