Abstract: Synergistic effects of shading and nitrogen (N) supply are the basis for establishing an efficient intercropping system of maize and potato. In this study, field experiments with monoculture and intercropping under four different N application levels (N0, 0 kg·hm^-2; N1, 62.5 kg·hm^-2; N2, 125 kg·hm^-2; N3, 187.5 kg·hm^-2) were conducted to assess the effects of N supply on the photosynthetic characteristics and yield of potato. The results showed that yield advantage of intercropping decreased with the increase of N application levels. Compared with that of monoculture, the potato yield of intercropping system was decreased by 2.66%-43.71%. There was a significant difference in P_n between the potato close to the maize side (I-M) and that close to itself side (I-P), with the value of P_n being greater in I-P than in I-M. In comparison to that under monoculture, the P_n of potato under intercropping system was decreased by 8.41%-31.09%, light compensation point decreased by 62.23%  and dark respiration rate decreased by 60.90% at the same N level. Excessive N application and intercropping with maize reduced photosynthetic rate, stomatal conductance and transpiration rate of potato, with the magnitude of decreases being enlarged with the increase of N application levels. Proper control of N application level, as N1 in this study, would be beneficial to maintaining high photosynthetic rate and alleviating the yield reduction of potato after intercropping with maize.

Key words: phloem, carbon allocation, non-structural carbohydrates, xylem, broadleaved Korean pine forest, Changbai Mountain.