Deficit Irrigation Regimes Research Articles

Евапотранспирация на средноранни домати в зависимост от приложения поливен режим

The aim of the present study is to determine the values of the seasonal evapotranspiration (ET) of mid-early tomatoes when applying an optimal and deficit irrigation regime and to determine the water use efficiency (WUE). A field experiment was conducted with mid-early tomatoes, variety “Nikolina F1”, in the period 2017-2018 on the territory of the Educational and experimental field at the Agricultural University - Plovdiv. The experiment was carried out in 4 repetitions by the method of long plots. The following options were tested: 1) optimal irrigation at pre-irrigation humidity 85% of FC, valid for the 0-50 cm layer; 2) irrigation with 75% of the irrigation rate compared to var.1; 3) irrigation with 50% of the irrigation rate compared to option 1. The plants are planted on a flat bed in a two-row strip according to the scheme 90+50x50 cm. Irrigation was carried out by means of a drip system with built-in drip generators with a distance between them of 25 cm and a flow rate of 2 l/h. The total values of evapotranspiration have been established, and with optimal irrigation, it is an average of 512 mm. When implementing 75% of the optimal irrigation rate, ET is 428 mm (83.6% of the maximum), and when applying ½ rate, it decreases on average by 30.3% and is 356.5 mm. The course of the average day-night evapotranspiration was established, and depending on the nature of the year, with optimal irrigation, the maximum values are in the range of 5.6 - 6.7 mm per day.

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.

Effect of different deficit irrigation regimes on vine performance, grape composition and wine quality of the “Primitivo” variety under mediterranean conditions

Climate change represents one of the current major challenges and the improper use of water resources is an impeding threat. Agricultural research can play a crucial role by developing innovative strategies and techniques to reduce water use without affecting crop productivity and quality, particularly in grapevine growing in Mediterranean areas, as both productivity and wine quality are quintessential for the economic and ecologic sustainability of this crop. The present study aimed to define a deficit irrigation strategy for the “Primitivo” grapevine cultivar, taking into account the overall pathway of the vineyard performance in terms of leaf functionality, starch reserves, vine productivity, and wine quality. The trial was carried out in Southern-Italy on a three year-old, drip irrigated vineyard, imposing four deficit irrigation regimes for two consecutive seasons, consisting of 29 (T29), 55 (T55), 85 (T85) and 100% (T100) of crop evapotranspiration (ETC). Mild water restriction (T85) did not affect vegetative nor reproductive vine performance. Deficit irrigation at 55% ETC lowered leaf functionality, starch accumulation, vine vigour and yield, due to a reduction of cluster weight; however, wine acidity and phenolic compounds were increased. T29 further decreased yield, as also the number of clusters was reduced. The most water-stressed treatment revealed a low concentration of malic acid in the must and a consequent increase of the ethanol sensation in the wine. After 9 months ageing, T85 had the highest wine colour intensity suggesting this treatment as the most promising in terms of quality and quantity of wine as well as for water saving.

Assessing the Seasonal Water Requirement of Fully Mature Japanese Plum Orchards: A Systematic Review

Japanese plums have relatively high water requirements, which depend on supplementing rainfall volumes with accurately quantified irrigation water. There is a lack of knowledge on the seasonal water requirements of plum orchards. This gap in the literature poses an imminent threat to the long-term sustainability of the South African plum industry, which is particularly plagued by climate change and diminishing water resources. The systematic literature review conducted in this study aimed to provide a foundation for supporting water management in irrigated Japanese plum [Prunus salicina Lindl.] orchards. Seventeen peer-reviewed articles obtained from the literature were analyzed. Approximately 66% of the cultivars were cultivated under different regulated deficit irrigation regimes for water-saving purposes and to increase fruit quality. This review of our knowledge provided benchmark figures on the annual water requirements of Japanese plums. The full-year plum crop water requirements obtained from the literature ranged between 921 and 1211 mm a−1. Canopy growth, pruning and growing season length were the most common causes of differences in the water requirement estimates. Further research is required to measure the water requirement of plums from planting to full-bearing age and the response of plum trees to water stress, especially in the South African context.

