Deficit irrigation and sustainable water-resource strategies in agriculture for China's food security

Physiological responses and yield performance of selected rice (Oryza sativa L.) genotypes under deficit moisture stress

Rice is an important food crop, while it is severely affected by drought stress. Viewing this point in mind we conducted an experiment to see the physiological responses and yield potential of selected rice genotypes under inadequate moisture condition. Two soil moisture condition: one is sufficient moisture condition (control; 95-100% field capacity (FC)) and another is deficit moisture condition (moisture stress; 40-45% FC) with five replications was maintained. Six drought tolerant one susceptible genotype and one standard check variety were used. Results revealed that tolerant genotypes BU Acc 37 and BU Acc 32 showed the highest RWC, WRC, rate of photosynthesis, conductance of stomata, transpiration rate, total chlorophyll content, proline and soluble sugar content, while susceptible genotype BU Acc 5 showed the lowest value of those parameters during water stress condition. In contrast, the lowest WSD, WUC, accumulation of H2O2 and malondialdehyde were noticed in tolerant genotypes BU Acc 37 and BU Acc 32, whereas those were the highest in susceptible genotype BU Acc 5 under deficit moisture condition. Tolerant genotype BU Acc 37 and BU Acc 32 also showed the higher antioxidant enzyme activity than the susceptible genotype BU Acc 5. Regardless of genotypes, yield contributing characteristics and yield were severely affected by deficit water stress. However, tolerant genotype BU Acc 37 showed the highest grain yield per hill, while susceptible genotype BU Acc 5 showed the lowest grain yield per hill. Hence, better accumulation ability of osmoprotectants, and the higher activity of antioxidant enzymes in the tolerant genotypes reduce the oxidative stress, enhance water relation and gas exchange attributes, and protect the yield reduction of rice.

Enhancing environmental sustainability in transferred farmlands through rural e-commerce: insights from China

The issue of farmers neglecting environmental concerns in transferred farmlands poses a serious challenge, contradicting the long-term ecological goals of establishing resource-efficient and environment-friendly agriculture. Amidst the pivotal trend of moderately scaled agricultural operations, rural e-commerce holds promise as a catalyst and driving force for enhancing long-term environmental governance of transferred lands. The effectiveness and mechanisms of this potential, however, remain to be empirically examined. This study gathers panel data on environmental positive and negative externalities from six provinces in China, spanning the period from 2013 to 2022, encompassing 6372 farmers. A quasi-natural experiment of farmers' e-commerce participation is designed using difference-in-differences methodology (DID), propensity score matching (PSM), and moderating models. The primary findings are as follows: E-commerce participation increases farmers' positive environmental inputs on transferred lands, such as water-saving irrigation, adoption of social services, and preservation of traditional varieties. Simultaneously, it decreases negative environmental inputs, such as the consumption of fertilizers, pesticides, and agricultural films. The environmental sustainability effects of e-commerce vary across the eastern, central, and western regions of China. E-commerce has a more pronounced impact on agricultural social services and chemical pollutants in the eastern and central regions, while its influence is more significant on water-saving irrigation and variety preservation in the western region. Land transfer forms and supply order contracts do not directly promote farmers' environmentally friendly cultivation practices. Instead, they catalyze the environmental effects of e-commerce through a significant positive interaction term. These conclusions hold after matching for e-commerce participation propensity, while passing sensitivity tests, parallel trend tests, and placebo tests. Consequently, rural e-commerce, without compromising farmers' income, enhances the proactiveness of farmers in environmental conservation, transforms agricultural management practices, and effectively reduces rural non-point source pollution. Policy recommendations include reducing institutional barriers to rural e-commerce participation at the national level, encouraging the establishment of region-specific agricultural environmental sustainability goals, and leveraging the rural e-commerce industry chain to establish a nationwide environmental credit database and incentive mechanism.

Projecting the impact of climate change and elevated CO2 concentration on rice irrigation water requirement in China

Climate change and elevated CO2 concentrations significantly affect rice growth and water consumption. Understanding the specific impacts of climate change and elevated CO2 concentrations on rice physiological phenology, crop water demand (ETC), and irrigation water requirement (IR) is of great significance for the sustainable utilization of water resources and food security. This is particularly true in China, the world's largest rice producer. In this study, with the help of two rice phenological models, the modified Penman-Monteith equation, and the paddy water balance model, we project the changes in rice phenological period, ETC, and IR in four main rice-producing regions of China in the period 2015-2100 based on the 11 GCM outputs. The results show that the rice growing period is shortened in most rice-producing regions, except for the parts of the middle and lower reaches of the Yangtze River. Meanwhile, the trend of ETC and IR of rice varies slightly among regions in the future scenario, with almost all regions decreasing yearly except for the middle and lower reaches of the Yangtze River, where the trend is increasing. The progressively increasing atmospheric CO2 concentration has a "fertilization effect" on the crop, which can reduce the water requirements of rice. In the SSP585 scenario, the " CO2 fertilization effect" can reduce up to 8.87 × 108 m3 of ETC and 6.94 × 108 m3 of IR in the middle and lower reaches of the Yangtze River in the period of 2090s. This study provides beneficial references to understand the response of rice ETC and IR to future climate change and CO2 concentration elevation in China and highlights that the simulation in terms of crop irrigation must account for the "CO2 fertilization effect".

Effects of nitrogen fertilization combined with subsurface irrigation on alfalfa yield, water and nitrogen use efficiency, quality, and economic benefits

Proper water and fertilizer management strategies are essential for alfalfa cultivation in arid areas. However, at present, the optimal amounts of subsurface irrigation and nitrogen (N) supply for alfalfa (Medicago sativa L.) cultivation are still unclear. Therefore, a field experiment was conducted in 2022 in Yinchuan, Ningxia, China, to explore the effects of different subsurface irrigation levels (W1, 50% of ETC (crop evapotranspiration); W2, 75% of ETC; W3, 100% of ETC) and N application rates (N0, 0 kg/ha; N1, 75 kg/ha; N2, 150 kg/ha; N3, 225 kg/ha; N4, 300 kg/ha) on alfalfa yield, crop water productivity (CWP), N use efficiency (NUE), quality, and economic benefits. Besides, the least squares method and multiple regression analysis were used to explore the optimal water and N combination for alfalfa cultivation under subsurface irrigation. The results showed that the alfalfa yield, crude ash content, and partial factor productivity from applied N (PFPN) were the highest under W2 level, but there was no difference in PFPN compared with that under W3 level. The branch number (BN), leaf area index (LAI), yield, CWP, irrigation water productivity (IWP), crude protein content (CPC), and economic benefits increased and then decreased with the increase of N application rate, reaching a maximum at the N2 or N3 level, while the NUE and PFPN decreased with the increase of N application rate. Considering the yield, CWP, NUE, quality, and economic benefits, W2N2 treatment was the optimal for alfalfa cultivation under subsurface irrigation. Besides, when the irrigation volume and N application rate were 69.8 ~ 88.7% of ETC and 145 ~ 190 kg/ha, respectively (confidence interval: 85%), the yield, CPC, and economic benefits reached more than 85% of the maximum. This study will provide technique reference for the water and N management in alfalfa cultivation in Northwest China.

