Abstract: A filed experiment of intercropping winter wheat and summer maize with young poplars was conducted to study the effects of poplar on crop yield and yield-forming factors. The results showed that compared with monoculture,intercropping with 1-2 years old poplar somewhat increased the wheat yield but decreased the maize yield by 31.3%-33.7%, while intercropping with 3-4 years old poplar decrease d the wheat and maize yield by 36.9%-42.5% and 80.8%-87.4%, respectively. Among the yield-forming factors of winter wheat, ear number was the main one affected by poplar,and thus, more attention should be paid to the water and fertilizer management at the tillering stage of wheat. For summer maize, the main affec ted yield-forming factor was from grain number to ear number with the growth of poplar, and thereby, it was necessary to ensure the resources supply at the elongation-silking stage of maize,and to strengthen the management of poplar after its 2-3 years growth.It was suggested that in the practice of agro-forestry,an integral consideration must be made on the biological characteristics and reasonable management of tree species and crops.

Key words: Intercropping, Root system, Wheat-soybean intercropping, Corn cabbage intercropping