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Upland rice (also called dry rice) is a variety of rice grown on dry soil rather than flooded rice paddy fields. [1]
Nearly 100 million people depend on upland rice as their daily staple food. Almost two-thirds of the upland rice cultivation occurs in Asia, with Bangladesh, Cambodia, China, Northeastern India, Indonesia, Myanmar, Nepal, Thailand, and Vietnam all being important producers. [2]
Upland rice is grown in rain-fed fields that are prepared and seeded when dry, much like wheat or maize. Ecosystems involving upland rice are often relatively diverse, including fields that are level, gently rolling, or steep. Such ecosystems also occur at altitudes up to 2,000 m, with average annual rainfall ranging between 1,000 and 4,500 mm.
Soils range from highly fertile to highly weathered, infertile, and acidic; however, only 15 percent of total upland rice grows where soils are fertile and the growing season is long.
Many upland farmers plant local rice that does not respond well to improved management practices, such as intensive farming using artificial fertilizers, yet they are well adapted to their environments and produce grains that meet local needs. [3]
Although the rice technology of the 1960s and 1970s focused on irrigated rice, research also studied the cultivation of upland rice. Researchers produced cultivars adapted to poor soils with improved pest resistance and drought tolerance. [4] Some have out-yielded traditional rice by more than 100 percent in evaluations. Scientists at national agricultural research systems have crossed these improved strains with local cultivars, introducing hybrid varieties of rice.
New challenges are emerging[ when? ] in the world's upland rice farming areas, where poverty is already a problem. These farmers try to make a living by farming on deficient soil, and that makes it hard to grow their crops.
Population growth, the demands of urbanism and industry, and the increasing adoption of high-value cash crop farming in the surrounding lowlands are leading to strong competition for upland terrain.
The uplands have always suffered from drought, infertile soils, weeds, and plant diseases. The soils there have been severely eroded and degraded as a result of the slash-and-burn agriculture that followed logging for many years. This destroys the watershed, producing problems in the lands below.
These new upward pressures result in a movement toward permanent agriculture and an intensification of land use in upland areas. In addition to the usual upland problems, those involved in growing upland rice find themselves facing an urgent need to conserve soil and the diversity of plant species and to deal with increasingly frequent and severe weed and disease infestations.
Recently, scientists have been improving their knowledge of the genetics of resistance to the blast fungus, one of the most damaging diseases of rice. Using the techniques of biotechnology, they are developing cultivars with more durable disease resistance.
In the uplands, the blast is particularly important because the environment favors its proliferation. Although many traditional upland cultivars show stable resistance to this disease under low-input cropping practices, they have other characteristics that make them difficult to use in intensified systems. So, the risk of blast increases as cropping practices intensify and improved varieties are introduced.
Scientists from the International Rice Research Institute (IRRI) have been working with colleagues in the Upland Rice Research Consortium to better understand pathogen populations and identify resistance genes found in some cultivars. Armed with this knowledge, they are working with IRRI's upland rice breeder to combine such genes with other desirable traits for incorporation into new upland varieties. [5]
Consortium scientists are also trying to understand how upland rice farmers' cropping systems contribute to soil erosion, with the aim of proposing possible erosion control techniques. Studies in the Philippines have shown that hedgerows of trees, shrubs, and grasses along hill contours can help reduce soil erosion by up to 90 percent. Rice or other crops are planted between these strips of permanent ground cover.
Leguminous plants in hedgerows make substantial amounts of atmospheric nitrogen available to both rice plants and annual crops and recycle other nutrients and organic matter.
Such legumes can simultaneously increase farmers' incomes and contribute to the sustainability of the farming system.
Weeds are the most serious biological constraint to upland rice production. IRRI scientists are pursuing projects on managing weeds with less herbicide use. One approach is to search for rice plant species that exhibit a characteristic known as allelopathy. Allelopathic plants can affect the growth of nearby plants through the production of biological compounds they release into the environment. If allelopathic rice—or other plant species—could be found to inhibit the growth of weeds important in rice production, it might be possible through genetic engineering to develop rice cultivars that would provide their own weed control.
