Water-saving Irrigation Strategies Research Articles

Intelligent sprinkler irrigation system for citrus orchard in plateau of Yunnan, China

This study was designed to develop water-saving irrigation strategy for citrus cultivation at Xinping County, Yunnan, China. This county has a mountainous landscape with resources of natural rivers. Based on the local standard water quota (DB53/T168-2019) of Yunnan Province, Xinping County falls into the dry-hot valley VI -2 zone. We developed a Smart Sprinklers irrigation system to meet the actual irrigation requirements of citrus plants with multiple benefits starting from economic to social and environmental protection. We considered the specific situation of the project area, and then design an irrigation system for citrus orchard. Hydraulic calculations determined the suitable materials and sizes for pipes, valves, and irrigation equipment, based on the area’s water demand favoring micro-sprinkler irrigation. Following technical standards, we selected appropriate equipment for designing the pipe network, including the layout, positioning, and installation of the pumping station, moisture meters, weather station, and pest monitoring system. Further research could investigate the adoption of renewable energy to enhance system sustainability and examine the transferability of these systems to different crops and similar geographic regions. It is concluded that this technology and design is very useful for the cultivation of citrus plants in hilly areas.

Deficit Irrigation Regime Improves Phytosanitary Status of Cultivar Arbosana Grown in a Super High-Density Olive Orchard

Super high-density (SHD) planting systems are very efficient in terms of production and water use. In these orchards, water-saving irrigation strategies are used precisely to keep the best sustainability compared to traditional orchards. With agro-climatic and eco-physiological parameter monitoring, the SHD planting system has become even more efficient. SHD orchards, however, could also be more so affected by other pests and diseases than traditional systems, but field responses are still unknown when olive trees are grown in SHD groves. The goal of this two-year field research was to investigate the seasonal changes of the phytosanitary status of ‘Arbosana’ grown in an SHD orchard under both regulated deficit (RDI) and full irrigation regimes (FI). This study investigated the influence of the two different irrigation regimes on the infections of three olive tree key diseases: cercosporiosis (Pseudocercospora cladosporioides), cycloconium (Fusicladium oleagineum), and olive knot (Pseudomonas savastanoi pv. savastanoi). RDI significantly reduced the severity of cercosporiosis in 2020 compared to FI but not in 2021. Cycloconium was observed only as a latent infection during the two studied years and olive knot was not influenced by irrigation but only by weather conditions. These findings suggest that irrigation management can play a key role in controlling cercosporiosis effectively in SHD olive orchards, but also that weather conditions have an even higher impact on the tree key diseases.

Enhancing growth and tolerance traits in pepper (Capsicum annuum L.) through water-saving irrigation practices

Due to their intensive cultivation, horticultural crops are particularly susceptible and vulnerable to the detrimental effects of drought stress, necessitating significant water inputs for optimal growth and yield. Accordingly, water-saving irrigation strategies, i.e., Partial Root zone Drying (PRD) and Regulated Deficit Irrigation (RDI) emerge as pivotal tools for bolstering the resilience of the horticultural sector. The current study aims to evaluate the impact of PRD and RDI strategies on pepper (Capsicum annuum L.) growth, and physio-biochemical attributes under semi-controlled greenhouse conditions. Research findings revealed pronounced enhancements in stem length under both irrigation strategies, with PRD exhibiting superior effects on shoot fresh and dry biomass (increases of 57.2% and 61.1%, respectively) compared to full irrigation. At the physiological level, PRD and RDI induced a significant reduction in stomatal conductance in pepper plants relative to full irrigation, while maintaining leaf water potential and relative water content. Biochemically, plants subjected to PRD and RDI methods exhibited significant accumulation of free proline, particularly pronounced with PRD (approximately 115.9% increase compared to full irrigation). Furthermore, Chl a and carotenoid concentration significantly increased under PRD, indicating sustained photosynthetic functionality. Comparatively, PRD appears as the more effective technique, offering the potential to conserve agricultural water about 50 without compromising growth parameters, while simultaneously enhancing tolerance traits in C. annuum. Nonetheless, further investigations on other traits across diverse soil types, climates, and cultivars under field conditions are imperative to ascertain the broader applicability of PRD and optimize its implementation.

