I wonder if you
should be asking different questions... My basic strategy for what went into baskets was that if I had 50 members then each member got 1/50th of the harvest. So perhaps the question you should be asking is how many plants would I need to
feed one family, and then multiply that by the number of members you are feeding... In my
experience with my climate and habits as a farmer an
acre (0.4 hectares) of
land can support about 25 CSA shares.
I was an early adopter of the CSA model, but I abandoned it because I hated being in debt to the buyers, and I hated having crop failures, and I didn't like people wasting the gorgeous food that I grew for them, and I hated people being unreliable and not picking up their boxes. For emphasis, I hated the crop failures. Two years in a row all of the brassica family crops failed. That really hurt my
ego and damaged my sense of self-worth as a farmer. No big deal at the farmer's market, I just say "I don't have brassicas today", but in the CSA it really sucked.
In my CSA, having a variety of crops available every week was more important than how many pounds of food I provided. So I used methods and varieties that would allow me to offer extended seasons on each crop. So I'd plant small early saladette tomatoes, just to get tomatoes into the baskets, and then stop picking those when the larger tomatoes ripened. Planning the crops so that they can ripen over extended periods was vital to me. Take carrots for example: A well grown carrot at the end of the season in September weighs up to two pounds, but ten weeks earlier it might take 20 carrots to make a pound. My strategy with crops like carrots that don't perish from week-to-week, but just get a little bigger, was to say things like: "There are 10 weeks left in the season, and I have 10 rows of carrots, so I can pick one row per week until the end of the season." Crops that fall into this category are things like beets, onions, and greens. With carrots, if I want to provide 8 carrots per week, for 18 weeks, for 50 members, then I need to grow 7200 plants. Spaced at one inch per plant that's 600 row-feet of carrots. If the lettuce season is 4 weeks long, and I want to include one head of lettuce in the baskets per week, then I'd want to plant 4 X 50 heads of lettuce. Perhaps the first two weeks since the heads are smaller I'd want to include 2 heads of lettuce per week, so my total planting would be 6 X 50 = 300 heads of lettuce.
Other crops are perishable on the vine: They are things like radishes, broccoli, green beans, shelling peas, sweet corn, and berries. In a week a zucchini can go from a flower to a 8 pound
fruit. But people don't want 8 pound fruits, they want 8 ounce fruits. So to get small zucchini into the baskets you need to pick several times per week, but then you gotta decide if you are having multiple pickup days, or if you are going to refrigerate the produce for a once a week pickup, or
sell the mid-week produce via other means. With things like summer squash, I used to plant 3 weeks earlier than anyone would ever plant summer squash around here, and then at the normal summer squash planting time, and then about 3 weeks and 6 weeks later. That gave me plants at all different stages of maturity and perhaps some would still be producing on any particular week. Perhaps the first planting gets frozen. No big deal. One of the other plantings will probably succeed. One zucchini plant will feed a family, so perhaps you would want to plant 50 early zucchini plants and 50 late zucchini plants to extend the harvest.
If well spaced, in a field with sufficient nutrients and
water, corn produces 2 cobs per plant, so 300 corn plants would provide about a dozen ears of corn to each family. If you want them to have 4 weeks worth of corn, then plant successive crops, of about 300 seeds of the same variety, when the previous crop is about 3" tall. Or plant crops on the same day which have different days to maturity. Basing things on days-to-maturity is sometimes iffy because that data tends to be unreliable.
Then there are the crops that are a one time harvest all at once: In my garden they are things like grains, dry beans, soup peas, sunroots, melons, flour corn, and winter squash. Winter squash in my garden produce about 2 fruits per vine. So if I want my members to have two winter squash I would plant 50 seeds. My strain of sunroots produce about 13 pounds of tubers per plant, but that's way too much for one family, so perhaps 1/3 of a sunroot per family would be about right. Around 17 plants. Dry beans in my garden produce anywhere from 40 to 140 ml per foot of row depending on variety. If 90 ml per foot is the average, then I'd need to grow 11 row-feet to provide one liter of dry beans to one member. So 550 row feet would take care of 50 members.
I guess that's a long winded way of saying perhaps it isn't pounds of produce that is the important number to be looking at, but rather numbers of plants. In a food forest setting, the fruit and nut bearing
trees get harvested and the produce is divided equally among the shareholders. It might be a single
apple per shareholder one year, and a bushel the next.
Did I mention enough times that crop failures really really suck in a CSA? I know it's part of the contract, but that doesn't take away the hurt.
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