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To evaluate the partitioning of net radiation ( R) and actual evapotranspiration ( ET), measurements of R, sensible heat flux ( H), soil heat flux ( G), latent heat flux ( LE), reference evapotranspiration ( ET), transpiration ( T) and soil evaporation ( E) were taken during the 2009/2010 and 2010/2011 growing seasons on a flat and uniform olive (cv. Arbequina) orchard, located in the Pencahue Valley, Región del Maule, Chile (35°23′ LS; 71°44′ LW; 96 m above sea level). Olive trees were trained on a triangular hedgerow system with a plant density of 1333 trees ha (superintensive). An eddy covariance system, sapflow sensors and microlysimeter were used to measure ET, T and E, respectively. Results indicated that the eddy covariance measurements showed a lack of the energy balance closure of 12.8 %. Values of LE, H and G were between 28-47, 34-68 and 2-6 % of R, respectively, while ratios of T and E to ET ranged between 0.64-0.74 and 0.26-0.36, respectively. During two growing seasons, the single crop coefficient ( K = ET/ ET) was between 0.27 and 0.66, while the dual crop coefficient ( T/ ET + E/ ET) ranged between 0.26 and 0.56. According to these results, H and T were the main component of R and ET, respectively, for the particular conditions of the drip-irrigated olive orchard with a fractional cover of 30 % and wetted area of 4.5 %. [ABSTRACT FROM AUTHOR]

The use of actual evapotranspiration (ETa) models requires an appropriate parameterization of the available energy, where the net radiation (Rn) is the most important component. Thus, a study was carried out to calibrate and evaluate three semiempirical approaches to estimate net radiation (Rn) over a drip-irrigated olive (Olea europaea L. 'Arbequina') orchard during 2009/2010 and 2010/2011 seasons. The orchard was planted in 2005 at high density in the Pencahue Valley, Maule Region, Chile. The evaluated models were calculated using the balance between long and short wave radiation. To achieve this objective it was assumed that Ts = Ta for Model 1, Ts = Tcv for Model 2 and Ts = Tr for Model 3 (Ts is surface temperature; Ta is air temperature; and Tcv is temperature inside of the tree canopy; Tr is radiometric temperature). For the three models, the Brutsaert's empirical coefficient (φ) was calibrated using incoming long wave radiation equation with the database of 2009/2010 season. Thus, the calibration indicated that φ was equal to 1.75. Using the database from 2010/2011 season, the validation indicated that the three models were able to predict the Rn at a 30-min interval with errors lower than 6%, root mean square error (RMSE) between 26 and 39 W m-2 and mean absolute error (MAE) between 20 and 31 W m-2. On daily time intervals, validation indicated that models presented errors, RMSE and MAE between 2% and 3%, 1.22-1.54 and 1.04-1.35 MJ m-2 d-1, respectively. The three Rn-Models would be evaluated and used in others Mediterranean conditions according to the availability of data to estimate net radiation over a drip-irrigated olive orchard planted at high density. [ABSTRACT FROM AUTHOR]

A two-layer model was evaluated to simulate latent heat flux (LE) and evapotranspiration (ET) of a drip-irrigated olive orchard during the 2009-2010 and 2010-2011 growing seasons. This orchard is located in the Pencahue Valley, Maule Region, Chile (35º 23'S; 71º 44'W; 96 m above mean sea level). A constant canopy size was maintained during the two study periods, with leaf area index (LAI) and fractional cover (fc) ranging between 1.29 and 1.34 m² m-2 and between 0.29 and 0.30, respectively. In addition, the olive orchard was maintained under non-water-stressed conditions, with a midday stem water potential greater than -1.96 MPa. The LE and ET obtained from the eddy covariance (EC) system were used to validate the performance of the two-layer model The validation including the two study periods indicated that mean values of root mean square error (RMSE) and index of agreement (Ia) for latent heat flux were 28 W m-2 and 0.98, respectively, while the RMSE and Ia values for olive evapotranspiration were 0.52 mm d¹ and 0.84, respectively. This study also indicated that the two-layer model overestimated LE and ET by about 2% and 6%, respectively. Finally, results indicated that the model was very sensitive to errors in the measurements of stomatal conductance and LAI. Major errors of the two-layer model to simulate ET directly were associated with very dry atmospheric conditions (vapor pressure deficit between 3.5 and 4.5 kPa) observed during the afternoon. However, the main errors did not significantly affect the overall performance of the two-layer model. [ABSTRACT FROM AUTHOR]

