Partial Root-zone Drying Treatments Research Articles

Improving mango production using partial root drying technique and organic fertilisation: Field and modeling study

ABSTRACT The decreasing in water availability due to climate change can affect agricultural production. The water shortage problem led to the development of several water saving techniques. One of the waters saving techniques in irrigation is the partial root-zone drying (PRD) method. Tow field experiments accompanied by a modeling study were carried out during seasons 2020/2021 and 2021/2022, respectively, using four deficit irrigation strategies [FI (100% of full irrigation), DI1 (0.75FI), DI2 (0.5FI) where water was supplied to both sides of the mango trees and DI3 (Partial Root-zone Drying, PRD = 0.5FI) where water was supplied to a single side of each tree in an alternating manner)]. The four irrigation methods were designated as the study’s major plots. Then, for the purpose of adding compost, each main plot was divided into four smaller plots [NC (No-Compost), C12 (12 ton ha−1), C18 (18 ton ha−1) and C24 (24 ton ha−1)] to investigate the effects of such treatments on increasing water productivity, yield, and the quality of mango fruits. The results indicated that adding compost with PRD irrigation method decreased water stress throughout the root zone and increased the yield, water productivity and fruit quality. Compost addition C24 (24 ton ha−1) with PRD irrigation increased the amount of soil organic matter and microorganism activity when compared to other treatments. Additionally, C24 treatment improved mango quality under both FI and PRD treatments, the PRD technique enhanced fruit yields by 3.8% and 7.3% and water productivity by 51.6% and 53.8% for 2021 and 2022 seasons, respectively, compared to FI, while reducing the applied irrigation water by 50% for each season. In comparison to other irrigation strategies, the PRD strategy had shown superior outcomes in enhancing the yield, water productivity, and quality of mango yield. With the use of compost “C24” as organic matter fertilizer, PRD proved to be an effective dual technique to save water and increase productivity. Under both current and future water scarcity caused by climate change, it could be a successful adaptation technique. The SALTMED model produced accurate simulations of the soil moisture content, mango production, and water productivity during the two seasons.

Aquaporin expression and changes in fatty acid levels in apple leaves subjected to partial root-zone irrigation

ABSTRACT Partial root-zone drying (PRD) can induce changes in levels of the membrane fatty acids, transporter channels such as aquaporins (AQPs) and drought stress-responsive transcription factors (TFs) expression. The apple (Malus domestica (Suckow) Borkh. cv. Braeburn) trees were exposed to different PRD treatments for two consecutive years. The plasma-membrane intrinsic proteins (PIP1;1) and tonoplast-intrinsic proteins (TIP1;1) AQPs presented the highest expression in alternate partial root-zone drying (APRD75) and fixed partial root-zone drying (FPRD75) treatments than FPRD50 and control throughout the entire irrigation season, which was 120-140-fold higher in these treatments during some times. The TFs were highly expressed in APRD75 and FPRD75 treatments. The highest unsaturated fatty acid content was observed in APRD75 and FPRD75 treatments, and the lowest saturated fatty acid content was obtained in FPRD50 in both years. In addition to improving the water use efficiency (WUE) and maintaining the yield, APRD75 and FPRD75 treatments had a higher jasmonic acid (JA) content than the control. These results implied that changes in levels of the membrane fatty acids, AQPs, JA and TFs induced by APRD75 and FPRD75 treatments may be one of the possible ways for apple trees to adapt to the changing environmental conditions caused by PRD.

Yield and water use relationships of potato under different timing and severity of water stress

