[29]Agrichemical

感谢收听,期待你对本期节目的评论留言哦～ 2017.2.18 Economist Science and Technology Agrichemicals Holding fast A simple way to stop fertiliser['fɜ:tɪlaɪzə]肥料 being washed away by the rain In Medival [ˌmediˈi:vl]中世纪的 England peasants were permitted to graze放牧 their sheep on the lands of the nobility贵族. There were no restrictions限制 on how much their livestock[ˈlaɪvstɒk]牲畜 could feed, but there was one ironclad ['aɪənklæd]严格的 rule: the peasants were not allowed to collect their animals’ droppings. Though the English nobles who came up with such regulations could not have known that the excrement [ˈekskrɪmənt]粪便 was rich in nitrogen[ˈnaɪtrədʒən]氮 and vital for plant growth, they clearly knew that lands denied faeces[ˈfi:si:z]粪便 were less productive. Today most farmers rely on synthetic [sɪnˈθetɪk]合成的fertilisers to do the nitrogen-enhancing job once reserved for dung[dʌŋ]施肥. Urea[jʊˈri:ə]尿素, a compound[ˈkɒmpaʊnd]复合物 of nitrogen,hydrogen[ˈhaɪdrədʒən]氢, carbon and oxygen, can be made cheaply by mixing ammonia[əˈməʊniə]氨 and carbon dioxide together at high pressure. The result is turned into pellets [ˈpelɪt]小球 that can be scattered[ˈskætə(r)]散开 easily over fields. Unfortunately, when such pellets are exposed to heavy rain, the urea they contain is quickly and wastefully washed away. A method of keeping it in place would thus be welcome. And Nilwala Kottegoda of the Sri Lanka[sriˈlæŋkə]斯里兰卡 Institute of Nanotechnology [ˌnænəʊtekˈnɒlədʒi]纳米技术 thinks she has one. As she and her team report in Nano, they have managed to bind[baɪnd]结合 urea molecules分子 to a material that stops them dissolving too quickly in water. This material is hydroxyapatite[haɪdrɒksɪ'æpətaɪt]羟磷灰石, one of the components of bone. Her choice of hydroxyapatite for investigation was no wild guess瞎猜. It is already used to make capsules[ˈkæpsju:lz]胶囊 that release certain drugs slowly, in the way she wanted to achieve for urea. Hydroxyapatite is made by mixing phosphoric acid [fɒsˌfɒrɪk ˈæsɪd] 磷酸and calcium phosphate[ˈkælsiəm ˈfɔsˌfeɪt] 磷酸钙, so Dr Kottegoda simply added urea to the process. The result, she found, was that each molecule of the material clung [klʌŋ]附着于on to six molecules of urea—a payload[ˈpeɪləʊd有效载荷] big enough to justify further testing. To this end she and her colleagues steadily flushed[flʌʃ]冲刷 water past samples of urea-enhanced hydroxyapatite held in tubes, while watching what happened using a spectroscope[ˈspektrəskəʊp]分光镜. The material shed流出 its urea load gradually: 40% after 1,000 seconds;60% after 2,000 seconds; 80% after 3,820 seconds. In contrast[ˈkɒntrɑ:st]相比之下, when the researchers treated pure urea the same way, it was all gone in 320 seconds. To find out whether the new fertiliser would make a difference in the field, Dr Kottegoda collaborated [kəˈlæbəreɪt]合作 with some farmers near Sammanthurai, in eastern Sri Lanka.She ran tests on equal-sized rice paddies[ˈpædi]当稻谷 for four months. Some plots received no fertiliser at all. Some got pure urea equivalent[ɪˈkwɪvələnt] to等于100kg of nitrogen per hectare[ˈhekteə(r)]公顷. Some got an amount of the newly created urea hydroxyapatite that contained the same quantity of nitrogen as the pure urea. And in all cases the level of phosphorus[ˈfɒsfərəs]磷 (another important plant nutrient[ˈnju:triənt]养分, levels of which were boosted提高 incidentally [ˌɪnsɪˈdentli]附带by the hydroxyapatite) were adjusted to match from plot to plot. The hydroxyapatite did, indeed, make a difference. Plots that received no nitrogen-based fertiliser at all averaged 5.5 tonnes of rice per hectare. Those that received urea alone yielded[ji:ld]生产 7.25 tonnes per hectare. Those fertilised with urea-hydroxyapatite managed 7.8 tonnes per hectare. Though the newly compounded fertiliser is more expensive to produce than its conventional [kənˈvenʃənl]传统的 equivalent对等物, Dr Kottegoda calculates that this cost would quickly be offset[ˈɒfset]补偿 if using urea-hydroxyapatite obviated[ˈɒbvieɪt] 避免 the need to re-scatter fertiliser over a paddy after heavy rain—and that does not even take into account the increase in yield it brings with a single application. There might also (though she did not measure this) be a bonus reduction in the amount of phosphorus-based fertiliser a farmer needs to deploy[dɪˈplɔɪ]施用 in addition to nitrogen-based pellets. A simple idea, then. But a potentially important one. 歌曲:color blind----Matt B