The relationship between phosphorus (P) availability and water restriction was explored in this study, focusing on its impact on phosphorus use efficiency (PUE) and water use efficiency (WUE) in various bromegrass (Bromus spp.) genotypes. Under controlled conditions, five bromegrass genotypes, as well as one ryegrass (Lolium perenne) cultivar, were compared by subjecting them to two P levels and two watering regimes. It was determined that combining water and phosphorus limitations led to reduced plant productivity. Initially, the ryegrass outperformed the bromegrass, but this result declined over time, while bromegrass exhibited consistent stability. Notably, under P and water stress, enhanced root development was observed in bromegrass compared to that in ryegrass. Distinct patterns of PUE and WUE allowed for the categorization of bromegrass genotypes into three groups. Genotype 3457 emerged as the most efficient, scoring 20 out of 24, while Pro 94-49 A achieved a score of only 10 out of 24. This study suggests that the drought resilience of bromegrass may be linked to increased root growth during the early vegetative stages, which potentially facilitates improved P acquisition. However, further validation through long-term field experiments is needed. The insights from this study are potentially valuable for use in shaping plant breeding programs by revealing the plant adaptation mechanisms for both P and water absorption. [ABSTRACT FROM AUTHOR]

Atmospheric longwave downward radiation (Ld) is one of the significant components of net radiation (Rn), and it drives several essential ecosystem processes. Ld can be estimated with simple empirical methods using atmospheric emissivity (εa) submodels. In this study, eight global models for εa were evaluated, and the best-performing model was calibrated on a global scale using a parametric instability analysis approach. The climatic data were obtained from a dynamically consistent scale resolution of basic atmospheric quantities and computed parameters known as NCEP/NCAR reanalysis (NNR) data. The performance model was evaluated with monthly average values from the NNR data. The Brutsaert equation demonstrated the best performance, and then it was calibrated. The seasonal global trend of the Brutsaert equation calibrated coefficient ranged between 1.2 and 1.4, and the K-means analysis identified five homogeneous zones (clusters) with similar behavior. Finally, the calibrated Brutsaert equation improved the Rn estimation, with an error reduction, at the worldwide scale, of 64%. Meanwhile, the error reduction for each cluster ranged from 18 to 77%. Hence, Brutsaert's equation coefficient should not be considered a constant value for use in εa estimation, nor in time or location. [ABSTRACT FROM AUTHOR]

The aim of this research was to evaluate the clumped model for estimating latent heat flux (LE) and actual evapotranspiration (ETa) over a non-water-stressed olive orchard. Additionally, submodels to compute the net radiation Rn, soil heat flux G, and canopy resistance were also included. For this objective, a database was used from an experimental unit inside a commercial superintensive drip-irrigated olive orchard located in the Pencahue Valley, Maule Region, Chile (35°23′S, 71°44′W; 96 m above sea level) during the 2009/10 and 2010/11 growing seasons. The evaluation was carried out using measurements of LE obtained from an eddy covariance (EC) system. In addition, estimated values of Rn, G, and were compared with ground-truth measurements from a four-way net radiometer, soil heat flux plates with soil thermocouples, and a portable porometer, respectively. Results indicated that the clumped model underestimated LE and ETa with errors of 11.0% and 3.0%, respectively. Values of the root-mean-square error (RMSE), mean bias error (MBE), and index of agreement dr for LE were 35 W m−2, −1.0 W m−2, and 0.96, while those for ETa were 0.48 mm day−1, 0.04 mm day−1, and 0.64, respectively. The submodels computed Rn and G with errors less than 6% and RMSE values less than 65 W m−2, while the Jarvis-type model predicted with RMSE = 41 s m−1 and MBE = 7.0 s m−1. Finally, a sensitivity analysis indicated that the ETa estimated by the clumped model was significantly affected by variations of ±30% in the values of the LAI and the minimum stomatal resistance rstmin. [ABSTRACT FROM AUTHOR]