Water scarcity is a prevailing problem that constrains crop production in many regions worldwide. The application of deficit irrigation strategy is a reliable approach, which may contribute to some degree to overcome the problem of global water scarcity. A two-year study was conducted to assess the effects of timing and severity of the deficit irrigation on yield, water productivity (WP) and yield response factor (Ky) of potato. In 2018, the treatments included: 100% (V100) of crop evapotranspiration (ET), 50% (V50–100) reduction of ET until end of tuber initiation, 50% (V100–50) reduction of ET during the middle of tuber bulking up to maturity stage and no irrigation following plant establishment (V0). In 2019, the treatments included: V100 and V0 as in the previous year, deficit irrigation at 50% of ET (DI50), partial root-zone drying (PRD) at 75 or 50% of ET applied during the whole growing season. Deficit irrigation at a reduced rate of 50% of ET crop during the first part of the crop cycle (V50–100) strongly depressed total yield while limiting irrigation water for the last part of the crop cycle (V100–50) did not induce significant losses in yield. Deficit irrigation positively affected water productivity, especially with V100–50, suggesting that water efficiency was closely related to the growth stage than to the available water in the soil. In 2019, reducing water to 75% of V100 with PRD75 did not significantly affect tuber yield, while the further reduction in the irrigation water with PRD50 or DI50 resulted in a substantial yield decrease. Although the same amount of water was applied to both treatments, the reduction in yield was 41% with DI50 compared to 28% with PRD50, where the latter proved to be superior in maintaining yield. However, an appreciable increment in WP was observed with both PRD treatments unless the water stress is too high to depress the yield. The sensitivity of potato to water stress was more remarkable when water was applied at individual growth stages than at different severities. In contrast, potatoes have been tolerant to both stress timing and severity in total dry matter. These results showed that using deficit irrigation late of the season or with PRD can improve water-saving, minimize yield losses, and consider optimal strategies for drip-irrigated potatoes in the arid regions.

Effect of arbuscular mycorrhizal fungi inoculation on growth and physiology performance of olive trees under regulated deficit irrigation and partial rootzone drying

Agriculture water resources are limited in several Mediterranean regions. In this context, the current study was conducted to examine the response of mychorrizal olive plants to two water-saving irrigation techniques, namely partial-root zone drying (PRD) and regulated deficit irrigation (RDI). Young olive (Olea europaea L., cv Picholine marocaine) trees were grown with (+AMF) or without (-AMF) Rhizophagus irregularis using a split-root experiment, which consists in dividing the root system of the plant in two parts placed in separate pots. The pots were exposed simultaneously to three different water regimes: Control, with both root compartments well irrigated; RDI, with both compartments irrigated (50% of the control); and PRD, with one compartment irrigated (50% of the control), while the other compartment was kept dry switching every 10 days. Stomatal conductance (gs), leaf relative water content (RWC), vegetative growth (shoot length, total leaf area and leaf number), proline and sugar contents and leaf carbon isotope discrimination (δ13C) were measured in order to evaluate the influence of arbuscular mycorrhizal (AM) symbiosis on the tolerance of the olive tree to water stress induced by RDI and PRD. The low soil moisture under this two water treatments have a negative effect on all studied parameters. However, the olive plants inoculated with the AM fungi (AMF) generally have significant great growth indices in comparison with the non-inoculated ones. Furthermore, at physiological (gs and RWC) and biochemical (proline, sugar and δ13C) level, +AMF olive plants exhibit better performance under drought than -AMF ones. These responses were mostly, earlier under PRD treatment. AM olive plants can tolerate better the water deficit stress of RDI and PRD treatments saving up to 50% of the irrigation water.

Impact of soil water regimes and partial root-zone drying in field-grown papaya in semi-arid conditions

This study aimed to evaluate in the papaya Tainung genotype, the effects of partial root-zone drying (PRD) technique on soil water regimes by using different frequencies of shifting irrigation-side of plant row and the effects of PRD technique on (1) crop agronomic performance, (2) titratable fruit acidity (TA), (3) total soluble solids (TSS), and TSS/TA ratio. Also, we analyze the spatial dynamic of papaya condition using normalized difference vegetation index (NDVI) from different satellite images. The study was conducted in the semi-arid region of Bahia (BA) and Minas Gerais (MG), Brazil. The combination of 100% (Full irrigation—FU), 50%, and 35% in the irrigation depth (WID) and frequencies of shifting plant-row side irrigation of 0 (Fixed Irrigation—FX), 7, 14, and 21 days were applied. Nine treatments were studied in BA and five in MG. The water available in the soil was reduced to 44% for frequencies of shifting plant-row side irrigation of 7 days, 50% for 14 days, and 85% for 21 days, compared to the soil water availability at field capacity. Partial water deficit in the soil through the PRD technique did not significantly reduce the total root length, effective root depth, and root effective horizontal distance of the papaya Tainung genotype. However, PRD treatments showed leaf abscission, which resulted in reduced leaf area and NDVI values, especially in the MG experiment. Papaya yield and fruit quality were not affected. However, except for PRD 21 35%, irrigation water depth reduced to 50 and 35% under PRD increased crop water productivity (CWP) in papaya plants. Thus, the PRD technique may save 35% of WID using the alternation of lateral shift irrigation of crop row every 7 days under water scarcity in semi-arid regions. The NDVI index was important to compare the papaya canopy vigor between the experimental areas studied. We also confirmed the potential of NDVI to monitor the vigor of papaya canopy, since we could notice the sensibility of NDVI to identify water stress in papaya in higher vapor pressure deficit (VPD) conditions occurred in October 2016 and January 2017 in Bom Jesus da Lapa-BA. Therefore, the PRD strategy can be a useful tool to save water in papaya cultivation under semi-arid conditions.