New strategies to address world food security and elimination of malnutrition: future role of coarse cereals in human health

As we face increasing challenges of world food security and malnutrition, coarse cereals are coming into favor as an important supplement to human staple foods due to their high nutritional value. In addition, their functional components, such as flavonoids and polyphenols, make them an important food source for healthy diets. However, we lack a systematic understanding of the importance of coarse cereals for world food security and nutritional goals. This review summarizes the worldwide cultivation and distribution of coarse cereals, indicating that the global area for coarse cereal cultivation is steadily increasing. This paper also focuses on the special adaptive mechanisms of coarse cereals to drought and discusses the strategies to improve coarse cereal crop yields from the perspective of agricultural production systems. The future possibilities, challenges, and opportunities for coarse cereal production are summarized in the face of food security challenges, and new ideas for world coarse cereal production are suggested.

Developing a tactical irrigation and nitrogen fertilizer management strategy for winter wheat through drip irrigation

Introduction

Agricultural activities in the North China Plain are often challenged by inadequate irrigation and nutrient supply. Inadequate and improper resource utilization may impose negative impacts on agricultural sustainability. To counteract the negative impacts, a deeper understanding of the different resource management strategies is an essential prerequisite to assess the resource saving potential of crops.

Methods

We explored plausible adaptation strategies including drip irrigation lateral spacings of 40 and 80 cm (hereafter referred to as LS40 and LS80, respectively), irrigating winter wheat after soil water consumption of 20 and 35 mm (hereafter represented as IS20 and IS35, respectively), and nitrogen fertilization scheme of a) applying 50% nitrogen as a basal dose and 50% as a top-dressing dose (NS50:50), b) 25% nitrogen as a basal dose and 75% as a topdressing dose (NS25:75), and c) no nitrogen application as a basal dose and 100% application as a top-dressing dose (NS0:100).

Results and discussion

The consecutive 2 years (2017-2018 and 2018-2019) of field study results show that growing winter wheat under LS40 enhanced the water use efficiency (WUE), grain yield, 1,000-grain weight, and number of grains per spike by 15.04%, 6.95%, 5.67%, and 21.59% during the 2017-2018 season, respectively. Additionally, the corresponding values during the 2018-2019 season were 12.70%, 7.17%, 2.66%, and 19.25%, respectively. Irrigation scheduling of IS35 treatment improved all the growth-related and yield parameters of winter wheat. Further, treating 25% nitrogen as a basal dose and application of 75% as a top-dressing dose positively influenced the winter wheat yield. While NS0:100 increased the plant height, leaf area index (LAI), and aboveground biomass as compared to the other application strategies, but high nitrogen was observed in deeper soil layers. Regarding soil environment, the lowest soil moisture and nitrate nitrogen contents were observed in LS80 during both growing seasons. Overall, coupling the IS35 with NS25:75 under 40-cm lateral spacing is a suitable choice for sustainable winter wheat production in theNorth China Plain. The results of our study may be helpful in advancing the knowledge of the farmer community for winter wheat production. The findings can also aid in advancing new insights among scientists working on soil water and nitrogen distribution in drip irrigation for better productivity.

Combined Effect of Salicylic Acid and Proline Mitigates Drought Stress in Rice (Oryza sativa L.) through the Modulation of Physiological Attributes and Antioxidant Enzymes

Salicylic acid (SA) and proline exhibit protective effects against a wide range of stresses. However, the combined impact of SA and proline on rice under drought stress is still unknown. Therefore, we investigated the protective roles of SA and/or proline in conferring drought tolerance in rice. There were eight treatments comprising the control (T1; 95-100% FC), 1.5 mM SA (T2), 2 mM proline (T3), 0.75 mM SA + 1 mM proline (T4), 45-50% FC (T5, drought stress), T5 + 1.5 mM SA (T6), T5 + 2 mM proline (T7), and T5 + 0.75 mM SA + 1 mM proline (T8), and two rice varieties: BRRI dhan66 and BRRI dhan75. Drought stress significantly decreased the plant growth, biomass, yield attributes, photosynthetic rate (Pn), stomatal conductance (gs), transpiration rate (Tr), photosynthetic pigments (chlorophyll and carotenoids content), relative water content (RWC), membrane stability index (MSI), soluble sugar and starch content, and uptake of N, P and K⁺ in roots and shoots. Drought-induced oxidative stress in the form of increased hydrogen peroxide (H₂O₂) production and lipid peroxidation (MDA) was observed. The combined application of SA (0.75 mM) + proline (1 mM) was found to be more effective than the single application of either for drought stress mitigation in rice. A combined dose of SA + proline alleviated oxidative stress through boosting antioxidant enzymatic activity in contrast to their separate application. The application of SA + proline also enhanced proline, soluble sugar and starch content, which resulted in the amelioration of osmotic stress. Consequently, the combined application of SA and proline significantly increased the gas exchange characteristics, photosynthetic pigments, RWC, MSI, nutrient uptake, plant growth, biomass and yield of rice. Therefore, the combined application of SA and proline alleviated the detrimental impacts of drought stress more pronouncedly than their separate application did by increasing osmoprotectants, improving nutrient transport, up-regulating antioxidant enzyme activity and inhibiting oxidative stress.

Automatic Crop Canopy Temperature Measurement Using a Low-Cost Image-Based Thermal Sensor: Application in a Pomegranate Orchard under a Permanent Shade Net House

Water scarcity in arid and semi-arid areas has led to the development of regulated deficit irrigation (RDI) strategies on most species of fruit trees in order to improve water productivity. For a successful implementation, these strategies require continuous feedback of the soil and crop water status. This feedback is provided by physical indicators from the soil-plant-atmosphere continuum, as is the case of the crop canopy temperature, which can be used for the indirect estimation of crop water stress. Infrared Radiometers (IRs) are considered as the reference tool for temperature-based water status monitoring in crops. Alternatively, in this paper, we assess the performance of a low-cost thermal sensor based on thermographic imaging technology for the same purpose. The thermal sensor was tested in field conditions by performing continuous measurements on pomegranate trees (Punica granatum L. 'Wonderful') and was compared with a commercial IR. A strong correlation (R² = 0.976) between the two sensors was obtained, demonstrating the suitability of the experimental thermal sensor to monitor the crop canopy temperature for irrigation management.

A Review on Regulation of Irrigation Management on Wheat Physiology, Grain Yield, and Quality

Irrigation has been pivotal in sustaining wheat as a major food crop in the world and is increasingly important as an adaptation response to climate change. In the context of agricultural production responding to climate change, improved irrigation management plays a significant role in increasing water productivity (WP) and maintaining the sustainable development of water resources. Considering that wheat is a major crop cultivated in arid and semi-arid regions, which consumes high amounts of irrigation water, developing wheat irrigation management with high efficiency is urgently required. Both irrigation scheduling and irrigation methods intricately influence wheat physiology, affect plant growth and development, and regulate grain yield and quality. In this frame, this review aims to provide a critical analysis of the regulation mechanism of irrigation management on wheat physiology, plant growth and yield formation, and grain quality. Considering the key traits involved in wheat water uptake and utilization efficiency, we suggest a series of future perspectives that could enhance the irrigation efficiency of wheat.

