Partial Root-zone Drying Treatments Research Articles

The Interactive Effect of Pruning Level and Irrigation Strategy on Water Use Efficiency of Vitis vinifera L. cv. Shiraz

A partial rootzone drying (PRD) irrigation technique (0.5 ML/ha) was compared with a standard irrigation treatment (1 ML/ha) at three different pruning levels of 30, 60 and 120 nodes per grapevine in Vitis vinifera L. cv Shiraz. The PRD irrigation technique was applied to a single side of the grapevine rootzone at a time, 45 cm from the trunk, and the sides were switched in 10-day cycles. For the standard irrigation treatment, both sides of the grapevine were irrigated. At the end of an irrigation cycle, the PRD treatment resulted in reduced midday readings of stomatal conductance and stem (ψS) and leaf (ψL) water potential relative to the control treatment. During the switch between irrigation cycles, when the soil water profile of both the ‘wet’ and ‘dry’ sides of the PRD-treated grapevines was refilled, stomatal conductance, ψS and ψL were restored to the same levels as for the control experiment. As node number per grapevine increased, berry size and winter pruning weight were reduced and yield increased. In the first season of the experiment, the PRD treatment did not have a significant effect on berry size, yield and pruning weight, although shoot length was reduced in response to PRD for all the pruning treatments. In a subsequent season, PRD was found to reduce yield, primarily through a reduction in berry set. Water use efficiency measured as t/ML irrigation water applied was increased significantly as crop load increased, and was enhanced in response to the PRD irrigation technique.

Soil Temperature and Maize Nitrogen Uptake Improvement Under Partial Root-Zone Drying Irrigation

Soil temperature is a major effective factor on the soil and plant biological properties. Irrigation can affect soil temperature and thereby induces a temperature effect on plant growth, which may result in an economic increase due to higher yield and plant nutrition. A field experiment was carried out to investigate the effects of three irrigation strategies including full irrigation (FI), partial root-zone drying (PRD) and deficit irrigation (DI) on soil temperature and the consequent results on the grain yield and N uptake of maize (Zea May L.). Soil temperature was measured by time domain reflectometry (TDR) sensors during the 2010 growing season. Irrigation treatments were applied from 55 to 107 d after planting. The PRD treatment caused soil temperature to be in a favorable domain for a longer period (for over 60% of the measuring dates) as a consequent result of water movement to deeper soil layers compared with the other treatments; the PRD treatment also reduced soil temperature at deeper soil depths to below the maximum favorable soil temperature for maize root growth, which resulted in deeper root penetration due to both water availability and favorable soil temperature. Compared to the FI treatment, the PRD treatment increased root water uptake by 50% and caused no significant reduction in total N uptake, while this was not observed in the DI treatment partially due to the negative temperature effect of DI on plant growth, which consequently affected the water and nutrient uptake. A longer vegetation period in the PRD treatment was observed due to higher leaf N concentrations and no significant reduction in maize grain yield occurred in the PRD treatment, compared with those in the FI treatment. Based on the results, having 15.2% water saving during the whole growing season, the PRD irrigation would positively affect soil temperature and the water and nutrient uptake as a consequent, which thereby would prevent significant reduction in maize grain yield.

A field-modeling study for assessing temporal variations of soil-water-crop interactions under water-saving irrigation strategies

Simulation models are useful tools that may help to improve our understanding of soil-water-plant interactions under innovative water-saving irrigation strategies. In this study, the HYDRUS-2D model was applied to evaluate the influence of deficit irrigation (DI) and partial root-zone drying (PRD) on maize water extractions during two cropping cycles of 2010 and 2011. The model was calibrated and validated using measured soil water content data (expressed as equivalent water depths). Reliable estimates of soil water content were provided by HYDRUS-2D, with root mean square error and mean bias error values of 2.3–5.11 and 1.63–4.93mm, respectively. Root water uptake and maize grain yields were reduced by 13.2–28.8% and 13.6–52.8%, respectively, under different water-saving irrigation treatments compared to full irrigation. However, different root and water repartitions in the PRD treatment with a 25% reduction in the irrigation depth (PRD75) improved soil water utilization and consequently, crop growth. Increased root water uptake (2.2–4.4 times higher than in other treatments) from the 60–100cm soil depth in the PRD75 treatment maintained a favorable daily evapotranspiration rate, resulting in no significant reduction in maize grain yield compared to full irrigation. Consequently, a 15.7–85% increase in water use efficiency for maize cultivation under PRD75 ensured 25% water savings without threatening food security in the study area. It can be concluded that HYDRUS-2D can be successfully used to optimize water management under local water-stress conditions.

