Irrigation Of Olive Orchards Research Articles

A GIS-based tool for integrated management of clogging risk and nitrogen fertilization in drip irrigation

Precipitation of insoluble compounds poses a relevant concern in the management of drip irrigation. This risk is controlled by acidification of irrigation water. The main objective of this work was the development of a GIS-based tool to control drip clogging risk in drip irrigation by nitric acid injection in irrigation water. The study was performed in the province of Jaen (south Spain) focused on the irrigation of olive orchards. The GIS-based model was developed incorporating climate and water data in order to identify zones with different risks of drip clogging which require different rates of acid injection in the irrigation water. Volume of nitric acid injected increased with irrigation frequency and acid injection time. The model provided information on the total amount of N supplied with acidulated irrigation water; e.g. with 30min injection time in daily irrigations, more than 10kgNha−1 were applied in 47% of land potentially irrigated with surface water, meanwhile this percentage was around 60% of that potentially irrigated with underground water. This means that N supply with acid injections to reduce clogging risk may account for a relevant portion of N fertilization requirements in olive orchards. Consequently, this supply should be integrated in fertilization programs to avoid agronomic and environmental constraints. The GIS-based tool proposed was able to provide complementary technical solutions to the clogging problem in drip irrigation. For each alternative released, a precise estimation of N supply to be considered in accurate N fertilizer management was provided. The tool also supplied graphical visualization of information and functionality of handling geographic data with an easy update. All this is necessary in planning and decision making at regional scale with changing properties in irrigation water.

Effects of irrigation treatments on the quality of table olives produced with the Greek-style process

The irrigation of olive orchards is commonly applied to produce table olives with optimal size. No data have been published on the microbiological quality of drupes from irrigated olive groves during fermentation. The trials T100 and T50 (receiving a water amount equivalent to 100 % and 50 % of the required amount, respectively) and control T0 (rainfed trial) were monitored during two consecutive years. The results showed a significant increase of equatorial diameter and flesh:pit ratio of irrigated drupes. The decrease of pH and the numbers of lactic acid bacteria (LAB) registered for the irrigated trials during the fermentation were more consistent than those displayed by control T0. Lactobacillus pentosus, Lactobacillus plantarum, Lactobacillus coryniformis, and Pediococcus pentosaceus for LAB and Candida boidinii, Candida diddensiae, and Wickerhamomyces anomalus for yeasts were isolated at the highest concentrations. The global sensory acceptance was better for irrigated trials than control T0. The statistical multivariate analysis showed that the effect of irrigation was independent of the seasonal variability and it clearly distinguished the T100 and T50 trials from rainfed control. Irrigation improves significantly the quality of table olives. Interestingly, all explorative multivariate analyses showed low dissimilarity between irrigated trials; thus, the thesis T50 represents an effective approach to save water in olive orchards without compromising the quality of table olives.

Water relations and yield of olive tree (cv. Chemlali) in response to partial root-zone drying (PRD) irrigation technique and salinity under arid climate

Water scarcity and the increasing water demand for irrigation in olive orchards are leading to adopt deficit irrigation approaches and the use of saline water. Field experiment was conducted on nine-year-old olive trees (Olea europaea L. cv. Chemlali) grown on sandy deep soil and drip irrigated with saline water (EC 6.7mscm−1) under arid Mediterranean climate in southern Tunisia during 2003–2006. Three irrigation treatments (i) Control: full irrigated, (ii) DRY: rain-fed and (iii) PRD: partial root-zone drying were applied. PRD30 and PRD15 supplied 50% of the Control with an alternate irrigation switched every 30 and 15 days, respectively. PRD achieved significantly better soil water status in comparison to DRY and less than 30% of soil moisture level under the Control. Soil salinity levels were significantly lower during wet season than that of the summer period. PRD reduced the quantity of salt incorporated in the root-zone. Predawn (ΨPD) and stem (Ψstem) water potentials across all irrigation treatments diverged progressively from one another throughout summer season. Minimum values of −0.9, −1.3, −1.2 and −1.3MPa for ΨPD and −2.2, −2.4, −2.4 and −2.9MPa for Ψstem were measured during the summer for the Control, PRD30, PRD15 and DRY, respectively. PRD showed statistically comparable values of water potentials to the Control which seemed to prevent an excessive drop in tree water status by modulating stomatal closure. High correlations of Ψstem with ΨPD and soil water potential indicated that Ψstem could be used for the control of water supply in olive orchards. An improvement of olive yield was achieved by irrigation with saline water. PRD30 achieved a slight cumulative yield reduction (11%) compared to the Control while applying half of irrigation quantity. The oil content showed an improvement with increasing deficits. PRD30 seems to realize a good compromise between yield, quality and environmental impact and could be recommended for irrigation of olive trees under similar situations of water quality, soil and precipitation regimes.

Effects of water supply on carbon and water exchange of olive trees

Little information is available on carbon exchange of olive orchards despite their agronomical and ecological importance. Measurements of CO2 and water vapour exchange were performed during 2006 and 2007 with large closed chambers in an olive orchard in Cordoba (Spain) under two irrigation regimes, full and regulated deficit irrigation.Canopy assimilation was higher for full (10.8–21.3gCO2m−2day−1) than for deficit irrigation (5.1–17.4gCO2m−2day−1). Forty-five percent of gross assimilation was lost in respiration being root respiration less than 30% of total respiration. Water use efficiency (WUE) typically decreased from maximum values around 30gCO2L−1 soon after sunrise to 2–7gCO2L−1 in the afternoon when vapour pressure deficit typically exceeded 5kPa. While water stress improved instantaneous WUE only slightly, the effect was dramatic for daily values. The measurements allowed the calibration of a model coupling canopy conductance and assimilation that showed a seasonal variation in the parameters suggesting changes in the physiology of olive trees. The improvement of WUE in olive trees under water stress supports the adoption of deficit irrigation in olive orchards although further research is required to prevent negative side effects.