Biochar Amendment Alleviates the Combined Effects of Salinity and Drought Stress on Water Productivity, Yield and Quality Traits of Sugar Beet (Beta vulgaris L.)

Salinity and drought are two commonly occurring major threats to agricultural yields worldwide, including sugar beet production. Therefore, this work aimed to determine the effectiveness of biochar amendment in improving soil health and alleviating the combined effects induced by salinity and drought on morphological, physiological and biochemical responses of sugar beet plants. Two field studies were established at the experimental farm of Fayoum University, Egypt over two successive winter seasons (2019/2020 and 2020/2021). The experiments were carried out in a split-split plot design with triplicate including three factors: 1) soil salinity, with two levels of ECe (< 4 dS m−1 as control and 10 dS m−1) as main-plot factor; 2) deficit irrigation regimes (I100, I80, and I60) representing 100%, 80%, and 60% of crop evapotranspiration (ETc), respectively as sub-plot factor; and 3) biochar amendment with three application levels (B0 as control, B10, and B20) corresponding to 0, 10, and 20 t ha−1, respectively as sub-sub plot factor. Drought and salinity stress induced significant reduction in growth attributes, relative water content, membrane stability, relative chlorophyll content (SPAD), yield and yield components of sugar beet plants. Meanwhile, the contents of sucrose, proline, Na, K, α amino-N were substantially increased with increasing stress severity. The application of biochar amendment improved the soil physical and chemical properties, resulting in better morphological, physiological and biochemical responses of saline-drought stressed sugar beet plants. Biochar at level (B20) produced the highest values of root yield (95.02 t ha−1) and sugar yield (20.24 t ha−1) for full irrigated sugar beet plants in non-saline soil. Moreover, the application of biochar enhanced water productivity for drought and saline stressed sugar beet plants. Biochar amendment could be effectively used as a helpful agro-management strategy in alleviating the detrimental impacts of salinity and water stress on sugar beet plants, improving soil quality and enhancing water productivity to ensure water sustainability and food security, especially in areas of limited water supply.

Integrating soil mulching and subsurface irrigation for optimizing deficit irrigation effectiveness as a water-rationing strategy in tomato production

Irrigated agriculture from now on should be implemented under water scarcity. Hence, this research was designed to determine the optimal interaction between irrigation water-rationing strategy (deficit irrigation), irrigation techniques, and soil mulching to improve water use efficiency and maintaining plant performance as well as yield productivity of tomatoes. The experiment was set up during the 2020-2021 and 2021-2022 growing seasons. Three factors were studied: two drip irrigation techniques, surface (SI) and subsurface (SSI) irrigation, and two irrigation rates, 100% ETc for full irrigation (FI) and 60% ETc for deficit-irrigation (DI) along with three treatments of soil mulching, bare soil (BS), organic mulch (OrM) and black polyethylene mulch (BPE). The results demonstrated that applying the absolute regular DI regime significantly reduced vegetative growth, fruit yield, and yield component along with water productivity. Also, it reduced the physiological function measures, and nutrient content of the tomato leaf. Meanwhile, applying the DI regime via the SSI technique and integrated with BPE soil mulching proved the best optimization of the DI negative effect followed by applying the DI regime through either SSI or SI technique combined with OrM or BPE soil mulching, respectively. As a result, it is advisable to use the integration of DI via the SSI accompanied by BPE soil mulching since this is considered a good method for conserving irrigation water from being lost by both evaporation and seepage out of the root zone improving water use efficiency without significantly reducing tomato yield.

