Perennial rice are varieties of long-lived rice that are capable of regrowing season after season without reseeding; they are being developed by plant geneticists at several institutions. Although these varieties are genetically distinct and will be adapted for different climates and cropping systems, their lifespan is so different from other kinds of rice that they are collectively called perennial rice. Perennial rice—like many other perennial plants—can spread by horizontal stems below or just above the surface of the soil but they also reproduce sexually by producing flowers, pollen and seeds. As with any other grain crop, it is the seeds that are harvested and eaten by humans. Perennial rice is one of several perennial grains that have been proposed, researched or are being developed, including perennial wheat, sunflower, and sorghum. Agronomists have argued that increasing the amount of agricultural landscapes covered at any given time with perennial crops is an excellent way to stabilize and improve the soil, and provide wildlife habitat. Perennial rice breeding was initiated at the International Rice Research Institute, Philippines and are currently being developed at the Yunnan Academy of Agricultural Sciences, People's Republic of China, and other institutions, but are not yet available for distribution.
Perennial and annual rice Domesticated Asian rice, Oryza sativa is a short-lived plant. Most cultivars die after producing seeds, though some can regrow (ratoon) and produce a second crop under favorable conditions. In regions with mild climates, two or three crops of rice may be grown each year. Except for ratoon crops, this means that the dead stalks must be removed, the soil cultivated, and new seed sown every few months. In contrast, the wild ancestor of Asian rice, Oryza rufipogon, often lives for many years, setting seed each year and spreading vegetatively. In addition to these perennial types, some O. rufipogon populations are annuals or intermediate in lifespan. Other wild species in the genus Oryza are also perennial. While perennial Oryza rufipogon spreads vegetatively by above-ground stems (stolons), O. longistaminata, O. officinalis, O. australiensis, O. rhizomatis spread by underground stems (rhizomes).
Potential benefits
Reduced soil erosion
Farm fields, especially those in the humid tropics, that have been cleared of vegetation or recently plowed are highly vulnerable to soil and nutrient loss through wind or water erosion, soil compaction, and decline in soil organic matter and microbial biomass. Eroded fields become less productive and the soil particles and dissolved nutrients cause environmental problems downstream, including hypoxia in oceans and rivers and the silting of reservoirs and waterways. Perennial plants regrow quickly after being harvested, re-establishing a protective cover. The fields do not need to be plowed after the initial planting. Researchers at The International Rice Research Institute (IRRI) believed that perennial rice would "improve the sustainability of food production in the hilly uplands and downstream."
Reduced rate of deforestation A high-yielding, nutritious, perennial cereal could allow poor farmers around the world to produce food on a plot of land indefinitely. Currently, many subsistence farmers clear plots in the forest for their crops. Once the soil and its nutrients have washed away, the plot is abandoned and a new piece of forest is slashed and burned. Forest may eventually regenerate on the abandoned plot, or weedy grasses may dominate. Environmental impacts of this cropping system include loss of biodiversity, carbon dioxide emissions, increased runoff and decreased rainfall. Deforestation could be reduced by practices that conserve soil productivity
Other potential benefits Drought resistance: Annual rice has a shallow root system and is very drought susceptible. A long-lived plant has time to develop a deep and extensive root system making it theoretically capable of accessing more moisture than an annual plant. Tilled soil dries out more quickly than untilled Resist weed invasion: Weed pressure has increased in upland rice systems as the fallow period has shortened. Ecologist Jack Ewel wrote: "Weeds are widely recognized as a major impediment to continuous cropping in the humid tropics, and fields are often abandoned more because uncontrollable weed populations are anticipated than because of declining fertility or pest buildups." Grassland restoration with perennials results in fewer annual weeds and perennial grasses, sown at appropriate densities, can out-compete even perennial weeds once they are established. Plant nutrition: While shallow rooted species, such as rice obtain most of their nutrients from the topsoil, deep rooted perennials can obtain significant proportion of their phosphorus from the subsoil. "Deep roots are especially important in nutrient-poor substrates because they increase the volume of soil exploited by the vegetation". Reduce the need for transplanting, weeding, and other backbreaking labor. More efficient use of applied fertilizer
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