Yield components and grape composition responses to seasonal water deficits in Tempranillo grapevines

A field experiment was carried out over three seasons on Vitis vinifera cv. Tempranillo in order to compare pre-veraison and post-veraison water restrictions on vine performance and fruit composition. Rain-fed vines were compared with a treatment named MAX that was constantly irrigated at 75?% of the estimated crop evapotranspiration (ETc). In addition, an early (pre-veraison) water deficit strategy (ED) was applied by withholding irrigation until plant water stress experienced by vines surpassed a threshold value of midday stem water potential of ?1.0?MPa. After that, 75?% of ETc was applied. A late season deficit (LD) treatment was irrigated as per the MAX up to veraison, and thereafter, water application was reduced to approximately 37?% of ETc. All irrigation regimes increased vine yield up to 58?% with respect to the rain-fed treatment, and no differences in yield among the irrigated treatments occurred. However, there were differences in berry composition among the different irrigation strategies. The ED strategy was more effective than the LD one in reducing berry growth leading to more concentrated berries in terms of sugars and anthocyanins. The LD water shortage impaired berry sugar accumulation due to the detrimental effect of water stress on leaf photosynthesis.     

Usefulness of trunk diameter variations as continuous water stress indicators of pomegranate (Punica granatum) trees

Pomegranate trees (Punica granatum L.) is a deciduous fruit tree included in the so-called group of minor fruit tree species, not widely grown but of some importance in the south east of Spain. Pomegranate trees are considered as a culture tolerant to soil water deficit. However, very little is known about pomegranate orchard water management. The objective of this research was to asses the feasibility of using trunk diameter variation (TDV) indexes, obtained by means of LVDT sensors, as a plant water stress indicators for pomegranate trees. The experiment was carried out with mature trees grown in the field under three irrigation regimes: control well watered trees; trees continuously deficit irrigated at 50% of the control regime (SDI); and trees that had a summer water stress cycle being irrigated at 25% of the control rates only in July and August (RDI). The seasonal variations of maximum diurnal trunk shrinkage (MDS) and trunk growth rates (TGR) were compared with midday stem water potential (Ψstem) measurements. During the course of the entire season, control trees maintained lower MDS values than the SDI ones. In the RDI treatment, as water restrictions began, there was a slow increase in MDS, in correspondence with a decrease in Ψstem. When water was returned at full dosage, the RDI quickly recovered to MDS and Ψstem values similar to the control. However, lower MDS for a given Ψstem values were observed as the season advanced. The magnitude of differences between well watered and deficit irrigated trees was much larger in the case of MDS than for Ψstem. However, the tree-to-tree variability of the MDS readings was more than four times higher than for Ψstem; average coefficient of variation of 7.5 and 36% for Ψstem and MDS, respectively. On the other hand, TGR did not clearly reflect differences in tree water status. Overall, results reported indicated that MDS is a good indicator of pomegranate tree water status and it can be further used for managing irrigation. However, the seasonal changes in the MDS-Ψstem relationship should be taken into account when attempting to use threshold MDS values for scheduling irrigation.     

Response of Clementina de Nules citrus trees to summer deficit irrigation. Yield components and fruit composition

The effects of mid-summer regulated deficit irrigation (RDI) treatments were investigated on Clementina de Nules citrus trees over three seasons. Water restrictions applied from July, once the June physiological fruit drop had finished, until mid September were compared with a Control treatment irrigated during all the season to match full crop evapotranspiration (ET_c). Two degrees of water restrictions were imposed based on previous results also obtained in Clementina de Nules trees ( [Ginestar and Castel, 1996] and [González-Altozano and Castel, 1999]). During the RDI period, deficit irrigation was applied based on given reductions over the ET_c, but also taking into account threshold values of midday stem water potential (Ψ_s) of −1.3 to −1.5 MPa for RDI-1 and of −1.5 to −1.7 MPa for RDI-2. Results showed that water savings achieved in the RDI-2 treatment impaired yield by reducing fruit size. On the contrary, the RDI-1 strategy allowed for 20% water savings, with a reduction in tree growth but without any significant reduction in yield, fruit size nor in the economic return when irrigation was resumed to normal dose about three months before harvest. Water use efficiency (WUE) in the RDI trees was similar or even higher than in Control trees. RDI improved fruit quality increasing total soluble solids (TSS) and titratable acidity (TA). In conclusion, we suggest that the RDI-1 strategy here evaluated can be applied in commercial orchards not only in case of water scarcity, but also as a tool to control vegetative growth improving fruit composition and reducing costs associated with the crop management.     

Grapevine cv. ‘Riesling’ water use in the northeastern United States

Vine water use was measured in a Vitis vinifera cv. Riesling vineyard located in New York. Vines were fully irrigated and were trained via vertical shoot positioning giving a narrow curtain intercepting about 30% of the incident light during the sunlight hours. Vine water use was estimated on six vines by sap flow gauges directly calibrated with whole canopy transpiration measurements. The regression analysis between estimates of transpiration showed that there were large differences between vines in the calibration values obtained. Sap flow monitoring started late in June, about 2 weeks after bloom, when the canopy already filled the trellis system, and continued until October. Results showed that vine water use during most of the summer days was between 1.0 and 2.0 mm day⁻¹, with peak values around 2.5 mm. The basal (e.g. vine transpiration/reference evapotranspiration) crop coefficient (K _cb) varied somewhat between days, but it was quite stable during the whole season. Averaged over the entire experimental period, the K _cb was 0.49. Some of the day-to-day variation in the K _cb was negatively related with daily average air vapour pressure deficit. This suggests that reference evapotranspiration models on grass may not be fully accurate for vines under these experimental conditions.     