PARTIAL ROOTZONE DRYING ADVANCES FRUIT MATURITY OF ROYAL GALA APPLE

Partial rootzone drying (PRD) is a feasible irrigation strategy for saving water, which might save up to 50 % water, while maintaining apple (Malus domestica Borkh) yield. More information is available on the effect of PRD on yield and fruit quality than on fruit maturity advancement (FMA). Therefore, the effect of PRD on FMA of Royal Gala apples grown in a dry area of New Zealand was studied. The irrigation treatments were commercial irrigation (CI) and PRD. Fruit growth and FMA were measured. FMA was estimated based on mean fresh mass of fruit (MFMF), fruit skin color (FSC), fruit diameter (FD), fruit volume (FV), fruit density (FDen), flesh firmness (FF), total soluble solids concentration (TSSC), dry mass concentration of fruit (DMCF), and starch pattern index (SPI). MFMF, FSC, FD, FV, FDen, and DMCF were similar between CI and PRD fruit. However, compared to CI fruit, PRD fruit showed a tendency for enhancing FF and TSSC. SPI was higher in PRD fruit than in CI fruit. Canonical discriminant analysis showed that fruit quality attributes collectively accounted for the significant separation between CI and PRD fruit. The separation was weighed toward higher SPI, which was indicative of FMA in PRD treatment. This has important implications for early marketing. So, PRD application may improve FMA and save irrigation water by 52 %. The PRD could therefore be recommended for similar agro-ecological areas of the world.

Performance of partial root-zone drip irrigation for sugar beet production in a semi-arid area

Partial root-zone drying (PRD), a water-saving irrigation strategy, is being tested in many field crops species. In this study, the effects of PRD on root yield, sugar yield, water use efficiency (WUE), and fertilizer-nitrogen use efficiency (FNUE) of field-grown sugar beet were compared with those of conventional deficit irrigation (CDI) and full irrigation (FI). The experiments were conducted at Konya-Çumra, a Central Anatolian region of Turkey, in 2012 and 2013. Five irrigation techniques were designed and three nitrogen levels were chosen for the current study. These five irrigation techniques were applied to the study crops with the help of a drip irrigation system. In FI (control), the irrigation water was applied to both sides of the root system such that 35–40% of the available soil moisture was consumed in the 0.90-m root zone. In CDI50 and CDI75, 50% and 75% irrigation water of FI, respectively, was supplied to both sides of the root system. In alternative PRD50 (APRD50), the half of the root system was exposed to soil drying and the other half was kept well-watered with 50% irrigation water of FI. In fixed PRD50 (FPRD50), 50% irrigation water of FI was supplied only to half of the fixed side of the root system. Furthermore, the three chosen nitrogen levels included N100, where the plant’s nitrogen requirement is met completely; N75, where 25% reduction was made in the plant’s nitrogen requirement; and N50, where 50% reduction was made in the plant’s nitrogen requirement. Although the effect of nitrogen levels on sugar beet root and sugar yields was not significant, irrigation treatments had a significant effect (5% of the level). Compared to the FI treatment, the CDI75, CDI50, APRD50, and FPRD50 treatments decreased the standardized root and sugar yields by 6.36%, 26.97%, 19.12%, and 23.50%, respectively. APRD50 and FPRD50 increased the standardized yield by 10.74% and 4.75% compared to CDI50, respectively. In addition, when same amount of irrigation water was used, PRD (APRD50 and FPRD50) treatments outperformed CDI50 in WUE and FNUE of sugar beets. Compared to FI and CDI50, APRD50 increased WUEroot by 19.8% and 8.5% and FNUEroot by 26.2% and 68.2%, respectively. The varying nitrogen levels had a significant effect on FNUEroot and FNUEsugar. The highest FNUEroot and FNUEsugar values were obtained with N50. Further, combinations of different irrigation treatments and nitrogen levels had a significant effect on FNUEroot.