Mitigating soil water deficit using organic waste compost and commercial water retainer: a comparative study under semiarid conditions

Semiarid regions have particularly been confronted with climate change effects reflected by the consistent decrease of rainfall and increase of evapotranspiration. This drought stress constitutes the main constraint for agricultural production improvement, which is aggravated by the fact that strategic (field) crops are mostly grown under rainfed systems. Therefore, the objective of this field study was to improve soil water retention by the application of two conditioners namely, an organic waste compost (DS) and a synthetic water-retaining hydrogel (WS). These amendments were applied to an agricultural soil for the cultivation of fodder maize under normal and deficit irrigation regimes. Advanced analysis showed a general disruption of plant growth parameters under water stress. However, both amendments attenuated this negative effect with respect to control by improving soil water status. More precisely, the measured soil water tension at the start of the dry season was the lowest in presence of DS (48 centibars), followed by WS (61 centibars), then unamended soil (83 centibars). Besides, compost application resulted in higher moisture (13.3%), nitrogen (0.36%), and organic matter (0.56%) in soil than the synthetic hydrogel at the end of the field experiment. Soil and plant characterization highlighted the combined effect of water deficit and conditioner type. Indeed, the consistent increase of soil water content in the presence of DS and WS improved all the addressed plant parameters when compared with untreated soil. Infrared thermal imaging showed that canopy temperature was lower in presence of both amendments while dry biomass yield increased by 38% when water supply was limited. Nevertheless, the long-term sustainability of the soil system appears to be better maintained in the presence of the organic waste compost. The latter has the added advantage of improving soil fertility in contrast to inert polymers.

Field study of irrigation strategies with treated wastewater and saline water on heavy metal accumulation in barley grain.

This study examines the effects of three irrigation regimes with a combination of saline water and treated wastewater on the accumulation of heavy metals in barley grains. A field experiment was designed as a split-split plot arrangement in a randomized complete block design, in which treatments were different irrigation regimes (50%, 70%, and 100% full irrigation) and irrigation water types (saline water [SW], treated wastewater [TW], mixed water resources [MWR], and alternative irrigation [AI]). After cultivation and harvesting of the barley crop, the grain yield, 1000-grain weight, and contents of heavy metals in the grains were measured. The grain yield was enhanced by TW alone, MWR, and AI to 12.8%, 5%, and 9.5% under 70%-deficit irrigation; and 58.3%, 21.7%, and 8.7% under full irrigation, respectively. Based on the guidelines for safe limits of heavy metals in edible plants and livestock feed, the barley grains were safe for livestock and toxic for humans. The trend of heavy metal contents in the grains was Fe > Zn > Pb > Cu ≥ Cr > Cd. Irrigation with SW compared with TW increased Fe, Cu, Zn, Pb, Cd, and Cr contents in the grains to 11.75%, 10.97%, 5.22%, 19.15%, 3.45%, and 9.21%, respectively. The amounts of toxic elements of Cd and Pb were maximized by using MWR, whereas the Cr content in the grain was maximized by using AI. There were no significant difference in the metal uptake by the grains among all irrigation regimes in any irrigation water resource. However, compared with the other irrigation regimes, the full irrigation resulted in lower Zn, Cu, and Cd contents, whereas the 50%-deficit irrigation led to lower Pb and Cr contents in the grains. Therefore, irrigation with TW is recommended based on the grain yield, whereas AI is suggested due to lower Cu, Pb, and Cd contents in the grain, and MWR is recommended due to lower Cr content. Furthermore, full and 50%-deficit irrigation regimes are recommended to, respectively, maximize grain yield and minimize the toxic metal contents in the grain. PRACTITIONER POINTS: Mixed saline water and treated wastewater and alternative irrigation enhanced grain yield. Saline water versus treated wastewater increased the grain heavy metal contents. Alternative irrigation decreased Fe, Cu, Pb, and Cd amounts in the grain. Grain Cu content had strong relationship with irrigation regime. 50%-deficit irrigation minimized Pb and Cr contents in the grain.