The Interactive Effects of Deficit Irrigation and Bacillus pumilus Inoculation on Growth and Physiology of Tomato Plant

The effects of inoculating plant growth promoting rhizobacteria (PGPR) and soil water deficits on crop growth and physiology remain largely unknown. Here, the responses of leaf gas exchange, growth, and water use efficiency (WUE) of tomato plants to Bacillus pumilus (B.p.) inoculation under four irrigation strategies (I1-I4) were investigated in a greenhouse. Results showed that soil water deficits, especially at I4 (20%, v/v), significantly decreased leaf stomatal conductance (g_s), transpiration rate (T_r), and photosynthetic rate (A_n), and the decrease of g_s and T_r were more pronounced than A_n. Reduced irrigation regimes significantly lowered dry matter and plant water use both in the non-B.p. control and the B.p. plants, while reduced irrigation significantly increased plant WUE, and B.p. inoculation had little effect on this parameter. Synergistic effects of PGPR and deficit irrigation on leaf gas exchange, leaf abscisic acid content, and stomatal density were found in this study, and specifically, B.p. treated plants at I4 possessed the highest WUE at stomatal and leaf scales, suggesting that B.p. inoculation could optimize water use and partly alleviate the negative effects of soil water deficit. These findings provide useful information for effective irrigation management and the application of PGPR in agriculture in the future.

Farmers' beliefs and concerns about climate change, and their adaptation behavior to combat climate change in Saudi Arabia

Climate change threatens the existence of humankind on the planet Earth. Owing to its arid climate and poor natural resources base, Saudi Arabia is particularly susceptible to the negative impact of ongoing climate change. Farmers' understanding of this global phenomenon is extremely important as it may help determine their adaptation behavior. This study was designed to analyze farmers' beliefs and concerns about climate change as well as their views about adaptation different obstacles. Data were collected from 80 randomly farmers of the Al-Ahsa region in Eastern Province using structured interviews. The findings revealed that farmers believed that climate change is mainly occurring due to anthropogenic activities. Drought, insects, crop diseases, and heat stress were their main concerns regarding adverse impacts of climate change. Lack of knowledge about adaptation practices, and poor government and financial support are perceived as the major obstacles to adaptation. The results of non-parametric analysis identified no significant differences in farmers' climate change beliefs and concerns, and their views about obstacles to adaptation in relation to their demographic characteristics. Based on the findings, we suggest that capacity building programs should be undertaken by the government for enhancing the adaptive capacity of the farmers as well the provision of financial incentives wherever deemed necessary for promoting the adoption of sustainable agricultural practices and building a resilient national food system.

Impact of single biochar application on maize growth and water-fertilizer productivity under different irrigation regimes

The improvement of soil water and nutrient availability through soil management practices are crucial in promoting crop growth and obtaining high water-fertilizer productivity under limited irrigation. In this study, a 2×4 fully randomized factorial design with two drip-irrigation regimes and four biochar rates was performed during maize crop growing seasons for a semiarid region of China in 2015 and 2016. Irrigation regimes was applied on the basis of the water lower limit of -15 kPa soil matric potential as W15 and -35 kPa as W35. Maize straw-derived biochar application rate of 0 (B0), 15 (B15), 30 (B30), and 45 (B45) t ha^-1 was once applied to sandy loam soil in the first growing season. Our results showed that the W15 and W35 regimes generally increased soil nutrient availability and organic matter content under all biochar treatment rates for the entire growth period. In comparison, the B45-induced increase in available P and K was higher in the W15 regime than in the W35 regime during the second growing season. Furthermore, biochar treatment improved the comprehensive fertility index (CFI), leaf area index, and yield of maize. Within the same biochar treatment, the CFI value was higher in the W15 regime than in the W35 regime during the first growing season. However, the opposite was observed in the second growing season. The average irrigation water productivity (IWP) increased by 11.6%, 8.8%, and 7.8% in the W35 regime and by 15.2%, 12.9%, and 10.2% in the W15 regime for the B15, B30, and B45 treatments, respectively. Moreover, biochar treatment enhanced maize grain yield and partial fertilizer productivity (PFP) of synthetic N, P, and K fertilizers under both irrigation regimes. The highest PFP values were observed in the B15 treatment under W15. In general, a one-time application of biochar treatment at a rate of 15 t ha^-1 in the first growing season is recommended in terms of increasing the availability of N, P, K, and organic matter in sandy loam and also improve water-fertilizer productivity under irrigation water lower limit of -15 kPa soil matric potential.

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.

Irrigation plays significantly different roles in influencing hydrological processes in two breadbasket regions

Agriculture is a major water user, especially in dry and drought-prone areas that rely on irrigation to support agricultural production. In recent years, the over-extraction of groundwater, exacerbated by climate change, population growth, and intensive agricultural irrigation, has led to a drop in water levels and influenced the hydrological cycle. Understanding changes in hydrological processes is essential for pursuing water sustainability. This study aims to estimate the amount and impact of irrigation on hydrological processes in two breadbasket regions, Jing-Jin-Ji (JJJ), China, and northern Texas (NTX), US. We used the Soil and Water Assessment Tool (SWAT) to explore spatiotemporal variations of irrigation from 2008 to 2013 and compared changes in hydrological processes caused by irrigation. The results indicated that deficit irrigation is more common in JJJ than in NTX and can reduce approximately 50 % of irrigation water use in areas with intensively irrigated cropland. The applied irrigation varies less over time in NTX but fluctuates in JJJ. Compared with NTX, the higher irrigation intensity in JJJ results in a more significant change in downstream peak streamflow of around 6 m³/s. Moreover, the difference in crop growing seasons can lead to different impacts of irrigation on hydrological processes. For example, the percentage change of surface runoff under real-world relative to the no-irrigation scenario was the greatest, around 40 %, in JJJ and NTX. However, the peak change occurred at different times, with the nearing maturity of winter wheat in May in JJJ and corn in August in NTX. The great potential to reduce groundwater extraction by adopting water conservation irrigation techniques calls for policies and regulations to help farmers shift towards more sustainable water management practices.

A Flashforward Look into Solutions for Fruit and Vegetable Production

One of the most important challenges facing current and future generations is how climate change and continuous population growth adversely affect food security. To address this, the food system needs a complete transformation where more is produced in non-optimal and space-limited areas while reducing negative environmental impacts. Fruits and vegetables, essential for human health, are high-value-added crops, which are grown in both greenhouses and open field environments. Here, we review potential practices to reduce the impact of climate variation and ecosystem damages on fruit and vegetable crop yield, as well as highlight current bottlenecks for indoor and outdoor agrosystems. To obtain sustainability, high-tech greenhouses are increasingly important and biotechnological means are becoming instrumental in designing the crops of tomorrow. We discuss key traits that need to be studied to improve agrosystem sustainability and fruit yield.

Proper irrigation amount for eggplant cultivation in a solar greenhouse improved plant growth, fruit quality and yield by influencing the soil microbial community and rhizosphere environment

Water scarcity is a worldwide problem, and in order to obtain plenty of production, agricultural irrigation water accounts for a large portion. Many studies have shown that the interaction of root microorganisms and soil can promote crop growth. Developing ways to reduce irrigation to maintain soil fertility and ensure crop yield by regulating the root microenvironment is an important research goal. Here, we developed a reasonable irrigation plan for eggplant cultivation in a solar greenhouse. The maximum theoretical amount of water demand during eggplant planting obtained from a previous study was used as the control (CK), and the irrigation in the treatments was reduced by 10, 20 and 30% relative to this amount. The 10% irrigation reduction treatment (T1) significantly improved soil nutrients and increased soil catalase, urease and alkaline phosphatase activities (p < 0.05). Further analysis of rhizosphere microorganisms revealed the highest richness and diversity of the microbial community under the T1 treatment, with Bacilli as the most abundant bacteria and Aspergillaceae as the most abundant fungi and lower relative abundances of Chloroflexi and Acidobacteria (p < 0.05). Changes in microbial community structure under the influence of different irrigation treatments resulted in improvements in rhizosphere N cycling and nutrient catabolism. The plant–microbe interactions led to significant increases in eggplant plant height, root vigour, root surface area, leaf chlorophyll a, leaf net photosynthetic rate, water use efficiency, transpiration rate, and stomatal conductance under the T1 treatment compared to the CK treatment; soluble sugar, soluble protein and free amino acid contents in eggplant fruit increased by 10.8, 12.3 and 6.7%, respectively; and yield increased by 3.9%. Our research proved that the 10% irrigation reduction treatment (T1) could improve microbial community richness and fruit yield, which would improve irrigation efficiency and cost reduction in agriculture.