Improved soil–plant water dynamics and economic water use efficiency in a maize field under locally water stress

ABSTRACTSoil–plant water dynamics is a major driving factor on crop yield which could be improved under optimal irrigation strategy. The soil water dynamics under partial root-zone drying (PRD) and its consequent effects on maize economics returns were investigated in a two-year field study in the research field of Sari Agricultural Sciences and Natural Resources University. Irrigation treatments included full irrigation (FI) and two PRD treatments including PRD1 and PRD2, receiving 100%, 75% and 55% of crop water demand at each irrigation event, respectively. TDRs were used for measuring soil water contents on a daily basis. Economic analysis was done based on net present value (NPV), benefit-to-cost ratio (B/C) and internal rate of return (INRR) indices. Applying PRD1 treatment increased soil wetting front advance by 110–330% compared those for other treatments which caused 50% increase in root water uptake. Improved soil water dynamics under PRD1 prevented a significant reduction in maize grain yield, leading to 37.7%, 6.14% and 192% increase in NPV, B/C and INRR, respectively, under PRD1 than those for FI treatment. Thus, PRD1 was the most economic water-saving irrigation strategy under which 25% of irrigation water would be saved due to a better utilization of soil water supply.

Partial Rootzone Drying Irrigation Increase Root Surface Area, Root Hydraulic Conductivity and Water Use Efficiency in Maize

Partial root-zone drying (PRD) is an effective water-saving irrigation method and the heterogeneous soil moisture distribution induced by the method may affect root activities, crop water use efficiency and participation of different part of organ. The effects of deficit irrigation (DI) and PRD on leaf and root surface areas, root hydraulic conductivity (KR), and gas exchange and water use efficiency, were studied in maize (Zea mays L. cv., a local variety) grown in pots in the field for two months in the arid climate of Gansu Province, northwest of China in 2009. The PRD treatment was applied in two modes as PRD1 and PRD2, and they were obtained by the soil water content of the dry compartment had decreased to 18% (vol.) and 11% (vol.) (approximate 60% and 30% of the pot holding capacity) before shifting side of irrigation, respectively. DI2 was irrigated with the same irrigation amount with PRD2, while water was equally separated to two compartments. The full irrigation (FI), PRD1, PRD2 and DI2 received 10.75, 8.70, 8.45 and 8.45 liters of water during the treatment period, respectively. The evapo-transpiration water use efficiency (WUEET) was significantly higher in the PRD2 than in the DI2. PRD1 and PRD2 significantly (P<0.05) increased the root surface areas compared to DI2 by 17.8% and 14.6%, respectively, and that resulted in ratio of root surface area to leaf area of PRD2 significantly higher than that of DI2. Further, compared to DI2 and FI, PRD2 significantly (P<0.05) increased KR by 15% and 34%, respectively. The intrinsic WUE, the net photosynthesis (A) and gs relationship (A/gs), were the highest in the PRD2 treatment as compared with the other treatments on 4 f 5 occasions. On 3 out of 5 occasions, the A/gs values of PRD2 plants were significantly higher than those of FI plants. Our results indicate that PRD2 increased root-shoot surface ratio and the root hydraulic conductivity and those might play a major role in enhancing WUEET.

EFFECTS OF PARTIAL ROOTZONE DRYING AND DEFICIT IRRIGATION OF 'GRANNY SMITH' APPLES ON FRUIT QUALITY DURING STORAGE

The effects of partial rootzone drying (PRD), deficit irrigation (DI) and control irrigation (CI) on fruit quality during storage of ‘Granny Smith’ apples were studied during a two-year period. Trees were planted in 120-L plastic pots. Fruits achieved earlier maturing at DI treatment, compared with fruits from PRD and CI treatments. Regulated drought has a positive effect on fruit firmness and weight loss during storage. After six months of cold storage, the highest decrease of flesh firmness was found in fruits from CI treatment. Effect of irrigation on changes in contents of soluble solids and total acids during storage were not found. Positive effect of DI on fruit firmness, compared with PRD, was not determined. The weight loss on PRD and DI was similar. Positive effects of DI on fruit storage were not found compared with PRD. Contrary, PRD showed good effects on fruit size and yield, compared with DI treatment.

