Effects of organic amendments on productivity, nitrogen uptake, and protein content in pea–barley intercrops

Cereal‐legume intercropping combined with organic amendments is considered to be a promising technique to improve crop productivity and efficiency in land use. The intercropping performance is influenced by pedoclimatic conditions, crop combinations, and crop management. Intercropping of pea ( Pisum sativum L.) and barley ( Hordeum vulgare L.) is commonly practiced in Denmark to produce both seeds and fodder. This study aimed to evaluate the effects of organic amendments on productivity, nitrogen uptake, and grain protein content in pea–barley intercrops (PB IC). A 1‐year field study was carried out in a strip‐plot design with three cropping systems, PB IC, pea sole (PS), and barley sole (BS), with six organic amendment treatments: unamended control, biochar, compost, insect frass, vermicompost, and pelletized frass. Averaged across amendments, PB IC increased grain yield by 12%–135%, aboveground dry biomass by 18%–57%, and grain nitrogen uptake by 66%–94% more than solecrops, while weed biomass was 83% lower relative to PS. Averaged across cropping systems pelletized frass increased grain yield by 105% and straw and grain nitrogen uptake by 49% and 101%, respectively, compared to the control. Among the treatments, the land equivalent ratio varied from 1.15 to 2.47, indicating improved land use efficiency in intercrops. Barley protein content in PB IC was consistently higher than BS across all treatments. The sygergistic effects of organic amendments in PB IC, particularly with pelletized frass, improved crop yield, N‐uptake, grain protein content, and land use efficiency. The present study provided robust evidence that combining pea–barley intercropping with organic amendments is beneficial in multiple ways to promote sustainable intensification.