Temporal complementarity drives nitrogen uptake in strip intercropping with or without legumes

Abstract

Cereal/legume intercropping enables complementary nitrogen (N) uptake, whereas relay intercropping allows temporal complementarity. However, how these mechanisms contribute to N uptake under moderate, species-tailored N fertilization remains unclear, and clarifying this could inform intercropping practices aligned with Good Agricultural Practices in Europe. We therefore determined N uptake of maize (Zea mays L.), wheat (Triticum aestivum L.), faba bean (Vicia faba L.), and pea (Pisum sativum L.) in six bi-specific strip intercrops and corresponding monocrops. We compared relay intercrops involving maize (late sown) with simultaneous intercrops without maize, across cereal/legume, cereal/cereal, and legume/legume combinations. All species received locally recommended fertilizer amounts for conventional agriculture in the Netherlands. In relay strip intercrops, the early-sown wheat, faba bean, and pea had higher N uptake than the respective monocrops, especially in the border rows of strips. Maize N uptake increased when intercropped with wheat or pea in a year with substantial temporal complementarity. Intercropping with faba bean did not result in increased N uptake for either cereals or pea. Relay intercrops showed land equivalent ratios for N uptake and fertilizer N equivalent ratios mostly above one, while for simultaneous intercrops these were mostly close to one. Therefore, relay intercrops used land more efficiently for N uptake and saved fertilizer N for yield compared to monocrops, whereas simultaneous intercrops did not. We investigated, for the first time, the relative importance of temporal complementarity and cereal-legume N acquisition complementarity for N uptake in strip intercropping under conventional European agriculture, showing that complementary N uptake was strongly associated with temporal complementarity. While inclusion of legumes in intercropping was not required to achieve complementary N capture, it allowed for reduced N input. Relay strip intercropping with species-tailored N input is a pathway toward more sustainable N use in agriculture that can complement cereal-legume complementarity.