Linking thermal imaging to physiological indicators in Carica papaya L. under different watering regimes

Water deficit is the most limiting factor for yield and fruit-quality parameters in papaya crop (Carica papaya L.), deficit-irrigation (DI) strategies offering a feasible alternative to manage limiting water resources. When DI is applied, it is crucial to assess the physiological status of the crop in order to maintain the plant within a threshold value of water stress so as no to affect yield or fruit-quality parameters. The aim of this work was to evaluate the feasibility of thermal imaging in young papaya plants to assess the physiological status of this crop when it is subjected to different DI regimes, studying the relationships between the changes in leaf temperature (Tleaf) and in the major physiological parameters (i.e., stomatal conductance to water vapor, gs; transpiration, E; and net photosynthesis, An). The trial was conducted in a greenhouse from March to April of 2012. Plants were grown in pots and subjected to four irrigation treatments: (1) a full irrigation treatment (control), maintained at field capacity; (2) a partial root-zone drying treatment, irrigated with 50% of the total water applied to control to only one side of roots, alternating the sides every 7 days; (3) a regulated deficit irrigation (50% of the control, applied to both sides of plant); (4) and a non-irrigated treatment, in which irrigation was withheld from both sides of the split root for 14 days, followed by full irrigation until the end of the study. Significant relationships were found between Tleaf and major physiological variables such as gs, E and An. Additionally, significant relationships were found between the difference of leaf-to-air temperature (ΔTleaf–air) and gas-exchange measurements, which were used to establish the optimum range of ΔTleaf–air as a preliminary step to the crop-water monitoring and irrigation scheduling in papaya, using thermal imaging as the main source of information. According to the results, we conclude that thermal imaging is a promising technique to monitor the physiological status of papaya during drought conditions.

Effect of partial root zone drying and deficit irrigation on nitrogen and phosphorus uptake in potato

Better understanding of the effects of deficit irrigation regimes on phosphorus (P) and nitrogen (N) uptake dynamics is necessary for sustainable water, P and N management. The effects of full (FI), deficit (DI) and partial root-zone drying (PRD) irrigation on potato P and N uptake with P fertilization (P1) or without (P0) were investigated in two split-root pot experiments in a soil with low plant available P. Under FI, the plants were irrigated to pot water holding capacity while under DI and PRD, 70% of the water amount of FI was applied on either both or one side of the pots, respectively. During potato growth, plant P uptake increased while P concentration decreased at P1 and was almost constant at P0. PRD and DI reduced plants P uptake to a same extent, ca. 22% compared to FI at P1, while at P0, plants P uptake was similar for the three irrigation treatments. Soil P transport to the root surface by diffusion was similar under DI and PRD. DI treatments had higher soil microbial biomass P, water soluble P, root biomass and leaf water potential than PRD treatments, while PRD treatments had higher plant N:P ratios than DI treatments and higher root secretion of acid phosphatases that may have compensated for the lower level of water soluble P. N was immobilized in soil in all the treatments. Plant N uptake under PRD was higher than DI at both P levels, which could be explained by the higher microbial biomass and N-immobilization under DI. In conclusion, when same amount of water was used, PRD was superior to DI in terms of N uptake, but not P uptake. Challenges remain how to maintain crop yield and P uptake under reduced irrigation regimes. Utilization of water and N fertilizer was low when the soil was deficient in P.

Physiological and biochemical responses to partial root-zone drying of three grape cultivars

Physiological and biochemical responses of three grapevine cultivars (Vitis Vinifera L., ‘Pinot Noir’, Vitis Labrusca Bailey, ‘Concord’ and French American hybrid (JS 23.416 × Gewurztraminer, ‘Traminette’) to partial root-zone drying (PRD) were investigated in potted plants under controlled environmental conditions. The treatments were either full irrigation (FI) where both sides of the root system were irrigated daily to pot capacity (the controls), or PRD where irrigation was withheld on the dried side for 14 days while the wet side was irrigated as FI. PRD and FI treatments did not exhibit any significant differences in leaf water potential (ΨL) or photosynthetic rate (A). Stomatal conductance (gs) was more sensitive to PRD than photosynthesis. PRD reduced stomatal conductance by 41, 28 and 47 % in Concord, Pinot Noir, and Traminette, respectively, compared to the controls. This resulted in increased water use efficiency (WUE) by 14, 76 and 67 % in Concord, Pinot Noir, and Traminette, respectively. ABA concentration in the PRD-dry side treatment was higher (P > 0.001) than both PRD-wet side and the full irrigation treatment. Shoot growth rate of PRD-treated vines was reduced by 36, 26 and 51 % in Concord, Pinot Noir, and Traminette, respectively, compared to fully irrigated vines. The inhibition of gs and shoot growth that occurred independently of changes in leaf water status could be due to enhanced accumulation of ABA in roots and shoots, which probably maintained a high water status by reducing water loss under PRD conditions.

