Partial Root-zone Drying Technique 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.

Water Conservation with the Application of Partial Root Zone Drying Technique in Increasing the Growth and Production of Tomato

Water Conservation with the Application of Partial Root Zone Drying Technique in Increasing the Growth and Production of Tomato

Yield, quality and plant nutrient contents of lettuce under different deficit irrigation conditions

This research was carried out in two separate periods (spring and autumn) in 2018 to reveal the lettuce response of yield, some quality, and plant nutrient content under different water stress conditions. In the study, the effects of different irrigation levels applied with traditional deficit irrigation (TI) and partial rootzone drying (PRD) techniques on lettuce growing were investigated. Lettuce (Lactuca sativa var. crispa cv. ‘Campania’) was used as plant material. There were traditional farmers’ method of irrigation (TF), 125% traditional irrigation (TI-125), 100% traditional irrigation (TI-100), 75% traditional irrigation (TI-75), 50% traditional irrigation (TI-50), 125% partial root-zone drying technique (PRD-125), 100% partial root-zone drying technique (PRD-100), 75% partial root-zone drying technique (PRD-75), 50% partial root-zone drying (PRD-50) technique treatments. According to the results of the research, it was determined that different water stress applications were effective on the criteria examined in lettuce. The highest total and marketable yield values were obtained from the TF application, the second-highest values from the TI-125 application, and the lowest yield from the PRD-50 in the autumn period. In the spring season, the lowest yield was obtained from TI-50 and PRD-50 applications. Based on the treatments, the yield values were decreased and changes were experienced with the increase of the water stress in other examined criteria.

The Effect of Deficit Irrigation Strategies on the Efficiency From Plant to Essential Oil Production in Peppermint (Mentha piperita L.)

The effect of deficit irrigation on water productivity in the water supply and utilization chain has been computed, employing a systematic and quantitative approach. By applying such an investigation, weaknesses and strengths of deficit irrigation strategies could be revealed, and actions and measures could be implemented to improve water productivity as much as possible. The peppermint plants were subjected to regulated deficit irrigation (RDI) and partial root-zone drying (PRD). Peppermint was cultivated under full irrigation (FI, control) and RDI treatments including RDI85, RDI70, RDI55, and RDI40, receiving 85, 70, 55, and 40% of FI treatment, respectively; PRD techniques including PRD70, PRD55, and PRD40, receiving 70, 55, and 40% of FI treatment in one side of the root-zone at each irrigation event, respectively during two cutting seasons. There was no significant improvement in leaves weight and dried yield step by applying deficit irrigation treatments. Leaves and aerial parts from the whole plant and dried yield as the main source of essential oil had the weakest function, which should be optimized to adjust and gain more efficiency. In the essential oil yield step, as a final procedure, the highest improvements were observed in PRD55 treatment with 90% improvement in efficiency compared to control treatment. According to the results and calculating water productivity, PRD55 treatment improved water productivity by 179% compared to the control treatment. Two-way ANOVA analysis, between deficit volume and the deficit applying method, showed that total water productivity was affected (increased) significantly by the deficit applying method. This implies the contribution of the PRD technique to enhance more signals than RDI-based signals, which resulted in more improvements in secondary metabolism production in peppermint.

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.

The Effect of Applying Partial Root Zone Drying Technique on Growth, Result and Quality of Tomato

The Effect of Applying Partial Root Zone Drying Technique on Growth, Result and Quality of Tomato

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.