The Impact of Water-Saving Irrigation on Rice Growth and Comprehensive Evaluation of Irrigation Strategies

To explore the effects of different water-saving treatments on rice plant growth and select suitable water-saving irrigation strategies for aerobic rice varieties, we conducted relevant field experiments from June to October 2023 at Jiangsu Runguo Agricultural Development Co., Ltd., China, which is located in a north subtropical monsoon climate where the soil is alkaline sandy loam. Four water treatments were set up, including the control of local conventional irrigation (CK, without water stress), mild water-saving treatment (W1, 20% more water saved than CK), moderate water-saving treatment (W2, 30% more water saved than CK), and severe water-saving treatment (W3, 40% more water saved than CK). The experiment results showed that rice plant heights were inhibited and leaf chlorophyll contents increased under all water-saving treatments compared to CK. Among them, the MDA content in paddy leaves under the W1 treatment decreased, while the activities of SOD and POD were enhanced and the membrane lipid peroxidation capacity of rice was also enhanced. Meanwhile, the results showed that the rice yield and quality under the W1 treatment significantly improved. Based on those experiments, a comprehensive evaluation of rice plant height, chlorophyll content, grain yield, yield components, and rice quality was conducted using the TOPSIS entropy weight method. It was preliminarily concluded that the suitable irrigation scheme for south and central Jiangsu was 20% water-saving irrigation compared with CK. In summary, under the premise of maintaining the economic yield of rice cultivation, an appropriate water irrigation plan helped save water resources and promote rice growth.

Effect of Irrigation and Nitrogen Management on Potato Growth, Yield, and Water and Nitrogen Use Efficiencies

Irrigation and nitrogen management are crucial for sustainable potato (Solanum tuberosum L.) production. A field experiment was conducted during the 2022 and 2023 growing seasons at Farmington, New Mexico, to evaluate the performance of two chip potato varieties (Lamoka and Waneta) under three irrigation regimes (full irrigation (FI), 20% deficit irrigation (DI) and 40% DI) and seven nitrogen fertilizer rates (0, 60, 115, 170, 220, 280, and 340 kg N/ha). The treatment combinations of irrigation regimes, nitrogen rates, and varieties were arranged in a split–split plot design with three replications as main plot, sub-plot, and sub-sub plot, respectively. The two-year results showed that irrigation regimes had the most significant effect on plant growth, physiology, and tuber yield of the potato varieties. For both Lamoka and Waneta, the plant height and canopy cover were lower under 40% DI than under 20% DI and FI treatments. The SPAD meter values were higher under 40% DI, followed by 20% DI and FI treatments, whereas the stomatal conductance was higher under FI, followed by 20% DI and 40% DI during both growing seasons. Regardless of nitrogen rates and variety, a 20% water-saving irrigation strategy reduced the total tuber yield by 4.5% and 22.1% in the 2022 and 2023 growing seasons, respectively, while the 40% water-saving irrigation strategy reduced total tuber yield by 36.8% and 58.2% in the 2022 and 2023 growing seasons, respectively, as compared to full irrigation. Shifting from full irrigation to 20% DI could save 711.2 to 1036.3 m3/ha of irrigation water. For Lamoka, the highest total tuber yield was obtained with 60 kg N/ha under 20% DI and 220 kg N/ha under FI in 2022 and 2023, respectively. For Waneta, the highest total tuber yield was obtained with 115 kg N/ha under 20% DI and 170 kg N/ha under FI in 2022 and 2023, respectively. Maximum water use efficiency (WUE) was obtained at 60 kg N/ha with 20% DI for both Lamoka and Waneta in 2022, while maximum WUE was obtained at 220 kg N/ha under FI for Lamoka and at 170 kg N/ha for Waneta in the 2023 season. The maximum nitrogen use efficiency (NUE) was achieved with 60 kg N/ha under 20% DI for both varieties during both growing seasons. Thus, for sustainable irrigation and nitrogen management, the application of a 20% deficit irrigation strategy with a lower nitrogen rate (60 to 170 kg N/ha) could be the best option to improve WUE and NUE with minimal tuber yield reduction. Our study suggested that 40% deficit irrigation would not be beneficial as compared to both full irrigation and 20% water-saving irrigation.

