Q. Other than being able to figure up the nutrient amounts for Grow-Boxes, is there a reason why they are only 18 inches wide?
A. Dr. Mittleider experimented with many different sizes and configurations over the years, and he settled on two widths as being the best. Eighteen inch-wide beds allow planting two rows of most plants, with a single PVC watering pipe down the middle of the box or bed able to accurately, thoroughly, and quickly water both rows of plants. Narrower boxes don’t give enough room between the two rows of plants, and there is crowding. And wider boxes don’t get watered as efficiently, and the space is wasted.
A 4′-wide box allows 4 rows of most plants (2 rows of climbing plants), with 2′ in the center for light and air. Planting is near both edges and 12″ in from the outside rows. Once again, this allows for very efficient watering with two drilled PVC pipes down the center of the two sets of rows. Boxes Wider than 4′ begin to waste space, and are more difficult to work the middle of the box. Narrower boxes don’t provide enough light in the center, and fewer plants can be grown.
Four foot box widths give the highest productivity in a given space, because the “aisle” between the two sets of rows is only 2′, rather than the 3 1/2′ of regular aisles.
The Mittleider Gardening books and Manuals teach all you need to know about this subject, and can be purchased in the Store section, or as digital downloads.
A digital copy costs 30-40% less, and is available instantly! I HIGHLY recommend you look here https://www.hightechhomestead.com/Products.htm for the best gardening books available anywhere! Get one NOW and be gardening TODAY!!