代田

Eighth of January, 2037, a Thursday, eight in the morning, Fresno, the fog thinner and the sun a white disc behind it. Nora's half of the farm lies across an irrigation ditch from her father's, and across the ditch the trellis changes: high wires overhead in a shallow roof, canes parted to either side, one slope fruiting this year, the other growing next year's wood. In August the fruiting side is cut, the grapes dry where they hang, and a machine passes underneath and shakes them down. From her coat she took a map in a mud-spattered plastic sleeve: twelve rows, each numbered, a letter by the odd rows and another by the even. "Last year the odd rows dried on the vine and the even rows on trays. The year before, the other way round. This year, round again."

Why swap? "Row three has a hardpan under it; the roots can't get down, it's always weak. Row eight is by the ditch; too much water, it always grows rank. If the odd rows always dried on the vine and the even on trays, by September I couldn't tell whether the difference was the method or the ground. Swap every year and every row has done both. In three years the ground's faults and the method's faults come apart." I thought of Chang Yushan's houses, of house nine running 0.8 lower than two and three and widening, and half a year chasing it before we learned the row had thirty-seven houses and nine was not at the east end. Then too we couldn't tell the house from the method.

On the back, a table: twelve rows, two years, and in each cell pounds per vine, sugar, days to dry, the inspector's grade. Dried on the vine: a tenth less per acre, but no trays, no turning, no rain soaking what isn't on the ground. On trays: more fruit, a slightly better grade, four times the hands. At the far right one more column, headed in Nora's hand: Grandma. Twelve cells, none filled. "When she says she's tasted it, I'll fill it in. She hasn't tasted one."

Waiting for the truck, in row five, a man in a grey-blue robe with sleeves bound tight for work was measuring a furrow with his hand, a small wooden plough with an iron share beside him. He looked along row four, then row six. "This row and that one, they change places every year?" Yes: what hangs this year lies on trays next year. He nodded as if he'd known. "Their places changed each year." Zhao Guo, who was put in charge of the empire's grain. — M.

Memo to file. Fresno, 8 January 2037. Test beside the neighbour; teach the doubter; and my father's column, twenty years old somewhere else.

1. Nora's alternation. Twelve rows; odd and even swap methods every year, vine-dried and tray-dried. Row three sits on hardpan and is always weak; row eight is by the ditch and always rank. Without the swap she could never separate the ground from the method. Three years, and the faults come apart.

2. Her table. Per row, per year: pounds per vine, sugar, days to dry, grade. Vine-dried: about a tenth less fruit per acre; no trays, no turning, no rain risk on the ground. Tray-dried: more fruit, slightly better grade, four times the labour. Far right: a column headed Grandma, twelve empty cells.

3. The alternating fields. Three furrows to a mu, crops sown in the furrows, which hold water and shelter the shoots; hoeing pushes the ridge soil into the furrow until the ridge is level and the roots are deep. Next year the furrow becomes the ridge and the ridge the furrow. "Ground needs rest too."

4. The trial. He didn't order the empire to plant his way. He first had palace guards farm the vacant ground inside the palace walls by the new method, and at harvest measured every plot against the fields next to it, farmed the old way. Every one yielded more, by over a hu per mu. "If you don't compare it with the field beside it, it's good because you say so. Compare it, and it's good because the ground says so. Same sky, same rain, much the same soil next door; what's left over is the method."

5. The teaching. Even then, not everyone at once: the officials brought in the village elders and the best farmers, gave them the ploughs and taught them. "The best farmers trust a new method least; their own has worked all their lives. So you teach them first. Once they believe it, the village, watching them, believes it. If they don't, teach ten thousand others and it's no use: the ten thousand go home, look at the best farm in the village, and farm like that." Shao Min's master Gu, who retires next year, is the least convinced of her five. If Gu nods, her two thousand suppliers need no persuading.

6. The line. "A new method is compared first with the field beside it, then taught to the person who least believes in it. When the ground says it's good and that person says it's good, it's good." Nora's ground has spoken. Her grandmother hasn't. Parting word, pointing at the map: three years isn't enough; swap for ten. My method was an old one; the ancients found it one year at a time.

