这已接近大豆所能承受的最高温度，而当温度超过这一水平时，玉米和水稻的产量就会受到影响。

This is close to the maximum temperature that beans can tolerate, while corn and rice yields suffer when temperatures exceed this level.

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1990 - 2008年，玉米产量上升1.8%左右，接近其长期平均水平，小麦产量增长不及玉米的一半，跟自己的历史平均水平相比增加了一半。

Maize yields in 1990-2008 rose by 1.8% a year, close to their long-term average; wheat yields increased by less than half that, half their historic average.

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玉米的产量在1990 - 2008年间以每年1.8%的幅度增长，接近它们长期的平均水平，但在该期间小麦的产量增幅比玉米产量增幅的一半还少，是它们历史平均水平的一半。

And it shows. Maize yields in 1990-2008 rose by 1.8% a year, close to their long-term average; wheat yields increased by less than half that, half their historic average.

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