Patterns in non-structural carbohydrate and nitrogen reserves in chicory (Cichorium intybus L.) and plantain (Plantago lanceolata L.) during regrowth in summer

Abstract

Chicory (Cichorium intybus L.) and narrow-leaved plantain (Plantago lanceolata L.) are capable of producing a large amount of high quality feed during summer. Like many species, grazing management decisions influence their dry matter (DM) production. One of the factors implicated in the grazing-management effect on yield of other forages are plant non-structural carbohydrate (NSC) or nitrogen (N) reserves. The aim of this experiment was to characterise the patterns of NSC and N reserve depletion and replenishment for chicory and plantain during a 35-day regrowth cycle in summer, and investigate the impact of residual height on NSC and N reserves. In chicory roots, the NSC concentration tended (P = 0.09) to decline for 7 days post-defoliation before replenishment began and pre-defoliation concentrations were attained by Day 21 of regrowth (310 growing degree-days; GDD). Similarly, the amount of NSC in plantain roots declined for 14 days post-defoliation (P < 0.001), increasing again from Day 21 and with full replenishment to pre-defoliation levels by Day 35 of regrowth (532 GDD). The two residual heights tested (30 and 60 mm) had minimal impact on NSC reserves during regrowth in either chicory or plantain, likely because the majority of NSC reserves are stored in the roots rather than the stubble. In other plant species, a failure to replenish NSC reserves before the next defoliation is one factor associated with reduced DM production. This also appears to be the case with chicory and plantain, with reductions in DM production occurring if swards are defoliated during NSC mobilisation or the early stages of replenishment (i.e. before 21 days of regrowth or 310 GDD in chicory and 35 days of regrowth or 532 GDD in plantain).