A long-term field plot experiment was conducted to study the effects of phosphorus and potassium runoff under different fertilization modes(none fertilization,chemical fertilization,combined application of chemical fertilizer with biochar,combined application of chemical fertilizer with organic manure,combined application of chemical and organic manure with biochar)on dryland.Results showed that:Applying chemical fertilizer could obviously increase all kinds of nitrogen runoff in dryland.Compared with chemical fertilization,the following fer...