Most weed species are victims of their own diseases. The purposeful application of the agents of such diseases to weed pests among rice crops could constitute another approach to weed control.
Researchers from IRRI, Maejo University, and Chiang Mai University launched a study in 1993 of the interactions between weeds, crop environmental conditions, and farmers' practices in upper northern Thailand. The goals are to understand the diversity of farmers' practices and decision-making processes and to grade the factors that limit rice crop yields.
IRRI scientists are also studying how fertilizer and cultural practices influence weed communities. In one project on phosphorus management, they are investigating how weed communities change as soil fertility is improved over time in the Philippines, Indonesia, and Thailand.
Rice plant cultivars differ in their ability to compete with weeds in the field. Scientists in the Philippines tested the competitiveness of a dozen cultivars against weeds to help farmers choose the most highly competitive one. By planting this cultivar and enhancing their competitive ability through good management practices, farmers should be able to reduce the amount of hand weeding necessary while achieving maximum yields.
Research on farms in Thailand, Laos and the Philippines confirmed that a lack of phosphorus in upland farms is a limiting factor in rice crop yields- arising from the fact that many highly weathered upland soils are inherently low in phosphorus and are acidic. [6]
This lack of phosphorus will limit production even if calcium is added to the soil to overcome the acidity, or if acid-tolerant cultivars are planted. Rotations of rice and legumes could lead to stable, higher-value production if phosphorus is added and that soil quality does not degrade over time.
The acidity present in the subsoil of many upland areas prevents plant roots from reaching the moisture and nutrients therein, thus reducing crop yield. Adding lime to the subsoil is not practical, but in 1994, IRRI and Indonesian scientists began experiments to see if components of lime applied to the soil surface could be leached down into the subsoil. This is done by manipulating soil chemistry and using deep-rooted, acid-tolerant rice cultivars to help capture the leached components.
Scientists are currently studying the processes that govern the rate of leaching of lime components and their accumulation in the subsoil. Using this data, they plan to construct mathematical models that will be used to develop practical technologies and to indicate under what conditions the technologies might be effective.
The experiments began at the Upland Rice Research Consortium site in Sitiung, Indonesia. French collaborators from l'Institut francais de recherche scientifique pour le développement en cooperation are planning similar experiments in Thailand and Vietnam.
Rice, like most cereal crops, is an annual plant, which leads to soil erosion in monocultured areas. A rice plant that would not need to be replanted annually could help reduce erosion by providing a permanent ground cover and deeper, tighter root systems. Perenniality exists in several wild species of rice from Southeast Asia, but their yields are low. These species, however, can be crossed with cultivated rice through selection to develop both high-yield and perennial crops. [7]
The challenge facing scientists is to produce a high-yielding perennial plant adapted to the poor soils of the uplands, with high yields from low-purchased inputs, and resistant to diseases and insects.
The development of high-yield, resilient, perennial rice varieties is an important focus at the International Rice Research Institute. Genomics allows the transfer of perennial genetic properties into traditional varieties of cultivated rice, and new knowledge of genetic diversity will be applied to develop pest resistance. [8]
Upland rice is being partially replaced by other crops, such as maize. On the other hand, the landraces are gradually disappearing from farmers' fields. Diversity of upland rice can be maintained while, at the same time, levels of production can be increased using participatory techniques. The addition of upland rice to fields allows for crop rotation and the improvement of diversity in fields.
Rice is a cereal grain, and in its domesticated form is the staple food for over half of the world's human population, particularly in Asia and Africa, due to the vast amount of soil that is able to grow rice. Rice is the seed of the grass species Oryza sativa or, much less commonly, O. glaberrima. Asian rice was domesticated in China some 13,500 to 8,200 years ago, while African rice was domesticated in Africa some 3,000 years ago. Rice has become commonplace in many cultures worldwide; in 2021, 787 million tons were produced, placing it fourth after sugarcane, maize, and wheat. Only some 8% of rice is traded internationally. China, India, and Indonesia are the largest consumers of rice. A substantial amount of the rice produced in developing nations is lost after harvest through factors such as poor transport and storage. Rice yields can be reduced by pests including insects, rodents, and birds, as well as by weeds, and by diseases such as rice blast. Traditional rice polycultures such as rice-duck farming, and modern integrated pest management seek to control damage from pests in a sustainable way.