How Surface Irrigation Contributes to Climate Change Resilience—A Case Study of Practices in Mexico

Climate change has brought increased temperatures and decreased rainfall on a global scale; however, population growth requires greater volumes of water and food each year that must be supplied in one way or another. In Mexico, application efficiencies in gravity irrigation are below 50%. Although in recent years the decision has been made to change to pressurized irrigation systems to increase the efficiency of water use, border or furrow irrigation is still the most widely used in agriculture. In this work, we show that with a methodology developed and applied in these systems, application efficiencies greater than 90% were obtained, while the Water Use Efficiency (WUE) increased by 27, 38 and 47% for the three crops where it was applied: sorghum, barley, and corn, respectively. Irrigation times per hectare and applied irrigation depths decreased by more than 30%, representing increased irrigation efficiencies and WUE. Finally, the water savings obtained can mitigate water scarcity in cities.

Climate Change Concerns of Saudi Arabian Farmers: The Drivers and Their Role in Perceived Capacity Building Needs for Adaptation

Climate change is a serious threat to the sustainability of global agriculture and food supply that necessitates taking appropriate action for building resilient food production systems and preserving rural economies. In this regard, farmers’ beliefs and concerns about the effects of climate change on agriculture may influence their adoption of adaptation and mitigation practices to address this emerging issue. This work was undertaken to evaluate farmers’ level of concern about climate change in the Jazan province of Saudi Arabia. The study also explored the role of various socioeconomic indicators in shaping farmers’ concerns and highlights various capacity-building initiatives that can be applied at the community level for effective adaptation. Ordered logistic regression was used to study the relationship between farmers’ level of concern and their need for capacity-building initiatives to tackle climate change. Results indicated that insect infestation is the farmers’ top concern, followed by higher crop-diseases incidence and drought. Regression analysis revealed that farmers’ income is a major factor that reduces their concern for insect infestation and crop disease while increases concern for drought. Credit access and information availability have a mixed impact on the farmers’ concern level. Capacity-building initiatives deemed necessary included establishing frequent contacts with extension personnel, timely warnings on droughts and other natural hazards, the training of farmers and extension workers, easy credit facilities, improvement in rural infrastructure and creation of awareness to address specific concern stimulus.

Suitable nitrogen application mode and lateral spacing for drip-irrigated winter wheat in North China Plain

To propose an appropriate nitrogen application mode and suitable drip irrigation lateral spacing, a field experiment was conducted during 2017-2018 and 2018-2019 growing seasons to quantify the different drip irrigation lateral spacings and nitrogen fertigation strategies effects on winter wheat growth, yield, and water use efficiency (WUE) in the North China Plain (NCP). The experiment consisted of three drip irrigation lateral spacing (LS) (40, 60, and 80 cm, referred to as D40, D60, and D80 respectively) and three percentage splits of nitrogen application modes (NAM) (basal and top dressing application ratio as 50:50 (N50:50), 25:75 (N25:75), and 0:100 (N0-100) respectively). The experimental findings depicted that yield and its components, and WUE were markedly affected by LS and NAM. Fertigation of winter wheat at N25:75 NAM notably (P<0.05) increased the grain yield by 4.88%, 1.83% and 8.03%, 4.61%, and WUE by 3.10%, 3.18% and 5.37%, 7.82%, compared with those at NAM N50:50 and N0:100 in 2017-2018 and 2018-2019 growing seasons, respectively. LS D40 appeared very fruitful in terms of soil moisture and nitrogen distribution, WUE, grain yield, and yield components than that of other LS levels. The maximum grain yield (8.73 and 9.40 t ha-1) and WUE (1.70 and 1.95 kg m-3) were obtained under D40N25:75 during both growing seasons, which mainly due to that all main yield components in D40N25:75 treatment, such as spikes per unit area, 1000-grain weight, and grains per spike were significantly higher as compared to other treatments. The outcomes of this research may provide a scientific basis of lateral spacing and nitrogen fertigation management for the production of drip-irrigated winter wheat in NCP.

Spatial differentiation and driving mechanism of rural water security in typical "engineering water depletion" of karst mountainous area-A lesson of Guizhou, China

Southwest China gets abundant rainfall, but in its rural areas, there is a severe shortage of water resources for irrigation and drinking. A case study was conducted in the Guizhou Province, which has the most concentrated karst distribution worldwide. The rural water security index was constructed, and Geodetector and ArcGIS were employed to systematically analyze the status quo, spatial differentiation, and driving mechanism of water security in rural areas of Guizhou in 2016. The results showed that (1) there was obvious spatial variation in the rural water security index in the study area, with only 3.85% of areas being maximally safe, and 20.51%, 35.89%, 15.38%, and 24.36% being sub-optimally safe, moderately safe, unsafe, and extremely unsafe, respectively. The spatial distribution of the rural water security index, it generally coincides with a gradual decay from the economically developed areas to the periphery. The water security of the geographical environment is inferior to those of domestic water and water for agricultural production. (2) For Guizhou Province, economic and social factors, such as the disposable income of rural residents and the incidence of impoverishment, were critical factors influencing rural water security. The critical influencing factors vary greatly among prefectures; however, there are some common factors that affect rural water security, such as the incidence of impoverishment, the penetration rate of rural piped water, the percentage of primary industry, and the percentage of karst area. The maximum value of the interactive driver of the percentage of groundwater and the disposable income of rural residents was 0.812, indicating that the interaction between the high percentage of groundwater caused by karst development and the low disposable income of rural residents was the primary reason for the low rural water security. (3) Rural water security was largely influenced by poor socioeconomic development, resulting in a low level of security and the availability of public water facilities and domestic water in rural areas. Significant improvements in rural water security depend on ameliorating the water security of agricultural production and domestic water, rather than improving the geo-environmental conditions of water resources at extremely high costs.