Mitigation of N2O emissions in water-saving paddy fields: Evaluating organic fertilizer substitution and microbial mechanisms

Water-saving irrigation strategies can successfully alleviate methane emissions from rice fields, but significantly stimulate nitrous oxide (N2O) emissions because of variations in soil oxygen level and redox potential. However, the relationship linking soil N2O emissions to nitrogen functional genes during various fertilization treatments in water-saving paddy fields has rarely been investigated. Furthermore, the mitigation potential of organic fertilizer substitution on N2O emissions and the microbial mechanism in rice fields must be further elucidated. Our study examined how soil N2O emissions were affected by related functional microorganisms (ammonia-oxidizing archaea (AOA), ammonia-oxidizing bacteria (AOB), nirS, nirK and nosZ) to various fertilization treatments in a rice field in southeast China over two years. In this study, three fertilization regimes were applied to rice cultivation: a no nitrogen (N) (Control), an inorganic N (Ni), and an inorganic N with partial N substitution with organic manure (Ni+No). Over two rice-growing seasons, cumulative N2O emissions averaged 0.47, 4.62 and 4.08 kg ha−1 for the Control, Ni and Ni+No treatments, respectively. In comparison to the Ni treatment, the Ni+No fertilization regime considerably reduced soil N2O emissions by 11.6% while maintaining rice yield, with a lower N2O emission factor (EF) from fertilizer N of 0.95%. Nitrogen fertilization considerably raised the AOB, nirS, nirK and nosZ gene abundances, in comparison to the Control treatment. Moreover, the substitution of organic manure for inorganic N fertilizer significantly decreased AOB and nirS gene abundances and increased nosZ gene abundance. The AOB responded to N fertilization more sensitively than the AOA. Total N2O emissions significantly correlated positively with AOB and nirS gene abundances while having a negative correlation with nosZ gene abundance and the nosZ/nirS ratio across N-fertilized plots. In summary, we conclude that organic manure substitution for inorganic N fertilizer decreased soil N2O emissions primarily by changing the soil NO3−-N, pH and DOC levels, thus inhibiting the activities of ammonia oxidation in nitrification and nitrite reduction in denitrification, and strengthening N2O reduction in denitrification from water-saving rice paddies.

Imaging of the electrical activity in the root zone under limited-water-availability stress: a laboratory study for Vitis vinifera

Abstract. Understanding root signals and their consequences for the whole plant physiology is one of the keys to tackling the water-saving challenge in agriculture. The implementation of water-saving irrigation strategies, such as the partial root zone drying (PRD) method, is part of a comprehensive approach to enhance water use efficiency. To reach this goal tools are needed for the evaluation of the root's and soil water dynamics in time and space. In controlled laboratory conditions, using a rhizotron built for geoelectrical tomography imaging, we monitored the spatio-temporal changes in soil electrical resistivity (ER) for more than a month corresponding to eight alternating water inputs cycles. Electrical resistivity tomography (ERT) was complemented with electrical current imaging (ECI) using plant-stem-induced electrical stimulation. To estimate soil water content in the rhizotron during the experiment, we incorporated Archie's law as a constitutive model. We demonstrated that under mild water stress conditions, it is practically impossible to spatially distinguish the limited-water-availability effects using ECI. We evidenced that the current source density spatial distribution varied during the course of the experiment with the transpiration demand but without any significant relationship to the soil water content changes. On the other hand, ERT showed spatial patterns associated with irrigation and, to a lesser degree, to RWU (root water uptake) and hydraulic redistribution. The interpretation of the geoelectrical imaging with respect to root activity was strengthened and correlated with indirect observations of the plant transpiration using a weight monitoring lysimeter and direct observation of the plant leaf gas exchanges.