Irrigation management strategies based on soil–plant–climate interactions are the key to improving water productivity and maintaining optimum yield and quality for apple orchards growing under Mediterranean conditions where water availability for irrigation is significantly decreasing. Thus, an experiment was carried out to investigate the effect of different irrigation levels on the yield, fruit quality, and water status of microsprinkler-irrigated apple trees (Malus domestica 'Fuji') located in a Mediterranean region in the central part of Chile. Four irrigation treatments were applied to a commercial orchard during the 2011/12 and 2013/14 growing seasons as follows: 125%, 100%, 75%, and 50% of actual evapotranspiration (ETa). Fruit yield (Y), crop load (fruits per tree, FP), fruit size (fruit weight (FW) and fruit diameter (FD)), fruit quality (firmness (FF), contents of soluble solids (SS), and starch (ST)), water productivity (WP), midday stem water potential (Ψ stem), and water stress integral (WSI) were measured in each growing season. The results indicate that trees at 125% and 100% ETa reached an average Ψ stem near − 1.0 MPa, whereas trees at 75% and 50% ETa reached Ψ stem ∼ − 1.5 MPa. With the exception of FP, irrigation treatment had significant effects on Y, FW, FD, FF, SS, ST and WP. In this regard, the apple trees irrigated at 50% ETa produced fruits with the highest SS, FF, and WP, but the Y and fruit size (FW and FD) were significantly reduced because of severe water stress (average Ψ stem ranged from −1.35 to −1.88 MPa). Apple trees with the 100% and 125% ETa treatments produced higher Y, FW, and FD than those with the 75% ETa treatment. In addition, the irrigation amount for apple trees irrigated at 125% ETa was 15% greater than for those irrigated at 100% ETa, but the yield and fruit quality were similar in both treatments. Finally, this study suggested that irrigation scheduling based on 100% ETa and Ψ stem closed to − 1.5 MPa could be a suitable strategy for microsprinkler-irrigated apple (cv. Fuji) orchards growing in Mediterranean climate areas. • Irrigating apple trees (cv Fuji) at 50% or 75% actual evapotranspiration (ETa) saved water but significantly reduced yield. • Over-irrigating apple trees at 125% ETa significantly reduces water productivity.100% ETa had great potential to increase yield and water savings. • Midday water potentials (Ψstem) > −1.5 MPa does not reduce the yield and quality of apple. • 100% ETa and Ψstem close to − 1.5 MPa was a suitable irrigation strategy for the irrigated apple orchard. [ABSTRACT FROM AUTHOR]