Effect of hydrogel composite reinforced with natural char nanoparticles on improvement of soil biological properties and the growth of water deficit-stressed tomato plant

Hydrogel polymers have been used to enhance water and nutrient retention in agricultural soils. The incorporation of nanoparticles to yield composite hydrogels has also gained substantial momentum over the years. The aim of the research was to investigate the effect of hydrogel-nano natural char composite (reinforced starch-based hydrogels with natural char nanoparticles) at three levels 0%, 0.3% and 0.6% (w/w) on nutritional and morphological responses of tomato plant (Lycopersicon esculentum Mill.) as well as on some soil biological properties under water-deficit stress at three levels 50% water-holding capacity (WHC) (severe stress), 75% WHC (mild stress), and 85% WHC (non-stress conditions). The different levels of nano-composite and water deficit stress significantly (P < 0.05) affected plant morpho-nutritional indices and soil microbial traits. Water-deficit stress decreased all measured parameters in this assay. However, the use of nanocomposite reduced the negative effects of water-deficit stress on tomato growth and development. The magnitude of the responses to the nanocomposite treatment depended on the concentration of applied nanocomposite and stress severity with the most positive effects on the growth (22-45% increase) and nutritional indices (P, Fe, and Zn concentration) (16-29% increase) of tomato at level 0.3% hydrogel nanocomposite and 85% WHC and on soil respiration rate (61% increase) and microbial population size ( 89% increase) at the level 0.6% hydrogel nanocomposite and 75% WHC. Accordingly, it is suggested that the application of hydrogel-nano natural char composite as a promising soil amendment, if used correctly, can be a successful method to maintain soil moisture content (improved tomato growth), plant nutrients, and soil microbial activity in the tomato growing medium.

Effects of regulated deficit irrigation applied at different growth stages of greenhouse grown tomato on substrate moisture, yield, fruit quality, and physiological traits

Given a critical water scarcity in arid and semi-arid Tunisian areas and aiming to reduce irrigation water request, it is crucial to identify and apply the best water-saving practices in these irrigated areas. Tomato is a high-water-requiring vegetable crop, thus increasing the pressure on water resources and environment. Its sustainable cultivation in such alarming conditions requires an adaptation of on-farm irrigation water-saving strategies preserving also the crop yield and leading to a fruit quality improvement. This study aimed to explore the effects of the regulated deficit irrigation (RDI) as an irrigation water-saving strategy, on yield, fruit quality, and physiological behavior of greenhouse grown potted tomato crop (Solanum lycopersicum L.) during three identified growth stages. The managed water regimes were (i) full irrigation (FI) ensuring 100% of the estimated water crop requirements, (ii) RDI1-25 and RDI1-50 ensuring respectively 75% and 50% of FI water supplies during the vegetative crop stage (stage I), (iii) RDI2-25 and RDI2-50 ensuring respectively 75% and 50% of FI water supplies from first truss blossom until first harvest (stage II), and (iv) RDI3-25 and RDI3-50 ensuring respectively 75% and 50% of FI supplies during the rest of the harvest period (stage III). The results showed that the substrate moisture vary significantly with the water deficit regime applied under different growth stages, thus providing different levels of substrate water content. Under RDI2, the tomato yield was the highest when compared with FI, RDI1, and RDI3 regimes. Indeed, saving the water by 20% under RDI2-50 reduced only 3% of tomato yield. Deficit irrigation under ripening fruit and flowering stages, mainly with 50% of water supplies shortage, resulted in higher fruit skin color, firmness, and refractometry index (°Brix) when compared to FI and RDI1. Physiological traits measurements indicated that FI exhibited the highest leaf stomatal conductance (gs) and chlorophyll index (CI) values while RDI3 exhibited the lowest gs and CI values among all the RDI treatments. Results are valuable in considering gs and CI as an efficient indicators of tomato plant water status. The results are also an important contribution to identify the second tomato growth stage as the best period that tomato plant tolerate water shortage without significant yield decrease, as well a rather fruit quality improvement. These results help to reach the challenge "more crop per drop" and can contribute to water scarcity remediation.

Impact of Economic Development Level and Agricultural Water Use on Agricultural Production Scale in China

The change of agricultural production scale is directly related to food security and the stable development of social economy. Particularly, the influence of economic development level and agricultural water use on agricultural production scale cannot be ignored. Therefore, this paper uses the fully modified ordinary least squares (FMOLS) and the Dumitrescu–Hurlin panel causality test models to discuss the effects of the level of economic development, agricultural water use, the level of urbanization, and the market price of agricultural products on the scale of agricultural production in China. The analysis results indicated that agricultural water use, the level of urbanization, and the market price of agricultural products promoted an increase of the scale of agricultural production at the total sample level; a 1% increase for these three variables will result in an increase of the scale of agricultural production of 0.634%, 0.377%, and 0.292%, respectively. The influence of economic development level on agricultural production scale accords with Kuznets curve. However, at the regional level, the influence of each variable on the eastern region is consistent with the trend of the total sample. In the central region, the impact of economic development on agricultural production scale shows a U-shaped curve, and the improvement of urbanization level inhibits the expansion of agricultural production scale. In the western region, all variables failed to pass the significance test. The results of the FMOLS model were validated by the fixed effects model. The results of causality tests showed that bidirectional causality existed between the scale of agricultural production and the level of economic development, the scale of agricultural production and agricultural water use, the level of economic development and the market price of agricultural products, and the level of urbanization and the market price of agricultural products. In different regions, there were differences in causality between variables. Therefore, based on the empirical results, we put forward some policy suggestions to maintain the scale of agricultural production.

Photosynthetic resistance and resilience under drought, flooding and rewatering in maize plants

Abnormally altered precipitation patterns induced by climate change have profound global effects on crop production. However, the plant functional responses to various precipitation regimes remain unclear. Here, greenhouse and field experiments were conducted to determine how maize plant functional traits respond to drought, flooding and rewatering. Drought and flooding hampered photosynthetic capacity, particularly when severe and/or prolonged. Most photosynthetic traits recovered after rewatering, with few compensatory responses. Rewatering often elicited high photosynthetic resilience in plants exposed to severe drought at the end of plant development, with the response strongly depending on the drought severity/duration. The associations of chlorophyll concentrations with photosynthetically functional activities were stronger during post-tasseling than pre-tasseling, implying an involvement of leaf age/senescence in responses to episodic drought and subsequent rewatering. Coordinated changes in chlorophyll content, gas exchange, fluorescence parameters (PSII quantum efficiency and photochemical/non-photochemical radiative energy dissipation) possibly contributed to the enhanced drought resistance and resilience and suggested a possible regulative trade-off. These findings provide fundamental insights into how plants regulate their functional traits to deal with sporadic alterations in precipitation. Breeding and management of plants with high resistance and resilience traits could help crop production under future climate change.

Developmental and water deficit-induced changes in hydraulic properties and xylem anatomy of tomato fruit and pedicels

Xylem water transport from the parent plant plays a crucial role in fruit growth, development, and the determination of quality. Attempts have been made to partition the hydraulic resistance of the pathway over the course of development, but no consensus has been reached. Furthermore, the issue has not been addressed in the context of changing plant and fruit water status under water deficit conditions. In this study, we have conducted a rigorous investigation into the developmental changes that occur in the hydraulic properties of tomato fruits and their pedicels under well-irrigated and water deficit conditions, based on hydraulic measurements, fruit rehydration, dye-tracing, light and electron microscopy, and flow modeling. We found that a decline in water transport capacity during development did not occur in the xylem pathway leading up to the fruit, but within the fruit itself, where the effect might reside either inside or outside of the xylem pathway. The developmental pattern of the hydraulic resistance of the xylem pathway was not significantly influenced by water deficit. The changes in xylem flow between the fruit and the parent plant resulting from the reduced driving force under water deficit could explain the reduced accumulation of water in the fruit. This study provides new insights that aid our understanding of xylem water transport in fleshy fruits and its sensitivity to water deficit from a hydraulic perspective.

Foliar Application of Zinc Oxide Nanoparticles Promotes Drought Stress Tolerance in Eggplant (Solanum melongena L.)

