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.     

Isohydrodynamic behavior in deficit-irrigated Cabernet Sauvignon and Malbec and its relationship between yield and berry composition

Cabernet Sauvignon and Malbec grapevines were irrigated at 70 or 23 % of estimated crop evapotranspiration throughout berry development over four growing seasons. Stomatal behavior was characterized by relating predawn leaf water potential and mid-morning stomatal conductance to mid-morning leaf water potential. Seasonal average weekly midday leaf water potential was lower in Cabernet Sauvignon than Malbec despite similar irrigation amounts. Both cultivars exhibited anisohydric behavior with midday leaf water potential decreasing linearly with declining predawn leaf water potential (r ² = 0.51) and stomatal conductance (r ² = 0.42). However, both cultivars utilized hydrodynamic mechanisms to maintain a soil-to-leaf water potential gradient of ?0.62 (±0.03) MPa under standard irrigation and ?0.75 (±0.04) MPa under reduced irrigation. Berry fresh weight and titratable acidity decreased, and the concentration of total anthocyanins increased in both cultivars in response to decreases in midday leaf water potential. The slope of regression equations for seasonal mean midday leaf water potential was used to estimate cultivar-specific levels of water stress associated with changes in berry weight and berry composition at fruit maturity.     

Production and oil quality in ‘Arbequina’ olive (Olea europaea, L.) trees under two deficit irrigation strategies

The effect of two deficit irrigation (DI) strategies on fruit and oil production and quality in a 12-year-old ‘Arbequina’ olive orchard with 238 trees ha^?1 was evaluated. The T1 treatment was a sustained DI regime (65% ETc, 2–3 irrigation events per week). The T2 treatment was a low-frequency DI (increasing stress/rewatering cycles, which consisted in withholding irrigation until fruit shrivelling and then applying a recovery irrigation providing the same amount of water that supplied in T1 for that period). As compared to full irrigation, both strategies reduced fruit production and increased the variability of fruit ripening, but favoured oil extraction. Free acidity, peroxide value, K₂₃₂, K₂₇₀ and sensory quality of oil were not affected by DI. Furthermore, carotenoid, chlorophyll, phenol, and oleic contents increased. The greatest phenol content and bitterness index were found in oil from T2 trees. Later harvesting caused sensory quality and tocopherol losses, although the oil synthesized in DI olives increased.     

Sorghum yield,water use and canopy temperatures under different levels of irrigation

This research was initiated to examine water use of differentially irrigated sorghum (Sorghum bicolor (L.) Moench) and to evaluate the plant water stress using canopy temperature measurements.Field experiments were conducted for 3 years characterised by different weather conditions at Montpellier, France. The crop was subjected to 14 differentially irrigated treatments which included, each year, a full irrigated and a dry treatment. Plant and soil measurements monitored during the crop cycle included soil water content, leaf water potential, and canopy temperature.Mid-day measurement of crop canopy temperature (Tc) /air temperature (Ta) difference reached a maximum of 7°C in the dry treatment and was maintained close to 0°C in full irrigated treatment. The relationships between (Tc-Ta) and vapour pressure deficit (VPD) commonly referred to as ‘baseline’ in the determination of crop water stress indicator (CWSI) were examined on function of wind speed and global solar radiation. Three approaches of estimating CWSI were compared. Summations of stress-degree-day (SDD) and temperature-stress-day (TSD) were well related to both relative evapotranspiration and yield (r² > 0.70).     

