Of Rice and Men: Questions You Never Thought to Ask about Harvesting Japan’s Meal Staple

One writer went around pestering people to find out exactly how much rice could be harvested from a field that measured one tatami mat in size. Here's what he found.

By 4 min read

This time last year, I visited Ukiha, a small farming town in the south of Fukuoka Prefecture, to see the tanada (terraced rice paddies) and the higanbana (red spider lilies) that bloom around the edges of rice fields from mid- to late-September. Because the bulbs of the higanbana are highly poisonous, they’re believed to keep mice and other pests away.

As I climbed up a trail that meandered among the rice fields, I was struck by how small many of the patches were. Most were only as wide as a swimming pool lane and half as long. Some of the paddies were so modest in size it begged the question: how much rice could even the most determined farmer ever hope to grow in them? I wondered if it was worth all the effort to lug heavy farm equipment up the mountain, then till the land, irrigate and plant the rice when the yield from such a small plot must surely be negligible?

And so, the following week I went around pestering people to find out exactly how much rice could be harvested from a field that measured, say, one tatami mat in size. Would there be enough rice to make an onigiri (rice ball) or two? I asked some of my college students this question and received answers that varied from 50 to 500 rice balls. Clearly, they hadn’t the slightest of clues. With only 3 percent of the population of Japan engaged in farming today —  it’s no wonder.

I eventually got around to talking to an in-law of mine, who like many rural Japanese, is a weekend farmer. He kindly provided the answer.

Rice fields in Japan, he explained, are measured in tan, which are equivalent to 992 square meters. Tan atari, or tanto, refer to how much of a crop can be harvested from a given field. A typical rice field produces a tan atari of eight to nine tawara (the straw bags for holding rice, similar to bushels in America), or 480 to 540 kilograms of the stuff. Since one tan corresponds to 300 tsubo (a unit of land measurement equal to 3.31 square meters) then one tsubo would provide 1.6 to 1.8 kilos of rice.

A tsubo is the standard unit of area used in Japan to measure land and floor space since it was adopted in 701 from the Tang Dynasty. If you’ve ever shopped around for an apartment, you may have come across this odd fellow.

Some of the paddies were so modest in size it begged the question: how much rice could even the most determined farmer ever hope to grow in them?

One tsubo is equal in size to two Nagoya-style tatami mats laid side by side, or 3.31 square meters. Tatami mats, interestingly enough, come in three main sizes: the kyouma, or Kyoto mats, which are the largest and measure approximately 190 centimeters by 95 centimeters; the kantoma or edoma (Tokyo mats) are the smallest measuring approximately 176 centimeters by 88 centimeters. Nagoya mats, which are also known as ainoma (in-between) mats, are 182 centimeters by 91 centimeters in size.

So, a paddy the size of two standard tatami mats would produce 1.6 to 1.8 kilos of rice. Mind you, this is genmai, or unpolished brown rice, we’re talking about — not the white stuff in your average rice bowl. Once polished, you would end up with about one shou of rice, something equal to about 1.5 kilograms.

And since one go, or about 150 grams, of uncooked rice is enough to make about two onigiri once cooked, then a single tsubo-sized rice paddy would yield about 20 rice balls in total. Likewise, a paddy the size of one tatami mat would provide you with enough rice to make ten rice balls — nori (seaweed sheet) and umeboshi (pickled plum), sold separately.

September and October are the months rice is typically harvested in northern Kyushu. (In the warmer southern prefectures of Kagoshima and Okinawa, rice can be planted and harvested twice a year, what is known as nimousaku). While the exact timing of the harvest depends on the weather, as a rule, rice is reaped about 45 days after the grains appear on the ine, or stalks, of the rice plants. Other ways to determine whether a field is ready to be harvested include looking at the field itself. If 90 percent of it has turned golden in color (from the rice grains), then it’s ready. Another way is to calculate the average daily high temperature and add it up. If that figure is between 1,000 and 1,200 degrees Celsius, then the rice is good to go.

This morning I asked my wife if she knew the answer to my original question, and after a moment’s thought replied, “I dunno. A thousand?” The disbelief must have registered in my face, because she then ventured: “More?”

“How ’bout less,” I said, shaking my head. “Considerably less.”I suppose that when you are in the habit of harvesting onigiri from the seemingly bottomless shelf of a konbini, it’s no wonder people lose their grip on the reality of food production.

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