Water shortage and salinity are major challenges for sustaining global food security. Using nutrients in the nano-scale formulation including zinc oxide nanoparticles (ZnO NP) is a novel fertilization strategy for crops. In this study, two field-based trials were conducted during 2018 and 2019 to examine the influence of three ZnO NP concentrations (0, 50, and 100 ppm) in eggplant grown under full irrigation (100 of crop evapotranspiration; ETc) and drought stress (60% of ETc). Plant growth, yield, water productivity (WP), physiology, biochemistry, and anatomy responses were evaluated. Drought stress significantly decreased membrane stability index (MSI), relative water content (RWC), and photosynthetic efficiency, thus hampered eggplant growth and yield. In contrast, exogenous ZnO NP to water-stressed eggplant resulted in increased RWC and MSI associated with improved stem and leaf anatomical structures and enhanced photosynthetic efficiency. Under drought stress, supplementation of 50 and 100 ppm ZnO NP improved growth characteristics and increased fruit yield by 12.2% and 22.6%, respectively, compared with fully irrigated plants and nonapplied ZnO NP. The highest water productivity (WP) was obtained when eggplant was irrigated with 60% ETc and foliarly treated with 50 or 100 ppm of ZnO NP, which led to 50.8–66.1% increases in WP when compared with nontreated fully irrigated plants. Collectively, these findings demonstrated that foliar spraying ZnO NP gives the utility for alleviating drought stress effects on eggplant cultivated in saline soil.

Efficient removal of dyes and proteins by nitrogen-doped porous graphene blended polyethersulfone nanocomposite membranes

Nitrogen-doped porous graphene oxide (N-PGO) was synthesized, characterized, and applied as a hydrophilic nanomaterial in fabrication of polyethersulfone (PES) membrane for Reactive Red 195 dye and bovine serum albumin (BSA) protein separation. The N-PGO nanosheets not merely showed a good adhesion towards polymers, but simultaneously promoted hydrogen bonding action. Therefore, high-efficiency permeation passageway in the separation layer of membranes was attained. X-ray photoelectron spectroscopy (XPS), energy dispersive spectroscopy (EDX) and Fourier transform infra-red spectroscopy (FTIR) analyses approved nitrogen doping, which increased hydrophilicity and hydrogen bonding ability of PGO in water filtration. The pure water permeation of nanocomposite membranes could reach as high as 190 L m^-2 h^-1 at 3 bar. A dye rejection efficiency higher than 92% and BSA rejection higher than 95% were accordingly obtained. Atomic force microscopy (AFM) images approved formation of a rough surface that was decreased by addition of low amounts of the PGO. SEM images provided from the surface also confirmed enlarged pore size and increased porosity. Antifouling properties were investigated by BSA filtration, and results showed that the flux recovery ratio of the N-PGO membrane was improved. Overall, the N-PGO hybrid membranes exhibited potential for application in separation of typical proteins and dyes with good antifouling properties.

Simulating the effects of water limitation on plant biomass using a 3D functional-structural plant model of shoot and root driven by soil hydraulics

BACKGROUND AND AIMS

Improved modelling of carbon assimilation and plant growth to low soil moisture requires evaluation of underlying mechanisms in the soil, roots, and shoots. The feedback between plants and their local environment throughout the whole spectrum soil-root-shoot-environment is crucial to accurately describe and evaluate the impact of environmental changes on plant development. This study presents a 3D functional structural plant model, in which shoot and root growth are driven by radiative transfer, photosynthesis, and soil hydrodynamics through different parameterisation schemes relating soil water deficit and carbon assimilation. The new coupled model is used to evaluate the impact of soil moisture availability on plant productivity for two different groups of flowering plants under different spatial configurations.

METHODS

In order to address different aspects of plant development due to limited soil water availability, a 3D FSP model including root, shoot, and soil was constructed by linking three different well-stablished models of airborne plant, root architecture, and reactive transport in the soil. Different parameterisation schemes were used in order to integrate photosynthetic rate with root water uptake within the coupled model. The behaviour of the model was assessed on how the growth of two different types of plants, i.e. monocot and dicot, is impacted by soil water deficit under different competitive conditions: isolated (no competition), intra, and interspecific competition.

KEY RESULTS

The model proved to be capable of simulating carbon assimilation and plant development under different growing settings including isolated monocots and dicots, intra, and interspecific competition. The model predicted that (1) soil water availability has a larger impact on photosynthesis than on carbon allocation; (2) soil water deficit has an impact on root and shoot biomass production by up to 90 % for monocots and 50 % for dicots; and (3) the improved dicot biomass production in interspecific competition was highly related to root depth and plant transpiration.

CONCLUSIONS

An integrated model of 3D shoot architecture and biomass development with a 3D root system representation, including light limitation and water uptake considering soil hydraulics, was presented. Plant-plant competition and regulation on stomatal conductance to drought were able to be predicted by the model. In the cases evaluated here, water limitation impacted plant growth almost 10 times more than the light environment.

Root architecture and hydraulics converge for acclimation to changing water availability

Because of intense transpiration and growth, the needs of plants for water can be immense. Yet water in the soil is most often heterogeneous if not scarce due to more and more frequent and intense drought episodes. The converse context, flooding, is often associated with marked oxygen deficiency and can also challenge the plant water status. Under our feet, roots achieve an incredible challenge to meet the water demand of the plant's aerial parts under such dramatically different environmental conditions. For this, they continuously explore the soil, building a highly complex, branched architecture. On shorter time scales, roots keep adjusting their water transport capacity (their so-called hydraulics) locally or globally. While the mechanisms that directly underlie root growth and development as well as tissue hydraulics are being uncovered, the signalling mechanisms that govern their local and systemic adjustments as a function of water availability remain largely unknown. A comprehensive understanding of root architecture and hydraulics as a whole (in other terms, root hydraulic architecture) is needed to apprehend the strategies used by plants to optimize water uptake and possibly improve crops regarding this crucial trait.

Elevated [CO2 ] alleviates the impacts of water deficit on xylem anatomy and hydraulic properties of maize stems

Plants can modify xylem anatomy and hydraulic properties to adjust to water status. Elevated [CO₂ ] can increase plant water potential via reduced stomatal conductance and water loss. This raises the question of whether elevated [CO₂ ], which thus improves plant water status, will reduce the impacts of soil water deficit on xylem anatomy and hydraulic properties of plants. To analyse the impacts of water and [CO₂ ] on maize stem xylem anatomy and hydraulic properties, we exposed potted maize plants to varying [CO₂ ] levels (400, 700, 900, and 1,200 ppm) and water levels (full irrigation and deficit irrigation). Results showed that at current [CO₂ ], vessel diameter, vessel roundness, stem cross-section area, specific hydraulic conductivity, and vulnerability to embolism decreased under deficit irrigation; yet, these impacts of deficit irrigation were reduced at elevated [CO₂ ]. Across all treatments, midday stem water potential was tightly correlated with xylem traits and displayed similar responses. A distinct trade-off between efficiency and safety in stem xylem water transportation in response to water deficit was observed at current [CO₂ ] but not observed at elevated [CO₂ ]. The results of this study enhance our knowledge of plant hydraulic acclimation under future climate environments and provide insights into trade-offs in xylem structure and function.