Effect of different irrigation strategies on vine physiology, yield, grape composition and sensory profiles of &lt;em&gt;Vitis vinifera&lt;/em&gt; L. Cabernet-Sauvignon in a cool climate area

&lt;p style="text-align: justify;"&gt;&lt;strong&gt;Aim&lt;/strong&gt;: The efficacy of partial root zone drying (PRD) and regulated deficit irrigation (RDI) on vine physiology, yield components, fruit composition and wine sensory profiles of ‘Cabernet-Sauvignon’ was investigated in a cool climate region in Ontario, Canada.&lt;/p&gt;&lt;p style="text-align: justify;"&gt;&lt;strong&gt;Methods and results&lt;/strong&gt;: Field experiments were conducted in a Cabernet-Sauvignon block in Niagara-on-the-Lake, ON Canada between 2006 and 2008. There were five treatments : non-irrigated control, PRD, full irrigation [100 % of crop evapotranspiration (ET&lt;sub&gt;c&lt;/sub&gt;)] and two levels of RDI (50 and 25 % ET&lt;sub&gt;c&lt;/sub&gt;). Treatments started immediately after fruit set and continued until post-veraison. Soil and vine water status were apparently controlled not only by the amount of water but also by the irrigation strategy used. In the PRD treatments, soil moisture, leaf water potential, and transpiration rate were generally lower than in 100 % ET&lt;sub&gt;c&lt;/sub&gt; but higher than non-irrigated and RDI treatments. Almost all treatments were different than in non-irrigated vines in fruit composition and wine sensory attributes. Wine sensory attributes differed considerably due to the amount of irrigation water applied in 2007. RDI strategies were more consistent than the PRD treatments in their effect on vine water status, grape composition and wine sensory profiles. Inconsistent patterns across seasons for some variables indicated that besides soil and vine water status, there were other factors that impacted vine physiology, yield components and berry composition.&lt;/p&gt;&lt;p style="text-align: justify;"&gt;&lt;strong&gt;Conclusions&lt;/strong&gt;: RDI treatments improved wine quality when compared with full or either non-irrigated treatments. Overall, use of RDI irrigation or PRD during dry and warm years can improve grape composition in cool climates.&lt;/p&gt;&lt;p style="text-align: justify;"&gt;&lt;strong&gt;Significance and impact of the study&lt;/strong&gt;: To the best of our knowledge, this is the first evaluation of PRD and RDI on Cabernet-Sauvignon in a cool humid climate. It suggests that although RDI strategies are more effective, PRD also has value, particularly in dry seasons.&lt;/p&gt;

Partial rootzone drying (PRD) and regulated deficit irrigation (RDI) effects on stomatal conductance, growth, photosynthetic capacity, and water-use efficiency of papaya

