"I worry because so many clever and decent people were killed," said high school student Pawel Kwas, 17.

“我担心，因为这么多聪明和正派的人遇难了，”17岁的高中学生帕维尔-克瓦说。

The aef of kwas negative in nk treatment while increased rapidly in npk treatment after10-year crop cultivation; k was also one of critical limited nutrients for crop yield .

k的农学效率在试验进行10年后nk处理平均为负值，同期npk处理中小麦k的农学效率却急剧增加，k成为作物高产的限制因素；