Effects of timing of nitrogen fertilization on shoot development in peach (Prunus persica) trees

Shoot development was studied for two consecutive years in poach trees fert ilized with N either in the previous fall or in the middle of the growing s eason. During the first year, two additional treatments were studied: no N supply and nitrate supplied in the irrigation water throughout the growing season. The number of shoots that developed depended on nitrogen availabili ty in the period following bud break. During shoot development, loaf emerge nce occurred in one, two, or three stages, which ended at about 500 to 600 degree days, 1000 to 1200 degree days, and 1500 to 2000 degree days after b loom, respectively. The proportion of shoots exhibiting a second or third d evelopmental stage depended on nitrogen availability at the beginning of th at stage. Increasing nitrogen availability during a developmental stage pro longed the stage and increased the number of leaves produced.