Papaya (Carica papaya, L.) is an important economic crop in tropical and subtropical countries. It is a giant herbaceous species; maintaining adequate tissue turgidity and water availability is necessary to maintain the rigidity of the stem as well as increase productivity. Water-saving irrigation techniques for papaya will be needed in the future due to the possibility of water shortages related to climate change. The morphological and physiological responses of ‘Grand Golden’ papaya to partial root drying (PRD), regulated deficit irrigation (RDI) and no irrigation followed by re-hydration (NI-gh) in a greenhouse study or no irrigation (NI-field) in a field study were compared with full irrigation (FI). In the greenhouse study, plants were grown in pot with roots split equally between two soil columns. In the field study, drip emitters on opposite sides of the plant delivered irrigation water. In FI, the whole root system was irrigated at 100% of water use; in RDI 50% or 70% of FI water use was supplied to the whole root system (greenhouse and field study, respectively); in PRD 100% of FI was supplied to half the root zone while the other was allowed to dry to 50% or 70% of FI (greenhouse, and field study, respectively). In the field study, PRD was achieved by applying different amounts of irrigation water to alternate sides of the root system within the plant row. The application of 50% water use in PRD and RDI in the greenhouse study decreased shoot and root dry weight production, with a more pronounced effect on root dry weight compared to FI. This decrease in biomass was associated with a decrease in the net photosynthetic rate in the day of most intense water stress for the plants in NI-gh. In the field study, a 30% water deficit in both PRD and RDI treatments did not significantly reduce vegetative growth or yield components (number fruitplant−1, average weight (g)fruit−1, kgfruitha−1, kgfruitplant−1), compared to FI. In greenhouse conditions there was evidence of a non-hydraulic signal in the PRD treatments decreasing Gs compared to RDI at comparable soil water tension but it was insufficient to affect shoot growth or yield components in field conditions. There was no difference in the instantaneous leaf water use efficiency (WUE, A/E) of PRD or RDI treatments in the greenhouse or the agronomic water use efficiency (AWUE) (kgfruitL−1 and number fruitL−1) in the PRD and RDI treatments in the field but both treatments improved AWUE compared to FI. It appears that papaya can tolerate some water deficits without a significant reduction in yield components indicating that <100% ET0 irrigation replacement can be scheduled but there is little or no benefit to PRD.

Long‐term impact of deficit irrigation on the physical quality of berries in ‘Crimson Seedless’ table grapes

In table grapes, berry firmness influences consumer acceptance so it is important to avoid berry shattering and dehydration during their post-harvest life. Since studies of irrigation effects on table grape quality are comparatively rare, sensory evaluation aimed to identify high-quality berries obtained under different deficit irrigation treatments. A 3-year study examined the effects of deficit irrigation strategies on some physical quality attributes at harvest, after 28 days of cold storage at 0 °C and after an additional shelf-life period of 3 days at 15 °C. Control vines were irrigated to ensure non-limiting water conditions (110% of crop evapo-transpiration), while both regulated deficit irrigation treatment (RDI) and partial root-zone drying (PRD) treatments applied 35% less water post-veraison. The null irrigation treatment (NI) only received natural precipitation (72% less water than control vines). Total yield and physical quality at harvest were not significantly affected by RDI or PRD. Only severe deficit (NI) decreased berry size, and this treatment had the most dehydrated berries and the worst sensory scores post-harvest. After cold storage, increased berry shattering of the PRD treatment was correlated with lower leaf xylem abscisic acid (ABA) concentration at the time of harvest. Overall quality, especially stem browning, determined the shelf-life, and longer storage duration tended to diminish treatment differences. Only NI clusters showed lower quality than their irrigated counterparts. Neither RDI nor PRD had any noticeable effect on berry quality at the end of cold storage and shelf-life, with the slight differences detected between these treatments related to stem browning and dehydration. Sensory results were similar in RDI and PRD, which provided grapes that were more acceptable to consumers than the control. Thus, it is possible to decrease irrigation of table grapes without adversely affecting the physical quality of the berries.

Evaluation of water use and yield responses of drip-irrigated sugar beet with different irrigation techniques

Effective water use should be investigated in terms of sustainable production strategy in arid and semi-arid regions. A 2 yr field study was conducted in order to investigate the effects of full root-zone wetting (FI) and partial root-zone drying (PRD) irrigation techniques with 4 and 8-d (I2) irrigation intervals and three different irrigation levels (W1, W2, W3) adjusted according to Class A pan evaporation on root, leaf, and sugar yields and irrigation water use efficiency (IWUE) of sugar beet (Beta vulgaris L.) Three different plant-pan coefficients (0.70, 0.60, and 0.50) were used for adjusting the three different irrigation levels. The irrigation techniques and levels affected yields significantly. Seasonal meanly irrigation quantities were 280.4 mm in FI treatments and 162.4 mm in PRD treatments. While mean root yield of 33.80 t ha-1 is obtained in FI treatments, it was 26.43 t ha-1 in PRD treatments. Similarly, mean white sugar yield (WSY) for FI treatments (5 t ha-1) was higher than PRD treatments (3.81 t ha-1). There were significant polynomial relationships between irrigation quantities and root yield or WSY in both FI and PRD treatment. PRD technique increased by 34.9% IWUE compared to FI. Although the highest root yield was determined in FI-I1W1 sub treatment as 37.57 t ha-1, the highest IWUE was determined in PRD-I1W3 sub treatment as 173.9 kg ha-1 mm-1 since it has the lowest irrigation water amount as 140.6 mm. However, among PRD treatments for more root yield and for more white sugar yield, I1W1 and I1W2 sub treatments were the best.

