rice terraces

Terraced rice paddies, masterpieces of ancient engineering, have existed in China, the Philippines, and elsewhere for as long as two millennia. You don't have to be an expert to know that the building of these stepped paddies is no minor undertaking, done without the aid of machinery.

Rice’s evolutionary origins go far back into history, so far that scientists can only make intelligent guesses as to where the rice genus (Oryza) first grew. One theory maintains that rice arose in the ancient supercontinent known as Gondwana. Then, when Gondwana fragmented into Africa, South America, Antarctica, Australia/New Zealand, India, and Madagascar beginning about 200 million years ago, Oryza went with the fragments.

Rice-growing methods are almost as varied as the grain’s geographical habitats. In the Western World, farmers use highly mechanized systems, but in most developing nations, rice farming remains extremely labor-intensive. The work is backbreaking and relentless, and in China, Japan and other Asian countries where farmers tend terraced paddies, it is also muddy.

Paddy rice is irrigated by water diverted from rivers and mountain streams into a complex system of canals and riverways developed and perfected through centuries of use. Terracing, which requires constant maintenance, allows water to flow continuously down through successive rice fields. Farmers usually plant rice seed in a seedbed, then transplant young plants into the paddies, which have about six inches of water at this stage. As the plants mature, cultivators allow the water level in the field to drop. By the time the plants reach full maturity, the ground is entirely dry, and farmers can easily harvest the rice.

Harvesters cut the ripe grain from the stalk and then, after it has dried, thresh it to separate the grains from the so-called rice straw. In Asia, oxen typically do the threshing by trampling the rice laid out before them. Milling then removes each grain’s hull to reveal the part of the rice plant that eventually ends up in our mouths. Milling both the hull and bran layers of the kernel renders so-called white rice; brown rice retains the bran. After the harvest, farmers turn over the soil, readying the paddy for another season.

The origins of rice
Folklore tells us that when the Kachins of northern Myanmar were sent forth from the center of the Earth, they were given the seeds of rice and were directed to a wondrous country where everything was perfect and where rice grew well. Rice is an integral part of their creation myth and remains today as their leading crop and most preferred food.

In Bali, it is believed that the Lord Vishnu caused the Earth to give birth to rice, and the God Indra taught the people how to raise it. In both tales, rice is considered a gift of the gods, and even today in both places, rice is treated with reverence, and its cultivation is tied to elaborate rituals.

A Malaysian aboriginal myth holds that all of the sky once lay flat on the Earth in the form of rice until the women of the tribe, wielding their long wooden rice brooms, heaved it upwards in the first harvest. From then on, rice fell back to Earth each year in time for a bountiful harvest.

Chinese myth, by contrast, tells of rice being a gift of animals rather than of gods. China had been visited by an especially severe period of floods. When the land had finally drained, people came down from the hills where they had taken refuge, only to discover that all the plants had been destroyed and there was little to eat. They survived through hunting, but it was very difficult, because animals were scarce. One day the people saw a dog coming across a field, and hanging on the dog’s tail were bunches of long, yellow seeds. The people planted these seeds, rice grew, and hunger disappeared.

How, do farmers construct the rice terraces?
A casual glance might lead you to believe that farmers carve them into hillsides, using the dug-up rock to build the retaining walls and the excavated earth to level the terraces. Well, looks can be deceiving.

This is the building site for the new rice terrace. A good terrace site has a gentle slope, a year-round water source, and easy access to building materials. The location of some of these materials, gravel and topsoil, for example, should be uphill from the site, and the stones that will form the retaining wall should be close by.

The terrace builders lay down marking stone, so called because they will mark the boundary between the new terrace and the existing one. These stones, sometimes split from boulders manually and carried to the site by hand, will serve as the foundation for the terrace’s retaining wall. Behind the stones the builders add a coarse fill.

The builders continue to work on the retaining wall, adding another course of stone on top of the wall, along its entire length. The builders move a large amount of gravel from the slope above to fill in the area behind the retaining wall. Whenever possible, they use fast-moving water to transport material. The waterway in this example is an existing stream, but builders can also use temporary channels dug into the hillside, a wooden sluice, or some other type of waterway.

Builders add one course of stone after another to the retaining wall. Since this wall is not self supporting, they need to add more gravel fill as the wall rises.

The builders now use the waterway to move earth to the terrace, where they tamp and smooth the material to produce a flat, horizontal surface. They also cover the top layer of the stone wall with the earth.

Again, the builders use water to transport material to the terrace, this time a soft, clayey topsoil. Eight to twelve inches deep, the topsoil is graded so that it slopes downward toward the hill. By doing so, if there’s ever a break in the rim or if part of the wall fails, some of the water will be retained, along with any fish that may live in the pond.

Finally, the terrace is flooded with water. The water depth in the terrace is controlled by an outlet, which also feeds into the terrace below. Later, perhaps the following season or perhaps many seasons hence, another terrace may be built above this terrace.

The spread of rice
From an early beginning somewhere in the Asian arc, the process of diffusion has carried rice in all directions until today it is cultivated on every continent save Antarctica. In this early hearth area, rice was grown in forest clearing under a system of shifting cultivation. The crop was grown by direct seeding and without standing water. Rice was grown on “farms” under conditions only slightly different from those to which wild rice was subject. A similar but independent pattern of the incorporation of wild rices into an agricultural system may well have taken place in one or more locations in Africa at approximately the same time.

It was in China that the processes of puddling soil and transplanting seedlings were likely refined. Both operations became integral parts of rice farming and remain very widely practiced to this day. Puddling breaks down the internal structure of soils, making them much less subject to water loss through percolation. In this respect, it can be thought of as a way of extending the utility of a limited supply of water. Transplanting is the planting of 1- to 6- wk-old seedlings in standing water. Under these conditions, the rice plants have an important head start over a very wide range of competing weeds, which leads to higher yields. Transplanting, like puddling, provides the farmer with the ability to better accommodate the rice crop to a finite and fickle water supply by shortening the field duration (since seedlings are grown separately, and a higher density) and adjusting the planting calendar.

With the development of puddling and transplanting, rice became truly domesticated. In China, the history of rice in river valleys and low-lying areas is longer that its history as a dry land crop. In Southeast Asia, by contrast, rice was originally produced under dry land conditions in the uplands, and only recently did it come to occupy the vast river deltas. Migrant peoples from South China or perhaps northern Vietnam carried the traditions of wetland rice cultivation to the Philippines during the second millennium B.C., and Deutero-Malays carried the practice to Indonesia about 1500 B.C. From China or Korea, the crop was introduced to Japan no later than 100 B.C.

Movement to western India and south to Sri Lanka was also accomplished very early. The date of 2500 B.C. has already been mentioned for Mohenjo-Daro, while in Sri Lanka, rice was a major crop as early as 1000 B.C. The crop may well have been introduced to Greece and neighboring areas of the Mediterranean by the returning members of Alexander the Great’s expedition to India ca. 344-324 B.C. From a center in Greece and Sicily, rice spread gradually throughout the southern portions of Europe and to a few locations in North Africa.