Abstract:

The poplar(.Populus tomentosa Carr.) shading on farm field, with shading index and shading degree, was reported under poplar crop intercropping system in Northern China farm region. The results demonstrate that poplar young growth (spacing 3 m×2 m×18 m) brought on shading index 1.3%～67.8% and shading degree 0.3%～16.5% on farm field when stand ages were 1～7 years, and near and mature stand (spacing 4 m×30 m) resulted in shading index 51.3%～76.0% and shading degree 22.8%～28.1% when stand 10～14 years as well. But using shading degree to express shading on farm field is better than shading index, and shading degree 15% is suggested the maximum shading degree that could be accepted in farm field.

Key words: Poplar-crop intercropping, Shading degree, Shading index, Populus tomentosa