NUMERICAL MODELING FOR SOIL WATER MOVEMENT UNDER DEFICIT IRRIGATION AND PARTIAL ROOT ZONE DRYING

The successful water management is considered one of the best solutions for the problem of water shortage. The first step in successful water management is to estimate the water requirements for crops accurately and monitoring the residual water content in soil during the growth season, but that cost a lot of everts and money. Others most important techniques for water saving are deficit irrigation (DI), partial root zone drying (PRD) and the integration between them. So, the aim of this study is to simulate the water flow in soil by Hydraus-1D as an easy and a cheap method. Also, studying the applied full irrigation (FI), two levels of sustainable deficit irrigation (DI) applied 75% of total crop evapotranspiration (ETc) (DI75%)and applied 50% of ETc (DI50%), partial root zone drying (PRD) and the integration between DI and PRD on eggplant yield and water productivity efficiency (WP). The experimental work was carried out during the summer seasons of 2017 and 2018 at the experimental farm of Faculty of Agriculture (Moshtohor), Benha University. The soil water content (θ) was measured several times during the growth season by using soil moisture sensor (ML3-Theta-Probe) at depths of 10, 30 and 50 cm. In addition, a numerical modeling was used for predicting the soil water content and comparing the output of model with the actual measured soil water content. The results of the numerical model showed that, the simulated and measured θ values were very close to each other. Moreover, the soil water content under subsurface drip irrigation (SSDI) at a depth of 10 cm were higher by 15.44 % than the corresponding ones under surface drip irrigation (SDI), while at depths of 30 and 50 cm, the values of θ under SDI were higher by 7.16 % and 11.41 % than the corresponding ones under SSDI, respectively. PRD technique with full irrigation (FIPRD) treatment increase the yield and WP by average values about 7.5 % and 16.25 % than that obtained without PRD, respectively under SDI and SSDI. In addition, the PRD technique associated with deficit irrigation treatments resulted in lower fluctuation in the water contents in the vertical distribution than that obtained by the corresponding treatments without PRD technique. While, the using DI decreased the yield and increase WP by different percentage. DI75% decrease the yield by average value 14.9 % than that obtained at FI and increase WP by 29.1 % under SDI and SSDI. DI50% significantly decreased the yield by average value 36.25 % and increase significantly the WP by 59.1 % than the corresponding values at FI. The statistical analysis showed that, there were no significant differences among the FIPRD, FI and DI75+PRD. The SDI resulted in increasing in yield by 4.11 % but not significant than that obtained by SSDI, and SSDI increased WP by 7.15 % than that achieved under the SDI, however the differences between these values were not significant.

Effects of Biochar and Compost on Growth and Yield of Sweet Pepper under a Partial Root-Zone Drying Irrigation System

This study was carried out to assess the effects of compost (CO2 and CO4), biochar (B2 and B4), and biochar–compost mixture (Mix2 and Mix4), at rates of 2% and 4%, on the yield and water use efficiency (WUE) of sweet pepper under greenhouse conditions. Pepper plants were irrigated by partial root-zone drying (PRD) using two levels of water irrigation, 75% from evapotranspiration (ETc) (PRD75%ETc) and 50% from ETc (PRD50%ETc). The objectives of this study were to evaluate the distribution of soil water, salinity, and root system of bell pepper and changes in the WUE of bell pepper due to the PRD technique. The contour lines showed that the salinity was improved by adding biochar, compost, and their combination because the moisture content of the amended soil was the highest compared to that of the control (untreated soil). The WUE of pepper under PRD75%ETc was 7.5, 6.1, 8.7, 6.69, 9.5, and 7.7 kg m-3 for B4, B2, CO4, CO2, Mix4, and Mix2, respectively. The WUE under PRD50%ETc was 9.8, 8.2, 10.2, 8.5, 11.7, and 10.1 kg m-3 for B4, B2, CO4, CO2, Mix4, and Mix2, respectively. The irrigation water saved was 35% and 57% under PRD75%ETc and PRD50%ETc, respectively.

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.

Partial Root-Zone Drying Technique: from Water Saving to the Improvement of a Fruit Quality

Due to climate changes and increased demands of different water users (agriculture, industry, domestic) water becomes scarce resources worldwide. Since irrigated agriculture is the one of the largest consumer of these resources (so called blue water footprint), irrigation management must be shifted from maximal production per crop area to maximal production per unit of water used by crops. Among the strategies for reducing water footprints, changing the full irrigation to the reduced crop’s water supply (deficit irrigation techniques) is one of the options. In this mini-review we present the latest advances of partial root-zone drying (PRD) applications in different agricultural plants, with the special emphases on the PRD effects on increasing WUE, yield and yield quality. We describe two PRD practical approaches (alternate and fixed), background of PRD induced increase in yield and water use efficiency and improved understanding about nutrient use efficiency. The evidence of PRD effect on the increase in nutritional and health attributes of yield in different species is also presented. Because of limited available data, further research is needed to understand complex biosynthetic pathway and synthesis of nutritive and healthy related metabolites and antioxidants in PRD treated plants. Practical application and promotion of this knowledge will allow farmers in water scarce areas to adapt PRD not only as a strategy for saving water, improving nutrient use and increase/sustain yield, but also for producing food with enhanced nutritive and health characteristics.

