The simultaneous assessment of nitrogen and water use efficiency by intercropped pea and barley under contrasting pedoclimatic conditions

Currently, there is a pressing need to study and improve both water and nitrogen (N) use efficiency (WUE and NUE). Surprisingly, this topic has not been adequately documented in recent literature, particularly for intercropping systems. This study aims to assess the simultaneous changes in WUE and NUE of the rainfed pea-barley intercropping as compared to their monocultures.

Field trials were conducted over two growing seasons at four experimental sites characterized by varying soil and pedoclimatic conditions. WUE (i.e. kg biomass dry matter per m3 water) and NUE (i.e. Kg biomass dry matter per Kg nitrogen available) were measured in monocultures and intercropping systems.

Our findings indicate that pea-barley intercropping had a greater advantage over monoculture in terms of grain yield (+ 61%) and yield quality (+ 83%) and to a lesser extent in term of plant biomass (+ 35%), except for site 4. Additionally, the results show that under higher rainfall conditions, intercropping exhibited the highest NUE values (5.07 kg grain N kg⁻¹ soil N at sowing), while the highest WUE values (1.40 kg m⁻³) were observed under low-rainfall. Quantifying the relationship between WUE and NUE indicated a positive correlation for intercropping (r² = 0.61, p ≤ 0.001) and pea monocrops for dry biomass during flowering (r² = 0.36, p ≤ 0.01).

These advantages of pea-barley intercropping can be attributed to the improved-use of N and water resources, considering their co-limitation under semiarid conditions.