Summer deficit irrigation in a hedgerow olive orchard cv. Arbequina: relationship between soil and tree water status, and growth and yield components

M Gómez-Del-Campo

doi:10.5424/sjar/2013112-3360

Abstract

Stem water potential (Phi-stem) is a useful tool for irrigation scheduling in tree crops, provided threshold values for growth and production are determined for each physiological period. Four irrigation treatments were evaluated in a hedgerow olive orchard. Control (CON) was irrigated using soil water sensors to maintain the root zone close to field capacity. Severe water deficits were applied by irrigating at 30% CON from end of fruit drop to end of July (DI-J) or from end of July until beginning of oil synthesis (DI-A). Less severe water deficit was applied in July and August by irrigating at 50% CON (DI-JA). Continuous measures of soil moisture, Phi-stem and shoot length were recorded in all treatments. Fruit dry weight and oil content were measured at the end of the experimental period and at harvest. Relative extractable soil water to 0.8 m depth (REW) and Phi-stem were highly correlated and influenced by irrigation treatment. Shoot growth, fruit characteristics and oil production were correlated to Phi-stem. Shoot growth was reduced by 50% relative to CON by irrigating at Phi-stem of -1.3 MPa. Fruit dry matter and oil content (g fruit-1) were linearly reduced as mean summer Phi-stem decreased. Oil production was highly related with Phi-stem in August but not in July. Water can be saved in July by irrigating at Phi-stem of -2.9 MPa but Phi-stem should be maintained higher than -2.0 MPa in August to prevent decrease of oil production.

Highlights

Olive (Olea europaea L.) is among the most drought resistant plant species, large production increases are commonly obtained when irrigation is applied in dry climates (Moriana et al, 2003)
Amounts of irrigation water applied differed from year to year according to the climatic conditions
Relative extractable water (REW) values in July were significantly higher in CON and DI-A (Table 1) than in DI-J and DIJA, while in August REW values were higher in CON and DI-J

Summary

Introduction

Olive (Olea europaea L.) is among the most drought resistant plant species, large production increases are commonly obtained when irrigation is applied in dry climates (Moriana et al, 2003). High oil yields are required to counteract the high capital cost of orchard establishment. In many olive cultivation areas, irrigation water is scarce and expensive and so deficit irrigation strategies are required that can optimize its use. One such strategy is regulated deficit irrigation (RDI) that reduces irrigation during known drought-resistant phenological stages (Chalmers et al, 1986). Water deficit can be applied from around the end of fruit drop until the start of oil synthesis. Deficit irrigation can reduce vegetative growth, but at the expense of greater flower

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