ENVIRONMENTAL AND PHYSIOLOGICAL PARAMETERS IN SCHEDULING IRRIGATIONS OF ORANGE TREES

Trials were carried during 1983 and 1984 in five plots each having 15 mature "Tarocco" orange trees grafted on sour orange, drip irrigated from 1975.

During the experiment the following data were collected: xylem potential ( xyl), leaf diffusion resistance (Rs), canopy – air temperature difference ( Δ T), fruit size, evaporation (E pan), Vapor Pressure Deficit (VPD), wind speed, solar radiation.

The readings for xyl, Rs and Δ T were made 3 times x 3 plants x 3 hours, whilst the measures for fruit growth result from the average of 30 readings in labeled fruits.

The observations gave the following linear correlations, relative to a non-stressed plot:

VPD (av. 4, 6, 8 hours) – xyl (av. 4, 6, 8 hours) r = 0.75

VPD (av. 9, 11, 13 hours) – Δ T (av. 9, 11, 13 hours) r = 0.43

E pan – Δ T (av. 9, 11, 13 hours) r = 0.71

xyl (av. 4, 6, 8 hours) – Δ T (av. 9, 11, 13 hours) r = 0.81

Several stress indexes have been worked out, according to Idso suggestions, and the index resulting from Δ T (canopy – air difference) plotted against E pan values appeared to be less sensitive than indices resulting from xyl and Rs plotted against VPD values; however, other simpler indices appeared to give a better response.

I International Symposium on Water Relations in Fruit Crops

V. Sardo, C. Germanà

https://doi.org/10.17660/ActaHortic.1985.171.38