Assessment of trunk diameter variation derived indices as water stress indicators in mature olive trees

Plant age and size, seasonal growth patters and crop load, among other factors, have been reported to decrease the usefulness of trunk diameter variation (TDV) derived indices as water stress indicators in olive trees. Our hypothesis, however, is that indices derived from TDV records in old, big olive trees are sensitive enough to detect levels of water stress in trees of orchards under deficit irrigation that, although severe, are below the threshold for fruit shrivelling. This is of importance for the production of good quality oils, since fruit shrivelling may affect oil quality. The aim of this work was to assess different TDV-derived indices as water stress indicators in 40-year-old ‘Manzanilla’ olive trees with heavy crop load. We derived the maximum daily shrinkage (MDS), daily growth (DG) and daily recovery (DR) from TDV records taken during the 2008 dry season both in well-irrigated FAO trees and in deficit-irrigated RI trees. Measurements of volumetric soil water content (θ_v), leaf water potential (Ψ_l), stomatal conductance (g_s), net CO₂ assimilation rate (A), water and oil accumulation in the fruits and yield parameters were made for both treatments. The trunks did not grow during the experimental season, either in the FAO or RI trees, likely because of the heavy crop load. Therefore, DG was useless as water stress indicator. For MDS and DR, which were responsive to the increase of the trees’ water stress, we calculated the variability, quantified by the coefficient of variation (CV), the signal intensity (S_I) and the sensitivity (S_I/CV) values. In addition, we derived reference equations for irrigation scheduling from the relationships between MDS values in the FAO trees and main meteorological variables. Values both of S_I-MDS and S_I-DR were steady until September 9, despite of increasing differences in θ_v between treatments from early in the dry season. The Ψ_l vs θ_v values showed an outstanding capacity of the RI trees to take up water from the drying soil, and the Ψ_l vs g_s values showed a near-isohydric behaviour of those deficit-irrigated trees. These results explain, at least in part, the lack of response of MDS and DR on that period. Both S_I-MDS and S_I-DR peaked for the first time on September 9, 16 days before the appearance of fruit shrivelling. Our results suggest that using TDV-derived indices as water stress indicators for irrigation scheduling in old olive orchards with medium to low plant densities, i.e. with large root zones, may be useless in case the irrigation strategy is aimed at keeping the soil close to field capacity. Nevertheless, the MDS and DR indices may be useful indicators for the avoidance of fruit shrivelling in deficit irrigated olive orchards for the production of good quality oil. Reliable reference equations for scheduling irrigation with the signal intensity approach were obtained from the regression of MDS values vs the daily maximum values of both the air temperature and the vapour pressure deficit of the air.     

Regulated deficit irrigation effects on growth, yield, grape quality and individual anthocyanin composition in Vitis vinifera L. cv. ‘Tempranillo’

Regulated Deficit Irrigation (RDI) is an irrigation scheduling technique, originally developed for fruit orchards, that has been successfully adapted for winegrape production. The aim of this work is to evaluate the effect of RDI in vegetative growth, yield and harvest quality in ‘Tempranillo’ vineyards grown under semiarid conditions typical in Mediterranean areas. Two RDI strategies were compared with conventional irrigation practices (CI). CI that consisted in a progressive increase in water deficit as summer progressed, whereas RDI strategies (RDI1 and RDI2) had in common a deficit period just after fruit set and, in RDI2, vines were subjected to an additional stress period shortly after veraison. The experiment was carried out in four consecutive seasons in a commercial vineyard.Water stress at the beginning of berry development resulted in an important reduction of both vegetative growth and berry weight in RDI strategies. No differences in sugar concentration were found between treatments, and RDI berries tended to have lower acidity. The most relevant effect of RDI strategies on grape quality was an increase in anthocyanin and phenolics concentration. In RDI1 berries, this increase was mainly an indirect consequence of smaller berry size. However, in the RDI2 treatment the higher berry anthocyanin concentration reported was not exclusively due to a reduction in berry size. Since harvest quality has been clearly improved by any of the RDI strategies in both years, it can be concluded that RDI constitutes an interesting technique to be applied in ‘Tempranillo’ vineyards grown in semiarid areas aiming to obtain high quality grape.     