Partial rootzone drying and regulated deficit irrigation can be used as water-saving strategies without compromising fruit yield and quality in tropically grown sweet orange

ABSTRACT We examined the effects of partial rootzone drying (PRD) and regulated deficit irrigation (RDI) on some physiological and agronomical traits in tropically grown sweet orange (Citrus sinensis (L.) Osbeck). Seven different irrigation strategies were applied over three consecutive years and compared regarding their effects on leaf gas exchange, vegetative growth, fruit yield and quality and gene expression of fruit quality-related genes. Stomatal conductance and leaf temperature were significantly affected by the different irrigation treatments and seasonal variations in the atmospheric vapour pressure deficit and air temperature. Both PRD treatments (with alternation of the irrigation side every 15 and 30 days) significantly increased the irrigation water use efficiency by 41–56% compared to the full irrigation treatment. RDI treatments induced a significant upregulation of genes related to the citrate metabolism and carotenoid biosynthesis. Trees exposed to PRD with alternation of the irrigation side at every 15 days, as well as to RDI at the fruit ripening stage, showed values of yield, productive efficiency, fruit mass, length and size, juice yield and ratio between soluble solids and titratable acidity similar to those of the full irrigation treatment. Therefore, PRD and RDI can be viable water saving irrigation strategies for sweet orange production in tropical conditions.

Partial Root Zone Drying Irrigation Improves Water Use Efficiency but Compromise the Yield and Quality of Cotton Crop

ABSTRACT Water shortage is the main limitation for agricultural production in many parts of the world. Drought or unavailability of water may seriously limit plant growth as well as yield. A pot experiment was carried out to evaluate the effects of various irrigation strategies, i.e., Full (FI), deficit (DI) and partial root-zone drying (PRD) on physiological, biochemical and yield-related attributes of cotton crop. Irrigation treatments started 60 days after planting and lasted for 60 days. For FI and DI, 100% and 50% of evapotranspiration (ET) was replaced by irrigating the entire pot surface every 4–5 days. For PRD, root system was split into two equal halves and during each irrigation event, only one-half of the root system was irrigated with the same amount of water as applied to DI, and subsequently, irrigation was switched to the second half.PRD irrigation significantly improved WUE, which was 21% and 26% higher than FI and DI, respectively. Higher ABA production under PRD reduced stomatal conductance and net photosynthesis. The activity of antioxidant enzymes namely superoxide dismutase, peroxidase, catalase and ascorbate peroxidase was significantly higher under PRD than DI and FI. Magnitude of osmotic adjustment (i.e. total sugar and proline content) was lowest and highest under FI and PRD, respectively. However, PRD reduced chlorophyll content index, seed cotton yield and fiber quality (fiber strength, fiber length, fiber fineness) as compared to FI. The results indicated that despite improving the WUE, PRD tended to compromise the yield and quality of cotton crop. Results imply that PRD treatment can be an option under water shortage; however, its suitability and efficacy should further be tested under field conditions by applying irrigation water in alternate rows.

