Spatial distribution of water status in irrigated olive orchards by thermal imaging (original) (raw)
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Spatial distribution of water status in irrigated olive orchard by thermal imaging
Information regarding tree water status in irrigated olive orchards is essential for managing growth to optimize yields and olive oil quality. One management practice option is to monitor or sample individual trees and use this information for orchard-scale management. This study assessed the ability of thermal imaging to provide the spatial distribution and variability of tree water status in a commercial irrigated olive orchard, and described strategies and a procedure for choosing which individual trees best represent the orchard. The study employed gradual upscaling from individual trees grown in lysimeters, through a controlled experimental field plot, to a commercial orchard. Thermal imaging of olive trees grown in lysimeters attested the sensitivity of the technique to identify mild-level water stress by correlating crown temperatures to stem water potential. Knowledgeable choice of five or ten representative trees in the experimental plot, based on the histogram distribution obtained for the entire experimental orchard, lead to successful reconstruction Nurit Agam and Eran Segal contributed equally to this work. of the spatial distribution of canopy temperature, and thus of water status. Positively skewed distributions of crown temperatures found in both the field plot and commercial orchard suggested distinct patterns, where the canopy temperature of the majority of the trees was lower than the average, and a relatively small number of trees had significantly higher temperatures and suggest commercial practicality of the proposed methodology. Thermal imaging can therefore serve as a useful tool for determining representative trees that, if frequently monitored, or instrumented with continuous water status sensors, can provide important information for orchard water management.
Agricultural Water Management, 2017
Characterization of the spatio-temporal variability of tree water status is a prerequisite to conducting precise irrigation management in fruit tree orchards. This study assessed the suitability of a crop water stress index (CWSI) derived from high-resolution aerial thermal imagery for estimating tree water status variability in super high density (SHD) olive orchards. The experiment was conducted at a commercial SHD olive orchard near Seville (southwestern Spain), with drip irrigated trees under three irrigation treatments (four plots per treatment in a randomized block design): a full irrigation treatment to replace the crop water needs (ETc) and two regulated deficit irrigation treatments to replace ca. 45% of ETc. Meteorological variables, soil moisture content, leaf water potential, stem water potential and leaf gas exchange measurements were performed along the irrigation season. Infrared temperature sensors (IRTs) installed approximately 1 m above the canopies were used to derive the required Non-Water-Stressed Baselines Postprint of: Agricultural Water Management (187) 210-221 (2017) 2 (NWSBs) for CWSI calculation. NWSBs were not common during the growing season, although the seasonal effect could be partly explained with solar angle variations. A thermal camera installed on a mini Remotely Piloted Aircraft System (RPAS) allowed for the recording of high-resolution thermal images on representative dates during the irrigation season. The CWSI values derived from aerial thermal imagery were sensitive to the imposed variations in tree water status within the SHD olive orchard. Among the recorded variables, maximum stomatal conductance showed the tightest correlation with CWSI. We concluded that high-resolution thermal imagery captured from a mini RPAS is a suitable tool for defining tree water status variability within SHD olive orchards.
Response of Olive Trees to Irrigation with Saline Water
VI International Symposium on Olive Growing, 2012
Water demand for irrigation is increasing in olive orchards due to enhanced yields and profits. Because olive trees are considered moderately tolerant to salinity, irrigation water with high salt concentration is often used without considering the negative effects on olive tree growth and yield. We studied salt effects in mature olive trees in a long term field experiment (1998)(1999)(2000)(2001)(2002)(2003)(2004)(2005)(2006). Eighteen-year-old 'Picual' olive trees were cultivated under drip irrigation with saline water composed of a mixture of NaCl and CaCl 2 . Three irrigation regimes (no irrigation, considering soil water content or without considering it and adding a 20% more as a leaching fraction) and three salt concentrations (0.5, 5 or 10 dS m -1 ) were applied. Growth parameters, leaf and fruit nutrition, yield, oil content and fruit characteristics were annually studied. Annual leaf nutrient analyses indicate that all nutrients were between the adequate levels. After eight years of treatment, salinity did not affect any growth measurement and leaf Na + and Cl -concentration were always below the toxicity threshold of 0.2 and 0.5%, respectively. Annual and accumulated yield, fruit size and pulp:stone ratios were not either affected by salts. However, oil content increased linearly with salinity, with differences observed since 2001. Soil salinity measurements showed that there was no accumulation of salts in the upper 30 cm of the soil (where most of the roots are present) because of leaching by rainfalls at the end of the irrigation period. Results suggest that a proper management of saline water, supplying Ca 2+ to the irrigation water, using drip irrigation until winter rest and enough rainfalls leach the salts, and growing a tolerant cultivar, can allow using high saline irrigation water for a long time without affecting growth and yield in olive trees.
Deficit Irrigation Effects on Yield Components of Olive Trees During the Onset of Fruit Production
VI International Symposium on Irrigation of Horticultural Crops, 2011
A 3-year deficit irrigation study was conducted on young olive (Olea europaea 'Frantoio') trees to determine the effect of reduced water supply from the onset of full fruit production on vegetative growth, fruit characteristics, and yield components. Irrigation was carried out from 5-6 until 5-19 weeks after full bloom (AFB) using subsurface drip lines. The volume of water applied to the fully-irrigated trees, calculated from effective evapotranspiration was 558, 1293, and 1857 m 3 ha -1 in 2006, 2007 and 2008, respectively. During the same irrigation period the deficitirrigated trees received approximately 50% total water of the fully-irrigated trees. Deficit irrigation reduced the trunk cross sectional area (TCSA) to 69% of the fullyirrigated treatment over the three years. Yield components were differently affected by deficit irrigation. Over the 3-year period fruit yield and oil yield of deficit irrigated trees were 79 and 83% those of well irrigated ones, respectively but, when expressed on a TCSA basis, they were 89 and 100%. Fruit fresh weight and pulp/pit ratio were decreased slightly, although non-significantly, with the 50% deficit irrigation, whereas oil in the mesocarp basis was similar in both watering regimes. These results show that deficit irrigation starting from the onset of fruit production is sustainable, allowing substantial saving of water in olive orchards.
Irrigation Science, 2009
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.
Use of infrared thermography on canopies as indicator of water stress in ‘Arbequina’ olive orchards
Irrigation scheduling is critical for olive orchards, since it affects both fruit yield and olives composition. Regulated deficit irrigation (RDI) strategies have been applied with positive results in the past. However, to successfully regulate stress levels, it is necessary to have accurate measurements of plant water status, which is usually done using a pressure chamber. Canopy temperature (T c ) is another potential accurate indicator of water stress. Therefore, the objective of this study was to evaluate three methods to obtain T c values from infrared thermal images to calculate the crop water stress index (CWSI). Furthermore, the relation between CWSI and midday stem water potential (MSWP) was also studied. The methods used to obtain T c were: i) T c1 obtained from a region of interest within the image; ii) T c2 obtained from whole image; iii) T c3 obtained from a filtered image using an interactive filtering process to exclude non-leaf material (low and high temperature values). The infrared thermal images were obtained using an infrared camera (Model i40, FLIR Instruments) in parallel with MSWP measurements from trees under different RDI strategies in a drip irrigated olive orchard (Olea europaea L. 'Arbequina') located in Pencahue valley, Maule Region, Chile (35°23'L.S; 71°44'L.W; 96 m a.s.l.) during the 2011-2012 season. Results obtained in this study showed that CSWI 3 calculated using T c3 had a better correlation with MSWP compared to the two other methods studied. The interactive filter process to obtain T c values could be used in olive orchards as a fast and cheap indicator of water stress. Further studies are required to automate the analysis process.