Abstract: Under high-yielding cultivation condition,this paper studied the spatiotemporal variations of soil NO₃^--N and NH₄⁺-N contents as affected by different nitrogen application rate and its basal-/top-dressing ratio,and calculated the apparent budget of soil nitrogen at different growth stages of wheat. The results indicated that compared with split application,applying all fertilizer nitrogen at jointing stage decreased the soil NO₃^--N content and apparent surplus of soil nitrogen before jointing stage,and decreased the nitrogen leaching to deeper soil layers. Applying fertilizer nitrogen at flagging stage had no significant difference with split application in soil NO₃^--N content,but increased soil NH₄⁺-N content.Applying fertilizer nitrogen at maturing stage increased the soil NO₃^--N content in 0～60 cm and 0～20 cm layers. In comparing with applying 240 kg·hm^-2 of fertilizer nitrogen at jointing stage,applying 168 kg·hm^-2 of fertilizer nitrogen at the same stage decreased the soil NO₃^--N and NH₄⁺-N contents at flagging stage,soil nitrogen deficit from flagging to maturing stage,and soil NO₃^--N content at maturing stage. The grain yield and its protein content had no significant difference among different treatments,but applying all 168 kg·hm^-2 fertilizer nitrogen at jointing stage induced the highest grain protein content.

Key words: Pear, Pear rust, Gymnosporangium haraeanum, Resistance, Niche breadth