Responses of water accumulation and solute metabolism in tomato fruit to water scarcity and implications for main fruit quality variables

Fruit is important for human health, and applying deficit irrigation in fruit production is a strategy to regulate fruit quality and support environmental sustainability. Responses of different fruit quality variables to deficit irrigation have been widely documented, and much progress has been made in understanding the mechanisms of these responses. We review the effects of water shortage on fruit water accumulation considering water transport from the parent plant into the fruit determined by hydraulic properties of the pathway (including xylem water transport and transmembrane water transport regulated by aquaporins) and the driving force for water movement. We discuss water relations and solute metabolism that affect the main fruit quality variables (e.g. size, flavour, nutrition, and firmness) at the cellular level under water shortage. We also summarize the most recent advances in the understanding of responses of the main fruit quality variables to water shortage, considering the effects of variety, the severity of water deficit imposed, and the developmental stage of the fruit. We finally identify knowledge gaps and suggest avenues for future research. This review provides new insights into the stress physiology of fleshy fruit, which will be beneficial for the sustainable production of high-quality fruit under deficit irrigation.

Sustainable Irrigation in Agriculture: An Analysis of Global Research

Irrigated agriculture plays a fundamental role as a supplier of food and raw materials. However, it is also the world’s largest water user. In recent years, there has been an increase in the number of studies analyzing agricultural irrigation from the perspective of sustainability with a focus on its environmental, economic, and social impacts. This study seeks to analyze the dynamics of global research in sustainable irrigation in agriculture between 1999 and 2018, including the main agents promoting it and the topics that have received the most attention. To do this, a review and a bibliometric analysis were carried out on a sample of 713 articles. The results show that sustainability is a line of study that is becoming increasingly more prominent within research in irrigation. The study also reveals the existence of substantial differences and preferred topics in the research undertaken by different countries. The priority issues addressed in the research were climatic change, environmental impact, and natural resources conservation; unconventional water resources; irrigation technology and innovation; and water use efficiency. Finally, the findings indicate a series of areas related to sustainable irrigation in agriculture in which research should be promoted.

Assessment of eco-sustainability vis-à-vis zoo-technical attributes of soybean meal (SBM) replacement with varying levels of coated urea in Nellore sheep (Ovis aries)

The contemporary environmental-stewardship programmes primarily aimed at curbing the global warming potential by adopting a multidisciplinary approach. Manipulating the feeding strategies has great potential in reducing the environmental footprints of livestock production. This study intends to assess the effect of soybean meal (SBM) replacement with varying levels of coated urea (SRU) on both zoo-technical (nutrient digestibility, heat increment, and physio-biochemical parameters) and environmental attributes. The coated urea was used to replace the SBM at 0, 25, 50, and 75 percent levels. Eight adult rams (43.02 ± 0.76) maintained in a conventional shed were used in a replicated 4 x 4 Latin square design. Not all the physiological parameters viz. rectal temperature, pulse rate, and respiratory rate were affected (P>0.05)f by varying levels of SRU incorporation. The SRU fed animals had higher (P<0.05) crude protein digestibility compared to SBM fed animals; however, the replacements did not affect the nutrient digestibility coefficients of DM, OM, NFC, NDFap, ADF, and hemicellulose components. The SRU did not affect various biochemical parameters such as serum glucose, total protein, albumin, globulin, urea, creatinine, ALT, AST, Ca, P and T3, and T4 levels; however, post-prandial serum urea N (SUN) values showed a diurnal quadratic pattern (P<0.05) with a dose-dependent relationship. Further, the SBM replacements had no effect on the calcium excretion, while the SRU incorporation decreased the faecal phosphorous content, thereby abating the eutrophication phenomenon. Although the SBM replacements did not affect in vivo water variables and faecal solid fractions, they managed to decrease the land and virtual water requirement along with global warming potential (GWP) of the entire trial. The GWP-perceptual map unveils the fact that replacement of conventional feed ingredients with NPN compounds aids in eco-friendly livestock production. Further, the conjectural analysis of the carbon footprint methodology revealed that agricultural by-products consideration could cause a huge increase in the GWP share of feed consumed, thus compelling the importance of research pertaining to feed production perspective as equal as ruminal methane amelioration.

The Main Drivers of Wetland Changes in the Beijing-Tianjin-Hebei Region

Wetlands are the most threatened ecosystem in China, and wetland conservation is a national priority because of their importance for water security, flood mitigation, and biodiversity conservation. A goal has been established for the Beijing-Tianjin-Hebei Region (BTH) to recover 340 km² of wetlands by 2020. To guide restoration and protection efforts, policymakers need information on the trends of wetland loss, conversion of wetlands, and their associated human drivers. The main drivers of changes in different wetland types in the BTH were identified and quantified from 2000 to 2015. In 2015, there was 6264.07 km² less wetland area than in 2000, with the remaining wetlands primarily located in Hebei and Tianjin. Reservoirs/ponds were the most abundant wetland type, followed by herbaceous swamps, rivers, canals and channels, and then lakes as the least represented. There were continuous losses of wetlands from 2000 to 2015, with marked decreases for rivers (30.48%), channels/canals (23.30%), and herbaceous swamps (16.12%). However, there was an increase in the area of lakes and reservoirs/ponds, with increases of 54.96% and 3.47%, respectively. The largest changes in natural wetlands were due to agricultural production followed by artificialization and grassland expansion. The driving forces of the observed changes were specific to each local region. According to an aggregated boosted trees (ABT) analysis, gross farm production, total aquatic products, and irrigated area were the top three drivers of the decrease in natural wetlands, which agreed with the main patterns of change in the BTH. The purpose of this study was to provide guidance for policy makers working to meet the 2020 BTH wetland recovery target. Recommendations were provided at the provincial level, including water transfers across provincial boundaries, the control of agricultural expansion, exploration of species-specific irrigation deficits, a reduction in the artificialization of land surfaces, the development of a sustainable intensified aquaculture model, and the promotion of awareness of wetland importance among local people.

Improving Water Use Efficiency of Spring Maize by Adopting Limited Supplemental Irrigation Following Sufficient Pre-Sowing Irrigation in Northwest China

In order to improve the water use efficiency (WUE) of spring maize in northwest China, the irrigation strategy of adopting limited supplemental irrigation following a high quota pre-sowing irrigation was evaluated under field conditions in 2016 and 2018. There were three treatments (W1, W2 and W3) differing in designed wetting depth (Dh) where soil water was replenished. Dh in W1, W2 and W3 were 0–40, 0–50 and 0–60 cm, respectively. The limited supplemental irrigation was adopted to improve soil water content (SWC) within Dh to field capacity (θFC) when SWC within 0–40 cm layer decreased to 60%θFC following a high rate of pre-sowing irrigation. Results showed that the smaller Dh was beneficial for improving root length density and enhance the utilization of water in subsoil. In both seasons, different Dh led to similar grain yields, which were comparable to the typical regional yield (14.3 t ha−1). The highest WUE (2.79 kg m−3) was achieved in W1 and was 13% more than the typical regional level of 2.46 kg m−3, implying it was adequate for achieving high yield and WUE to maintain SWC in 0–40 cm above 60% θFC with not replenishing soil water in 40–100 cm during the growth season after pre-sowing irrigation.

