Maize-bean intercropping yields in Northern Germany are comparable to those of pure silage maize

Maize-bean intercropping is currently gaining popularity among farmers in Germany, although there is hardly any data available on the yield potential under moderate maritime climate conditions in comparison to pure maize cultivation as well as on the choice of the bean cultivar. To assess the agronomic potential of maize-bean intercropping for organic farming, field-experiments over two growing seasons were conducted in Northern Germany (53°46′N, 10°30′E). A split-plot design with two sowing times of the beans as main-plot-factor and different bean species and cultivars (Phaseolus vulgaris, cv.: Cobra, Eva, Tarbais, P. coccineus, cv.: Preisgewinner, Weiße Riesen, Vicia faba cv.: Isabell) as subplot-factor was applied. In both years, the average intercropping yield (11 t ha⁻¹ in 2011 and 14 t ha⁻¹ in 2012) of the two sowing dates was comparable to that of maize-control, except for Maize-Eva in 2011. The highest intercropping yields in 2011 were shown by cv. Tarbais and Preisgewinner with bean shares ranging from 34% to 39%. By contrast, the late-sown beans in 2012 had a share of 6–12% only, reflecting the overall higher maize yield level. Compared to maize control, the intercropping with Tarbais and Preisgewinner, which achieved the highest leaf mass scores, led to a significant improvement in crude protein yield by 36% and 18% in 2011, respectively. Earlier ripening bean cultivars (e.g. cv. Eva and Cobra) tend to lose their leaves before harvest. So cultivars with a longer growth period (e.g. cv. Tarbais), similar to maize, should be used to achieve high bean and crude protein yields. Our results demonstrate the importance of cultivar choice for achieving high bean yields that have the potential to improve feed quality. Tarbais and Preisgewinner were the most suitable cultivars for maize-bean intercropping, as they achieved the highest bean yields and improved the crude protein yield in 2011. Even though further optimization is indispensable, we have shown that maize-bean intercropping can fit into organic farming systems under moderate maritime climate.