Financial feasibility of implementing regulated and sustained deficit irrigation in almond orchards

This study aims to assess the long-term economic viability of deficit irrigation (DI) strategies in almond trees (cv. Marta) grown in a semiarid area (southeast Spain). A discounted cash flow analysis (DCFA) was performed to determine the profitability of the different irrigation regimes. Four irrigation treatments were evaluated over the first 6 years of an almond plantation: (1) full irrigation (FI); (2) regulated deficit irrigation (RDI) receiving 40 % ETc during kernel-filling and 100 % ETc during the remainder of the growing season; (3) mild-to-moderate sustained deficit irrigation (SDI_mm), irrigated at 75 % ETc (first half of the experiment) and 60 % ETc (second half of the experiment) over the entire growing season; and (4) moderate-to-severe SDI (SDI_ms), irrigated at 60 % ETc (first half of the experiment) and 30 % ETc (second half of the experiment) over the whole growing season. Irrigation water profit was mainly determined by the annual volume of irrigation water applied (water costs are around 50 % of variable costs). DCFA indicates that RDI and SDI_mm are the most economically feasible treatments, whereas FI and SDI_ms presented a similar degree of profitability over the 6-year period. Simulation outputs derived for the whole useful life of the investment indicate that SDI_mm would be the most suitable irrigation treatment to be adopted by almond farmers in the study area. We conclude that in a context of water scarcity, DI is a financially feasible alternative to FI.     

Response of Navel Lane Late citrus trees to regulated deficit irrigation: yield components and fruit composition

The effects of mid-summer regulated deficit irrigation (RDI) treatments were investigated on Navel Lane Late citrus trees over four seasons. Water restrictions applied from July until mid-September were compared with irrigation at full crop evapotranspiration (ETc). Two degrees of water restrictions were imposed: (1) RDI-1, irrigated at around 50% ETc and, (2) RDI-2, irrigated at 30–40% ETc. In addition, threshold values of midday stem water potential (Ψs) of ?1.3 to ?1.5 MPa for RDI-1 and of ?1.5 to ?1.7 MPa for RDI-2 were also taken into account. Results showed that Navel Lane Late is a citrus cultivar sensitive to water deficit since both RDI strategies reduced fruit size every year and water use efficiency in RDI trees was similar to control trees. However, the RDI-1 strategy allowed water savings up to 19% without reduction in yield when the water stress integral did not surpass 70 MPa day. RDI improved fruit quality, increasing total soluble solids and titratable acidity, while the fruit maturity was delayed. In conclusion, we suggest that RDI-1 strategy since it did not significantly impair the economic return can be applied in commercial orchards in case of water scarcity. Nevertheless, Navel Lane Late fruit is sensitive to water deficit and the fruit weight can be detrimentally affected.     

Time trend in reference evapotranspiration: analysis of a long series of agrometeorological measurements in Southern Italy

This study aims to evaluate the potential effects of the climatic variations on the reference evapotranspiration (ET₀) and, consequently, on the crop water requirements in the Apulian Tavoliere, one of the largest irrigated districts of Southern Italy. To reach this purpose, both climatic parameters (air temperature and rainfall) and estimated water requirements of ??processing?? tomato (among the most representative irrigated crops in the district since the mid-1970s and, therefore, chosen as a study-case) were analyzed in order to find out if a time trend exists or does not. The analysis covered the period from 1957 to 2008. The analysis showed that the rainfall amounts decreased (?3.4 mm per year in the analyzed period), while air temperature increased (0.18 °C and 0.25?°C per decade for minimum and maximum, respectively). As a consequence of the climatic variation during the considered period, a growth trend of the ET₀ (1.4 mm per year) and water deficit (3.2 mm per year) took place. As a consequence, the water amounts for irrigating the same crop in the considered period were growing. This increased consumption is in agreement with the perception of the farmers of the district but never documented. Through the FAO AquaCrop model, the tomato irrigation water requirements have been simulated during the considered period. The trend analysis of the seasonal evapotranspiration values simulated in 52 years confirmed the increase in tomato water requirements (0.7 mm per year).     

