ISHS Acta Horticulturae 470: II International Symposium on Pistachios and Almonds
PATTERNS OF NITROGEN UPTAKE AND STORAGE IN MATURE, ALTERNATE BEARING PISTACHIO TREES |
| Authors: | R. C. Rosecrance, Steven A. Weinbaum, P. H. Brown |
| Keywords: | Pistacia vera L., crop load, fruit crops, N use efficiency, source-sink relationships |
| Abstract:
Knowledge of the magnitude and seasonal patterns of tree nitrogen (N) uptake is needed to improve the efficiency of fertilizer N recovery and reduce the contribution of fertilization to nitrate contamination of ground water. Nitrogen uptake patterns were studied using periodic excavations and analyses of mature, alternate bearing pistachio (Pistacia vera L. cv 'Kerman') trees. On- and off-year trees absorbed 167 and 153 kg N ha-1 yr-1, respectively, and N uptake was concentrated to a large extent between late May and early September, i.e. the nut-fill period. Above-ground annual organs (including leaves, fruit, and current-year shoots) represented 60% and < 30% of the total tree N content at the time of nut maturity in on- and off-year trees, respectively. That difference was the result of significantly greater allocation of the N absorbed to perennial tree parts (i.e. storage) in off- relative to on-year trees. Our understanding of the size of the storage N pool and the dynamics of storage N accumulation is limited in most tree fruit species. The implications these findings with respect to efficient fertilization practices will be discussed. | |
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