Due to drought intensification in Mediterranean-type climates, raspberry growers need to implement irrigation scheduling to save water without decreases in yield and fruit quality. A study was performed to evaluate the effects of four irrigation levels on yield (Y), fruit number (FM2), fruit weight (FW), water productivity (WP), fruit quality (titratable acidity (TA), soluble solids (SS), weight to volume ratio (WV)), midday stem water potential (Ψ stem), and water stress integral (WSI) in a furrow-irrigated red raspberry (Rubus ideaus L. 'Heritage') orchard. An experimental plot was established within a commercial raspberry orchard located in the Colbún valley, Maule Region, Chile, during the 2012/13 and 2013/14 growing seasons. The irrigation treatments were 125 (T 1, farmer irrigation management), 100 (T 2), 75 (T 3) and 50% (T 4) of crop evapotranspiration (ETc). The results showed significant differences among treatments for Y and FM2, with the highest and lowest values observed under the T 3 and T 1 treatments, respectively. The T 4 treatment had the highest values of WSI and WP compared to the other treatments. The effects of irrigation levels were not significant for SS and WV, but the lowest TA was observed under the T 1 treatment. Results suggested that water application based on the 75% of ETc associated with Ψ stem > −1.0 MPa was the most appropriate irrigation strategy for the furrow-irrigated red raspberry orchard because it had the highest Y (9.25 kg m−2) and saved water by 20–28% compared to the 125% and 100% ETc treatments. • Over- and under irrigation reduced significantly yield in a furrow-irrigated red raspberry orchard. • Raspberry plants irrigated at 75% of actual evapotranspiration (ETc) had the highest yield and water productivity. • Raspberry plants irrigated at 75% of ETc had midday stem water potential (Ψ stem) > −1.0 MPa. • Ψ stem values and 75% of ETc seem to be an appropriate irrigation management strategy in furrow-irrigated raspberry orchards. [ABSTRACT FROM AUTHOR]

It is well known that phosphorus (P) addition helps mitigate the adverse effects of water deficit stress on plants. However, the efficiency of spring wheat genotypes in the use of both components has not been addressed. The objective of this study was to evaluate the combined effect of P and water limiting conditions over phosphorus use efficiency (PUE) and water use efficiency (WUE) to categorize different spring wheat genotypes. Eight spring wheat genotypes were selected based on their yield tolerance index score (YTI) obtained from a previous screening of 384 wheat genotypes. They were evaluated for their ability to use P and water. Plants were grown under semi-controlled conditions on an Andisol with soil P-concentration of 3.4 mg P kg−1 (-P), which was enriched to 30 mg P kg−1 (+P). Irrigation was applied at two levels: well-watered (+W) and 30% +W (water-stressed, -W). Wheat was grown until the end of its phenological cycle. The P and water scarcity produced a delay in wheat development, especially in the first vegetative stages. Genotypic differences in growth, development, P accumulation, and yield were observed in response to P and water limiting conditions. The lowest performance in plant growth and grain yield was regarded when the P and water restrictions were applied. However, differences were observed in terms of PUE and WUE. In this sense, spring wheat genotypes were grouped into three and four classes for PUE and WUE, respectively. The most efficient genotype for all the conditions was "QUP2418", which obtained the highest score in the consolidated PUE and WUE ranking. On the contrary, "FONTAGRO 92″ and "F6CL091337″ were the most inefficient genotypes. Strong correlations were observed between PUE components and WUE, enabling the future selection of co-adapted wheat genotypes efficient in the use of P and water. • The P and water scarcity produced a delay in plant growth and development, especially in early vegetative stages. • High genetic variability among the wheat genotypes was observed for their use of P and water. • There is an interactive role between phosphorus use efficiency (PUE) and water use efficiency (WUE). • The categorization for PUE and WUE could allow the selection of co-adapted genotypes adapted to water and P limiting conditions. [ABSTRACT FROM AUTHOR]

