In a field micro-plot experiment in China of three intercropping systems (barley/maize, wheat/maize, faba bean/maize) and their corresponding sole cropping systems, nitrogen (N) was applied at N 0 and 225 kg/ha, and N absorption and use efficiency and its accumulation on the soil profile were investigated. The competitive ability of crops for nutrients was closely related to the concentration and accumulation of mineral nitrogen in the root zone of the plants. Accumulation of mineral nitrogen under barley or wheat strips intercropped with maize decreased by 203-282 or 107-171 kg/ha in the 0-100 cm soil profile, respectively, compared with faba bean intercropped with maize. Accumulation of mineral nitrogen under maize strips intercropped with barley or wheat was reduced by 93-120 or 56-87 kg/ha compared with maize intercropped with faba bean, respectively. Crop types, interspecific competition and soil condition affected accumulation of mineral nitrogen in the soil profile. Interspecific interaction increased nitrogen recovery efficiency for barley and wheat intercropped with maize and decreased that for maize intercropped with barley and wheat. Nitrogen use efficiency was the highest in the no-N treatment for competitive intercropping systems (barley/maize or wheat/maize). Nitrogen harvest index was reduced in barley and wheat with N fertilizer application, but increased in maize and not changed in faba bean. It is concluded that competition between crops, soil fertility status, fertilizer rate and cultural measures should be considered carefully in order to achieve intercropping advantage when associated crops are chosen. Complement systems of legumes/cereals are recommended for low soil fertility and competitive systems of cereals/cereals for high soil fertility.