Effect of long-term un-treated domestic wastewater re-use on soil quality, wheat grain and straw yields and attributes of fodder quality

In 2006 a comprehensive sampling program was undertaken in two pre-selected peri-urban villages in Faisalabad, Pakistan to evaluate the soil and agronomic impacts of long-term (25–30 years) untreated wastewater re-use on wheat grain and straw yields and attributes of wheat straw fodder quality. Soil SAR, ESP, RSC and ECe were 63%, 37%, 31%, and 50% higher under wastewater (WW) as compared with canal water (CW) irrigated plots. Further, 2.7 and 6.65 fold increases in soil NO ₃ ^? + NO ₂ ^? - N and Olsen-P were observed in WW as compared with CW irrigated plots. However, no significant differences in grain yield, wheat straw biomass, or fodder quality attributes were observed between WW and CW irrigated plots. In addition, for both CW and WW irrigated plots wheat straw, Cd and Pb concentrations were orders of magnitude below the EC Maximum permissible levels for Pb and Cd in feed materials and thus pose no threat to the fodder-livestock food chain. Further, elevated soil N associated with WW irrigated plots has a significant (p?<?0.01) positive influence on fodder quality by increasing the N content. Factorial ANOVA with covariance indicates that effective management of the elevated soil ECe in WW irrigated plots would increase grain yield and wheat straw biomass by 853 kg ha^?1 (19.5%) and 819 kg ha^?1 (18.6%) respectively as compared with CW irrigated plots. In Faisalabad, if managed appropriately to address emerging salinity issues the contribution of wastewater irrigation to the achievement of MDGs 1 and 7 could be significant if adverse impacts remain as marginal as found in this study.     

The effects of partial root-zone irrigation and regulated deficit irrigation on the vegetative and reproductive development of field-grown Monastrell grapevines

The effects of regulated deficit irrigation (RDI) and partial root-zone irrigation (PRI) strategies that apply the same irrigation volumes on vegetative and reproductive development were analyzed during a 3-year-period in field-grown Monastrell grapevines under semiarid conditions. Five treatments were applied: control irrigated at 60?% ETc (crop evapotranspiration) for the whole season (308?mm?year^?1); RDI-1 and PRI-1 that received the same irrigation as the control before fruit set, 30?% ETc from fruit set to harvest and 45?% ETc post-harvest (192?mm?year^?1); and RDI-2 and PRI-2 that were the same, except with 15?% ETc from fruit set to harvest (142?mm?year^?1). Distinctive PRI effects on vegetative and reproductive development were observed depending on the total soil water content and the vine water stress level. PRI-1 vines showed less restriction of vegetative growth, lower leaf abscission, and higher leaf area during post-veraison than RDI-1 vines. Higher supply of water (close to field capacity) via half of the root system in PRI-1 vines maintained better water supply and more favorable phloem sap flow (water and carbohydrates) into the fruit during post-veraison and showed a positive differential effect on fruit growth compared with RDI-1 vines. This was reflected in a higher solute content per berry (12?% higher) and higher fresh berry weight (8?% higher) at harvest in PRI-1 compared to RDI-1 berries. However, this positive effect in fruit growth was not reflected in either an improved final yield or the water use efficiency of PRI-1 vines. In PRI-2, the soil water in the wet half was insufficient to maintain more favorable shoot water supply and phloem sap flow into the berry, and no substantial changes were observed in vine vigor, leaf and fruit growth between PRI-2 and RDI-2. Higher irrigation amount in the wet root zone and higher depth of irrigation under PRI seem to be more effective for 1103P–Mourvedre combination to produce a favorable effect in berry growth and development.     