Değişen Sulama Suyu Seviyeleriyle Toprağa Farklı Oranlarda Biyoçar Uygulanarak Yetiştirilen Kıvırcık Marulun Fiziksel ve Fizyolojik Özellikleri ile Mineral Madde İçeriği

The crisis experienced from the water supply causes food production to be adversely affected in the agriculture sector, which is the biggest consumer of water. The deficit irrigation strategy ensures the continuity of food production as well as using water effectively. However, since the plant grown in this strategy is exposed to abiotic stress, it experiences significant yield and quality losses. For this reason, it is necessary to develop approaches to improve yield and quality losses of the plant grown with deficit irrigation. In this study, the physical and physiological properties and mineral content of curly lettuce (Lactuca sativa L. var. Crispa) grown by applying different rates of biochar to the soil (0%, 1%, 2%, 3%) with varying irrigation water levels (100%, 67%, 33%) researched. The study determined that decreasing irrigation water level decreased plant height, stem diameter, number of leaves, root wet and dry weights, plant weight, chlorophyll and leaf relative water contents, stomatal conductivity and N, P, K, Ca, Mg, Na, Fe, Cu, Mn and Zn contents of curly lettuce, while increasing the membrane damage index, but the physical and physiological properties and mineral content affecting the yield and quality of curly lettuce improved with increasing biochar rates. In the study, as a result of the emergence of the highest stress factor in irrigation at 33% level, it was observed that physical and physiological properties and mineral content of curly lettuce were affected at the highest level, and the dose of biochar, which managed the stress most effectively, was 3%. As a result, considering that biochar has an important potential to improve yield and quality losses of curly lettuce grown under deficit irrigation conditions, the use of biochar in the deficit irrigation regime were found to be recommendable.

Biostimulant Application Alleviates the Negative Effects of Deficit Irrigation and Improves Growth Performance, Essential Oil Yield and Water-Use Efficiency of Mint Crop

The scarcity of water is limiting crop production and is one of the most important stressors that severely affects crop yield, and it may also decrease the quality of the final products. Most of the medicinal and aromatic plants are considered resilient to water stress and constitute a sustainable choice for crop production in arid and semiarid conditions. In the present study, we examined the effect of scheduled deficit irrigation (e.g., I1: 40% of field capacity); I2: 70% of field capacity; and I3: 100% of field capacity) combined with biostimulant application (four different products that consisted of nitrogenous compounds and carboxylic acids (M1); nitrogenous compounds and seaweed extracts (M2); humic and fulvic acids and seaweed extracts (M3); and CaO, SiO2, calcium mobilization and translocation factor and microminerals (M4)) on crop performance and essential oil production of mint plants (Mentha arvensis L.). Our aim was to define an irrigation regime that increases water-use efficiency and the biostimulant products that alleviate water stress effects. Our results indicate that moderate deficit irrigation (I2 treatment) and biostimulants that contained seaweed extracts and nitrogenous compounds and humic and fulvic acids (M2 and M3 treatments, respectively) significantly improved yield parameters in terms of fresh and dry herb yield and essential oil production. Moreover, the same biostimulant treatments significantly increased water-use efficiency of mint crops based on the various yield parameters tested in this study. In conclusion, our results indicate that selection of proper biostimulatory products may allow to apply deficit irrigation regimes in mint cultivation without compromising the crop performance in terms of both biomass production and essential oil yield. Therefore, the combination of these agronomic tools could facilitate water saving strategies in arid and semiarid regions and contribute to the sustainable management of water resources.