Application of water-saving irrigation and biostimulants on the agronomic performance of maize (Zea mays)

Water deficit can limit maize yield; therefore, appropriate choices of irrigation schemes or water-saving irrigation strategies to maximize WUE are needed for sustainable agriculture in response to environmental challenges and climate change. The objectives of our study were to evaluate and compare the effects of regulated deficit irrigation (RDI) and partial root-zone drying irrigation (PRDI) schemes with various field capacity (FC) conditions on yield components, water use efficiency (WUE), photosynthesis capacity, and chlorophyll fluorescence parameters of the maize plant in a pot experiment. Moreover, we also investigated foliar application of glycine betaine (B, 50 mM) and soil-treated chitin (C, 2 g/kg) to plants against water supply limitations and highlighted their potential for the sustainable production of maize. Significantly higher plant height, cob fresh and dry weights, and total dry weight of maize were observed in RDI with the 75 % FC condition compared to the control (full irrigation with 100 % FC). PRDI treatment resulted in significantly higher economic yield, WUEyield, and WUEbiomass compared to RDI treatment. Total water used in PRDI at 50 % FC saved 72 % of water resources compared to the control. Furthermore, values for effective quantum yield (ФPSII), photochemical quenching (qP), and electron transfer rate (ETR) of maize subjected to 75 % FC were higher than under 50 % FC and the control, while maximal quantum efficiency (Fv/Fm) levels of maize were higher under 50 % FC than under 75 % FC. All agronomic traits, chlorophyll content (as SPAD value), transpiration rate, net photosynthesis value, WUEyield, and WUEbiomass of plants subjected to PRD-50 %FC with spraying B alone showed higher values compared to other chemical applications and no chemical treatment. Applying C alone to maize plants under PRDI-50 % FC increased qP and Fv/Fm compared to other chemical treatments. Evaluating water deficits with non-destructive measurements are applicable to large-scale water management of maize plants, thereby enabling scarce water resources to be conserved.

Effects of water-saving irrigation planning on the underground water in the low area of Yellow River, China

Abstract The Yellow River Delta is considered one of the most water-stressed regions in China as the competition for water between various industrial sectors and agriculture is increasing. Since 2007, the regional governments have taken a leading role in agricultural water-saving planning by upgrading irrigation systems and constructing water-saving facilities. In this study, the effects of water-saving irrigation strategies on the groundwater table and quality were investigated in the Yellow River basin during the last two decades. The average phreatic water level of bore-wells was monitored as 13.47 m during 2011–2020 compared to the level of 12.09 m during 2011–2020. Besides, the depth of the deep confined aquifer dropped dramatically during 2001–2013 with a declining rate of 2.55 meters per annum (m/a) compared to the value of 0.385 m/a after 2014, suggesting the reduced exploitation of deep groundwater and increased availability of groundwater after the water-saving campaign. In addition, the physicochemical parameters of both phreatic water and deep confined aquifer indicated improved water quality. Consequently, understanding how the water-saving planning influences the groundwater availability is important, which would provide an insightful guidance for the water managers to protect the groundwater environment in the Yellow River Delta.

Irrigation schedule impact on greenhouse gas mitigation, carbon sequestration, and yield improvement of double rice-cropping systems in southern China

