Effects of intercropping and nitrogen application on protein and starch contents of wheat grain and faba bean seeds

Objectives We assessed the characteristics of grain starch and protein content of wheat and faba bean under intercropping and nitrogen (N) application.

Methods The wheat and faba bean intercropping field trial was conducted in Kunming, Yunnan in 2019 and 2020. The tested cultivar for wheat was Triticum aestivum L, and that of faba bean was Vicia faba L. The cropping pattern treatments included mono-wheat (MW), mono-faba bean (MF), and wheat and faba bean intercropping (W/F). Four N levels were setup under each cropping pattern. The four N application levels for wheat were N 0, 90, 180, 270 kg/hm², and those of faba bean were N 0, 45, 90, 135 kg/hm². The protein and starch content of wheat grains and faba bean seeds were determined at maturity stage.

Results The total starch content in both inter- and mono-cropped wheat grains decreased with increasing N application rates. In 2019 and 2020, intercropping increased wheat total starch by10% and 22%, amylopectin by 5% and 18%, and amylose by 18% and 28%, as compared to mono-wheat. N application levels did not affect the starch content of faba beans over the two years. Compared to mono-faba bean, intercropping decreased amylopectin, amylose and total starch contents of faba bean seeds in 2019. Regardless of N application levels, intercropping increased the total protein and gliadin contents of wheat grains by 5% and 9% in 2019, and 6% and 15% in 2020, respectively, as compared to MW. Intercropping increased globulin and gliadin contents of faba bean seed in 2019, but did not have effect on the content of gliadin in 2020.

Conclusions Wheat and faba bean intercropping increased wheat grain protein and starch contents, and showed little influence on those of faba bean seeds. Hence, wheat and faba bean intercropping is a promising planting pattern for high quality wheat production.