A Comparative Analysis for a Novel Irrigation Method: Partial Rootzone Drying

Partial Rootzone Drying (PRD) is an irrigation technique which offers a means of modifying the growth and development of crops through relatively simple changes to the method of water delivery. The technique causes the stimulation of physiological responses which are normally associated with water stress and this results in a significant reduction in water use through the production of chemical signals in drying roots. Partial drying of one half of the roots of plants grown with two root systems is rapidly translated into a reduction in transpiration and assimilation of all the crop leaves. The aim of this research is to examine and simulate the novel irrigation method (PRD), which would stimulate the endogenous stress response mechanisms of Conocarpus erectus trees in the pilot area of the Arabian Gulf University in Bahrain and wheat and maize crops in the Mashtul Pilot Area (MPA), Egypt using Saltmed model so that vigor is reduced and the efficiency of water use is enhanced. This is to be achieved by the manipulation of the hydration status of parts of a crop’s roots that could be used to control vegetative vigor without detrimental effects on canopy water relations. The PRD technique is researched for wheat as a winter crop and maize as a summer crop in Egypt. The technique causes the stimulation of physiological responses which are normally associated with water stress and this results in a significant reduction in water use through the production of chemical signals in drying roots. The results confirmed an increase in irrigation water use efficiency using PRD comparing with conventional flood irrigation. The research highly recommends applying the PRD method in the Gulf Cooperation Council (GCC) countries and in new reclaimed areas in Egypt to save water and improve crop quality.

Deficit Irrigation and Partial Root-Zone Drying Techniques in Processing Tomato Cultivated under Mediterranean Climate Conditions

Due to climate change, the application of water saving strategies is of particular interest. The aim of this study was to evaluate the effects of deficit irrigation (DI) and partial root-zone drying (PRD) techniques on the crop water stress index (CWSI), water use efficiency (WUE), and quality parameters in processing tomatoes grown in open field conditions in a Mediterranean climate. Two cultivars were grown for two growing seasons under four irrigation regimes as follows: (i) IR100: full irrigation by restoring 100% of the maximum tomato evapotranspiration (ETc); (ii) IR70DI: 70% of the amount of water given to the IR100; (iii) IR70PRD: 70% of the amount of water given to the IR100 by applying partial root-zone drying and (iv) IR0: irrigation only at transplanting and during fertigation. During the flowering period, the first growing season was characterized by an absence of rainfall and by higher temperatures also showing a higher CWSI. Despite, under IR70PRD, the CWSI was significantly higher than under IR70DI, the marketable yield obtained was significantly higher. Both IR70DI and IR70PRD regimes received approximately 24% less water than IR100, but the yield reduction with relation to the optimum regime was equal to 16.2% under IR70DI, and only 7.6% under IR70PRD. The WUE increment of IR70PRD with respect to IR100 was equal to 27% in the first growing season and to 17% in the second one, showing that the positive effect of PRD on the WUE is more evident in the more stressed year. Finally, the results from the principal component analysis (PCA) showed that the two cultivars had different qualitative responses in the two extreme regimes (IR100 and IR0) but not under PRD and DI regimes.

Partial Root-Zone Drying of Olive (Olea europaea var. 'Chetoui') Induces Reduced Yield under Field Conditions.

