100 ▣0-15cm 0607050 ☐15-30cm 554302000 <100 100-120 120-150150-180180-200 200-250 >250 Nitrogen Fertilizer Ration(lbs ay) Levels of root colonization in upper 15 cm decreased with increasing N fertilization rate 菌根侵染率随施氮量增加而降低 果制卷业须士生瀑程yao2果树专业硕士生课程-yao2 Levels of root colonization in upper 15 cm decreased with increasing N fertilization rate 菌根侵染率随施氮量增加而降低