The phosphorus (P) addition can be helpful in the mitigation of the adverse effects of water deficit stress. However, the efficiency of wheat in utilizing both components has not been assessed in field conditions. This research aims to assess the effects of P and water addition on phosphorus use efficiency (PUE) and water productivity (WP) in field conditions for select wheat cultivars co-adapted to climate-induced agronomic challenges. Three wheat cultivars were selected based on their PUE and water WP from a previous experiment. The trials were conducted in field conditions over two consecutive years, from 2020 to 2021 (Season 1) and 2021–2022 (Season 2). The plants were grown on an andisol with a soil P concentration of 10 mg P kg−1 and 30 mg P kg−1. Two irrigation treatments were imposed: Well-watered (+W) and dryland (-W). The plants were sampled at three stages: tillering (Z25), anthesis (Z65), and ripening (Z95). At the end of the phenological cycle, grain yield components, grain yield, grain quality, PUE, and WP were evaluated. Phosphorus addition promotes plant growth, especially in the early vegetative stages, by enhancing tiller development and nutrient and water uptake. These effects were critical during the anthesis and ripening stages, enhancing yield components and higher grain production. Differential responses were observed across cultivars, underscoring the genotype-specificity in PUE and WP. Seasonal water deficit stress modulated these effects, highlighting a more complex genotype-environment-nutrient interaction. The water addition promoted PUE and WP, suggesting a synergy between the two components. Among the cultivars, Chevignon outperformed in grain yield, PUE, and WP. However, while phosphorus, water, and environmental factors influenced grain quality, the genetic background of the cultivar was the primary determinant of these components. This study advocates for implementing individual nutrient management strategies tailored to the specific cultivar and adaptable to environmental conditions under climate change. [Display omitted] • Phosphorus boosts wheat growth by 30% under dryland conditions. • Phosphorus enhances gluten and protein content in wheat under dryland conditions. • Phosphorus use efficiency (PUE) varies across phenological stages and wheat cultivars. • The genetic background of cultivars predominantly determines wheat grain protein and gluten composition. [ABSTRACT FROM AUTHOR]

As blueberries are susceptible to water stress and their future cultivation in semiarid Mediterranean areas will be challenged by drought, irrigation management strategies will be needed to optimize water productivity and maintain sufficient levels of fruit yield and quality. This study aim was to evaluate the effect of different irrigation levels on plant water status, yield, fruit quality, and water productivity in a drip-irrigated rabbiteye blueberry (Vaccinium ashei Reade 'Tifblue') orchard. Four irrigation treatments based on crop evapotranspiration (ETc) were applied to blueberry plants during two consecutive growing seasons (2012/2013 and 2013/2014): 125 (farmers' irrigation management, T 1), 100 (T 2), 75 (T 3), and 50 (T 4) % ETc. During the study, the average values of midday stem water potential (Ψ stem) were −0.85, −0.86, −0.97 and −1.11 MPa for the T 1 , T 2 , T 3, and T 4 treatments, respectively. Fruit weight (FW), yield (Y), fruits per plant (FP), soluble solids (SS), and the water stress integral (WSI) were significantly affected by the irrigation treatments. The water productivity (WP), juice pH, and weight/volume ratio were statistically similar among the treatments. The highest values of Y, FP, and FW were observed in the T 1 and T 2 treatments, while the lowest values were found in the T 4 treatment. In addition, the Y, FP, FW and WSI in the T 1 and T 2 treatments were significantly similar, but the total water application in the T 2 treatment was between 20% and 27% lower than that in the T 1 treatment. For the T 1 and T 2 treatments, the values of Y were between 8.8 and 9.4 kg plant −1, and the Ψ stem was >−0.85 MPa during the two growing seasons. The interaction between irrigation treatments and growing season was only significant for the FW, with the lowest values observed in the T 4 treatment during the 2012/2013 growing season. • Irrigation at 100% evapotranspiration (ETc) reduced water use without affecting yield and quality. • Irrigation at 100% ETc reduced the water use between 950 and 1130 m3 ha−1 season−1. • Irrigation at 100% ETc maintained midday stem water potential >−1.0 MPa. • Irrigation at 50% ETc significantly decreased fruit weight and yield. • Irrigation at 50% ETc increased soluble solids and the water stress integral. [ABSTRACT FROM AUTHOR]