Partial Root-Zone Drying and Deficit Irrigation Effect on Growth, Yield, Water Use and Quality of Greenhouse Grown Grafted Tomato

The tomato is an important horticultural crop, the cultivation of which is often under influence of abiotic and biotic stressors. Grafting is a technique used to alleviate these problems. Shortage of water has stimulated the introduction of new irrigation methods: deficit irrigation (DI) and partial root-zone drying (PRD). This study was conducted in two spring–summer season experiments to evaluate the effects of three irrigation regimes: full irrigation (FI), PRD and DI on vegetative growth, leaf gas-exchange parameters, yield, water-use efficiency (WUE), nutrients profile and fruit quality of grafted tomatoes. In both years, the commercial rootstocks Emperador and Maxifort were used. In the first year, the scion cultivar Clarabella was grown on one stem and in the second year the cultivar Attiya was grown on two stems. Self-grafted cultivars were grown as a control. In both experiments, higher vegetative traits (leaf area and number, height, shoot biomass) were recorded in tthe plants grafted on commercial rootstocks. The stomatal conductance and transpiration rate were higher under FI. Under DI, transpiration was lowest and photosynthetic WUE was highest. Photosynthetic rate changed between irrigation treatments depending on plant type. In both years, the total yield was highest in grafted plants as result of more and bigger fruits per plant. In the 2nd year, grafted plants under FI had higher yield compared to PRD, but not to DI, while self-grafted plants did not differ between irrigation treatments. WUE was highest in DI and PRD treatments and in grafted plants. Leaf N, P, K and Ca was highest in tthe plants grafted on Emperador and Maxifort, while more Mg was measured in self-grafted plants. More Ca and Mg were recorded in tthe plants under DI and PRD. Fruit mineral concentrations were higher in tthe plants grafted on commercial rootstocks. Total soluble solids differed between irrigation regarding plant types, while fruit total acidity was higher in Emperador and Maxifort. In conclusion, our study showed that grafted plants could be grown under DI with minor yield reduction with 30–40% less water used for irrigation. Moderate DI could be used before PRD for cultivation of grafted tomato and double stemmed plants did not show negative effect on tomato yield so it can be used as standard under reduced irrigation.

The effect of different irrigation treatments on yield and water productivity of Arachis Hypogaea L. under semi‐arid conditions in Iran

AbstractThe aim of this study was to assess the impacts of varied irrigation regimes on the yield, irrigation water productivity (IWP) and crop water productivity (CWP) of Arachis hypogaea L. under pressurized irrigation in the south‐west of Iran (Hamidiyeh, Khuzestan Province, Iran). The test was performed in a split‐plot pattern. The main treatments were three irrigation frequencies (Fs) based on varied levels of cumulative pan evaporation (CPE) amounts (F1: 35 mm; F2: 60 mm; F3: 85 mm of CPE). The subtreatments were seven irrigation water levels (Is) (I1 = 60%, I2 = 85%, I3 = 100%, I4 = 135% (of actual evapotranspiration (ETc)), I5 = PRZD60, I6 = PRZD85 and I7 = PRZD100 treatments) with four replications. The partial root‐zone drying (PRZD) treatments received 60, 85 and 100% of the actual evapotranspiration (ETc), respectively, from replacing laterals. Crops were planted on 1 June 2017 and 1 June 2018. The results indicated that the F2I4 treatment in both years showed the greatest peanut yield (PY). Moreover, in order to avoid greater PY loss the PRZD method was a proper and favourable option compared with traditional deficit irrigation (DI). However, PY declined by an average of 11.1 and 3.4% compared to the F2I4 treatment in 2017 and 2018, respectively, but the F2I7 treatment had about 16.3 and 16.1% lower water value than the F2I4 treatment. PRZD treatments (I5 and I6) have effective amended PY than deficit irrigation treatments (I1 and I2) in both growing seasons, whereas these treatments received the same amount of moisture for all Fs (F1, F2 and F3). In the end, crop water productivity and IWP amounts also declined with rising irrigation frequency. © 2020 John Wiley & Sons, Ltd.

