Effect of harvesting frequency and maturity stage of Jerusalem artichoke forage on yield, chemical composition and in vitro fermentation of the tubers and forage

Aim of study: To evaluate the effect of maturity stage and harvesting frequency of Jerusalem artichoke (JA) forage on the nutritional quality of the tubers and forages.Area of study: The plant cultivation and laboratory experiments were carried out in Karaj (Alborz, Iran) and Tehran (Tehran, Iran), respectively.Material and methods: Forages were harvested every 60, 90 and 120 days during the growing season (four, three and two harvests per year, respectively). Tubers were harvested just once, at the end of the growing season, from plots with four, three and two forage cuts per year. Biomass production, chemical composition and in vitro ruminal fermentation of the forages and tubers were assessed.Main results: Compared to 90 and 120 days, the forages harvested every 60 days contained the highest (p<0.05) yearly dry matter (DM) biomass (27.16 t/ha), crude protein (98.6 to 145 g/kg DM), organic matter digestibility (0.607 to 0.691) and microbial biomass production (350 to 369 g/kg DM). Compared to 60 and 90 days, harvesting JA forage every 120 days caused the tubers with the higher (p<0.05) water-soluble carbohydrates (WSC), in vitro digestibility and DM yield (7.63 t/ha). Jerusalem artichoke forages and tubers contained the low phenolics (4.93 to 13.2 g/kg DM) and nitrate (1.12 to 3.19 g/kg DM). Overall, the best harvesting interval of JA forage to achieve tubers with the highest yearly yield, WSC and digestibility was every 120 days, while the highest nutritive value and yield of the forages were observed with harvesting JA every 60 days.Research highlights: The best harvesting interval of JA forage to obtain the highest yearly DM, protein and energy biomass from both tubers and forage was every 60 days