Is durum wheat-winter pea intercropping efficient to improve the use of N in low input farming ?

Nitrogen acquisition and grain protein concentration (GPC) of durum wheat is often a major concern, particularly in low input systems where mineral N is a limited resource. In this present paper we assessed the hypothesis that the performance of durum wheat and winter pea, grown in intercrop (IC) is better than in sole crops (SC) for their ability to improve the use of N resources. Field experiment was carried out in SW France in 2005-2006 with three fertiliser-N supply: no fertilizer (N0), 100 kg N ha-1 (N100), and 180 kg N ha-1 (N180). For all treatments, N uptake of durum wheat was significantly greater in SC than in IC but was always lower than the whole IC cover. The nitrogen status (NNI) and the GPC of wheat were higher in IC than SC and obviously increased with N availability. The greatest NNI and GPC of wheat in IC was mainly due to a greater N uptake of soil mineral N per plant. Moreover, the complementary use of soil and symbiotic N2 fixation sources allowed a better N acquisition by the whole IC compared to wheat SC. This advantage was not observed for N180 because fertilizer-N increased wheat growth and induced a reduction of pea growth due to light competition