The development of water-saving irrigation in paddy soils is crucial because of the increasing demand for water resources. There is a need to improve the understanding of water use strategies that save water and reduce greenhouse gas (GHG) emissions without causing yield losses in double rice-cropping systems. The current study was conducted to examine the net global warming potential (NGWP) and net greenhouse gas intensity (NGHGI) based on the net GHG emissions, including soil organic carbon (SOC) change and indirect emissions (IEs). An experiment was conducted under flood irrigation (FI), shallow irrigation (SI), and intermittent irrigation (II) conditions. The average double rice yields under the SI and II treatments were significantly higher than those under FI by 4.7% and 12.1%, respectively. The SI and II treatments could save 44% and 67% of irrigation water in the entire double-cropping rice-growing season, respectively. However, the SOC sequestration rate over 4 years was not significantly different among the three irrigation regimes. Compared to FI, the annual methane (CH4) emissions decreased by 34% and 45% under SI and II, respectively. In contrast, nitrous oxide (N2O) emissions under SI and II increased by 27% and 50%, respectively. IEs were nearly the same among the three irrigation regimes, with fertilizer use as the top contributor, and followed the order FI > SI > II. The NGWP and NGHGI decreased by 37% and 44%, respectively, under II compared to FI. In conclusion, water-saving irrigation strategies, especially the II practice, are an effective method that can simultaneously achieve great success in saving water, increasing rice production, and reducing GHG emissions.

Deficit Irrigation with Ascophyllum nodosum Extract Application as a Strategy to Increase Tomato Yield and Quality

Deficit irrigation is applied to several agricultural crops as a water-saving irrigation strategy. The tomato plant is sensitive to water stress; however, integration with biostimulant applications, based on seaweed extracts, could be a strategy for plants adapting to this abiotic condition. The objective of this study was to evaluate agronomic and quality aspects of tomato cultivated under deficit irrigation combined with Ascophyllum nodosum extract (ANE) application. The experiment was conducted using a completely randomized design with two water replacement levels, 70 and 100% of crop evapotranspiration (ETc), and five doses of ANE (0, 0.1, 0.2, 0.3 and 0.4%) applied via soil drench. The interaction between ANE and ETc was significant (p < 0.05) in terms of plant growth, physiological parameters, fruit yield, yield components and fruit quality. Results indicated that when the tomato plant is under deficit irrigation, a higher ANE dose is required to achieve better development when compared to the 100% ETc condition, where the dose is lower. Under deficit irrigation, the largest fruit yield was obtained with 0.3 and 0.4% ANE, and with 100% ETc, the largest fruit yield was obtained with 0.2% ANE. ANE applications were also effective in increasing plant height, stem diameter, plant biomass, leaf area, chlorophyll and relative water content. In addition, tomato quality was also favored under deficit irrigation and seaweed extract application. We conclude that ANE applications attenuate water deficit effects in tomato plants and provide a strategy to ameliorate tomato yield, tomato quality and water use in agriculture.

Integrated omic analysis provides insights into the molecular regulation of stress tolerance by partial root-zone drying in rice.

Partial root-zone drying (PRD) is an effective water-saving irrigation strategy that improves stress tolerance and facilitates efficient water use in several crops. It has long been considered that abscisic acid (ABA)-dependent drought resistance may be involved during partial root-zone drying. However, the molecular mechanisms underlying PRD-mediated stress tolerance remain unclear. It's hypothesized that other mechanisms might contribute to PRD-mediated drought tolerance. Here, rice seedlings were used as a research model and the complex transcriptomic and metabolic reprogramming processes were revealed during PRD, with several key genes involved in osmotic stress tolerance identified by using a combination of physiological, transcriptome, and metabolome analyses. Our results demonstrated that PRD induces transcriptomic alteration mainly in the roots but not in the leaves and adjusts several amino-acid and phytohormone metabolic pathways to maintain the balance between growth and stress response compared to the polyethylene glycol (PEG)-treated roots. Integrated analysis of the transcriptome and metabolome associated the co-expression modules with PRD-induced metabolic reprogramming. Several genes encoding the key transcription factors (TFs) were identified in these co-expression modules, highlighting several key TFs, including TCP19, WRI1a, ABF1, ABF2, DERF1, and TZF7, involved in nitrogen metabolism, lipid metabolism, ABA signaling, ethylene signaling, and stress regulation. Thus, our work presents the first evidence that molecular mechanisms other than ABA-mediated drought resistance are involved in PRD-mediated stress tolerance. Overall, our results provide new insights into PRD-mediated osmotic stress tolerance, clarify the molecular regulation induced by PRD, and identify genes useful for further improving water-use efficiency and/or stress tolerance in rice.

