In the last post I estimated the amount of calories, protein, and calcium that this year’s vegetable garden design can provide, using a combination of yields obtained for crops already harvested and the best yields I have obtained from previous years’ gardens for those crops still in the ground or that failed. I want to emphasize once again that I used actual yields that I have obtained for actual varieties in my actual garden in order to do this nutritional analysis. All other attempts that I know of to analyze the nutrition available from a small backyard garden have assumed Ecology Action’s mid-range yields for a small number of crops that may or may not grow in a particular region. Furthermore, the minimum-area designs in One Circle do not allow for easy crop rotation, so it might be difficult to sustain yields over a period of years.
My 2021 garden falls far short of providing enough nutrition to sustain one adult human for a year because it does not grow a large enough area of high-calorie crops such as grains, potatoes, leeks, and garlic. Suppose, then, I design the garden in blocks that I can rotate such that no plant family is repeated in the same bed more often than once in four years and include higher percentages of the high-calorie crops in the design than I do in my actual garden. Crop rotation reduces the buildup of pests and diseases that can happen when crops of one plant family are grown repeatedly on the same land area, and it also helps to avoid imbalances in soil minerals that can build up under the same conditions. What is the minimum area of this type of design to provide an adult with a full year’s worth of calories, protein, and calcium?
Ecology Action suggests that a minimum-area garden should have grain and fava bean crops planted in about 60% of the garden, potatoes or other high-calorie root crops in about 30% of the garden, and the rest planted to all the other crops. If we are to have a four year rotation between crop families like the grass family (corn), the bean family (soybeans) and the nightshade family (potatoes), then a garden plan allowing for that rotation would include one block of corn; one block of soybeans; one block of potatoes; and one block containing crops in plant families other than those three. This last block should contain substantial amounts of Ecology Action’s other special root crops, as given on page 40 of the 8th edition of How to Grow More Vegetables (HTGMV).
Let’s start with a 1600 square foot garden design containing four blocks of 400 square feet each. Each 400 square foot block contains four 100 square foot beds. I’ll design the garden as follows.
Block 1: four 100 square foot beds of dent corn.
Block 2: four 100 square foot beds of soybeans, harvested green.
Block 3: four 100 square foot beds of potatoes. After the potato harvest two of the beds are planted to turnips (cabbage family), with both the greens and the roots being eaten, while the other two beds are planted to bok choy (cabbage family).
The four beds in Block 4 will be planted as follows:
One 100 square foot bed to winter squash (cucurbit family)
One 100 square foot bed to beets (amaranth family)
One 100 square foot bed planted half to leeks and half to elephant garlic (allium family)
One 100 square foot bed planted to potato onions (allium family)
Notice that the garden design allots about 25% of the garden area to a grain (corn) and another 25% to soybeans (not fava beans as HTGMV recommends, which don’t grow well in this climate). About 30% is planted to potatoes, garlic, and leeks among the special root crops. The other beds are planted to other crops that yield well in my garden and are good sources of various nutrients but are not as efficient at producing either calories or protein.
The spreadsheet below shows the calories, protein, and calcium this garden design provides. The values for calories, protein, and calcium per pound for each crop were obtained from the 8th edition of HTGMV. The yields are the best I have obtained for that crop as shown in the spreadsheet in my post on the 2020 garden results or, for crops that have already been harvested, the yields I have obtained in 2021. As with the previous post, I compared the result to the daily requirements for calories, protein, and calcium as given in the book One Circle.
This is encouraging; the calories have more than doubled compared to the 2021 garden design although still not up to the daily need, protein is borderline, and there is more than enough calcium. Suppose I increase the garden design to 2000 square feet, planted as follows:
Block 1: five 100 square foot beds of dent corn.
Block 2: five 100 square foot beds of soybeans.
Block 3: five 100 square foot beds of potatoes followed by three 100 square foot beds of turnips and two 100 square foot beds of bok choy.
Block 4: one 100 square foot bed each of garlic, leeks, beets, potato onions, and squash.