Night-time sap flow is parabolically linked to midday water potential for field-grown almond trees

To quantify night-time (S _n) and diurnal (S _d) tree water uptake, two sets of sap flow sensors (heat-pulse compensated) were installed per tree in the north-east and south-west sides of the trunk in three trees per treatment. There were two treatments: (1) control, irrigated with 100 % ETc (T₁₀₀), and (2) deficit, irrigated at 60 % ETc (T₆₀) with daily irrigations at the peak atmospheric demand (December–January). Normalised S _n by trees was in the range of 15–25 % throughout the season, compared to normalised S _d, for T₁₀₀ and T₆₀, respectively. Furthermore, S _n was parabolically correlated to plant water status from the previous day, measured as midday stem water potential. We also found strong correlations between S _n and nocturnal vapour pressure deficit for T₁₀₀ and T₆₀, indicating that nocturnal transpiration was significant for both treatments. Differences in S _n were observed for the NE and SW sensors for T₆₀, being significantly less for the NE side (sunny side) compared to the SW side (more shaded). No differences were observed for T₁₀₀ regarding probe positioning.     

Varying irrigation rates effect on yield and yield components of chickpea

This study was conducted to determine the effect of different supplemental irrigation rates on chickpea grown under semiarid climatic conditions. Chickpea plots were irrigated with drip irrigation system and irrigation rates included the applications of 0 (I ₀) 25 (I ₂₅), 50 (I ₅₀), 75 (I ₇₅), 100 (I ₁₀₀), and 125 % (I ₁₂₅) of gravimetrically measured soil water deficit. Plant height, 1,000 seed weight, yield, biomass, and harvest index (HI) parameters were determined in addition to yield-water functions, evapotranspiration (ET), water use efficiency (WUE), and irrigation water use efficiency (IWUE). Significant differences were noted for plant height (ranging from 24.0 to 37.5 cm), 1,000 seed weight (ranging from 192.0 to 428.7 g), and aboveground biomass (ranging from 2,722 to 6,083 kg ha^?1) for water applications of I ₀ and I ₁₂₅. Statistical analysis indicated a strong relationship between the amount of irrigation and yield, which ranged from 256.5 to 1,957.3 kg ha^?1. Harvest index values ranged between 0.092 and 0.325, while WUE and IWUE values ranged between 1.15–4.55 and 1.34–8.36 (kg ha^?1 mm^?1), respectively.     

Yield and size of deficit irrigated potatoes

Controlled deficit irrigation (CDI) has been studied in a potato crop cultivated in a semi-arid zone (Albacete, Spain). Ten drip irrigation treatments were differentiated by the level of fulfilment of the water requirements. The effect of deficit irrigation at three crop stages (growth, tuber bulking and ripening) has been studied. Tuber yield and its components were highly influenced by the total volume of irrigation water. The treatments with deficit during the last part of the cycle have had the lowest productions. The larger potatoes were obtained in the treatments which had not undergone deficit in the ripening period. Against this, the smallest potatoes were obtained in the treatments with deficit in growth period due to a higher number of tubers per plant. The effect of water on tuber size relies on the combination of deficits during the growth and the ripening stages, through the influence of the number of tubers per plant. The mathematical function that better fits the production obtained with the water volume received is a second-degree polynomial. The irrigation regime that leads to moderate deficit in the beginning of the season (growth and tuber bulking periods) can achieve production results of the order of those obtained by the test treatment, well irrigated along the whole cycle, it being a clearly advisable regime. On the other hand, the least advisable regimes are those that lead to deficit in the ripening stage as well as at growth or tuber bulking.     

Financial analysis of wine grape production using regulated deficit irrigation and partial-root zone drying strategies

