PLANTS THAT PRODUCE

Plants That Produce

Self-Sufficient Produce Gardening

By Richard Frost^♦

I am very curious about the growing number of advertisers offering “self-sufficient crop systems” for outdoor patios and indoor/outdoor hydroponics. I see them at the Fairgrounds, Garden Shows, and the like. One sign read “Never Go To The Grocery Store Again”. Now in my childhood there were several years we did grow all of our vegetable foods – and of course went to the store for grains and meats. I’m really having a hard time imagining the magnitude of our vegetable crops fitting on a balcony at Chateau de Del Mar or in a suburban San Diego backyard, let alone the additional area it would take to produce the grains et al. So I decided to do some checking on what really is possible.

In the world of high-efficiency commercial agriculture, you can find farmers achieving amazing outputs, such as last year’s 93 ton per acre tomato harvest by a Kings County CA farmer¹. Ninety three tons of tomatoes would meet the 2,000 calorie per day requirement for 21 people for an entire year. But of course, we need more nutrients in our diet than just those found in tomatoes.

Agronomic studies have shown that by conventional farming methods, a minimum of 1.2 acres per person are needed annually to produce the volume and varieties of foods that constitute a nutritionally balanced diet. Using updated high-density commercial farming methods, this figure can be reduced to about 0.6 acres per person per year when averaged over a large population. About ¼ of that is for vegetables, another ¼ for grains, a little less than a ¼ for fruits, and the remainder for dairy, fish, meat, or vegetable protein production².

A homeowner can’t benefit from some of the efficiencies of scale possible on a medium size farm, but they can make improvements over traditional gardening practices. For this I refer you to the classic book “Five Acres and Independence” which details how to meet the annual food requirements for 5 people on 5 acres³. From the presentation in this book and many subsequent publications it is clear that a homeowner can not be completely self-sufficient with soil-based crops on much less than an acre.

Hydroponics does offer higher crop densities over conventional methods, not only because it can be done in isolation from the weather but also because the fertilizer program can be tailored to maximum crop performance. To understand what is possible hydroponically in a home setting, I first examined the proper spectrum of crops to grow from Cornell University studies⁴ and then computed capacity requirements from papers published by the University of Florida Institute of Food and Agricultural Sciences. Allowing for re-use of idle space, I obtained 1200 to 1600 linear feet of hydroponic troughs per person on an annual basis. In a very compact factory-like implementation, this works out to 4500 square feet of floor space, or 1/10^th of an acre. The largest system I have seen advertised to date is 120 linear feet, so apparently these sellers of balcony and small backyard food garden kits for “self-sufficiency” are only offering false advertising.

¹http://westernfarmpress.com/mag/farming_huge_tomato_crop/.

²Food, Population, and the U.S. Economy. Pimentel & Giampietro, 1994. http://dieoff.org/page40.htm

³Five Acres and Independence. Kains, 1973. ISBN 0486209741.

⁴Testing a complete-diet model. Peters & Wilkins, 2007. Renewable Agriculture & Food Systems, v.22 #2.

^♦SDHS member Richard Frost is a certified edible gardening nut. For copies of past articles and more information, please see www.PlantsThatProduce.com.

Reprinted with permission from May 2010 "Let's Talk Plants," the newsletter of the San Diego Horticultural Society, www.sdhortsoc.org