Physiological, biochemical and gene-expressional responses to water deficit in apple subjected to partial root-zone drying (PRD)

Water scarcity is one of the major factors limiting apple production. Partial root-zone drying (PRD) is a water-saving irrigation technique necessary to improve the efficiency of irrigation techniques to optimize the amount of fruit produced with the volume of water used. The apple trees cv. Red Delicious were exposed to four treatments, including (1) control with 100% of the crop evapotranspiration (ETc) needs; (2) alternate partial root-zone drying with 75% of the ETc needs (APRD75); (3) fixed partial root-zone drying with 75% of the ETc needs (FPRD75); (4) fixed partial root-zone irrigation with 50% of the ETc needs (FPRD50) in a semiarid region of Iran. Results showed that leaf water potential (Ψ leaf), and chlorophyll were significantly decreased in FPRD50 compared to control and other PRD treatments. APRD75 and FPRD75 treatments significantly enhanced (+) -catechin (+C), epicatechin (EC), chlorogenic acid (CGA), caffeic acid (CA) as well as increased water use efficiency (WUE) (by 30–40% compared to control) without significant reduction of yield. PRD reduced gibberellic acid (GA3) and kinetin, while, increased the abscisic acid (ABA) and salicylic acid (SA) levels. The abiotic stress-responsive transcription factors (TFs) MdoMYB121, MdoMYB155, MdbZIP2, and MdbZIP48 were highly expressed in all PRD treatments. Our results demonstrated that APRD75 and FPRD75 have the potential to stimulate antioxidant defense mechanisms, hormonal signaling pathways, and expression of drought-tolerance TFs to improve WUE while maintaining crop yield. Therefore, APRD75andFPRD75 with water savings as compared to full irrigation might be a suitable strategy for irrigation apple trees under water scarcity.

Does partial root-zone drying have advantages over regulated deficit irrigation in pear orchard under desert climates?

The impacts of partial root-zone drying (PRD) and regulated deficit irrigation (RDI) with the same irrigation volume on vegetative and fruit growth and leaf physiological parameters of pear trees planted under desert climate were evaluated. The experiment involved RDI and PRD treatment, irrigated with the 50 % replacement of pan evaporation (Ep) during the slow fruit growth stage, and 80 % replacement of Ep during rapid fruit enlargement stage. Control trees were irrigated with the 80 % replacement of Ep during the whole growing season. No significant differences in the soil and leaf water status between PRD and RDI were observed, which resulted in the similar vegetative growth, fruit yield and leaf gas exchange between PRD and RDI trees. In conclusion, the leaf gas exchange, the vegetative and fruit growth of pear trees planted under extreme drought condition were mainly controlled by the irrigation volume rather than the irrigation method. Therefore, application of the PRD technique was not recommended in the extremely arid region compared with the RDI strategy.

Soil water status and growth of tomato with partial root-zone drying and deficit drip irrigation techniques

This study addresses water-saving irrigation strategies, including deficit irrigation (DI) at 70% and 50% crop evapotranspiration, ETc (DI70 and DI50, respectively), and partial root-zone drying (PRD) at 70% and 50% ETc (PRD 70 and PRD 50, respectively) to investigate the response of the tomato (Lycopersicon esculentum L.) using a surface drip system in the field on a sandy loam soil during years 2017 and 2018. Full irrigation (FI) at 100% ETc was used as the control treatment. Results revealed that the soil water content values for the DI and PRD treatments were lower than those in the FI treatment. The net photosynthesis rate, stomatal conductance, and transpiration rate decreased with decreasing irrigation water, whereas the xylem abscisic acid content increased. A significant decrease in fresh and dry vegetative parts for DI and PRD treatments was detected compared to the FI treatment in 2017, whereas there were no significant differences in 2018. Both DI70 and PRD70 treatments had fresh and dry tomato yields similar to the ones in the FI treatment, whereas the corresponding yields were significantly lower under DI50 and PRD50 treatments. This resulted in a water productivity increase by, on average, 28.15% and 38.24%, for DI70 and PRD70 treatments, respectively, compared to the FI treatment. The DI and PRD treatments significantly affected the tomato fruit quality. Fruits under DI and PRD treatments accumulated higher amounts of total soluble solids, vitamin C, and titratable acidity compared to FI Fruits. Therefore, the use of water-saving practices is feasible for tomato production in areas where water supply is limited.