Cost-benefit analysis was performed to determine the profitability of producing wine grapes under different irrigation regimes. Vines irrigated by regulated deficit irrigation (RDI) and partial root-zone drying (PRD) were compared with vines grown under full irrigation in a typical vineyard in a semiarid environment with scarce water resources (south-eastern Spain) during three consecutive years. Five irrigation treatments were applied. The Control treatment irrigated at 60% of the ETc (Crop evapotranspiration) throughout the orchard cycle. PRD-1 and RDI-1 provided deficit irrigation from fruit set to harvest (irrigated 30% ETc) and post-harvest (45% ETc). PRD-2 and RDI-2 provided deficit irrigation from fruit set to harvest (irrigated 15% ETc) and post-harvest (45% ETc). From an economic point of view, only the Control, PRD-1 and RDI-1 treatments were economically viable since their profitability indicators were positive, although low, especially PRD-1. The more severe deficit irrigated treatments (PRD-2 and RDI-2) were unviable. The most profitable treatment was the Control which had a Net Margin/total cost ratio (NM/C) (representing the overall profitability of the vineyard) of 25.37% compared with the 1.90% of RDI-1 and 0.57% of PRD-1. The threshold price of water indicates that only the Control remains profitable with higher water prices of up to 0.46 € m⁻³. When the cost-benefit analysis took into account the extra quality achieved in PRD-2 and RDI-2, it indicated that these treatments, which were otherwise economically unviable, achieved high returns (17 and 16%, respectively) and were close to the Control treatment. Thus, a low or moderate bonus that encourages extra berry quality for premium wine production would make deficit irrigation practices profitable. Moreover, the financial indices estimated suggest that in the present situation, and with our soil and climatic conditions, PRD is less economically profitable (higher installation cost, lower NM/C, and threshold price of water) than RDI under the same conditions.     

Effect of full and limited irrigation amount and frequency on subsurface drip-irrigated maize evapotranspiration,yield, water use efficiency and yield response factors

The objectives of this study were to: (1) to evaluate the effects of subsurface drip irrigation amount and frequency on maize production and water use efficiency, (2) develop production functions and quantify water use efficiency, and (3) develop and analyze crop yield response factors (Ky) for field maize (Zea mays L.). Five irrigation treatments were imposed: fully irrigated treatment (FIT), 25 % FIT, 50 % FIT, 75 % FIT, rainfed and an over-irrigation treatment (125 % FIT). There was no significant (P > 0.05) difference between irrigation frequencies regarding the maximum grain yield; however, at lower deficit irrigation regime, medium irrigation frequency resulted in lower grain yield. There was a decrease in grain yield with the 125 % FIT as compared to the FIT, which had statistically similar yield as 75 % FIT. Irrigation rate significantly impacted grain yield in 2005, 2006 and 2007, while irrigation frequency was only significant during the 2005 and 2006 growing seasons (two dry years) and the interacting effect was only significant in the driest year of 2005 (P = 0.006). For the pooled data from 2005 to 2008, irrigation rate was significant (P = 0.001) and irrigation frequency was also significant (P = 0.015), but their interaction was not significant (P = 0.207). Overall, there were no significant differences between irrigation frequencies in terms of grain yield. Ky had interannual variation and average seasonal Ky values were 1.65, 0.91, 0.91 and 0.83 in 2005, 2006, 2007 and 2008, respectively, and the pooled data (2005–2008) Ky value were 1.14.     

Soil water depletion in irrigated mature pecans under contrasting soil textures for arid Southern New Mexico

Relationship between plant water stress and soil water depletion (SWD) is not investigated thoroughly for irrigated pecans of southern New Mexico. In this study, transient soil water contents, rootzone SWD, and midday stem water potential (SWP) were monitored in mature pecan orchards in sandy loam (Site 1) and silty clay loam (Site 2) soils near Las Cruces, New Mexico. Corresponding to transient variations of soil water content at different depths, daily SWD varied with soil depth but not spatially. The SWD within the rootzone (0–80 cm) was higher in the shallow depths (0–40 cm) where root length density (RLD) was also higher than in the deeper depths (40–80 cm). The SWD at Site 1 was higher compared to Site 2 due to the higher clay content of the latter. The SWD patterns at outside the tree driplines were similar to those under-canopy locations because of similar RLD at the shallow depths. At both pecan orchards, differences in SWP at 2.5, 4.5, and 7.6 m tree heights were evident particularly 10–14 days after irrigation. This was due to the stress caused by decreasing soil water contents at different depths, which were generally significantly correlated with SWP. Midday air temperature was as useful as midday atmospheric vapor pressure deficit for interpreting SWP. Combined influence of soil water content (0–40 cm) and air temperature on midday SWP was significant at both orchards, which can be used as an adjunct for the clear interpretation of SWP to help refine irrigation scheduling.     

