Rice has been cultivated as a food crop for at least 12,000 years, most of that period grown almost exclusively in Asian countries as a vital staple crop. That remains largely true today, with rice serving as the dominant staple crop in Asia and is an important part of the diet in many parts of Africa, Latin America and the Middle East as well, feeding about 1.5 billion people on a regular basis. According to data from the UN’s Food and Agriculture Organization (FAO), global rice harvested area averaged 164 million hectares (405 million acres) between 2013 and 2017, and 87 percent of that rice crop was raised in Asian countries.
Historians believe that it was first introduced in Greece as a crop brought back by Macedonian soldiers who served in Alexander the Great’s wars in Asia in about 320 B.C, and in Spain by Moorish (Muslim) conquerors in the 8th century A.D. European conquistadors brought the crop with them to the New World in the 16th century, initially by the Spanish to Mexico in about 1520 and by the Portuguese to Brazil in roughly the same period. Among the original American colonies, rice was first produced in the Virginia colony early in the 17th century, from seeds originating in Africa rather than from Asia. It later became a significant cash crop on plantations in Georgia and South Carolina, cultivated primarily by slaves from Africa.
Over the last few decades, rice yields have been increasing more slowly than other major crops. Since 1990, the global average rice yield has increased from 3.5 tonnes per hectare to 4.6 tonnes per hectare in 2017, a 30 percent increase. Over the same time span, global average corn yields increased from 3.7 tonnes per hectare to 5.7 tonnes, a 56 percent increase.
Part of the lag can be attributed to relatively slow adoption of hybrid rice varieties, especially in Asia. Although the scientific technique of cross-breeding crop varieties to capture superior traits in hybrid seeds proved its worth to corn producers nearly a century ago in the United States, use of rice varieties developed using such techniques still have not really caught on in global rice markets. Although rigorous testing has shown that hybrid rice varieties clearly generate greater yields and higher net returns than open-pollinated varieties, they have only made headway in a few countries such as China, where about half the rice area is cultivated with hybrid seed, and in India, where 3 million hectares of hybrid rice was being grown as of 2016 (about 7 percent of total India rice area). In other parts of Asia, hybrid rice varieties have not been as widely adopted because of higher costs and/or difficulties with accessing seed.
In the United States, about 40 percent of rice area was planted with hybrid seed in 2012, primarily in the southern rice-producing states such as Arkansas and Louisiana. In addition to higher yields, the hybrid rice varieties help farmers cope with red rice infestation, which is a weedy rice variety that can reduce milled rice quality when present in a field at harvest. The Clearfield hybrid rice varieties were bred with resistance to a herbicide (Newpath) which is particularly effective in combating red rice.
Extensive research has been undertaken in recent decades to address other challenges faced by rice producers around the world, including improving the nutritional value of the crop, the need to be more water-efficient in rice production, and the need to deal with seawater intrusion in groundwater and thus the salinization of cropland near ocean coasts.
On the nutrition front, scientists have been working for years to develop and commercialize a GMO rice variety with enhanced beta carotene content, to help tackle vitamin A deficiency problems in Asia, which leads to blindness among the malnourished in that region. In April, I blogged about the decision by the government of Bangladesh to approve cultivation of this variety, called Golden Rice, the first major rice-producing nation to do so.
Scientists at the University of Nottingham in the United Kingdom are working on developing varieties of rice that are able to convert arsenic into a form that it can push back into the soil, thus leading to lower concentrations of arsenic in the milled product than in conventional varieties. In the past, this tendency of rice to absorb this toxic substance made it a less than ideal ingredient for baby foods.
Scientists at the University of California at Davis have worked to popularize a new rice cultivation practice called Alternative Wetting Drying, under which farmers allow their rice fields to dry out before irrigating them again, rather than cultivating under constant flooding conditions. Using this approach reduces water consumption, lowers energy costs if the irrigation requires pumping of any kind, and lowers the methane emissions from the fields during the growing season. This practice was first developed in Africa during the 1980’s, but hasn’t really caught on in the United States yet.
In China, a research team headed by Dr. Yuan Longping, who won the World Food Prize in 2004 for his work in rice genetics, is working on developing rice varieties that are tolerant of higher levels of salt in groundwater. Some of this new variety, called Green Super Rice, is already being grown in the Philippines.