What Yield Actually Means

Yield is the most misused word in permaculture. In the handouts it means output per unit of area, a number that is easy to measure and nearly useless by itself. A system can yield heavily per acre and still leave the household short in March, because the household does not eat acres. It eats food, and food arrives in the kitchen at the end of somebody's hours. Any claim about yield that does not name the hours is a claim about a farm that has not been built yet.

Three yields, and only one of them feeds you

Start with the measure everybody quotes. Yield per unit area is the right measure when land is the scarce input. Pelman's farm is the strongest published case for a small-area system: one adult's complete diet produced on 740 square metres in the western Galilee since 2013, roughly 728 kilograms of food a year covering about 2,000 kilocalories a day and meeting or exceeding every recommended intake except calcium, which came in around 80 percent. The same system ran about 96 hours of labour a year, around twelve and a half days.

Now read the second yield, output per hour of labour, and the picture changes character. The 740 square metre farm is not a demonstration that land is abundant. It is a demonstration that Mediterranean rainfed staples plus a small irrigated garden produce an extraordinary return on a small number of hours. Note what Pelman has said since: vegetables take about 100 square metres per person while the seed crops are the land hogs, and wild boar took seventy percent of his crop in the worst year.

The third yield is the one that matters to a household and is almost never published: what reaches the plate and the cellar. That figure is a total rather than a rate. A farm that produces a kilogram per square metre in August and nothing in February has not yielded a year's food.

Yield, and its opposite

Extraction looks like yield for a while. It means taking more out of a system than the system can put back, and the bill arrives later. Feed a pasture hard enough for an extra cut of hay and lose two centimetres of topsoil, and the yield was real and the asset is gone.

On a farm with outside inputs this is easy to obscure, because the missing fertility arrives on a truck. On a closed farm it can be counted. The closed-loop ledger for a two-acre holding feeding a family of five puts the annual harvest drain at about 45 pounds of nitrogen, 15.5 of phosphorus, 22 of calcium and 38 of potassium out of the topsoil, with the household's waste quarantined away from the field. Those figures come from a modeling report with stated assumptions, so read them as an order of magnitude. The question they force is the useful part: does the system return that much, and if not, how many years before the account is empty?

The stacking claim hides a labour question

Stacking functions is the idea that one element can do many jobs, so the design gets more output for less space and less money. The jobs are real. A chicken tractor controls pests, spreads fertility and turns the ground in one pass. A swale holds water, grows mulch and marks the terrace line.

Here is what the framing leaves out. Those functions are performed by somebody's hours, and a stack of functions is usually a stack of chores. The chicken tractor that does three jobs also has to be moved, watered and protected every day. The hedge that yields four products has to be cut on a rotation that runs for decades. If the labour is not counted, the stack looks free, and the design that looked elegant on paper is abandoned in the second year.

Cato states the household rule that follows from it in De Agri Cultura 2: "The appetite of the good farmer is to sell, not to buy." The same chapter tells the owner to sell the surplus oil, wine and corn, the old cattle and the cull sheep, and to buy only what the year will need.

That order is the argument of the next part of this course. Subsistence first: the ground feeds the household before it feeds a market. Then a fair price for the surplus, which is worth having and worth being paid for. Part 3 puts this arithmetic onto the ten thousand square feet, the staple block, the calories, the store and the hours.