Differential agro-physiological responses induced by partial root-zone drying irrigation in olive cultivars grown in semi-arid conditions

Olive cultivation is mostly practiced under Mediterranean agro-ecosystems with limited availability of water. With current climate change conditions, water scarcity will continue to challenge agricultural sustainability. Therefore, great emphasis is placed on irrigation management in arid regions with the aim of increasing water use efficiency.The present study was conducted during two growing seasons (2015 and 2016) consisting of a low yields year (‘Off’ year) and a high yields year (‘On’ year), respectively. The photosynthetic performance in terms of gas exchange and chlorophyll fluorescence, as well water status, vegetative growth and yield responses of three olive cultivars (Arbequina, Arbosana and Chetoui) grown under partial root zone drying (PRD) irrigation in semi-arid conditions of Tunisia were investigated. Olive trees were subjected to four irrigation treatments which corresponded to control irrigated at 100% of the crop evapotranspiration (100%ETC) on both sides of the root system and three PRD treatments. These later were irrigated on a 14-day alternating cycle on one side of the root system and received respectively 100%, 75% and 50% of the control (100%PRD, 75%PRD and 50%PRD). In ‘Off’ year shoot length was lower in PRD irrigated trees than in control trees, mainly for Arbequina and Chetoui cultivars and the lowest values were associated with 50%PRD treatment. However, in ‘On’ year shoot length increased slightly for all treatments, whereas remained lower under PRD irrigation treatments. Relating to water status, all cultivars under PRD treatments show a clear decrease in stem water potential (Ψstem) and relative water content (RWC). A clear difference in the regulation of leaf gas exchange parameters under different irrigated regimes was observed between the studied cultivars. Results indicated that the PRD induced a decrease in maximum efficiency of photosystem II (Fv/Fm), effective efficiency of PSII (Φ PSI), stomatal conductance (gs) and transpiration rate (E). Nevertheless, this decrease did not limit the overall photosynthesis process mainly in the two cultivars Arebquina and Chetoui; since assimilation rates and intrinsic water use (WUEi) still maintained under 50%PRD treatment independently of the decreased value of fluorescence parameters.Furthermore, reducing irrigation volumes by 25% (75% PRD) and 50% (50% PRD) compared to the control (100%ETC) increased oil yield and water productivity mainly for Arbequina cultivar without significant reductions on yield components. Based on agronomic and physiological adaptations to reduce water loss, it can be concluded that Arbequina is very promising for cultivation under PRD irrigation strategy compared to Arbosana and Chetoui.

Water-Saving Irrigation Strategies in Potato Fields: Effects on Physiological Characteristics and Water Use in Arid Region

In this study, field experiments were conducted to investigate the effects of two water-saving practices—partial root-zone drying (PRD) and deficit irrigation (DI)—on potato growth and yield in comparison with full irrigation (FI). The required FI amount was applied to the potato plants to enable 100% crop evapotranspiration, and the plants received 70% and 50% of the irrigation amount of FI for DI (DI70 and DI50) and PRD (PRD70 and PRD50), respectively. The physiological characteristics of the potatoes during the 2014–2015 seasons indicated that the relative chlorophyll contents were not significantly higher for the DI and PRD treatments than for the FI treatment. The DI50 had the lowest net photosynthesis rate (p < 0.05) while DI50 and PRD50 had significantly lower stomatal conductance (gs) values in both years. Meanwhile, the values of the PRD treatments were lower than those of DI treatments based on the transpiration rates. The xylem (abscisic acid) based on PRD50 had an average increase of 0.38 mol/m2 s due to decreasing gs values compared with other water-saving irrigation treatments. However, the FI and DI treatments had increased fresh tuber yields compared with the yields of PRD treatments. Furthermore, the PRD70 and PRD50 treatments significantly reduced the water productivity (WP) values by 30.16% and 41.32%, respectively, relative to that of FI.

