Rapeseed-pea intercrop outperforms wheat-legume ones in land-use efficiency in Mediterranean conditions

Abstract

Context

Intercropping has gained attention as a strategy to diversify cereal-based systems and enhance sustainability. However, its performance in Mediterranean conditions, especially in non-organic farming, remains less explored.

Objective

Assess the performance of intercropping under contrasting nitrogen (N) fertilisation levels to enhance productivity in the Mediterranean region.

Methods

Three intercropping (IC) systems were compared with their respective sole crops under on-farm irrigated conditions in the Ebro Valley (NE Spain). The mixtures included rapeseed/pea (IC-RP) and durum wheat/pea (IC-WP) over three seasons from 2021 to 2023, and durum wheat/faba bean (IC-WF) in 2022 and 2023. A row intercropping design was set at a 50/50 replacement ratio, with two N fertilisation treatments: 0 N (no mineral N) and +N (75 kg mineral N ha⁻¹, with additional pre-sowing fertilisation with pig slurry applied at 165 kg N ha⁻¹ in 2023 only). Key variables included grain yield, land equivalent ratio (LER), overyielding index, biomass and N concentration.

Results

The IC-WP and IC-WF showed reduced legumes yields due to competition, with no overyielding or increased land use efficiency (LER=0.94 and 0.86, respectively). In contrast, IC-RP exhibited increased land use efficiency (LER=1.43), though with high variability, and achieved overyielding (+9 %) in only one out of the three years.

Conclusions

Intercropping productivity in Mediterranean areas depends heavily on species selection. Pairing species with different physiology, like rapeseed and pea, promotes temporal niche differentiation and compensation mechanisms. Conversely, closer-matched species like wheat and legumes tend to intensify competition, reducing benefits.

Implications or significance

Several indicators are necessary to assess intercropping performance. Rapeseed-pea intercropping warrants deeper exploration in Mediterranean conditions.