USING PLANT-BASED INDICATORS TO SCHEDULE IRRIGATION IN OLIVE

Results from the literature and from recent experiments were used to evaluate the usefulness of indices derived both from sap flow (SF) and trunk diameter variation (TDV) records for scheduling irrigation in olive orchards. The sensors and related equipment of both methods are robust and reliable, and suitable for operating in the field for entire irrigation seasons. Both allow for automatic data collection and transmission. They are still expensive and some training is required for proper installation, but they are easy to operate and maintain. Both SFand TDV-derived indices may show a high tree-to-tree variability, especially in old trees, but the signal intensity is usually big enough to achieve an acceptable sensitivity. Outputs from SF records are easier to interpret than those from TDV measurements, since the latter are affected by a variety of factors, apart from water stress. This limits the suitability of TDV records for automatic irrigation control. Both methods can potentially be used to schedule low-frequency irrigation in olive orchards, and are particularly useful when a deficit irrigation strategy is applied. They may fail, however, when the irrigation strategy is designed to maintain the soil close to field capacity, especially in the case of mature trees with big root systems growing in soils with medium-to-high water retention capacities. The development of water stress according to both methods lags a few days behind the reduction or cease of water supplies, making them unacceptable for the control of high frequency irrigation. For severely stressed trees, the analysis of the TDV trend may be more useful for scheduling irrigation than the signal-intensity approach.

Optimization of the Abencor system to extract olive oil from irrigated orchards

AbstractStudying the composition of olive oil requires cold‐press olive oil extraction. One of the most common laboratorial mills is the Abencor system. However, its operation protocol was formulated decades ago for Spanish olive varieties from traditionally rain‐fed orchards. We modified this protocol for use with “Barnea” and “Picual” olives from irrigated orchards that are characterized by high water content. Independent effects of malaxation time, temperature, water addition and talc addition on extraction efficiency, and major quality indices of virgin olive oil were studied. Overall, addition of talc to the fruit paste was the most significant treatment in terms of yield and quality of the oil although its effect was cultivar dependent. Improved oil yield was particularly significant for “Picual.” Extended malaxation time was also effective in improving oil extractability. Addition of talc generally improved oil‐quality parameters, while water addition had the opposite effect. Yet, quality parameters remained within the extra virgin level. Temperature increments reduced oil quality. The need to adapt a modified protocol for use with fruits from irrigated orchards that will facilitate critical comparison of results obtained from different agronomic theses and different laboratories is highlighted. It is recommended that each laboratory develops an appropriate protocol for the operation of the Abencor system in accordance to the characteristics of the olive fruit they are working with.Practical applications: Abencor system serves as the major laboratorial mill world‐wide. Those mills allow the researchers to characterize olive oil in accordance to the treatments received by the trees. This cannot be done in commercial mills. The system operation protocol was established decades ago for fruits from rain‐fed orchards. In the past decade there was a rapid increase in the use of irrigation in olive orchards and therefore it is crucial to optimize the operation protocol for fruit with relatively high water content. In the current work we have evaluated the influence of a series of technological parameters (i.e., talc and water addition, malaxation time, and temperature) on the extraction efficiency and quality indices of olive oil. This allowed us to present a modified protocol for the Abencor system operation suitable for olive fruit of irrigated orchards that will facilitate a reliable representation of the influence of different treatments on the yield and characteristics of the olive oil.

Computer-assisted sizing of photovoltaic systems for drip irrigation of olive orchards in semi-arid climate

One of the most promising applications of photovoltaic solar power, especially in areas which have high levels of solar radiation, is for pumping the water needed to irrigate the existing crops. However, it is absolutely necessary to accurately dimension the installations due to the high prices of photon capture devices. In this paper, a simple method, implemented in a spreadsheet, to calculate the design requirements of a photovoltaic system to power the drip irrigation of a field is proposed. The methodology is based on the link between the existing photovoltaic pumping techniques and the procedure to determine the crop water requirements. In the case study, 10 ha of olive grove, a photovoltaic field with 18 solar panels for 1.43 kWp is required. Besides the advantages for the environment, since it uses a renewable energy, a study on the economic viability of a photovoltaic system shows that it is similar to conventional systems which use a generator unit (twice the net present value for the photovoltaic system). Moreover, the high price of fossil fuels guarantees a progressive advantage of photovoltaic systems.

Evaluating water stress in irrigated olives: correlation of soil water status, tree water status, and thermal imagery

Irrigation of olive orchards is challenged to optimize both yields and oil quality. Best management practices for olive irrigation will likely depend on the ability to maintain mild to moderate levels of water stress during at least some parts of the growing season. We examined a number of soil, plant and remote sensing parameters for evaluating water stress in bearing olive (var. Barnea) trees in Israel. The trees were irrigated with five water application treatments (30, 50, 75, 100 and 125% of potential evapotranspiration) and the measurements of soil water content and potential, mid-day stem water potential, and stomatal resistance were taken. Remote thermal images of individual trees were used to alternatively measure average canopy temperature and to calculate the tree’s crop water stress index (CWSI), testing empirical and analytical approaches. A strong non-linear response showing similar trends and behavior was evident in soil and plant water status measurements as well as in the CWSI, with decreasing rates of change at the higher irrigation application levels. No statistically significant difference was found between the analytical and the empirical CWSI, suggesting that the relative simplicity of the analytical method would make it preferable in practical applications.