Study of Organic Matter Evolution in Citrus Compost by Isoelectrofocusing Technique

Three composts from citrus-processing industry wastes, sampled at prefixed times during the composting process, were studied with the aim to follow the organic matter evolution by using the isoelectrofocusing (IEF) technique. Results indicated that IEF qualitative analyses allowed evaluation of the organic matter transformation during composting process, showing a decrease of IEF peaks focused at lower values of pH (less stabilized organic matter) and a corresponding increase of peaks focused at higher value of pH (more humified material). The parameter A %, defined as the areas sum of IEF peaks focused at pH>4.7, could be considered particularly effective as a “threshold value” to evaluate the level of organic matter evolution for the considered composts.     

Bosonic stimulation in the formation of a bose-einstein condensate

The formation of a Bose-Einstein condensate of a dilute atomic gas has been studied in situ with a nondestructive, time-resolved imaging technique. Sodium atoms were evaporatively cooled close to the onset of Bose-Einstein condensation and then suddenly quenched to below the transition temperature. The subsequent equilibration and condensate formation showed a slow onset distinctly different from simple relaxation. This behavior provided evidence for the process of bosonic stimulation, or coherent matter-wave amplification, crucial to the concept of an atom laser.     

Using high resolution UAV thermal imagery to assess the variability in the water status of five fruit tree species within a commercial orchard

This paper deals with the assessment of heterogeneity in water status in a commercial orchard, as a prerequisite for precision irrigation management. Remote sensing-derived indicators could be suitable for mapping water stress over large areas, and recent studies have demonstrated that high resolution airborne thermal imagery enables the assessment of discontinuous canopies as pure tree crowns can be targeted, thus eliminating the background effects. Airborne campaigns were conducted over a drip-irrigated commercial orchard in Southwestern Spain composed of five different orchard tree crops. An unmanned aerial vehicle with a thermal camera onboard was flown three times during the day on 8 July 2010, at 9, 11 and 13 h (local time). Stem water potential was measured at the same time of the flights. In some irrigation units, irrigation was stopped prior to the measurement date to induce water deficits for comparative purposes. Several approaches for using the thermal data were proposed. Daily evolution of the differential between canopy and air temperature (T _c  ? T _a ) was compared to tree water status. The slope of the evolution of T _c  ? T _a with time was well correlated with water status and is proposed as a novel indicator linked with the stomatal behavior. The Crop Water Stress Index (CWSI) was calculated with the temperature data from the 13.00 h flight using an empirical approach for defining the upper and lower limits of T _c  ? T _a . The assessment of variability in water status was also performed using differences in relative canopy temperatures. Ample variability was detected among and within irrigation units, demonstrating that the approach proposed was viable for precision irrigation management. The assessment led to the identification of water-stressed areas, and to the definition of threshold CWSI values and associated risks. Such thresholds may be used by growers for irrigation management based on crop developmental stages and economic considerations.     

Borehole Temperatures and a Baseline for 20th-Century Global Warming Estimates

Lack of a 19th-century baseline temperature against which 20th-century warming can be referenced constitutes a deficiency in understanding recent climate change. Combination of borehole temperature profiles, which contain a memory of surface temperature changes in previous centuries, with the meteorological archive of surface air temperatures can provide a 19th-century baseline temperature tied to the current observational record. A test case in Utah, where boreholes are interspersed with meteorological stations belonging to the Historical Climatological Network, yields a noise reduction in estimates of 20th-century warming and a baseline temperature that is 0.6° ± 0.1°C below the 1951 to 1970 mean temperature for the region.     

Shipboard geophysical indications of asymmetry and melt production beneath the east pacific rise near the MELT experiment

Near the Mantle Electromagnetic and Tomography (MELT) Experiment, seamounts form and off-axis lava flows occur in a zone that extends farther to the west of the East Pacific Rise than to the east, indicating a broad, asymmetric region of melt production. More seamounts, slower subsidence, and less dense mantle on the western flank suggest transport of hotter mantle toward the axis from the west. Variations in axial ridge shape, axial magma chamber continuity, off-axis volcanism, and apparent mantle density indicate that upwelling is probably faster and more melt is produced beneath 17 degrees15'S than beneath 15 degrees55'S. Recent volcanism occurs above mantle with the lowest seismic velocities.     

Vineyard yield estimation by combining remote sensing,computer vision and artificial neural network techniques

In viticulture, it is critical to predict productivity levels of the different vineyard zones to undertake appropriate cropping practices. To overcome this challenge, the final yield was predicted by combining vegetation indices (VIs) to sense the health status of the crop and by computer vision to obtain the vegetated fraction cover (F_c) as a measure of plant vigour. Multispectral imagery obtained from an unmanned aerial vehicle (UAV) is used to obtain VIs and F_c, which are used together with artificial neural networks (ANN) to model the relationship between VIs, F_c and yield. The proposed methodology was applied in a vineyard, where different irrigation and fertilisation doses were applied. The results showed that using computer vision techniques to differentiate between canopy and soil is necessary in precision viticulture to obtain accurate results. In addition, the combination of VIs (reflectance approach) and F_c (geometric approach) to predict vineyard yield results in higher accuracy (root mean square error (RMSE)?=?0.9 kg vine^?1 and relative error (RE)?=?21.8% for the image when close to harvest) compared to the simple use of VIs (RMSE?=?1.2 kg vine^?1 and RE?=?28.7%). The implementation of machine learning techniques resulted in much more accurate results than linear models (RMSE?=?0.5 kg vine^?1 and RE?=?12.1%). More precise yield predictions were obtained when images were taken close to the harvest date, although promising results were obtained at earlier stages. Given the perennial nature of grapevines and the multiple environmental and endogenous factors determining yield, seasonal calibration for yield prediction is required.