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 shoots of peach [Prunus persica (L.) Batsch.] trees that were planted in 1989 and grown in three vegetation-free areas contained within plots planted to tall fescue (Festuca arundinacea Schreber), orchardgrass (Dactylis glomerata L.), or a mixture of Lolium perenne E. and Festuca rubra 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. Individual 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 uptake, which, in turn, reduced fruit yield but not stem and leaf growth.