María Gómez-del-Campo

Yield determination in olive hedgerow orchards. II. Analysis of radiation and fruiting profiles

Profiles of fruit density, fruit size, and oil content were measured on 12 occasions in 7 olive orchards in Spain and 2 in Australia. Orchard structure varied widely. Height ranged from 2.0 to 5.5 m, row spacing from 3 to 6 m, and canopy width from 0.7 to 3 m. Most orchards were oriented north–south (N–S) but one in Spain was oriented close to east–west (E–W) (20° NE–SW). All orchards in Spain were cv. Arbequina, and in Australia they were cvv. Barnea and Picual. Analyses with a model of interception and transmission that estimated interception by individual sides of hedgerows revealed that fruit size and oil content were strongly related to intercepted radiation during the month before harvest across all orchards. Relationships were also evident between fruit density and interception but varied among orchards and years, indicating the importance of other environmental and probably physiological effects. In N–S orchards of cv. Arbequina, average fruit size and oil content increased linearly from 0.40 g (dry weight) to 0.72 g, and from 36 to 49% (of dry weight), as daily intercepted PAR increased from 6 to 25 mol/m2 (15–60% of horizontally incident radiation). The general principles of response extended to E–W orchards. There, it was shown that generally large fruit with high oil content on S sides was consistent with the plateau responses to radiation evident in the more extensive N–S data. On the N side, however, and accounting for transmission through the hedgerow, both fruit size and oil content were greater than in positions intercepting equivalent radiation in N–S orchards. Examples are provided of the utility of responses of fruit density, size, and oil content in establishing combinations of row height, row width, and row distance to improve or maintain productivity in some of the orchards included in the study.

Summer deficit-irrigation strategies in a hedgerow olive orchard cv. ‘Arbequina’: effect on fruit characteristics and yield

Maximum production in hedgerow olive orchards is likely not achieved with maximum evapotranspiration over the long term. Thus, regulated deficit irrigation (RDI) should be considered as a management option. Four irrigation treatments were evaluated during the summer, when olive is most drought resistant. Control (CON) was irrigated to maintain the root zone close to field capacity. Severe water deficit was applied by irrigating 30% CON from the end of fruit drop to end July (DI-J) and from end July until beginning of oil synthesis (DI-A). Less severe water deficit was applied during July and August (DI-JA) by irrigating 50% CON. Flowering, fruiting, abscission, fruit development, fresh and dry weight of fruits, and oil production were evaluated. There were not significant differences in number of buds initiated, number of fruits per inflorescence and fruit drop. Oil production was significantly different between irrigation treatments in all experimental years. CON produced more oil and fruit with higher oil % than DI-A and DI-JA. Oil production of DI-J was not significantly reduced compared with CON and oil% was greater. DI-J was the most effective RDI strategy; with 16% less applied water relative to CON. Average loss in oil production of 8% was not significantly different to CON. While DI-JA saved most water (27%), oil production was reduced by 15%. Greatest loss in oil production (21%) was observed in DI-A with water saving of 22%.

Yield determination in olive hedgerow orchards. I. Yield and profiles of yield components in north-south and east-west oriented hedgerows

A study of the vertical distribution of flowering and fruit set and of components of yield (fruit numbers, fruit size, and fruit oil content) was maintained for 2 years in N–S- and E–W-oriented olive hedgerows of comparable structure (row spacing 4 m, hedgerow height to 2.5 m, width c. 1 m) near Toledo, Spain (39.9°N). Mean yield of the N–S orchard was 1854 kg oil/ha without difference between sides or years. Yield of the E–W orchard was greater in 2006, producing 2290 kg/ha, but only 1840 kg/ha in 2007, the same as the N–S orchard. The S side of the E–W orchard yielded more (59%) than the N side in 2007. In both orchards and years, most fruit was produced at 1.0–2.0 m height and fruit density was the most influential component in these differences, reflecting more intense bud initiation in these upper layers. Other components that determined fruit number, fertile inflorescences, fruits per fertile inflorescence, and fruit drop were not significantly different between layers. Fruit characteristics depended on hedgerow position. In both N–S and E–W hedgerows, fruit high in the hedgerow was the largest, most mature, and with highest oil content. These differences were more marked in N–S than in E–W hedgerows. Fruit growth and development were concentrated from the middle of September until the end November. Oil content per fruit increased linearly during that period when 65% of final oil content was accumulated. Similar patterns were observed between sides. The results of yield and yield profiles are discussed in the general context of light interception. The results suggest the importance of hedgerow porosity, and distinct penetration patterns of direct-beam radiation through N–S and E–W hedgerows, as the basis for explanation of the high yield of the N side of E–W hedgerows.

