Triticale–lupin intercropping offers a viable option for low-input systems in Mediterranean environments

Triticale and lupin are promising candidates for sustainable intercropping in low-input, mixed crop–livestock farming systems in the Mediterranean basin, where they can be grown as rain-fed crops during the autumn-winter period. A 2-year field trial was conducted in Sardinia, Italy, to compare triticale–lupin row intercropping (IC) with triticale sole cropping (TSC) and lupin sole cropping under four fertilization treatments: nitrogen only (‘N,’ 100 kg ha⁻¹), phosphorus only (‘P,’ 39 kg ha⁻¹), nitrogen and phosphorus combined (‘NP,’ 100 kg ha⁻¹ of N + 39 kg ha⁻¹ of P), and an unfertilized control (‘0’). Measurements included radiation interception, dry matter (DM) production, N percentage, and N uptake per unit area (N yield) at various samplings, along with grain and N yield at maturity. While both species shared a common growing cycle duration, lupin's slower canopy development and shorter height limited its radiation interception and DM production in the intercrop. However, complementarity in DM and N yield was observed across all four sampling dates under the 0 and P treatments, with land equivalent ratio values peaking at 1.71 under the 0 treatment and 1.63 under the P treatment for DM, and around 2 for N yield. The higher DM at maturity translated into greater grain yields for IC compared to TSC under the 0 (3.9 vs. 3.2 t ha⁻¹) and P treatments (4.3 vs. 3.6 t ha⁻¹). IC also outperformed TSC in terms of DM N percentage, particularly at triticale anthesis, with notable differences in the 0 (N% = 1.09 for IC, 0.79 for TSC) and P treatments (N% = 1.17 for IC, 0.83 for TSC). This higher DM N percentage of IC was likely associated with the higher radiation-use efficiency of IC compared to TSC under the 0 fertilization treatment. Furthermore, intercropping triticale with lupin demonstrated potential to replace N fertilization without compromising DM or N content in DM and in straw. The observed complementarity in the absence of fertiliser suggests that this intercrop could be especially suitable for low-input systems. The experimental approach helped link the N-related benefits of cereal–legume intercrops to radiation acquisition and radiation-use efficiency, while highlighting the critical role of canopy developmental rates, and hence of cultivar choice, when height differences are substantial.