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  3. Most shoppers know the feeling. You stand in front of piles of organic produce and wonder what those premium prices are buying y

Most shoppers know the feeling. You stand in front of piles of organic produce and wonder what those premium prices are buying y

admin2012-05-28  72
问题     Most shoppers know the feeling. You stand in front of piles of organic produce and wonder what those premium prices are buying you over and above what you get from standard foods. Not a lot nutrition-wise, it seems. Organic farming may not even be more sustainable. But could the whole debate about organic versus non-organic be missing the point?
    Understanding nutrition is, of course, vital when it comes to choosing food. In a report published recently, a team from the London School of Hygiene & Tropical Medicine examined 162 papers that compared organic and conventionally produced food. They concluded that there was no evidence to back up claims that organic food is more nutritious.
    But this is only one of the aspects of organic food that shoppers care about, and things get even more complicated when other, factors are brought into the equation. Many buy organic fruit and vegetables because they are not sprayed with pesticides. We know these can cause birth defects, cancer, and even the diabetes epidemic but it remains unclear whether the amounts in conventionally grown fruit and vegetables are high enough to be a health hazard.
    And then there are issues unrelated to health. Take energy use. True, some organic farming systems are more energy-efficient, partly because they do not use synthetic fertilizers, which are energy-intensive to produce. However, there is limited pressure on organic farmers to cut emissions. They don’t yet have to do so to qualify for organic status. As Laurie Drinkwater, an expert in sustainable agriculture at Cornell University in New York, points out, "Organic agriculture is not without environmental consequences." Indeed, according to Jules Pretty, an agricultural scientist at the University of Essex in Colchester, some organic farms keep weeds down with propane burners (丙烷加热器), which produce carbon dioxide.
    Soil erosion is another confounding factor. Many organic farms emphasize crop rotation, in part to ensure that fields are not left uncovered and vulnerable to erosion. The trouble is some organic farmers actually cause erosion by tilling the soil frequently to tackle the weeds.
    It’s not about whether organic food is good or a sham. That’s the wrong question. We should be asking how we can make all of agriculture more sustainable. Rather than compare organic and conventional systems in a simplistic way, Drinkwater and Pretty say we should identify the things we want from farms and then design a farming system — organic or otherwise — that best meets those goals.
    Producing enough food is an obvious aim, but farmers can also help boost biodiversity, keep rivers free of certain kinds of pollution, and fight climate change. There is also the question of animal welfare. You would probably end up with a system that borrows techniques from many existing farming methods. That would be good news for farmers and the rest of society, even though it might not produce so many snappy headlines.
How does the crop rotation affect the environment?
选项 A、It efficiently increases soil fertility.
B、It maintains the highest soil organic matter levels.
C、It theoretically preserves soil but produces opposite results for frequent ploughing farms.
D、It makes soil become immune to erosion.
答案C
解析 第五段提到，许多有机农场强调作物轮作，部分是为了保证土地没有荒芜，免遭水土腐蚀。问题是，有些农场频繁地翻地除草，实际上却导致了水土流失。由此推断出农场实施作物轮作制的本意是为了避免土壤腐蚀但对于频繁翻地的农场却适得其反，造成了水土流失，故答案为[C]。
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