Impact of partial root-zone drying on growth, yield and quality of tomatoes produced in green house condition

Water resources are limited for irrigation worldwide especially for the arid and semi-arid regions; therefore, there is an urgent need to reassess an alternative technique for conventional irrigation. Partial root-zone drying (PRD) is considered a new water-saving irrigation technique which has been tested for some crop species. The PRD technique simply requires wetting half of the rooting zone and leaving the other half dry, thereby utilizing reduced amount of irrigation water. The wetted and dry sides are interchanged in the subsequent irrigations. The focus of this article is to evaluate the effect of PRD on growth, yield and quality of tomatoes as compared to conventional irrigation. To evaluate the effect of PRD, a greenhouse experiment was conducted where two irrigation treatments were tested during a 160-day growing period: (1) control treatment where drip irrigation was applied to both sides of the plants; (2) PRD treatment in which half of the irrigation water in drip irrigation was given alternately only to one side of the root system with each irrigation. PRD treatment had 15% and 7% decreases in shoot fresh weight and leaf area of plant, respectively; however, PRD had 20% higher fruit per cluster and 18% increase in fruit production in comparison to the control treatment. No significant difference was detected on fruit size between PRD treated plants and control plants. But, fruits from PRD treated plant exhibited better appearance, higher lycopene content, firmness, total soluble solid (TSS), and TSS/titratable acidity (TA) ratio than control ones. Fruit from control treatment contained higher chlorophyll content than fruit from the PRD treatment. Postharvest storage results indicated that higher percentage of rot and chilling injury were observed in control fruits than PRD treated fruits. The results of this study indicated that PRD is a promising water saving irrigation technique which is able to produce higher yield and better quality tomatoes than conventional drip irrigation.

Prolonged drying cycles stimulate ABA accumulation in Citrus macrophylla seedlings exposed to partial rootzone drying

Partial rootzone drying (PRD) establishes discrete wet and dry parts of the rootzone (for example using parallel drip lines on either side of the crop row), and alternates them to stimulate root growth and root-to-shoot ABA signalling. To assess whether alternation frequency affects plant physiological responses, Citrus macrophylla Wester seedlings were grown with the root system split between two pots and 5 irrigation treatments applied: Control, PRD-Fixed (where wet and dry parts of the rootzone were not alternated) and three alternate PRD treatments where the wet and dry parts were swapped at 3 (PRD1), 6 (PRD2) and 12 (PRD3) days intervals, to dry the soil to different degrees before alternating the irrigation. Water was equally distributed between both pots in Control plants, whereas only one pot was watered and the other allowed to dry in PRD plants, with all plants receiving the same irrigation volume. After 24 days, soil water content (θv), leaf water potential (Ψleaf), root water potential (Ψroot), abscisic acid (ABA) concentration in roots ([ABA]root), leaves ([ABA]leaf) and shoot xylem sap ([X-ABA]shoot), biomass allocation and leaf area were measured. Higher soil water availability of the dry side (PRD1 and PRD2) had no significant effects on leaf water relations, ABA status and plant biomass allocation. However, increasing the duration of exposure of part of the root system to dry soil (PRD3 and PRD-Fixed) further decreased Ψroot and stimulated root ABA accumulation, while decreasing Ψleaf and increasing [ABA]leaf of PRD3 plants compared to the other treatments. Differences in physiological response between PRD3 and PRD-Fixed plants were attributed to differences in the proportion of root mass exposed to drying soil: PRD3 plants had a lower Ψleaf and a higher [ABA]leaf with a smaller proportion of their root mass in wet soil. Since long drying cycles were required to alter plant biomass allocation and physiological responses in PRD plants, these should be implemented in designing suitable PRD strategies for field application.

Comparative effects of two water-saving irrigation techniques on soil water status, yield, and water use efficiency in potato

This study was conducted to compare two water-saving techniques: deficit irrigation (DI) and partial root-zone drying (PRD) with full irrigation (FI) on potato (Solanum tuberosum L.). These techniques were studied using drip irrigation in an arid region of Saudi Arabia in 2014 and 2015. Five irrigation treatments, i.e., FI (control treatment where the full amount of irrigation water was applied to both sides of the plant), DI70, DI50 (70% and 50% of the FI treatment, respectively, supplied to both sides of the plant), PRD70, and PRD50 (70% and 50% of the FI treatment, respectively, supplied to a single side of each plant in an alternating manner), were applied. The dry and wet sides of the plant in the PRD treatments were switched weekly. The soil water content was the highest in the FI treatment followed by DI70 and PRD70 and DI50 and PRD50 thereafter in 2014 and 2015. The fresh weight of the vegetative parts for both the FI and PRD70 treatments (average of 14.7Mgha−1 and 11.9Mgha−1, respectively) was significantly (p<0.05) higher than that of the other irrigation treatments. The FI and PRD70 treatments increased (p<0.05) the dry weight of the vegetative parts by approximately 48.3%–57.7% relative to the other treatments in 2014. The highest number of branches per plant occurred in the PRD treatments, and the lowest number was in the DI70 treatment. The DI and PRD treatments decreased (p<0.01) the fresh and dry tuber yield compared to FI. The FI produced the highest number of tubers per plant. The DI treatments did not have a significantly lower irrigation water use efficiency (IWUE) compared to FI in 2014, whereas PRD had significantly (p<0.01) lower IWUE than FI in both years.

