Influence of harvest time and frequency on light interception and biomass yield of festulolium and tall fescue cultivated on a peatland

Abstract

Abstract In this study, we report efficiencies of light capture and biomass yield of festulolium and tall fescue cultivated on a riparian fen in Denmark under different harvesting managements. Green biomass targeted for biogas production was harvested either as two cuts (2C) or three cuts (3C) in a year. Three different timings of the first cut in the 2C systems were included as early (2C-early), middle (2C-mid) and late (2C-late) cuts corresponding to pre-heading, inflorescence emergence and flowering stages, respectively. The fraction of intercepted photosynthetically active radiation (f PAR ) was derived from the canopy reflectance measured on 61 dates throughout a year, and cumulative interception of PAR (IPAR) and radiation use efficiency (RUE) was calculated. The dynamics of f PAR and biomass accumulations was similar for both crops before the first cuts in all managements. Festulolium f PAR in 2C-early and 2C-mid managements declined faster than in 2C-late and 3C managements in the second growth period and thus growing period IPAR of 2C-early and 2C-mid declined by 8% as compared to 3C management where IPAR was 925 MJ m −2 . Annual festulolium dry matter (DM) yield in 2C-early and 2C-mid managements (average 14.1 Mg DM ha −1 ) decreased by 22% compared to 3C management (18.2 Mg DM ha −1 ). The highest and the lowest RUE of festulolium were observed in 3C and 2C-mid managements as 1.97 and 1.59 g MJ −1 , respectively. For tall fescue f PAR declined rather slowly in the second growing period in all 2C managements, which contributed to similar IPAR (908–919 MJ m −2 ), total biomass yield (16.4–18.8 Mg DM ha −1 yr −1 ) and RUE (1.80–2.07 g MJ −1 ) for all managements. Whereas both crops were highly productive under both 3C management and 2C management with first harvest after flowering (i.e., 2C-late), the 2C-late strategy is recommended as the least intensive of the two management systems.