Perennial wild plant mixtures for biomass production: Impact of species composition dynamics on yield performance over a five-year cultivation period in southwest Germany

Abstract

Abstract Wild plant mixtures (WPMs) are a promising perennial cultivation system for biogas production with numerous ecological benefits. However, to date, there is little information on their long-term development. To investigate this, two different WPMs (S1, Rieger-Hofmann GmbH, 2016 ; S2, Saaten-Zeller GmbH, 2016 ) of up to 27 native, mainly wild species with a combination of annual, biennial and perennial life cycles were established at three sites in southwest Germany in 2011. At Hohenheim (HOH), fertilization was varied (0, 50, 100 kg ha −1 nitrogen) and a split plot design with three replications was used. At Renningen (REN) and Sankt Johann (SJO) single plots were used and fertilized with 50 kg ha −1 . Harvest and sample analysis were conducted each year over a five-year cultivation period. The development of dry matter yield (DMY), dry matter content (DMC) and species composition dynamics of the WPMs were investigated. The DMYs varied strongly between the mixtures, sites and years, ranging from 2.9–22.5 Mg ha −1 yr −1 . Significant effects of mixture (P −1 s). For both mixtures, a high number (up to 19) of WPM species were recorded, but this declined over the cultivation period at all sites. The DMYs at REN and SJO increased with time, whereas at HOH the high weed pressure from the grassland pre-crop resulted in decreasing yields. Here, the nitrogen mineralization of the grassland residues was high enough to mask fertilization effects. A good substrate quality for ensilaging (DMC >28%) was achieved at all sites every year except 2011. From these findings, we can recommend the WPM concept based on the S2 mixture as a feasible cultivation system with potentially high ecological benefits, in particular for marginal sites.