Finger millet is an annual herbaceous plant widely grown as a cereal crop in the arid and semiarid areas in Africa and Asia. It is a tetraploid and self-pollinating species probably evolved from its wild relative Eleusine africana.
Crop rotation is the practice of growing a series of different types of crops in the same area across a sequence of growing seasons. This practice reduces the reliance of crops on one set of nutrients, pest and weed pressure, along with the probability of developing resistant pests and weeds.
Intensive agriculture, also known as intensive farming, conventional, or industrial agriculture, is a type of agriculture, both of crop plants and of animals, with higher levels of input and output per unit of agricultural land area. It is characterized by a low fallow ratio, higher use of inputs such as capital, labour, agrochemicals and water, and higher crop yields per unit land area.
Weed control is a type of pest control, which attempts to stop or reduce growth of weeds, especially noxious weeds, with the aim of reducing their competition with desired flora and fauna including domesticated plants and livestock, and in natural settings preventing non native species competing with native species.
In agriculture, cover crops are plants that are planted to cover the soil rather than for the purpose of being harvested. Cover crops manage soil erosion, soil fertility, soil quality, water, weeds, pests, diseases, biodiversity and wildlife in an agroecosystem—an ecological system managed and shaped by humans. Cover crops can increase microbial activity in the soil, which has a positive effect on nitrogen availability, nitrogen uptake in target crops, and crop yields. Cover crops reduce water pollution risks and remove CO2 from the atmosphere .Cover crops may be an off-season crop planted after harvesting the cash crop. Cover crops are nurse crops in that they increase the survival of the main crop being harvested, and are often grown over the winter. In the United States, cover cropping may cost as much as $35 per acre.
In agriculture, polyculture is the practice of growing more than one crop species together in the same place at the same time, in contrast to monoculture, which had become the dominant approach in developed countries by 1950. Traditional examples include the intercropping of the Three Sisters, namely maize, beans, and squashes, by indigenous peoples of Central and North America, the rice-fish systems of Asia, and the complex mixed cropping systems of Nigeria.
Panicum virgatum, commonly known as switchgrass, is a perennial warm season bunchgrass native to North America, where it occurs naturally from 55°N latitude in Canada southwards into the United States and Mexico. Switchgrass is one of the dominant species of the central North American tallgrass prairie and can be found in remnant prairies, in native grass pastures, and naturalized along roadsides. It is used primarily for soil conservation, forage production, game cover, as an ornamental grass, in phytoremediation projects, fiber, electricity, heat production, for biosequestration of atmospheric carbon dioxide, and more recently as a biomass crop for ethanol and butanol.
New Rice for Africa (NERICA) is a cultivar group of interspecific hybrid rice developed by the Africa Rice Center (AfricaRice) to improve the yield of African rice cultivars. Although 240 million people in West Africa rely on rice as the primary source of food energy and protein in their diet, the majority of this rice is imported. Self-sufficiency in rice production would improve food security and aid economic development in West Africa.
Hybrid rice is a type of Asian rice that has been crossbred from two very different parent varieties. As with other types of hybrids, hybrid rice typically displays heterosis or "hybrid vigor", so when grown under the same conditions as comparable purebred rice varieties, it can produce up to 30% more yield. To produce hybrid seeds in large quantity, a purebred sterile rice variety is fertilized with fertile pollen from a different variety. High-yield crops, including hybrid rice, are one of the most important tools for combatting worldwide food crises.
Intensive crop farming is a modern industrialized form of crop farming. Intensive crop farming's methods include innovation in agricultural machinery, farming methods, genetic engineering technology, techniques for achieving economies of scale in production, the creation of new markets for consumption, patent protection of genetic information, and global trade. These methods are widespread in developed nations.
