The analysis of nursery seedling quality requires measures of content and distribution of seedling biomass, which involves constant destructive sampling. To avoid this, it is possible to get biomass estimations throughout allometric equations from easy-measure variables; however, it is necessary to compute these relationships by species and for the different production environments. The aim of the study was to identify allometric relations between biomass and variables as root collar diameter (D), shoot height (H) and D²H of Pinus pseudostrobus seedlings growing under different production systems, with the purpose of defining if there is an allometric equation for each production system which could estimate total, aboveground and root biomass of seedlings. The analysis of covariance was performed to evaluate the effect of the production system on the relation between biomass and independent variables (D, H, D²H). Influence of the production system on intercepts and slopes of some relations between biomass was found. The full models to predict aboveground biomass and total biomass, considering the production system, had better goodness-fit statistics than those belonging to reduced models; whereas for root biomass, the reduced models shown less relative prediction error than those shown by full models. Root collar diameter explains most biomass variation for the three components.