CARBOHYDRATE AND NITROGEN PARTITIONING WITHIN ONE-YEAR SHOOTS OF YOUNG PEACH-TREES GROWN WITH GRASS COMPETITION

Carbohydrate and. nitrogen were measured during 1992 and 1993 in shoot s of peach [Prunus persica (L.) Batsch.] trees that were planted in 19 89 and grown in three vegetation-free areas contained within plots pla nted to tall fescue (Festuca arundinacea Schreber), orchardgrass (Dact ylis glomerata L.), or a mixture of Lolium perenne E. and Festuca rubr a L. Trees grown in 9.3-, 3.3-, and 1.5-m(2) vegetation-free areas had the greatest to the least fruit yield, respectively. Fruit number and mass were negatively correlated with stem mass. Grass type had little effect on mass, carbohydrate, or N partitioning within the tree. Indi vidual sugars and carbohydrate partitioning were not affected by grass competition. In contrast, the proportion of shoot N partitioning into stem and leaves declined markedly as the size of the vegetation-free area increased. Proximity of peach trees to grass may have limited N u ptake, which, in turn, reduced fruit yield but not stem and leaf growt h.