Nitrogen application to non-bearing 'Bing' sweet cherry trees on Gisela~R6 rootstock: Effects on accumulation and partitioning of biomass and nitrogen

摘要

Newly planted sweet cherry (Prunus avium L.) orchards in Chile have mainly been established at high densities, extensively using Gisela~R6 rootstock. There is no published information to establish adequate N fertilization in young non-bearing sweet cherry trees on dwarfing rootstocks, despite major influence of N on tree vigor and dry matter allocation. In order to study the effect of N application on accumulation and partitioning of biomass and N in young trees, an experiment was conducted in 'Bing'sweet cherry trees on Gisela~R6 rootstock during the first three years after planting. The orchard was planted in 2006 at a plant density of 889 plants ha~(-1) in central Chile with warm temperate climate. Three N rates (0.60, and 120 kg ha~(-1)) were applied as urea during each growing season in a four-replicate completely randomized design. At the end of the first, second and third seasons, one tree per experimental unit was removed, and then divided into their individual components for dry weight and total N concentration analysis.Young trees experienced a pronounced accumulation of biomass and N during first three seasons (on average 4600 g dry weight tree and 73 gN tree~(-1)), which was mainly due to growth and N uptake of perennial organs. Whole-tree biomass production and whole-tree N content were linearly related, with a N productivity of 59 g dry weight tree~(-1) per each g of N in the tree. Young trees had a low apparent recovery efficiency of the applied N (less than 15%), which was attributed to a high N supply in relation to tree demand (20 and 53 gN tree for the second and third seasons, respectively). N fertilization did not affect tree growth, but increased N tissue concentration, which demonstrates that soil N supply was sufficient to meet N demand of the trees ofthe control treatment. Even under such condition. N fertilization should not be discarded because of the significantly increased levels of N accumulated in storage organs. We observed that N concentration in senescent leaves could be an acceptable indicator of size of the N-storage pool.