Abstract
Maize is grown on a large area in Germany and there is a growing concern in society about negative environmental effects related to this. The objective of the study was to test the performance of mixtures of maize and climbing beans as an alternative to monocropped maize under different site and management conditions. The effects of sowing density of maize and beans as well as the sowing time of beans on total dry matter (DM) yield and bean DM contribution to the total yield were investigated. Further, various mechanical and chemical weed control methods were tested and the resulting total DM yield was compared with that of a reference treatment (manual weeding). Hardly any consistent yield difference between maize/bean mixtures and monocropped maize occurred. The proportion of beans varied over a wide range among sites and was consistently higher when beans were sown at an early growth stage of maize. Mixtures did not suppress weeds efficiently and at two of the three sites their yield clearly declined with increasing weed coverage in the mixtures. A weed coverage of up to circa 10% may be tolerated, as the corresponding yield reduction is less than 1 t ha−1. Considering the additional effort (i.e., two sowings, high costs for bean seeds, complicated weed control) in managing such mixtures, it can be concluded that maize/bean mixtures can currently hardly be recommended as an alternative to monocropped maize for feedstock production.
Highlights
The amount of monocropped maize in Germany increased from 0.8 million (m) ha in 1980 to2.5 m ha in 2015 [1]
Considering the additional effort in managing such mixtures, it can be concluded that maize/bean mixtures can currently hardly be recommended as an alternative to monocropped maize for feedstock production
Weed infestation in GRU was higher in 2014, mixtures performed much better (39.5% weed coverage, 14.95 t dry matter (DM) yield ha−1 on average) in this year than in 2015 (10.7% weed coverage, 7.34 t DM yield ha−1 on average)
Summary
The amount of monocropped maize in Germany increased from 0.8 million (m) ha in 1980 to2.5 m ha in 2015 [1]. Maize is primarily used as fodder for livestock and, in the last 10 years, has been increasingly cultivated to produce silage as an input for biogas plants due to its high yields and advanced breeding activities. This dominance and the cultivation of maize as a monocrop can cause ecological problems like loss of biodiversity, soil erosion, and nitrogen leaching [2,3]. The reduction of diversity may be accompanied by an increasing vulnerability to climatic and other stresses, which raises the risk of harvest losses for individual farmers and undermines the stability of agriculture [4]. Intercropping is considered a suitable management strategy for small farmers [9] to increase the diversity of their products and the stability of their annual output through the effective use of land and other resources
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