Zinc oxide nano-flowers improve the growth and propagation of mulberry cuttings grown under different irrigation regimes by mitigating drought-related complications and enhancing zinc uptake

Silkworm larvae mainly consume mulberry leaves; therefore, mulberry cultivation is important for the production of raw silk. Drought stress and micronutrient deficiency (Zn) are known to affect the propagation of mulberry cuttings. In this purview, the current investigation attempted to inspect the efficacy of different concentrations of zinc oxide nano-flower (ZnNFs) applied through both soil admixture and foliar spray on the propagation of mulberry cuttings grown under deficit irrigation regimes. The overall results demonstrated that the ZnNF-treated plant cuttings were well-adapted to drought stress and performed better in comparison to the control set. Out of the tested concentrations – ZnNF-10 (applied as 10 mg/kg soil and 10 ppm as foliar spray thrice) was found to be optimum, showing relatively better initial root establishment, the emergence of leaves, and survival and sprouting percentage. Further studies also confirmed an improvement in the accumulation of photosynthetic pigments, carbohydrates, and protein content even under extreme drought conditions. Most importantly, the ZnNF-10 treatment contributed to ROS detoxification and cell membrane protection by enhancing the pool of antioxidant enzymes. The study further demonstrated that ZnNF-10 application enhanced zinc content by 147.50%, 179.49%, and 171.99% in root, shoot, and leaves of the treated cuttings; thereby, improving the bioaccumulation factor of the plant parts. All of these interactive phenomena led to an increment in shoot height, biomass, leaf area, and leaf number of cuttings. These findings, therefore, indicated that ZnNFs can be developed as a promising nano-fertilizer for mulberry growth facilitating Zn uptake and mitigation of drought-induced complications.

Effects of Deficit Irrigation and Anti-Stressors on Water Productivity, and Fruit Quality at Harvest and Stored ‘Murcott’ Mandarin

A two-year experiment using ‘Murcott’ mandarin (Citrus reticulata) was conducted under deficit irrigation (DI) strategies with an anti-stressor application and then stored. The three DI regimes were 70% crop evapotranspiration (70% ETC), 85% ETc, and full irrigation (100% ETc). Anti-stressor treatments consisted of a foliar application of either sodium nitroprusside (SNP), selenium nanoparticles (NanoSe), microalgae (Spirulina platensis), or a non-treated control. Mean water productivity values were highest for trees at 70% ETc and 85% ETc when they were sprayed with microalgae, which was 42% and 51% greater, respectively, compared to control trees at 100% ETc, but only 6.5% and 13% greater, respectively, compared to trees sprayed with microalgae at 100% ETc. Trees sprayed with microalgae at 100% ETc or 85% ETc had the highest and second-highest fruit yields. The percentage of fruit water loss after 15 d storage at either 1.5 °C + 90% RH or 16 ± 2 °C + 60–65% RH was reduced at all DI regimes when trees were sprayed with an anti-stressor compared to control trees at the same DI regime. Trees sprayed with 150 μmol L−1 SNP had the only fruit peel that maintained the carotenoid content after cold storage. In general, trees sprayed with SNP were most successful at each DI regime for reduced Malondialdehyde (MDA), but after 15 d of cold storage, only trees sprayed with 150 μmol L−1 SNP at 85% ETc or 100% ETc and/or trees sprayed with NanoSe at 70% ETc had fruit that maintained low MDA content. Catalase and peroxidase enzyme activities and proline content were enhanced when trees were sprayed with 150 μmol L−1 SNP during DI strategies. This study demonstrates the effectiveness of deficit irrigation combined with anti-stressor applications to improve water productivity, fruit yields, and post-storage quality of ‘Murcott’ mandarin trees. These findings offer valuable insights into sustainable citrus production under limited water resources.

