Root biomass and shoot to root ratios of perennial forage crops in eastern Canada

Shoot to root ratios (S:R) at peak standing crop are commonly used to estimate the annual crop residue C inputs to the soil from the root biomass left in the soil at harvest. However, root biomass has often been neglected in field studies and estimates of S:R for many commonly grown forage species are not available. Our objective was to determine root biomass and S:R of seven perennial grass species and two perennial legume species under eastern Canadian soil and climatic conditions. Root biomass in three soil layers (0–15, 15–30 and 30–45 cm) was measured shortly after the second harvest in the first (1995) and second (1996) year of production. Two harvests of aboveground DM were taken each year. The total root biomass (0–45 cm) in the second year of production (average of 1437 g m-2) was twice that measured in the first year of production (average of 683 g m-2). This temporal variation was mainly explained by the increase of root biomass in the 0- to 15-cm layer. The proportion of total root biomass (0–...