The spreadsheet below gives the calories, protein, and calcium for this garden design. The values are higher, but still short of the daily requirement for calories.
If I designed a garden with a higher percent of the area devoted to corn and potatoes, a garden of about this size would provide an even higher fraction of the daily requirement for calories and protein. To do this, let’s consider a design with a three year rotation, as in my real-life garden. Here’s a design for a 1500 square foot garden with a three year rotation:
Block 1: five 100 square foot beds of dent corn.
Block 2: five 100 square foot beds of potatoes, followed by three 100 square foot beds of turnips and two 100 square foot beds of bok choy.
Block 3: two 100 square foot beds of potato onions followed by soybeans, harvested green; 50 square feet of garlic followed by soybeans; 50 square feet of leeks; one 100 square foot bed of beets; one 100 square foot bed of winter squash.
This design provides almost as many calories as the 2000 square foot design in a smaller space than the 1600 square foot design. My three year rotation scheme has kept pests and disease at a low-enough level for the past decade, so I think that a three year rotation plan is good enough.
Could a 2100 square foot garden with a three year crop rotation provide enough calories for one vegan adult for a year? Let’s find out. Here is the design:
Block 1: seven 100 square foot beds of dent corn.
Block 2: seven 100 square foot beds of potatoes, followed by six 100 square foot beds of turnips and one 100 square foot bed of bok choy.
Block 3: two 100 square foot beds of beets; one 100 square foot bed of winter squash; one 100 square foot bed of leeks; one 100 square foot bed of garlic; two 100 square foot beds of potato onions. The garlic and potato onion beds are followed by soybeans (three 100 square foot beds).
And here is the spreadsheet:
Finally, a design that provides marginally enough calories and more than sufficient protein and calcium for one vegan adult for a year; that allows for an easy three year crop rotation; and that uses crops I actually grow, plants them as I do in my garden, and assumes yields I have actually attained!
Now let’s step back and look more closely at the design with a gardener’s eye.
First, remember that yields vary from year to year for many different reasons, such as unusual weather conditions, spotty germination of seeds, pest or disease problems, and/or other issues. Thus in any one year the actual amount of calories, protein, and calcium obtained from the harvest may not be as high as the amount shown.
Could that be compensated for by increasing yields? Possibly. For one, there are far more varieties of each of these crops than I have tried. Maybe a different variety would yield more than the variety that I grow.
Or I might be able to plant certain crops more closely spaced than I have been. I think I could plant garlic, potato onions, and maybe leeks the same distance apart within the row (6 inches) as I do now but with rows 8 to 9 inches apart rather than 12 inches apart. It’s possible that corn stations could be 18 inches apart within a row. Potatoes might be planted 8 or 9 inches apart rather than 12 inches. All of these would increase the number of plants in a 100 square foot bed, which could increase the yield as long as the plants still can access sufficient resources from the soil. I haven’t grown soybeans enough years to know how to best plant them, so I might be able to increase their yield as well.
Earlier this year I read Kelly Winterton’s publications on potato onions (look toward the bottom for the links). He suggests doing two things to increase the yield of potato onions: soak them in a weak bleach solution before planting them, and plant them in early spring rather than in autumn (he spring plants in Utah). While most of the larger bulbs that I plant in autumn survive the winter under mulch, many to most of the smaller ones – which is most of what I plant – rot either before the mulch is removed or in the first month or so afterward. Following Kelly’s methods might lead to higher yields.
Taking all this together, I feel reasonably safe in saying that a 2100 square foot garden in the St. Louis region, planted according to my design, could potentially provide all of the calories, protein, and calcium for one vegan adult for one year if year-to-year yield variability can be compensated for by increasing the yields through good variety choice and closer plant spacing.
However, there is much more to the minimum-area garden than a design on paper. As I have discussed before, there are a host of other issues, from garden labor to preserving the harvest to meal planning to psychological and cultural issues surrounding diet that I need to address with the garden design that I have developed, just as I did with the minimum-area designs in One Circle. In the next post I’ll tackle these.