Leaf N Concentration on Citrus Trees during the First Eight Years in the Field

摘要

A field experiment was conducted from 1999 (plantation year) to 2006, with Lane * Late' oranges (Citrus sinensis) on 'Carrizo' citrange (Porcirus trifoliata X C. sinensis) rootstock, in Gleyic Podzol, located at Algarve (South of Portugal) , to establish the optimum N leaf concentration along the first eight years of the orchard. The experimental design included five treatments of increasing N rates. Leaf samples from spring flushes (eight months old) were collected yearly and chemically analysed for N. Assuming that the mean values of leaf N concentration for all treatments correspond to the adequate nutritional status of the trees, the optimum leaf N concentrations obtained in this experiment, expressed as g N/kg DW, could be fitted in accordance with the following logarithmic adjustment: N=34. 5 -6. 8 * Iog10(x) , where x=" number years after planting" , with an r2=0. 81 for P=0. 001, corresponding to 34. 5, 32. 5, 31. 3, 30.4, 29. 7, 29. 2, 28. 8 and 28.4 respectively from the first to the eighth year.