Mineral Nutrition Of ‘Petopride’ Processing Tomato Under Partial Rootzone Drying

Information is scant on the mineral nutrition of plants undergoing partial rootzone drying (PRD). Researchers applied PRD to ‘Petopride’ tomato in a glasshouse by alternating irrigation to one side of the plant with half of the water in control (C). Roots in PRD treatment had higher magnesium (Mg) and copper (Cu) than C roots. Leaves in PRD treatment had lower P and higher K than C leaves. Minerals in leaves of C and PRD were within literature reported sufficiency ranges. Fruit of the PRD treatment had higher nitrogen (N) and zinc (Zn), but lower phosphorus (P), calcium (Ca), manganese (Mn) and boron (B) than C fruit. Mineral nutrition of fruit was most affected by PRD compared to that of leaf and root. Fruit of the PRD treatment had a higher incidence of blossom end rot (BER) than C fruit. Incidence of BER notwithstanding, although PRD affected the mineral nutrition of the tomato plant, there was no evidence that the lower yield in PRD was due to poor mineral nutrition.

Physiological responses of citrus to partial rootzone drying irrigation

The effect of partial rootzone drying (PRD) on whole plant water use efficiency (WUEwp=tree growth per water applied) and physiological responses of two-year-old split-root potted grapefruit trees was studied in a greenhouse. Four treatments were applied through above and below tree evapotranspiration (ETc) requirements for 12 weeks: optimum PRD (100% ETc applied on one split rootzone, no water on the other side), excess PRD (200% ETc applied on one side, no water on the other side), deficit PRD (50% ETc applied on one side, no water on the other side), and control (50% ETc on both pots). Optimum PRD and deficit PRD trees used 18% and 79% less water than control trees, respectively, while excess PRD trees used 70% more water than control trees. Deficit PRD trees, imposing severe water stress by the end of the experiment, had the highest WUEwp, however, decreased efficiency of photosystem II, impaired stomatal conductance, increased concentrations of ABA in leaf tissues, and reduced tree growth. Both optimum PRD, imposing mild water stress, and excess PRD had similar physiological responses, growth, and leaf ABA concentration to control trees. Excess PRD trees did not increase growth with excess water application compared to the other treatments, resulting in drastically reduced WUEwp. On the other hand, optimum PRD trees increased growth allocation to roots over shoots without decreasing growth compared to control trees. Thus, optimum PRD resulted in water-savings without impairing growth or any physiological parameters.

Effects of partial root-zone drying irrigation on yield, fruit quality, and water-use efficiency in processing tomato

SummaryPrevious partial root-zone drying (PRD) experiments on tomato, carried out under controlled conditions, have occasionally shown significant positive results in terms of increased water-use efficiency and fruit quality. These results raised expectations for the transfer of PRD to commercial-scale tomato growing. However, PRD experiments in the open field are completely lacking for processing tomato varieties. An experiment was conducted, in two consecutive growing seasons, to assess the potential of PRD compared to deficit irrigation (DI) or full irrigation (FULL), on two varieties of processing tomato, using drip irrigation. Both the DI and PRD treatments delivered a 50% recovery of crop evapotranspiration (ETc), whereas the FULL treatment delivered 100% of ETc. Soil moisture measurements highlighted the difficulty in attaining the desired alternate wet and dry pattern in different parts of the root-zone prescribed by PRD, as well as the considerable water stress experienced under PRD or DI. On average, over the 2 years, marketable yields were significantly reduced, by 56% under DI and by 52% under PRD, compared to FULL irrigation. Yield decreases were caused by reductions in fruit fresh weight (FW), rather than in the number of fruit per plant. DI and PRD improved fruit quality in terms of total soluble solids contents (TSSC) as well as titratable acidity (TA) and juice pH, but not lycopene concentrations or fruit colour. Water-use efficiency (WUE), calculated as the ratio of marketable yield to actual evapotranspiration (ETa; calculated using the water balance) was not significantly different among treatments. However, when computed as the ratio of above-ground dry weight (biomass) to ETa, WUE was higher, on average, in the PRD (2.1 kg m–3) and DI (1.9 kg m–3) treatments than in the FULL treatment (1.4 kg m–3).

