The faeces contain nitrogen and it is that which fertilises the desert soil.粪便含氮，而正是氮可以肥化荒芜的土地。What is that which you have just stuffed into the plastic cup?你刚才塞在塑胶杯里的是什么东西？ The faeces contain nitrogen and it is that which fertilizes the desert soil.粪便含氮，而正是氮使荒芜的土地变得肥沃。