Wheat yield response to line source sprinkler irrigation and soil management practices on medium-textured shallow soils of arid environment

A field experiment was conducted for 3 years to evaluate the effect of deficit irrigation under different soil management practices on biomass production, grain yield, yield components and water productivity of spring wheat (Triticum estivum L.). Soil management practices consisted of tillage (conventional and deep tillage) and Farmyard manure (0 and 10 t ha^?1 FYM). Line source sprinkler laterals were used to generate one full- (ETm) and four deficit irrigation treatments that were 88, 75, 62 and 46 % of ETm, and designated as ETd₁, ETd₂, ETd₃, and ETd₄. Deep tillage significantly enhanced grain yield (14–18 %) and water productivity (1.27–1.34 kg m^?3) over conventional tillage. Similarly, application of FYM at 10 t ha^?1 significantly improved grain yield (10–13 %) and water productivity (1.25–1.31 kg m^?3) in comparison with no FYM. Grain yield response to irrigation varied significantly (5,281–2,704 kg ha^?1) due to differences in soil water contents. Water productivity varied from 1.05 to 1.34 kg m^?3, among the treatments in 3 years. The interactive effect of irrigation × tillage practices and irrigation × FYM on grain yield was significant. Yield performance proved that deficit irrigation (ETd₂) subjected to 75 % soil water deficit had the smallest yield decline with significant water saving would be the most appropriate irrigation level for wheat production in arid regions.     

Effect of amount and timing of subsurface drip irrigation on corn yield

A field study was conducted at North Platte, Nebraska in 2007–2009, imposing eight irrigation treatments, ranging from dryland to fully irrigated. Four of the eight treatments allowed for various degrees of water stress only after tasseling and silking. In 2007, corn yield ranged from 8.9 Mg ha^?1 with a season total of 41 mm of irrigation water to 11.5 Mg ha^?1 for the fully irrigated treatment (264 mm of irrigation water). The treatment with the greatest reduction in irrigation water after tasseling and silking (158 mm) had a mean yield of 10.9 Mg ha^?1, only 0.6 Mg ha^?1 less than the fully irrigated treatment. In 2009, yields ranged from 12.6 to 13.5 Mg ha^?1. There were no significant yield differences between the irrigation treatments for several possible reasons: more in-season precipitation and cooler weather required less irrigation water; much of the irrigation water was applied after the most water-stress sensitive stages of tasseling and silking; and lower atmospheric demand allowed for soil water contents well below 50 % management allowed depletion (MAD) not to cause any yield losses.     

Early morning fluctuations in trunk diameter are highly sensitive to water stress in nectarine trees

The sensitivity to water stress of different plant water status indicators was evaluated during two consecutive years in early nectarine trees grown in a semi-arid region. Measurements were made post-harvest and two irrigation treatments were applied: a control treatment (CTL), irrigated at 120 % of crop evapotranspiration demand to achieve non-limiting water conditions, and a deficit irrigation treatment, that applied around 37 % less water than CTL during late postharvest. The plant water status indicators evaluated were midday stem water potential (Ψ _stem) and indices derived from trunk diameter fluctuations: maximum daily shrinkage (MDS), trunk daily growth rate, early daily shrinkage measured between 0900 and 1200 hours solar time (EDS), and late daily shrinkage that occurred between 1200 hours solar time and the moment that minimum trunk diameter was reached (typically 1600 hours solar time). The most sensitive [highest ratio of signal intensity (SI) to noise] indices to water stress were Ψ _stem and EDS. The SI of EDS was greater than that of Ψ _stem, although with greater variability. EDS was a better index than MDS, with higher SI and similar variability. Although MDS was linearly related to Ψ _stem down to ?1.5 MPa, it decreased thereafter with increasing water stress. In contrast, EDS was linearly related to Ψ _stem, although the slope of the regression decreased as the season progressed, as in the case of MDS. Further studies are needed to determine whether EDS is a sensitive index of water stress in a range of species.