Relationship of stem water potential and leaf conductance to vegetative growth of young olive trees in a hedgerow orchard

In 2005, four irrigation treatments were applied to a 3-year-old cv. Cornicabra orchard. In T1, wetted soil volume was maintained close to field capacity by irrigating when soil sensors indicated that soil water potential in the root zone had fallen to –0.03 MPa and 0.06 MPa from spring until 15 August and from 15 August until September, respectively. On those days, 8, 6, 4, and 2 h of irrigation was applied to T1, T2, T3, and T4, so that over the season they received 106, 81, 76 and 31 mm of irrigation, respectively. The high value for T3 was the result of a valve failure on 13 June. Measurements were maintained throughout the experimental period of relative extractable water (REW) to 1 m depth at the wetted volume (0.30 m from a drip emitter), shoot length, trunk diameter, stem water potential (Ψstem) and leaf conductance (gl). The irrigation treatment significantly affected REW (P < 0.10), Ψstem, gl and vegetative growth (P < 0.05). Ψstem, and trunk diameter were the least variable parameters and Ψstem and shoot growth were the most sensitive to water stress. Although T1 received 24% more water than T2, no significant differences were detected in vegetative growth. T2 should be considered the optimum irrigation value. The mean monthly Kc for T2 was 0.086. The failure of the valve in T3 simulated a wet spring followed by limited irrigation. Irrigation applied was similar to T2 but shoot growth stopped one month earlier and lower values of Ψstem and gl were observed after mid August. REW was highly related to vegetative growth, 66% of maximum being achieved at REW 0.53 and 50% at 0.45. gl was independant of plant or soil water status and did not determine vegetative growth. A strong relationship established Ψstem as a good indicator of vegetative growth and hence of water stress. Shoot growth was 66% of maximum at Ψstem –1.5 MPa and 50% at –1.8 MPa.

Effect of water supply on leaf area development, stomatal activity, transpiration, and dry matter production and distribution in young olive trees

Two-year-old olive trees cv. Cornicabra, trained in a central leader form for hedgerow planting, were grown outdoors in 45-L weighing lysimeters to evaluate the effect of water supply on growth and development. Four treatments were established and maintained for 155 days during spring–autumn. Treatment T100 was irrigated to maintain the potting medium close to water-holding capacity by progressive replenishment of consumption that was measured at weekly intervals by weighing and recording drainage. Treatments T80, T60, and T40 received 80, 60, and 40%, respectively, of the water applied to T100. For these treatments, transpiration and leaf area were measured every fortnight. Dry matter in roots, stems, and leaves was measured at the beginning and end of the experiment. Leaf conductance was measured at 09 : 00 and 12 : 00 solar time every fortnight and at c. 2-hourly intervals throughout one day each month. Over the experimental period, T100 produced 0.42 ± 0.01 m2 leaf area, 319.6 ± 60.4 g dry biomass, and transpired 77.5 ± 1.1 L water. Water stress significantly reduced leaf area development and dry matter production (P < 0.05) in T60 and T40, but not in T80. There was no effect on dry matter partitioning to the various organs of the trees or the roots/aerial part ratio. Leaf conductance was more sensitive to water stress than vegetative growth, with significant differences (P < 0.05) established among treatments 3 weeks before differences were observed in transpiration. In autumn, transpiration and leaf conductance increased in all treatments independently of soil water status. Over the experiment, transpiration efficiency (TE, g/L) increased with reduced water supply, with a significant difference (P < 0.10) between T100 and both T60 and T40. The study has established that maximum growth of young olive plants can be achieved, without effect on the distribution of biomass between organs, at water supply less than that required to support maximum transpiration.

Long-term Effect of Intra-Row Spacing on Growth and Productivity of Super-High Density Hedgerow Olive Orchards (cv. Arbequina)

Intra-row spacing is known to determine early productivity of super-high density olive orchards depending on growing conditions, cultivar growth characteristics, planting geometry and subsequent pruning management but few experiments have been carried out in this olive hedgerow orchard design. In 2008 an experiment of 4-m spaced hedgerows was established with 8 intra-row spacings (from 1.0 to 2.5 m) in Toledo (Spain) resulting in orchards of density ranging from 2,500 to 1,000 trees ha−1. Tree growth was evaluated as height, trunk diameter and leaf area during the first 4 years. Hedgerow porosity was calculated from the 4th until the 9th year. In the 8th year hedgerow height, width, leaf area and branch angles were measured. Olives were harvested from 3rd to 9th year for measurements of fruit characteristics and productivity. Tree growth was not affected by intra-row spacing during the first 4 years. In the 8th year leaf area, external surface area and volume per tree were significantly greater in the more spaced trees; but hedgerow characteristics of leaf area per hectare, number of effective leaf layers horizontally through the hedgerow, and leaf density were not affected. In the more spaced trees insertion angles of branches to the vertical were significantly greater, mainly in the lower canopy. Intra-row spacing did not affect fruit characteristics. Oil production ha−1 decreased linearly with spacing during the first 4 harvests while production per tree increased significantly with spacing after the 3rd harvest. As a result, oil production ha−1 from the seven harvests combined only increased for tree spacing less than 1.2 m; wider spacing had no effect. Annual oil production ha−1 increased linearly as porosity was reduced by greater tree density and canopy development along the seasons.