The productivity of olive trees in arid and semi-arid environments is closely linked to irrigation. It is necessary to improve the efficiency of irrigation techniques to optimise the amount of olive fruit produced in relation to the volume of water used. Partial root-zone drying (PRD) is a water saving irrigation technique that theoretically allows the production of a root-to-shoot signal that modifies the physiology of the above-ground parts of the plant; specifically reducing stomatal conductance (gs) and improving water use efficiency (WUE). Partial root-zone drying has been successfully applied under field conditions to woody and non-woody crops; yet the few previous trials with olive trees have produced contrasting results. Thirty year-old olive trees (Olea europaea ‘var. Chetoui’) in a Tunisian grove were exposed to four treatments from May to October for three-years: ‘control’ plants received 100% of the potential evapotranspirative demand (ETc) applied to the whole root-zone; ‘PRD100’ were supplied with an identical volume of water to the control plants alternated between halves of the root-zone every ten-days; ‘PRD50’ were given 50% of ETc to half of the root-system, and; ‘rain-fed’ plants received no supplementary irrigation. Allowing part of the root-zone to dry resulted in reduced vegetative growth and lower yield: PRD100 decreased yield by ~47% during productive years. During the less productive years of the alternate bearing cycle, irrigation had no effect on yield; this suggests that withholding of water during ‘off-years’ may enhance the effectiveness of irrigation over a two-year cycle. The amount and quality of oil within the olive fruit was unaffected by the irrigation treatment. Photosynthesis declined in the PRD50 and rain-fed trees due to greater diffusive limitations and reduced biochemical uptake of CO2. Stomatal conductance and the foliar concentration of abscisic acid (ABA) were not altered by PRD100 irrigation, which may indicate the absence of a hormonal root-to-shoot signal. Rain-fed and PRD50 treatments induced increased stem water potential and increased foliar concentrations of ABA, proline and soluble sugars. The stomata of the olive trees were relatively insensitive to super-ambient increases in [CO2] and higher [ABA]. These characteristics of ‘hydro-passive’ stomatal behaviour indicate that the ‘Chetoui’ variety of olive tree used in this study lacks the physiological responses required for the successful exploitation of PRD techniques to increase yield and water productivity. Alternative irrigation techniques such as partial deficit irrigation may be more suitable for ‘Chetoui’ olive production.

The Effect of Partial Root-zone Drying on Tomato Fruit Growth

Tomato fruit growth and productivity are complex processes depending on the interaction between physiological, genetic and environmental factors. Under current climate conditions of drought and scarce water supply, the challenge is to increase water use efficiency and to sustain tomato yield. Partial root-zone drying technique (PRD) is one of the irrigation methods with the potential to increase the water use efficiency and sustain the yield of many crops including tomato. The aim of presented results was to investigate the effects of PRD on tomato fruit growth, the activity of cell wall-associated peroxidase and ABA content in pericarp of tomato cultivar Ailsa Craig.The experiment was done in controlled conditions and plants under PRD received 70% of water given to full irrigated plants (FI) plants. In PRD irrigation is applied to one half of the root system while the other half dried down and then the treatment was reversed. ABA content in fruit pericarp was measured by ELISA test and cell wall-associated peroxidase activity by a guaiacol test.Fruit growth parameters showed that the maximal growth rate was significantly higher in FI plants than PRD but because the longer period of cell expansion the final diameter of PRD tomato fruits was slightly higher in PRD than in FI fruits. ABA content in tomato pericarp declined during the tomato development until the end of cell growth phase without significant differences between PRD and FI treated plants. The activity of peroxidase was significantly higher in PRD compared to FI. The significantly increase in the activity of enzyme cell wall-associated peroxidase in tomato fruit pericarp under PRD conditions coincided with the end of cell growth and the beginning of the ripening process. These results pointed out that this enzyme may control tomato fruit maturation.

MODIFICATION OF FAO CROP MODEL TO SIMULATE YIELD RESPONSE TO WATER FOR PEACH TREES

Although, as compared to other crop models, AquaCrop has a significantly smaller number of parameters and a better balance between simplicity, accuracy and robustness, AquaCrop model is not yet available for fruit trees. So, AquaCrop model was studied and modified to suit the deciduous fruit trees such as peaches under drip irrigation system and the conditions of light soil in the arid and semi arid climate. The modified model is able to simulate the growth cycle of the deciduous fruit trees and estimate the yield under different stress condition. After that, a computer program was planned and developed with easy interface and few requirements to estimate the resulting yield by means of yield response factors under different stress condition. To validate the simulation program, two seasons experiment were designed to determine the yield for peach trees (Prunus persica) which is as an example of a deciduous tree, under water stress conditions by two different techniques Partial root-zone drying (PRD) and Regulated deficit irrigation (RDI) in the west noubaria rural development project research station. PRD and RDI are examples of new water-saving irrigation strategies used for reducing applied irrigation water. These techniques have been successfully adopted to produce many crop and fruit species and improve the water use efficiency. The validation of simulation program was performed using the results of an experiment peach field in 2011 and 2012 seasons. The simulated yield was close to those measured; with index of agreement (d) and correlation coefficient (r) were close to 1 in both seasons. Also, the simulation program was tested to simulate the peach fruit yield under different irrigation deficit percentages Also, the simulation program was tested to simulate the peach fruit yield under different irrigation deficit percentages using PRD and RDI techniques, 100 % to 30% of the irrigation control treatment water volume, during the slow fruit growth phase until the maturity. Yield response factor corresponding to the levels of shortage of irrigation water was determined in RDI and PRD strategy, were 1.32 and 0.72, respectively.

