So feeding Russian thistle to farm animals is not always safe.

因此，用俄罗斯蓟喂养农场动物并不总是安全的。

This happens because Russian thistle is very efficient at taking water out of the soil.

发生这种情况是因为俄罗斯蓟能够非常有效地从土壤中吸收水分。

You see, under certain conditions, Russian thistle can absorb high levels of nitrogen from the soil and store it in the form of nitrate.

你看，在某些条件下，俄罗斯蓟可以从土壤中吸收高含量的氮，并以硝酸盐的形式储存起来。