Paspalum scrobiculatum, commonly called Kodo millet or Koda millet, is an annual grain that is grown primarily in Nepal and also in India, Philippines, Indonesia, Vietnam, Thailand, and in West Africa from where it originated. It is grown as a minor crop in most of these areas, with the exception of the Deccan plateau in India where it is grown as a major food source. It is a very hardy crop that is drought tolerant and can survive on marginal soils where other crops may not survive, and can supply 450–900 kg of grain per hectare. Kodo millet has large potential to provide nourishing food to subsistence farmers in Africa and elsewhere.
A weed is a plant considered undesirable in a particular situation, growing where it conflicts with human preferences, needs, or goals. Plants with characteristics that make them hazardous, aesthetically unappealing, difficult to control in managed environments, or otherwise unwanted in farm land, orchards, gardens, lawns, parks, recreational spaces, residential and industrial areas, may all be considered weeds. The concept of weeds is particularly significant in agriculture, where the presence of weeds in fields used to grow crops may cause major losses in yields. Invasive species, plants introduced to an environment where their presence negatively impacts the overall functioning and biodiversity of the ecosystem, may also sometimes be considered weeds.
Crop diversity or crop biodiversity is the variety and variability of crops, plants used in agriculture, including their genetic and phenotypic characteristics. It is a subset of a specific element of agricultural biodiversity. Over the past 50 years, there has been a major decline in two components of crop diversity; genetic diversity within each crop and the number of species commonly grown.
Chloris gayana is a species of grass known by the common name Rhodes grass. It is native to Africa but it can be found throughout the tropical and subtropical world as a naturalized species.
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.
The Irrigated Rice Research Consortium (IRRC) focuses on agricultural research and extension in irrigated rice-based ecosystems. In partnership with national agricultural research and extension systems (NARES) and the private sector, the IRRC provides a platform for the dissemination and adoption of natural resource management (NRM) technologies in Asian countries. The IRRC is currently active in 11 countries: Bangladesh, Cambodia, China, India, Indonesia, Laos, Myanmar, the Philippines, Sri Lanka, Thailand, and Vietnam. It aims to strengthen NARES-driven interdisciplinary research, link research and extension, facilitate rice farmers' uptake of technological innovations, and enable environmentally sound rice production to expand to feed growing populations.
Digitaria eriantha, commonly known as digitgrass or Pangola-grass, is a grass grown in tropical and subtropical climates. It grows relatively well in various soils, but grows especially well in moist soils. It is tolerant to droughts, water lodging, suppresses weeds and grows relatively quickly after grazing. This grass demonstrates great potential for farmers in Africa in subtropical and tropical climates, mostly for livestock feed.
Chickpeas are a major pulse legume grown in Nepal, either by themselves or as an intercrop with maize or rice. Chickpeas are an important legume to the population, as it is the primary protein source for nearly 2 million Nepalese people. In 2013, Nepal imported approximately US$10.1 million in dried shelled chickpeas, mostly from Australia and also from Canada, creating a need to increase production for its own people and to balance bilateral trade. Chickpeas are an excellent source of protein, especially when compared to other legume pulses. They are high in unsaturated fatty acids and minerals, including calcium, magnesium, phosphorus and potassium.
Climate change and agriculture are complexly related processes. In the United States, agriculture is the second largest emitter of greenhouse gases (GHG), behind the energy sector. Direct GHG emissions from the agricultural sector account for 8.4% of total U.S. emissions, but the loss of soil organic carbon through soil erosion indirectly contributes to emissions as well. While agriculture plays a role in propelling climate change, it is also affected by the direct and secondary consequences of climate change. USDA research indicates that these climatic changes will lead to a decline in yield and nutrient density in key crops, as well as decreased livestock productivity. Climate change poses unprecedented challenges to U.S. agriculture due to the sensitivity of agricultural productivity and costs to changing climate conditions. Rural communities dependent on agriculture are particularly vulnerable to climate change threats.