Highbush blueberries require sufficient water throughout the growing season, especially during fruit development. Regulated deficit irrigation (RDI) has been used in many fruit crops to save water and potentially increase fruit quality without reducing yield. Our aim was to determine the effects of RDI on yield, plant-water relations, and fruit quality at harvest. Three irrigation treatments based on actual evapotranspiration (ETa) were applied: 50, 75 and 100% (control) to six-year-old 'Brigitta' highbush blueberries in Colbún, Maule Region, Chile, for seasons 2013-2014 and 2014-2015 and to 26-year-old 'Brigitta' plants in South Haven, Michigan, USA, during the 2014 season. Severe water deficit treatment (50% ETa) decreased photosynthetic rate, vegetative growth (second season in Colbún and South Haven's trial), and fruit quality (berry size, titratable acidity, soluble solids, weight), and increased oxidative stress during both seasons in Colbún. The 50% ETa treatment also had the highest yield reduction during Colbún's second season. In contrast, mild water stress (75% ETa) resulted in similar fruit yields and quality (firmness, fruit size, titratable acidity, soluble solids and berry weight) but with higher water productivity than the 100% ETa treatment, while it achieved intermediate values for antioxidant capacity compared to the 50% ETa treatment. [ABSTRACT FROM AUTHOR]

Reference evapotranspiration (ETo) has a key role in irrigation scheduling. In this sense, the Hargreaves-Samani equation (HS) is a reliable and widely used method to estimate ETo. The HS equation just requires temperature and solar radiation data, making it a suitable method for places that lack of wind speed and relative humidity information. However, literature shows that a local calibration of its empiric parameter is needed for its complete application. This work shows a calibration for the Maule region in central-southern Chile. For this purpose, the Penman-Monteith equation from FAO-56 (PM) was considered as a reference, using a network of 400 meteorological stations between the 32° and 39° of south latitude for the 1973-2011 period. The calibration was based on the computation of the ratio of ETo calculated by HS and PM and the spatial behaviour of input variables and parameters. The spatial distribution was done by geographical weighted regression and ordinary Kriging with a linear variogram, assisted by a digital elevation model from the Shuttle Radar Topography Mission and surface reflectances from Moderate Resolution Imaging Spectroradiometer. The process of calibration was validated with daily data through all months, with comparative errors of 5% against PM. [ABSTRACT FROM AUTHOR]

The current scientific evidence shows that phosphorus (P) appears to mitigate the adverse effects derived from water deficit stress. However, the efficiency of wheat in the use of both components have been not addressed. The objective of this study was to investigate the combined effect of P and water limiting conditions over phosphorus utilization efficiency (PUTE) and water use efficiency (WUE) to categorize different wheat genotypes. Ten wheat genotypes, including old, current and advanced lines were screened for their ability to utilize phosphorus (P) and water. Plants were grown under controlled conditions on an Andisol with soil P-concentration of 4 mg P kg−1 (Inadequate P-4 P-), which was enriched to 30 mg P kg−1 (Adequate P-30 P-). Irrigation was applied at two levels: adequate irrigation (W1) and 30% of W1 (Inadequate irrigation -W2-). Wheat was grown until end of its phenological cycle. The inadequate P and water produced a long delay on plant development, especially on early vegetative stages. As expected, the genotypes showed differences in their growth, development, P accumulation and yield in response to inadequate P and water conditions. The lowest performance in terms of plant growth, development and yield was observed when both the P and water restrictions were applied. Genotypic differences were observed in terms of utilization of P and water. On this basis, wheat genotypes were grouped into three and four classes for PUTE WUE, respectively. The most efficient genotype for all the conditions was "Fritz", which obtained the highest score in the consolidated ranking for PUTE and WUE. On the contrary, "Kirón" was the most inefficient genotype. A strong correlation (~85%) was observed between PUTE and WUE, which could enable the future selection of co-adapted wheat genotypes efficient in the utilization of P and water. • The P and water scarcity produced a delay on plant growth and development, especially on early vegetative stages. • A high genetic variability among the wheat genotypes was observed for their utilization of P and water. • There is an interactive role between phosphorus utilization efficiency (PUTE) and water utilization efficiency (WUE). • The categorization for PUTE and WUE allow the selection of co-adapted cultivars adapted to water and P limiting conditions. [ABSTRACT FROM AUTHOR]