Combination of Water-Saving Irrigation and Nitrogen Fertilization Regulates Greenhouse Gas Emissions and Increases Rice Yields in High-Cold Regions, Northeast China.

Increased rice production, which benefitted from cropping areas expansion and continuous N applications, resulted in severe increases in greenhouse gases (GHG) emissions from 1983 to 2019 in Heilongjiang Province, China. Therefore, field trials were performed in the high-cold Harbin region, Northeast China, to determine the efficiency of incorporating water regimes with N fertilization in minimizing the impact of rice production on GHG emissions. Two water-saving irrigation strategies, intermittent irrigation (W1) and control irrigation (W2), were used relative to continuous flooding (W0), and we combined them with six fertilized treatments. Our results demonstrated that W1 and W2 significantly decreased seasonal CH4 emissions by 19.7-30.0% and 11.4-29.9%, enhanced seasonal N2O emissions by 77.0-127.0% and 16.2-42.4%, and increased significantly yields by 5.9-12.7% and 0-4.7%, respectively, compared with W0. Although trade-offs occurred between CH4 and N2O emissions, W1 and W2 resulted in significant reductions in global warming potential (GWP). Moreover, low N rates (<120 kg N ha-1) performed better in GWP than high N rates. N fertilization and irrigation regimes had remarkable effects on rice yields and GWP. In conclusion, the incorporation of W1 and a N application under 120 kg N ha-1 could simultaneously mitigate GWP while enhancing production in black soils in high-cold Northeast China.

Effect of Partial Root Drying and Deficit Irrigation on Yield and Water Use Efficiency of Tomato Grown Under Greenhouse

Water conservation strategies are becoming increasingly important as a result of the shortage of water and climate change. The purpose of this study is to address water-saving irrigation strategies by evaluating the effect of partial root drying irrigation (PRD) and Deficit Irrigation (DI) practice on the yield and water use efficiency of tomatoes (Shivam variety). The treatments were partial root drying (PRD) at 75% and 50% crop evapotranspiration, ETc (PRD25 and PRD50, respectively), and deficit irrigation (DI) at 75% and 50% of ETc (DI25 and DI50, respectively). The PRD practice requires wetting one half of the root zone and keeping the other half dry, consequently using less amount of irrigation water that was applied. In the successive irrigations, the wet and dry sides were alternated. Over a growing season after transplanting, the highest fruit yield was obtained under FULL irrigation (225 t ha-1). In comparison to deficit irrigation that received the same quantity of water, the PRD treatments produced an increased yield of 5–10%. PRD and DI irrigation improved WUE considerably, and that was 30.35% and 25.71% respectively higher than FI. Results suggest that PRD treatment may be an option in a water shortage.

Effect of Organic Amendments and Nano-Zinc Foliar Application on Alleviation of Water Stress in Some Soil Properties and Water Productivity of Barley Yield

The scarcity of water resources in arid and semi-arid areas is considered a threat to agricultural sustainability. Therefore, approaches are needed to rationalize use of irrigation water without reducing crop productivity or degrading soil properties. The objective of this study was to investigate the effect of different organic amendments (O1 = control, O2 = compost, and O3 = vermicompost) combined with different rates of nano- zinc foliar spraying (Zn1 = 0, Zn2 = 1 and Zn3 = 2 gm/L), under irrigation supplements (I1 = 100%, I2 = 85%, and I3 = 65% of water requirements) on clay soil characteristics, on the production of Egyptian barley Giza 126. Over two successive winter growing seasons, 2018/2019 and 2019/2020, field experiments were conducted as a split-split plot design with three replications. The results show that using vermicompost is an appropriate organic amendment to improve the physical and chemical properties of soils as compared with compost. Application of vermicompost led to a reduction in soil salinity (ECe), exchangeable sodium percentage (ESP), and soil bulk density (BD), of −5.67%, −5.44%, and −2.21%, respectively; there was a significant increase in soil organic carbon (SOC), available nitrogen (A.N), and field capacity (F.C.), of 43.75%, 14.37%, and 18.65%, respectively, compared with unamended soil (O1). The maximum values for grain yield were increased by 13.2% and 14.9% in both seasons, respectively, and the irrigation water productivity of barley was increased more than compost and control. Vermicompost increased the irrigation water productivity for grain (1.69 and 1.69 kg grain m−3) and straw (1.23 and 1.17 kg straw m−3) in the first and second season, respectively. Similar trends were also observed from treatments on the water applied, stored water, and water application efficiency. Application of vermicompost and nano-Zn foliar spraying could be exploited for the development of barley growth and yield, which are enhanced under water-saving irrigation strategies.

