He says that is because the farmer used rich soil to produce the sod, so it might not do well in clay soils.

VOA: special.2009.07.07

The answer is--this goes way back-- it's an old tradition and they used to have to do this by hand.

答案要追溯到很久之前,这是个古老的传统,他们过去用手工计算

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There it is. He used the prism spectrograph to analyze his results. So what do we have here?

在这里，他用了棱镜分光图来分析他的结果,得到些什么呢？

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