In traditional soil gardens seeds are planted in rows, and the spacing between each plant is normally referred to as the “in-the-row” spacing and is determined by how much room a mature plant will occupy.
In Straw Bale Gardening, we still use this standard in-the-row spacing but it is common practice to NOT plant in rows, but instead to plant like a checkerboard.
Or more accurately, plant every black square on a checkerboard.
The seed spacing should still follow the standard in-the-row distance for spacing, so no seeds are closer than that distance from one another.
The reason this works with bales is because the raised height of the bales allows better air circulation, and with vining plants we encourage the vines to grow up onto the trellis we build above the bales.
The trellis allows the plants to stretch upward and outward and utilize more of the vertical space above the bale.
Root growth in typical soil, tends to be somewhat more restricted than root growth inside of a bale. This can be a factor of compaction, or lack air space in the soil, whereas with Straw Bale Gardening the inside of the bale is much less compacted and allows much easier root growth down into the bale, allowing young vegetables to get a larger root system established earlier in the season.
This larger root system translates to a larger capacity to take up moisture and nutrients, which in turn translate to larger, healthier, and more plentiful production of produce.
Spacing in soil has to allow for these smaller roots which tend to grow wider instead of deeper where the soil is more compacted. In bales, this isn’t an issue, because roots can grow deeper that is traditional in a soil environment.
Seeding in a bale will be tighter per square foot that in a soil planting, but this ability to grow deeper roots helps compensate for that density.