Trakya Bölgesi Koşullarında Kısıntılı Sulama Programlarının Darıda (Panicum miliaceum L.) Verim Üzerine Etkileri

Millets are indigenous to many parts of the world and are more widely grown, especially in areas where water is limited. The most widely grown millet type is sorghum (Sorghum bicolor L.). A field study was carried out to determine the effect of deficit irrigation regimes on grain yield and seasonal evapotranspiration of proso millet (Panicum miliaceum L.) in the Thrace Region of Turkey. The field trials were conducted on a loam Entisol soil, on Öğretmenoğlu and Beydarı, the most popular varieties in the research area. In the study, the split plots experimental design with three replications was used. Eight different irrigation issues are considered, including combinations of the vegetative (V), flowering (F) and grain formation (Y) phases of the plant (including dry conditions, NoI). Results showed that proso millet was significantly affected by water stress during the sensitive flowering stage. The highest grain yield was obtained with 4.09 t ha-1 from Öğretmenoğlu and 4.03 t ha-1 from Beydarı, which was rinsed (VFY) in all development periods. Seasonal irrigation water use and evapotranspiration of the irrigated (VFY) in all development periods were 318 and 579 mm, respectively, for the non-stressed treatment. The seasonal water yield function was calculated as Y = 0.4087 ET + 144.03, and the seasonal yield-water response factor value was calculated as 0.57'.

Compost Improving Morphophysiological and Biochemical Traits, Seed Yield, and Oil Quality of Nigella sativa under Drought Stress

This study aimed to determine the effects of compost amendment on the soil properties, as well as the morphophysiological responses, seed yield, oil content, and fatty-acid profile. of Nigella sativa plants under drought stress conditions. In a split-plot design, the field experiment was carried out during two seasons (2020/2021 and 2021/2022), involving three irrigation regimes (named I100, I75, and I50 of crop evapotranspiration) with three levels of compost application (C0, C15, and C30). Soil porosity, permeability, pore geometry, water-holding capacity, organic content, and soil cation exchangeable capacity were improved in response to applied compost levels. The growth, physiology, biochemistry, and yield characteristics of Nigella sativa plants were positively affected by compost addition but negatively affected by increasing water stress severity. Deficit irrigation regimes increased osmoprotectant substances (i.e., proline, total free amino acids, carbohydrates, and total soluble sugar). Compared to the control (I100), deficit irrigation (I50) reduced fixed and essential oil by 16.64% and 39.57% over two seasons. Water stress increased the content of saturated fatty acids, while unsaturated fatty acids decreased. Compost application of (C30) resulted in a significant increase in seed yield, fixed oil, and essential oil of Nigella sativa plants by 34.72%, 46.55%, and 58.11% respectively, compared to the control (C0). Therefore, this study concluded that compost amendment improved soil properties and significantly mitigated the detrimental effects of drought on Nigella sativa plants, resulting in a considerable increase in seed yield and its oil content, particularly polyunsaturated fatty acids, which are distinguished by their beneficial effects on human health.

Kaolin Foliar Application Enhanced Physiological Functions and Pods Quality of (phaseolus vulgaris L.) under Deficit Irrigation Regimes

Kaolin Foliar Application Enhanced Physiological Functions and Pods Quality of (phaseolus vulgaris L.) under Deficit Irrigation Regimes

Modeling actual water use under different irrigation regimes at district scale: Application to the FAO-56 dual crop coefficient method

The modeling of irrigation in land surface models are generally based on two soil moisture parameters SMthreshold and SMtarget at which irrigation automatically starts and stops, respectively. Typically, both parameters are usually set to optimal values allowing to fill the soil water reservoir with just the estimated right amount and to avoid crop water excess at all times. The point is that agricultural practices greatly vary according to many factors (climatological, crop, soil, technical, human, etc.). To fill the gap, we propose a new calibration method of SMthreshold and SMtarget to represent the irrigation water use in any (optimal, deficit or even over) irrigation regime. The approach is tested using the dual-crop coefficient FAO-56 model implemented at the field scale over an 8100 ha irrigation district in northeastern Spain where the irrigation water use is precisely monitored at the district scale. Both irrigation parameters are first retrieved at monthly scale from the irrigation observations of year 2019. The irrigation simulated by the FAO-56 model is then evaluated against observations at district and weekly scale over 5 years (2017–2021) separately. The performance of the newly calibrated irrigation module is also assessed by comparing it against three other modules with varying configurations including default estimates for SMthreshold and SMtarget. The proposed irrigation module obtains systematically the best performance for each of the 5 years with an overall correlation coefficient of 0.95 ± 0.02 and root-mean square error of 0.27 ± 0.07 hm3/week (0.64 ± 0.17 mm/day). Unlike the three irrigation modules used as benchmark, the new irrigation module is able to reproduce the farmers’ practices throughout the year, and especially, to simulate the actual water use in the deficit and excess irrigation regimes occurring in the study area in spring and summer, respectively.

