ISHS Acta Horticulturae 713: VI International Peach Symposium
IRRIGATION SCHEDULING OF PEACH - DEFICIT IRRIGATION AT DIFFERENT PHENOLOGICAL STAGES AND WATER STRESS ASSESSMENT |
| Author: | A. Naor |
| Keywords: | peach, nectarine, Prunus persica, irrigation, deficit irrigation, irrigation scheduling, water potential |
| Abstract:
Deficit irrigation of peach at different phenological stages has been studied for more than two decades, with extensive research activity during the past decade. The effects of deficit irrigation on productivity, fruit size and fruit quality will be discussed. There are three phenological stages of fruit growth: initial fruit growth (Stage I) when the cell-division phase occurs, followed by a lag phase, the pit-hardening stage (Stage II), and thereafter the main fruit-growth stage up to harvest (Stage III). Deficit irrigation in both stages I and III decreases the final fruit size. Deficit irrigation in stage II decreases the fruit size but the fruit recovers in size under subsequent unstressed conditions. The duration of stage II is short and it is practically non-existent (from the irrigation point of view) in early-maturing cultivars; the later the genotype is, the longer the duration of stage II. The transition from stage II to stage III is not easy to determine, therefore deficit irrigation should be stopped before the end of stage II, to avoid the risk of water stress during stage III. Deficit irrigation in both stages I and II decreases shoot growth and it may improve fruit color. Moderate water stress maximizes the bloom intensity and yield in the subsequent season. Severe water stress from July onwards delays flower bud development and increases the occurrence of double pistilate flowers. Most of the increase in flowers with double pistils occurs in response to severe water stress up to the end of August. High temperatures in the bud development stage enhance the occurrence of double fruits and of fruits with a deep suture. It seems that high temperatures create a potential for double fruit development, and that the fulfillment of that potential is dependent on tree water status during the bud development stage. A few practical aspects of irrigation scheduling will be discussed: the uncertainty in the determination of the crop coefficient for a particular orchard; the use of water stress indicators for irrigation scheduling in particular, the use of midday stem water potential for irrigation scheduling in stage III and in the postharvest stage; and the effect of crop load on midday stem water potential. | |
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