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.

Water use optimisation based on the concept of Partial Rootzone Drying

Partial Rootzone Drying (PRD) is the creation of simultaneous wet and dry (or drying) areas within the root zone. Only part of the root zone is irrigated and kept moist at any one time. This new irrigation strategy allows the exploitation of drought-induced abscisic acid (ABA) based root to stomata signaling system to water saving. In this research, the PRD technique is examined and simulated for wheat and maize crops in the Mashtul Pilot Area (MPA), Egypt using Saltmed model. The technique causes the stimulation of physiological responses which are normally associated with water stress and this result in a significant reduction in water use through the production of chemical signals in drying roots. The results confirmed an increase in irrigation water productivity using PRD comparing with conventional flood irrigation. The research highly recommends applying the PRD method in new reclaimed areas in Egypt to save water and improve crop quality.

ECONOMIC ANALYSIS OF DRIP‐IRRIGATED KINNOW MANDARIN ORCHARD UNDER DEFICIT IRRIGATION AND PARTIAL ROOT ZONE DRYING

ABSTRACTThe profitability of regulated deficit irrigation (RDI), sustained deficit irrigation (SDI), and SDI with partial root zone drying (PRD) strategies was compared to that with full irrigation (FI: 100% crop evapotranspiration) in drip‐irrigated Kinnow mandarin in northern India. RDI was scheduled with two irrigation levels: no irrigation and 50% crop evapotranspiration (ETc.) imposed in the early fruit growth period (EFGP) and final fruit growth period (FFGP) singly and in combination, whereas SDI was scheduled at 50% ETc and 75% ETc with and without the PRD technique. The highest fruit yield was recorded with FI, which was statistically on a par (p > 0.05) with that with SDI at 50% ETc with PRD (PRD50). Economic‐based comparison shows that all the treatments were economically viable since their profitability (net return, INR 137 000–1 300 000 ha‐1 and benefit–cost ratio, 2.1–14.3) were viable. The net return generated with PRD50 was statistically (p > 0.05) at par with that generated with FI. However, the benefit–cost ratio and economic water productivity calculated with PRD50 were found to be significantly (p < 0.05) higher (36 and 87%, respectively) than that with FI. These results lead us to conclude that the PRD50 strategy could be used to improve irrigation water productivity substantially in commercial Kinnow mandarin orchards in sandy loam soil. Copyright © 2013 John Wiley & Sons, Ltd.

Partial root-zone drying irrigation and water utilization efficiency by the potato crop in semi-arid regions in China

Two field experiments were conducted in two semi-arid areas in northern China to test the response of three potato varieties to supplemental irrigation. Conventional furrow irrigation was compared to the partial root-zone drying (PRD) irrigation system at different watering levels, with and without plastic mulching. Reducing the supplementary water to one half, under both soil-climate conditions tested, did not affect fresh tuber yield; whereas water use efficiency (WUE) was equally incremented by all the reduced water treatments. When this reduction in the amount of supplementary water was managed through the PRD system, the distribution of moisture in the soil seemed to be improved and the potential evaporation was decreased due to the reduced evaporative surface exposed by PRD. The results showed that application of irrigation water per unit area can be reduced relative to common practice in Inner Mongolia and Gansu, maintaining the tuber yields currently obtained by local farmers. A further reduction in the amount of supplemental water, without a substantial decrease in yield, might be feasible with the PRD technique but this may require a more sophisticated irrigation management; and further research to estimate the cost-benefit ratio of such sophistication is needed. Results also showed that under low precipitation and low water retention capacity, the use of plastic mulching and a potato variety selected for drought-prone environments can make the difference for maintaining a high yield while reducing the wasteful use of the water resources.