Effect of Mycorrhizal Inoculation on Melon Plants under Deficit Irrigation Regimes

The shortage of good quantity and quality of water for irrigated agriculture is a major problem in arid and semiarid regions. To deal with this problem, deficit irrigation (DI) or arbuscular mycorrhizal fungi (AMF) inoculation have been proposed and adopted for many crops as a tool to save water, or to improve crop tolerance to drought stress. An experiment was conducted for two consecutive years to evaluate the effect of mycorrhizal inoculation on the physiological, morphological, yield, and quality characteristics of melon plants grown under deficit irrigation. Melon crop (Cucumis melo L. cv. Helios) was grown under field conditions adopting a split-plot design with four replications, where DI was the main factor and AMF inoculation was the secondary factor. DI treatments consisted of applying 60%, 80%, or 100% of crop evapotranspiration (ETc) on melon plants inoculated or not with a commercial biostimulant containing 50% of Rhizophagus irregularis, and 50% of Funneliformis mosseae. Moderate and severe deficit irrigation significantly reduced the relative water content, stomatal conductance, yield, nitrogen applied efficiency (NAE), and fruit firmness of the uninoculated plants, but significantly increased irrigation water use efficiency (IWUE) and the ascorbic acid content of the fruit. AMF had a positive effect on plant tolerance to moderate water stress, and on some fruit quality parameters (fruit length, firmness, and sugar content). The combined use of moderate deficit irrigation (80%) and soil inoculation with AMF on melon plants allows water savings without affecting fruit yield, and increases IWUE, NAE, and some fruit quality characteristics (firmness, SSC, and SSC/TA). Furthermore, the use of AMF plants could be worth it to reduce the yield loss and increase fruit quality, even with severe deficit irrigation (60%).

UAV-Based Multi-Temporal Thermal Imaging to Evaluate Wheat Drought Resistance in Different Deficit Irrigation Regimes

Deficit irrigation is a common approach in water-scarce regions to balance productivity and water use, whereas drought stress still occurs to various extents, leading to reduced physiological performance and a decrease in yield. Therefore, seeking a rapid and reliable method to identify wheat varieties with drought resistance can help reduce yield loss under water deficit. In this study, we compared ten wheat varieties under three deficit irrigation systems (W0, no irrigation during the growing season; W1, irrigation at jointing; W2, irrigation at jointing and anthesis). UAV thermal imagery, plant physiological traits [leaf area index (LAI), SPAD, photosynthesis (Pn), transpiration (Tr), stomatal conductance (Cn)], biomass and yield were acquired at different growth stages. Wheat drought resistance performance was evaluated through using the canopy temperature extracted from UAV thermal imagery (CT-UAV), in combination with hierarchical cluster analysis (HCA). The CT-UAV of W0 and W1 treatments was significantly higher than in the W2 treatment, with the ranges of 24.8–33.3 °C, 24.3–31.6 °C, and 24.1–28.9 °C in W0, W1 and W2, respectively. We found negative correlations between CT-UAV and LAI, SPAD, Pn, Tr, Cn and biomass under the W0 (R2 = 0.41–0.79) and W1 treatments (R2 = 0.22–0.72), but little relevance for W2 treatment. Under the deficit irrigation treatments (W0 and W1), UAV thermal imagery was less effective before the grain-filling stage in evaluating drought resistance. This study demonstrates the potential of ensuring yield and saving irrigation water by identifying suitable wheat varieties for different water-scarce irrigation scenarios.