Physiological and biochemical assisted screening of wheat varieties under partial rhizosphere drying

Wheat is one of the major staple food of the world, which is badly affected by water deficit stress. To fulfill the dietary needs of increasing population with depleting water resources there is need to adopt technologies which result in sufficient crop yield with less water consumption. One of them is partial root zone drying (PRD). Keeping in view these conditions, a wire house experiment was conducted at University College of Agriculture and Environmental Sciences, The Islamia University Bahawalpur during 2015, to screen out the different wheat genotypes for PRD. Five approved local wheat cultivars (V1= Galaxy-2013, V2= Punjab-2011, V3 = Faisalabad-2008, V4 = Lasani-2008 and V5 = V.8200) and two irrigation levels (I1 = control irrigation and I2 = PRD irrigation) with completely randomized design having four replications were used in the experiment. Among the varieties Galaxy-2013 performed the best and attained maximum plant height, leaf area, stomatal conductance, photosynthesis, total sugars, proline contents and antioxidant enzymes activities and minimum values of all growth and physiological parameters were recorded in variety V.8200. For irrigation levels, higher values of growth, physiological and water related parameters were recorded in control treatment (I1) except leaf water potential, osmotic potential, total sugars and proline contents. However enzymes activities were higher under PRD treatment for all varieties. It was concluded that Galaxy-2013 was the most compatible and V.8200 was the most susceptible variety under PRD condition, respectively and more quality traits and enzymatic activities were recorded under PRD condition as compared to control treatment.

Growth, Yield and Water Use Efficiency Response of Greenhouse Grown Capsicum under Deficit and PRD Method of Irrigation

A study was conducted to compare two water-saving practices, deficit irrigation (DI) and partial root zone drying (PRD), and to examine how they affect water use, growth and yield of greenhouse grown capsicum compared to control irrigation (CI). The effect of PRD on the growth of capsicum plant was significant. The results showed that capsicum fruit yield was highest for control (full irrigation), followed by the deficit irrigation treatment (DI-75 %) and then 1 PRD treatment. The analysis suggested that the treatment 1 PRD outperformed 2 PRD and DI-50 in terms of fruit yield. The yield loss in PRD treatment was only 11.1 % compared to control, whereas amount of water applied was 50 % less than through control irrigation. The highest water use efficiency was achieved for treatment of 1 PRD with 63 % improvement in irrigation efficiency over control. The treatment 1 PRD used 20.60 litres of water to produce 1 kg capsicum as against 33.61 litres under control treatment.

The Interactive Effect of Pruning Level and Irrigation Strategy on Grape Berry Ripening and Composition in 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. Berry size was found to decrease as node number per grapevine increased, but was not significantly altered by the PRD treatment. The influence of these treatments on the accumulation of total soluble solids per berry was investigated during berry ripening and was shown to be reduced at higher node number (120 nodes). There was no effect of PRD on the accumulation of total soluble solids. Juice titratable acidity and the concentration (per g) and content (per berry) of grape anthocyanins and phenolics were compared between treatments at harvest. In one season of the study, juice titratable acidity, anthocyanin and phenolic concentration was unaltered by the PRD treatment. In a further season, juice titratable acidity was decreased in response to the PRD treatment and was associated with increases in grape anthocyanin and phenolic concentration in response to PRD. Where there was a small increase in anthocyanin concentration in response to PRD, this was found to be independent of berry size. In addition, linear regression analysis showed a poor relationship between berry size and anthocyanin concentration, but a significant relationship was found between berry size and anthocyanins per berry.