Lessons from processing tomato irrigation trials in Hawke's bay, New Zealand

Variable effects on tomato (Lycopersicon esculentum (L.)) yield were found in irrigation trials carried out in five seasons from 1973-74 to 1980-81. O nly in one season was there a consistent positive response to irrigation; t his was the season when soil moisture deficit was highest. The causes of th e general lack of an irrigation response were not identified in this study; but observations suggested that the crop's water requirements were being s upplied by subsurface water as well as rainfall, irrigation, and soil moist ure storage in the 0-430 mm depth (A and B horizon). The subsurface water c ould have been supplied either by upward flux or by deep rooting. Further i nvestigations are needed to clarify the character of tomato rooting systems and the contribution of upward flux from a water table to the root zone wa ter economics.