几十年来，美国玉米产量提高的关键是氮肥的利用，该肥在非洲的使用成本远比在美国的要高得多，林奇表示。

A key component in raising American corn yields in recent decades, nitrogen fertilizer, is more expensive in Africa than in the United States, Lynch says.

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尽管产量显然对农民很重要，但对抗饥荒更关键的是别把赌注下在一种作物上，要通过在多个地方、多个季节里种植多种作物来分散风险。

Although yield is obviously important to farmers, even more crucial is hedging their bets against famine, spreading the risk by growing many crops, over many seasons, in many locations.

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泰勒称石油的四个关键问题——产量下降，发现量下降，需求增加及石油管道工程不足——已出现多年。

Taylor said the four key issues about oil – declining output, declining discoveries, increasing demand and insufficient projects in the pipeline – have been apparent for many years.

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