Evaluation of the establishment of lowland and upland switchgrass (Panicum virgatum L.) varieties under different tillage and seedbed conditions in northern Italy

Information is needed on potential biomass crops for marginal lands in southern Europe. The objective of this study was to investigate switchgrass establishment in four seedbed preparation treatments (sowing, rolling before sowing, rolling before and after sowing and no till) for two varieties (small and large seed types). A 4×2 split-plot factorial design with four blocks was adopted over a 2 years period. Trials were conducted in Bologna (latitude 44°33′N, longitude 11°21′E, 32 m a.s.l.), in a silt loam soil (Udic Ustochreps fine silty, mixed, mesic). In general, emergence was lower in the autumn trials than in the spring one. Emergence on rolled soil (single and double) was statistically higher than tilled unrolled soil. Cumulative analysis of the two autumn trials including no till showed a significant (P≤0.05) interaction between treatment and varieties: the large seed variety had a better performance only with no till, particularly in the first year. Overall, if no till was not considered, no significant interactions between variety and tillage treatments were found for final seedling numbers. The statistical analysis on both varieties was therefore combined. Although the double rolled tillage treatment consistently showed a slightly higher average seedling emergence than the single rolled treatment, the final number of emerged seedlings was never significantly different. In all cases, the rolled treatments (single and double) had significantly higher final emergence rates than the treatment with no soil compaction. The average emergence index of unrolled plots was 20% lower than rolled plots. A function was calculated to predict the seedling numbers at the end of emergence based on the seedling numbers at the beginning of emergence. Generally rolling was needed to obtain best switchgrass performances. In northern Italy both varieties had a good emergence when soil conditions were appropriated.