Seedling-Stage Deficit Irrigation with Nitrogen Application in Three-Year Field Study Provides Guidance for Improving Maize Yield, Water and Nitrogen Use Efficiencies.

Deficit irrigation (DI) was acknowledged as an effective technique to improve water use efficiency (WUE) without significant yield reduction. In this study, a 3-year field experiment was conducted in Northeast China during 2017-2019 to investigate the combined effects of 3-week DI from 3-leaf stage and N fertilization on maize seedling growth and determine the resulting impacts on silking growth and yield formation, N use efficiency (NUE) and WUE. Results showed that seedling-stage DI decreased leaf area and photosynthesis, thus significantly limited shoot and root dry biomass for maize seedling, compared to well-watered (WW) plants. In 2017 and 2019, seedling-stage DI positively improved seedling growth with higher root: shoot ratio and enhanced drought tolerance, under higher initial soil water contents (SWC) with sufficient precipitation before DI. The DI-primed plants showed similar or better performances on reproductive growth, grain yield, WUE and NUE compared to WW plants, even experiencing heavy rainfall or drought stresses around the silking stage. However, the contrasting results were observed in 2018 with negative DI effects on seedling and silking growth and final yield, probably due to less rainfall and lower SWC before DI. In all 3 years, N fertilization had significant compensatory effects on limited seedling growth under DI, and its effect was much less in 2018 than other years due to adverse early climate. The principal component and correlation analysis revealed maize silking growth, grain yield, NUE and WUE were strongly related to the seedling growth as affected by water and N managements under various climatic conditions. In conclusion, a short-term and moderate DI regime-adopted at the seedling stage under higher initial SWC and coupled with an appropriate N fertilization-is beneficial to control redundant vegetative growth while optimizing root development, therefore effectively improving drought tolerance for maize plants and achieving higher grain yield, WUE and NUE.

Berry flavonoids are differently modulated by timing and intensities of water deficit in Vitis vinifera L. cv. Sangiovese.

In this work, we tested the effect of different regulated deficit irrigation (RDI) regimes on berry flavonoid content and its relative biosynthetic pathways. Vines were subjected to six irrigation regimes over two consecutive years: a) full irrigation during the entire irrigation period (FI); b) moderate (RDI-1M) or c) severe (RDI-1S) water deficit between berry pea-size and veraison; d) severe water deficit during the lag-phase (RDI-LS); and e) moderate (RDI-2M) or f) severe (RDI-2S) water deficit from veraison through harvest. Berries from both RDI-1 treatments showed the highest accumulation of anthocyanins, upregulating the expression of many genes of the flavonoid pathway since the beginning of veraison until harvest, far after the water deficit was released. Although to a lesser degree than RDI-1, both post-veraison water deficit treatments increased anthocyanin concentration, particularly those of the tri-substituted forms, overexpressing the F3'5'H hydroxylases. The moderate deficit irrigation treatments enhanced anthocyanin accumulation with respect to the severe ones regardless of the period when they were applied (pre- or post-veraison). The water deficit imposed during the lag-phase downregulated many genes throughout the flavonoid pathway, showing a slight reduction in anthocyanin accumulation. The measurements of cluster temperature and light exposure highlighted that under deficit irrigation conditions, the effects induced by water stress prevailed over that of light and temperature in regulating anthocyanin biosynthesis. Flavonol concentration was higher in RDI-1S berries due to the upregulation of the flavonol synthases and the flavonol-3-O-glycosyltransferases. In this case, the higher cluster light exposure induced by water deficit in RDI-1S berries had a major role in flavonol accumulation. We conclude that the timing and intensity of water stress strongly regulate the berry flavonoid accumulation and that proper management of deficit irrigation can modulate the phenylpropanoid and flavonoid pathways.