Combined effect of partial root drying and elevated atmospheric CO2 on the physiology and fruit quality of two genotypes of tomato plants with contrasting endogenous ABA levels

Elevated CO2 concentration (e[CO2]) could induce the decline of nutrient concentration in tomato fruit, although it enhances the yield. Alternate partial root drying (PRD) irrigation is a water-saving irrigation strategy, which may enhance tomato fruit quality including both organic and inorganic attributes. Yet, it remains unknown whether PRD could alleviate the negative impact of e[CO2] on the quality attributes of tomato fruit. To investigate that, two genotypes of tomato plants differing in their endogenous abscisic acid level, i.e. Ailsa Craig (wild type, WT) and its correspondent ABA-deficient mutant (flacca), were grown in ambient CO2 (a[CO2], 400 ppm) and e[CO2] (800 ppm) environment, respectively. And three irrigation regimes including full irrigation (FI), deficit irrigation (DI) and PRD were applied during anthesis to fruit ripping stages. The results showed that e[CO2] increased net photosynthetic rate, decreased stomatal conductance and transpiration rate. Tomato yield was more sensitive to irrigation regimes than [CO2], and the reduction of fruit yield caused by PRD was attenuated under e[CO2], especially in flacca. Both e[CO2] and PRD enhanced water use efficiency. The concentration of total soluble solid, total sugar and total acid, as well as fruit firmness were improved in PRD. A negative effect of e[CO2] on fruit mineral nutrition was seen only in flacca, and as expected, such impact was attenuated by the reduced irrigation regimes (DI and PRD). Collectively, it is suggested that the responses of tomato fruit quality to e[CO2] and reduced irrigation regimes are genotypic-dependent, where the endogenous ABA level of the plants plays an important role, and this must be considered in climate management in greenhouse tomato cultivation.

High-Resolution Monitoring and Assessment of Evapotranspiration and Gross Primary Production Using Remote Sensing in a Typical Arid Region

Land surface evapotranspiration (ET) and gross primary productivity (GPP) are critical components in terrestrial ecosystems with water and carbon cycles. Large-scale, high-resolution, and accurately quantified ET and GPP values are important fundamental data for freshwater resource management and help in understanding terrestrial carbon and water cycles in an arid region. In this study, the revised surface energy balance system (SEBS) model and MOD17 GPP algorithm were used to estimate daily ET and GPP at 100 m resolution based on multi-source satellite remote sensing data to obtain surface biophysical parameters and meteorological forcing data as input variables for the model in the midstream oasis area of the Heihe River Basin (HRB) from 2010 to 2016. Then, we further calculated the ecosystem water-use efficiency (WUE). We validated the daily ET, GPP, and WUE from ground observations at a crop oasis station and conducted spatial intercomparisons of monthly and annual ET, GPP, and WUE at the irrigation district and cropland oasis scales. The site-level evaluation results show that ET and GPP had better performance than WUE at the daily time scale. Specifically, the deviations in the daily ET, GPP, and WUE data compared with ground observations were small, with a root mean square error (RMSE) and mean absolute percent error (MAPE) of 0.75 mm/day and 26.59%, 1.13 gC/m2 and 36.62%, and 0.50 gC/kgH2O and 39.83%, respectively. The regional annual ET, GPP, and WUE varied from 300 to 700 mm, 200 to 650 gC/m2, and 0.5 to 1.0 gC/kgH2O, respectively, over the entire irrigation oasis area. It was found that annual ET and GPP were greater than 550 mm and 500 gC/m2, and annual oasis cropland WUE had strong invariability and was maintained at approximately 0.85 gC/kgH2O. The spatial intercomparisons from 2010 to 2016 revealed that ET had similar spatial patterns to GPP due to tightly coupled carbon and water fluxes. However, the WUE spatiotemporal patterns were slightly different from both ET and GPP, particularly in the early and late growing seasons for the oasis area. Our results demonstrate that spatial full coverage and reasonably fine spatiotemporal variation and variability could significantly improve our understanding of water-saving irrigation strategies and oasis agricultural water management practices in the face of water shortage issues.

