Grower perspectives on perennial wild plant mixtures for biogas production in Germany

Abstract

‘Perennial wild plant mixtures’ (WPM) cultivation is a novel approach to combine biomass provisioning for biogas production with biodiversity enhancement at field scale in Germany. But the methane yield is about 40% lower compared with silage maize. Therefore, the cultivation of WPM is incentivized with about 250–927 Euro per hectare and year. However, agronomic and best management practices of WPM cultivation are unclear, so that large parts of the yield potential of WPM are likely to remain untapped. Hence, this study aims to shed light on farmers’ current perspectives and experiences with WPM cultivation by carrying out a nationwide survey in 2021. The feasibility of inferential statistics was examined in detail, but was not possible due to an insufficient number of responses. Nevertheless, the descriptive analysis revealed valuable information on farmers’ experiences with and their motives for cultivating WPM such as biodiversity enhancement and landscape beauty. Generally, WPM were proven to be much less productive compared with common biogas crops such as maize. Nevertheless, 59% of the farmers cultivated WPM on less favorable soil, and 67% of the farmers used nitrogen fertilization rates of less than or equal to 50 kg ha−1, resulting in generally higher yields compared with results from unfertilized areas. However, while there is common agreement on the positive effects of WPM cultivation on agrobiodiversity, more agronomic research on best management practices is required to make WPM more competitive to common biogas crops without additional subsidies.