7. Carol. USDA inspector, thirty years, retiring this year. A handful into a moisture meter; too high and the bin is refused. A handful on a paper plate, tweezers: underdeveloped, shrivelled, capstemmed, mouldy, sandy; weigh both piles; 3.1 per cent defects; over the line and it's docked, well over and it's rejected. Is this bin good? "My numbers only say whether it meets the rules. Good is another matter. In thirty years, what meets the rules hasn't always been good to eat, and what failed has sometimes been the best. I can only write down whether it meets the rules." My father's notebook, line after line: pass.

8. The whiteboard. At the end of the processing line: lot numbers, bin counts, and after each line one word: breakfast cereal, bakery, snack packs, export. Dave, quality manager: raisins for cereal boxes must be drier so they don't clump; for bakery they can be moister and softer; snack packs need even sizes; export depends on the country. "Same grade, different destination, different handling." Do you ask what it's for when the order comes in? "Of course. There's a column on the order: end use. Without it, the product's within spec, the customer uses it, it's wrong, and it all comes back." How long have you had it? "Twenty years or so. It was there when I came." My father's letter was March 2019. The column already existed in another trade on the other side of the country. Not in his factory.

9. Three footnotes. On land and labour, from the man who wrote less labour, more grain: his method won on both counts; Nora's wins only one, a tenth less fruit for a quarter of the hands. "How you reckon it depends on what you're short of. Where land is short you want more grain; where people are short you want less labour. She's short of people; that tenth buys people." Turpan is short of people too. On where his method came from: where families couldn't keep two oxen, a county magistrate named Guang taught him to have several households pull the plough together by hand, and he made Guang his deputy. "Half my alternating fields came from the ancients and half from people in the counties." On my own trials in Turpan: always this year against last, and last year's sky is not this year's sky.

10. Calibration and the column. Carol: two inspectors on the same bin may not differ by more than half a point; every spring all of them sit in one room and grade the same lot; whoever is off goes back and practises. In her early years she always picked more than the others; later they were told she was right. She let me pick a plate: 4.6. "You picked too much. Like my first year." Dave: the column doesn't settle it either. His first year, a bakery wanted soft fruit and got cereal-dry, forty cases came back; the column existed; the salesman hadn't filled it in. "Add a column and somebody still has to ask." My father's letter had that too: when the order is taken, ask. I photographed the whiteboard and sent it not to Shao Min but to my mother. An hour later: "Your father's column."

11. Why Rose keeps a ledger. "My husband didn't believe me. I'd say rain tomorrow; he'd say the forecast says no; it rained; he said it was luck. So I wrote it down, what I said and what the sky did, a line a day. After five years I showed him. He read it and said nothing, and after that, every September, before the trays went down, he asked me first." He died in 2009; that September it didn't rain.

12. Next. Eleven at night in New Jersey: it snowed all day, this deep. Who shovelled? "It's shovelled." The neighbour's son came? "He came." Her voice ordinary, only slower, a pause between sentences. Tired? "No." Told her Carol's line; "That's what your father said." On the porch, stars, no fog. Rose: "Rain tomorrow." The forecast says clear tomorrow and the day after. "I know what the forecast says." From under her bed, a box: seventy-one notebooks, one a year, 1966 to last year, every day's weather. "If you want to know September, read these."

"If you don't compare it with the field beside it, it's good because you say so. Compare it, and it's good because the ground says so."
Zhao Guo was a Han dynasty official in charge of agriculture under Emperor Wu. He is remembered for promoting the "alternating field" method, in which crops were sown in furrows and the positions of furrow and ridge were exchanged each year. The History of the Han records how he introduced it: first on vacant land around a palace, where the harvest from each plot was measured against the adjacent fields farmed the old way, and only then by training village elders and the best local farmers, who were given the new implements and taught to use them.
The two steps are still the core of sound agricultural extension, and of most sound testing. A comparison with a nearby control removes the effects of weather and soil. Alternating treatments between plots over several years separates the effect of the plot from the effect of the method. And adoption spreads through the practitioners others already watch, who are often the most sceptical.
Measurement has a second limit, which an inspector near the end of a thirty-year career put simply: the numbers say whether a product meets the rules, not whether it is good.
"My numbers only say whether it meets the rules. Good is another matter."