Sustainable management of limited water resources in a young orange orchard

In the study, deficit irrigation (DI) strategies were imposed on a young orange orchard in Sicily (Southern Italy) with the aim to monitor and analyze crop physiological features, first yield and fruit quality data for possible negative effects. The orchard includes trees irrigated with drip and sub-drip irrigation systems. Irrigation strategies, based on DI concepts, including regulated deficit irrigation (RDI) and partial root-zone drying (PRD), were adopted during the irrigation seasons 2011 and 2012, each supplying different percentages of the crop evapotranspiration (ETc). Several physiological indices indicative of plant water status were analyzed during the trial, including, stem water potential, stomatal conductance, canopy temperature, trunk diameter variations, leaf area index (LAI). The imposed DI strategies allowed maximum water saving of 41% (PRD treatment), without conditioning the first yield data. Fruit composition resulted positively affected by water restrictions. The impact of the imposed deficit on trees depends mainly on its degree of severity (i.e. lowering of stem water potential above the threshold of −1.3MPa for citrus orchards). A certain growth reduction was observed in DI treatments causing WUE (plant water use efficiency) increase, in terms of reducing competition between vegetative and reproductive growth. Subsurface drip irrigation system, designed for supplying 75% of ETc allowed plant water status, yield and quality data quite comparable with those obtained in the control treatment, supplying 100% of ETc by surface drip irrigation systems. Overall, the obtained results show that the studied DI strategies were successfully applied in a young orange orchard allowing water saving without significant detrimental effect on trees.

Effect of different irrigation strategies on vine physiology, yield, grape composition and sensory profile of Sauvignon Blanc (&lt;em&gt;Vitis vinifera&lt;/em&gt; L.) in a cool climate area

&lt;p style="text-align: justify;"&gt;&lt;strong&gt;Aim&lt;/strong&gt;: The impacts of partial root zone drying (PRD) and regulated deficit irrigation (RDI) on soil moisture, vine water status, yield components, fruit composition and wine sensory profile of Sauvignon blanc were studied in a cool climate region.&lt;/p&gt;&lt;p style="text-align: justify;"&gt;&lt;strong&gt;Methods and results&lt;/strong&gt;: Field experiments were conducted in a commercial Sauvignon blanc block in Ontario, Canada between 2006 and 2008. Treatments were: non-irrigated control, PRD, full irrigation [100% of crop evapotranspiration (ET&lt;sub&gt;c&lt;/sub&gt;)] and one level of RDI (25% ET&lt;sub&gt;c&lt;/sub&gt;). Treatments began immediately after fruit set and continued until the beginning of September. Reference evapotranspiration (ET&lt;sub&gt;o&lt;/sub&gt;) was calculated using the Penman–Monteith equation. Soil moisture and vine water status (leaf water potential and transpiration rate) in the PRD treatments were generally less than in 100% ET&lt;sub&gt;c&lt;/sub&gt; but higher than in non-irrigated and 25% ET&lt;sub&gt;c&lt;/sub&gt; treatments. Almost all treatments were different than non-irrigated vines in fruit composition and wine sensory attributes. RDI strategies were more consistent across vintages than the PRD treatments in their effect on vine water status, grape composition and sensory profiles.&lt;/p&gt;&lt;p style="text-align: justify;"&gt;&lt;strong&gt;Conclusions&lt;/strong&gt;: Use of RDI or PRD in cool climates during dry and warm years can improve grape composition. In very dry and hot seasons, like that of 2007, irrigation improved grape composition and wine aroma typicity. RDI enhanced fruity aroma attributes, which suggests that this could be a viable strategy to improve grape and wine quality in cool areas. However, due to high climatic variation over the period studied, no consistent pattern of irrigation effects was found for berry composition, suggesting that plant water status was not the only factor that controlled fruit and wine quality.&lt;/p&gt;&lt;p style="text-align: justify;"&gt;&lt;strong&gt;Significance and impact of the study&lt;/strong&gt;: To the best of our knowledge, this study is the first evaluation of PRD in a cool, humid climate, and highlights the potential value of both RDI and PRD irrigation techniques in cool climate regions, particularly during dry growing seasons.&lt;/p&gt;