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.

Economic Indices for the Application of Irrigation to Enhance Cactus Pear Fruit Yield

Aims: Cactus pear cultivation for fruit production is under rainfed conditions, mainly. Hence, irrigation uses for this purpose is expensive in arid and semi-arid agricultural lands. The objective of this study was to derive agro-economic indicators associated with supplemental irrigation to improve fruit yield of commercial cactus pear cultivars grown in a semiarid agroecosystem of Mexico.&#x0D; Study Design: The irrigation treatments tested were fully irrigated (FI) and supplemental irrigation (SI), with non-irrigated as a control (NI).&#x0D; Place and Duration of Study: The experiment was set up at the Campo Experimental Zacatecas, Calera, Zacatecas, Mexico from 2011 to 2013.&#x0D; Methodology: Five-year-old cactus pear plants of ‘Cristalina’ (O. albicarpa Scheinvar; white-pulped fruit) and ‘Roja Lisa’ [O. ficus-indica (L.) Mill.; red-pulped fruit] were included. The experiment was conducted in a split-block design. There were three blocks; each included both cultivars, randomly allocated to each irrigation treatment. The response variables were: fruit yield (FY), cultivation costs (CC), gross return (GR), net return (NR), benefit-cost ratio (BC), irrigation use efficiency (IUE), gross water productivity (GWP), net water productivity (NWP), labor productivity (LP), break-even-point (BEP), and credit vulnerability (CV).&#x0D; Results: In all years but 2013, FI ‘Cristalina’ plants had the highest CC, reflected in their greater GR and NR; however, BC values were similar between SI and FI plants or greater in SI plants for 2013. Therefore, SI plants had the highest IUE, GWP, NWP, LP, EP, and equal or greater credit vulnerability than FI plants. The NI plants produced positive values for BEP and CV. The economic indices for ‘Roja Lisa’ were similar to those of ‘Cristalina’.&#x0D; Conclusion: The SI treatment produced the best agricultural economic indices and it is also a feasible water-saving irrigation strategy for cactus pear cultivation in semiarid agroecosystems worldwide.

A review on Partial root-zone drying (PRD): A modern irrigation technique

Field experiments were conducted for 3 years from 2000 to 2002 to assess proportional crop yield differences obtained under conventional deficit irrigation (CDI) and partial root-zone irrigation (PRI) practices, compared with full irrigation (FULL) where plant water requirements were fully met. The experimental crops included vegetables (tomato and pepper), field crops (maize and cotton) and citrus. The fruit yield of greenhouse-grown tomato with FULL irrigation was higher than with PRI (7–22% lower) but was not significantly different. The PRD irrigation is a novel improvement of deficit irrigation in which half of the root zone is irrigated alternatively in scheduled irrigation events. In the last decade, scientists across the world, especially from arid to semi-arid countries, have extensively evaluated this irrigation as a water-saving irrigation strategy on agronomic and horticultural plants. This review paper focuses on the physiological and morphological aspects of PRD on plants and its ultimate impact on yield and water productivity. Overall, under limited water resources where water is precious, PRD is a viable irrigation option to increase water productivity while margining the yield, rather than only increasing the economic yield without concerning the value of water in limited water environments.