Методические указания к контрольным заданиям для студентов агробиологических и агроинженерных направлений заочной формы обучения
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Crop production1 systemsCropping systems vary among farms depending on the available resources, geography and climate of the farm, government policy, economic, social and political pressures, the philosophy and culture of the farmer. Shifting cultivation2 (or slash and burn) is a system in which forests are burnt, releasing nutrients to support cultivation of annual and then perennial crops3 for a period of several years. Then the plot is left fallow to regrow forest, and the farmer moves to a new plot, returning after many more years (10-20). This period is shortened if population density4 grows. Annual cultivation is the next phase of intensity in which there is no fallow period. This requires even greater nutrient and pest control inputs. Further industrialization lead to the use of monocultures, when one cultivar5 is planted on a large acreage. Multiple cropping, in which several crops are grown sequentially in one year, and intercropping, when several crops are grown at the same time are other kinds of annual cropping systems known as polycultures. In tropical environments, all of these cropping systems are practiced. In subtropical and arid environments, the timing and extent of agriculture may be limited by rainfall, either not allowing multiple annual crops in a year, or requiring irrigation. In all of these environments perennial crops are grown (coffee, chocolate). In temperate environments6, where ecosystems were predominantly grassland or prairie, highly productive annual cropping is the dominant farming system. The last century has seen the intensification, concentration and specialization of agriculture, relying upon new technologies of agricultural chemicals (fertilizers and pesticides), mechanization, and plant breeding (hybrids and GMO's7). Notes: 1 crop production- растениеводство 2 shifting cultivation-изменяющееся возделывание почвы ( вырубка и сжигание) 3 annual, perennial crops- однолетние, многолетние культуры 4 population density- плотность населения 5cultivar- культура 6temperate environments- умеренный климат 7GMO’s-измененный генетический код Вариант №3 Transgenic plants Transgenic plants1 have been engineered to possess several desirable traits, including resistance to pests, herbicides or harsh environmental conditions2, improved product shelf life, and increased nutritional value. Since the first commercial cultivation of genetically modified plants in 1996, they have been modified to be tolerant to the herbicides glufosinate and glyphosate, to be resistant to virus damage as in Ringspot virus3 resistant GM papaya, grown in Hawaii, and to produce the Bt toxin, a potent insecticide. Most of transgenic varieties grown today are known as first generation transgenics4, because the transgenic trait provides benefits to farmers. Plants of the second generation should directly benefit the consumer with nutritional enhancement, taste, texture etc. Transgenic plants of the second generation are being developed by both public research institutions and private companies. However currently there is no such transgenic variety5 on the market. Genetically modified sweet potatoes have been enhanced with protein and other nutrients, while golden rice, developed by the International Rice Research Institute, has been discussed as a possible cure for Vitamin A deficiency. In January 2008, scientists altered a carrot so that it would produce calcium and become a possible cure for osteoporosis; however, people would need to eat 1.5 kilograms of carrots per day to reach the required amount of calcium. The coexistence6 of GM plants with conventional and organic crops has raised significant concern in many European countries. Since there is separate legislation for GM crops7 and a high demand from consumers for the freedom of choice between GM and non-GM foods, measures are required to separate foods and feed produced from GMO plants from conventional and organic foods. European research programmes such are investigating appropriate tools and rules. At the field level, biological containment methods include isolation distances and pollen barriers. Notes: 1transgenic plants-трансгенные растения 2 resistance to pests, herbicides or harsh environmental conditions-устойчивость к насекомым-вредителям, гербицидам и неблагоприятным климатическим условиям 3 ring spot virus-вирус кольцевой гнили 4 first generation transgenic-первое поколение трансгенной продукции 5 transgenic variety- трасгенный сорт 6 coexistence-сосуществование 7separate legislation-отдельные правовые нормативы на ГМ культуры |
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