In agroforestry systems (AFS), trees shade the understory crop to a certain extent. Potato is considered a shade-tolerant crop and was thus tested under the given total solar irradiance and climatic conditions of Southwestern Germany for its potential suitability in an AFS. To gain a better understanding of the effects of shade on growth, yield and quality; a three-year field experiment with different artificial shading levels (12%, 26% and 50%) was established. Significant changes in growth occurred at 50% shading. While plant emergence was not affected by shade, flowering was slightly delayed by about three days. Days until senescence also showed a delay under 50% shade. The number of tubers per plant and tuber mass per plant were reduced by about 53% and 69% under 50% shade. Depending on the year, tuber dry matter yield showed a decrease of 19–44% at 50% shade, while starch content showed no significant differences under shade compared to unshaded treatment. The number of stems per plant, plant height and foliage mass per plant as well as tuber fraction, black spot bruise and macronutrient content were unaffected. Overall, potato seems to tolerate shading and can therefore be integrated in an AFS, and can cope with a reduced total irradiance up to 26%.

Maize cultivation faces some challenges, particularly in terms of low biodiversity in fields. Since maize is a highly efficient and economic crop, it is cultivated on large areas in Germany, with a high share in crop rotation, especially where cattle farming takes place. Such landscapes provide less habitat and food resources for small vertebrates and arthropods. Intercropping maize with flowering partners might have a positive effect on the environment and might promote biodiversity in agricultural ecosystems. Therefore, in two-year field experiments on three sites in south-western Germany, plants were tested for their suitability as intercropping partners in maize crops (Medicago sativa, Melilotus officinalis, Vicia sativa, Tropaeolum majus, Cucurbita pepo, and Phaseolus vulgaris). Almost all tested partners produced flowers, except M. officinalis. Intercropping maize with P. vulgaris or T. majus achieved comparable dry matter yields as sole maize, without changes in the biomass quality. For maize-intercropping, site adapted weed control and practicable sowing technique are mandatory, which already exist for P. vulgaris and T. majus. The study shows that intercropping maize with biodiversity-enhancing flowering partners can provide an applicable alternative to sole maize cropping and enhance biodiversity. The large production areas of maize have great potential for ecological improvements in agriculture.

Agroforestry, as an improved cropping system, offers some advantages in terms of yield, biodiversity, erosion protection or habitats for beneficial insects. It can fulfill the actual sustainability requirements for bioenergy production like food supply, nature conservation, stop of deforestation. However, competition between intercropped species for water, nutrients and light availability has to be carefully considered. A field trial with shading nets was conducted in Southwest Germany to evaluate the influence of different shading levels (−12, −26, and −50% of full sunlight) on biomass growth, dry matter yield and biogas quality parameters of maize (Zea mays L., cv. ‘Corioli CS’). Shading the plants causes a delayed development, a reduction in height and leaf area index and a slower senescence. Dry matter yields were reduced about 18%, 19%, and 44% compared to 21.05 Mg ha−1 year−1 at full sunlight. Biogas and methane yields were also significantly reduced, the 50% shading treatment showed a reduction of 45% for both parameters. Further, shading led to higher crude protein and crude ash contents. If silage maize is grown under shade, the yields of dry matter, biogas, and methane are nearly halved under 50% shade. Cultivation up to 26% shading could be possible.

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