Interactive Regimes of Reduced Irrigation and Salt Stress Depressed Tomato Water Use Efficiency at Leaf and Plant Scales by Affecting Leaf Physiology and Stem Sap Flow

Interactive effects of reduced irrigation and salt stress on leaf physiological parameters, biomass accumulation, and water use efficiency (WUE) of tomato plants at leaf and whole plant scales were investigated in a field experiment during 2016 and a greenhouse experiment during 2017. Experiment utilized two irrigation regimes (full, 2/3 of full irrigation) and four soil salt regimes (0, 0.3, 0.6, 0.9% in 2016 season; and 0, 0.2, 0.3, 0.4% in 2017 season). Three salts, sodium chloride, magnesium sulfate, and calcium sulfate (mass ratio of 2:2:1), were homogeneously mixed with soil prior to packing into containers (0.024 m3). Li-COR 6400 was used to measure tomato leaf physiological parameters. Instantaneous water use efficiency (WUEins, μmol mmol-1) and intrinsic water use efficiency (WUEint, μmol mol-1) were determined at leaf scale, yield water use efficiency (WUEY, g L-1), and dry biomass water use efficiency (WUEDM, g L-1) were determined at whole plant scale. Plants irrigated with 2/3 of full irrigation with zero soil-salt treatment had higher dry biomass and yield per plant, resulting in the highest WUEDM and WUEY at whole plant scale. Increasing soil salinity decreased dry biomass and yield, leading to greater decreases in whole plant WUEDM and WUEY under both irrigation treatments. At full irrigation, no decreases in stomatal conductance (gs, mol m-2 s-1) and slight increase in photosynthetic rate (Pn, μmol m-2 s-1) led to higher WUEint at leaf scale during both years. Under full and reduced irrigation, increasing soil salt content decreased Pn and transpiration rate (Tr, mmol m-2 s-1) and led to reductions in WUEins at the leaf scale. However, compared to full irrigation, reduced irrigation improved WUEins with a significant decline in Tr in no salt and 0.3% soil-salt treatments during both years. For soil salt content of 0.6%, stomatal limitation due to salt stress resulted in higher WUEint, but soil salt content of 0.9% decreased WUEint due to non-stomatal limitation. Soil salt content significantly decreased sap flow, with the maximum variation of daily sap flow per plant of 7.96-31.37 g/h in 2016 and 12.52-36.02 g h-1 in 2017. Sap flow rate was linearly related to air temperature (Ta, °C), solar radiation (Rs, W m-2), and vapor pressure deficit (VPD, kPa). These results advance knowledge on tomato response to abiotic stresses and could improve management of tomato production in water- and salt-stressed areas.

Improving Irrigation Water Use Efficiency: A Review of Advances, Challenges and Opportunities in the Australian Context

The demand for fresh water is on the increase, and the irrigation industry in Australia is looking to a future with less water. Irrigation consumes the bulk of the water extracted from various sources, and hence the efficiency of its use is of outmost importance. This paper reviewed the advancements made towards improving irrigation water use efficiency (WUE), with a focus on irrigation in Australia but with some examples from other countries. The challenges encountered, as well as the opportunities available, are also discussed. The review showed that improvements in irrigation infrastructure through modernisation and automation have led to water savings. The concept of real-time control and optimisation in irrigation is in its developmental stages but has already demonstrated potential for water savings. The future is likely to see increased use of remote sensing techniques as well as wireless communication systems and more versatile sensors to improve WUE. In many cases, water saved as a result of using efficient technologies ends up being reused to expand the area of land under irrigation, sometimes resulting in a net increase in the total water consumption at the basin scale. Hence, to achieve net water savings, water-efficient technologies and practices need to be used in combination with other measures such as incentives for conservation and appropriate regulations that limit water allocation and use. Factors that affect the trends in the irrigation WUE include engineering and technological innovations, advancements in plant and pasture science, environmental factors, and socio-economic considerations. Challenges that might be encountered include lack of public support, especially when the methods used are not cost-effective, and reluctance of irrigations to adopt new technologies.

Stable isotope measurements show increases in corn water use efficiency under deficit irrigation

Deficit irrigation has usually improved crop water use efficiency (WUE), but there are still gaps in our understanding of the mechanisms. Four irrigation treatments were a conventional furrow irrigation (CFI), border irrigation (BI), alternate furrow irrigation (AFI), and an AFI(M/2) (the amount of irrigation was 50% of the AFI). The volume of irrigation water applied were nearly the same for CFI, BI, and AFI. The isotope (δ18O and δD) method was used to quantify corn root water uptake (RWU) during 2013-2014. Compared to CFI and BI, corn yield and WUE were 17.0-30.2% and 13.3-33.8% higher in AFI, respectively. No significant yield reduction were observed between AFI and AFI(M/2). Corn RWU was more from deeper soil with increasing growth stage for AFI(M/2), AFI, and CFI, but from shallower depth for BI. The depth for RWU varied in the order of AFI(M/2)  > AFI > CFI > BI. The maximum root density was in the depth of 40-80 cm at the growing stage in AFI, and 4-26% more water was extracted from the wetter and deeper root zones. The WUE increased under deficit irrigation, and stimulated the root growth with attendant decreases in water loss to deep percolation.

Satellite-Based Water Consumption Dynamics Monitoring in an Extremely Arid Area

Evapotranspiration (ET) involves actual water consumption directly from the land surface; however, regional ET maps are usually neglected during water management and allocation. In this study, an integrated satellite-based ET monitoring approach with two spatial resolutions is proposed over an extremely arid basin in China that has experienced crop area expansion and has been the focus of a water-saving project since 2012. The proposed ETWatch approach combined with an empirical downscaling strategy based on vegetation condition was employed to produce monthly ET maps. This method achieves satisfactory accuracy and is validated by its reasonable spatial and temporal pattern results. Yearly results exhibit an increasing ET trend before 2012, which subsequently gradually decrease. This trend fits well with the dynamics of the basin-wide vegetation condition, indicating that there is a stronger correlation between water consumption and vegetation than between other environmental indicators. The average ET over three main crop types in the region (grape, cotton, and melon) decreased by approximately 5% due to optimizations of the irrigation timeline during the project, while 13% of the water savings can be attributed to the fallowing of crop areas. Based on the irrigation distribution in 2012, a comparison between drip and border irrigation that achieves water savings of 3.6% from grape and 5.8% from cotton is conducted. However, an afforestation project that involved planting young trees led to an approximate 25% increase in water consumption. Overall, since 2012, the water-saving project has achieved satisfactory performance regarding excessive groundwater withdrawal, showing a reduction trend of 3 million m3/year and an increase in Lake Aiding water levels since 2011. The results reveal the potential of the ET monitoring strategy as a basis for basin-scale water management.

Hydrotropism: how roots search for water

Fresh water is an increasingly scarce resource for agriculture. Plant roots mediate water uptake from the soil and have developed a number of adaptive traits such as hydrotropism to aid water foraging. Hydrotropism modifies root growth to respond to a water potential gradient in soil and grow towards areas with a higher moisture content. Abscisic acid (ABA) and a small number of genes, including those encoding ABA signal transducers, MIZ2/GNOM, and the hydrotropism-specific MIZ1, are known to be necessary for the response in Arabidopsis thaliana, whereas the role of auxin in hydrotropism appears to vary depending on the plant species. This review will describe recent progress characterizing the hormonal regulation of hydrotropism. Recent advances in identifying the sites of hydrotropic perception and response, together with its interaction with gravitropism, will also be discussed. Finally, I will describe putative mechanisms for perception of the water potential gradient and a potential role for hydrotropism in acclimatizing plants to drought conditions.

Simulation of Stomatal Conductance and Water Use Efficiency of Tomato Leaves Exposed to Different Irrigation Regimes and Air CO2 Concentrations by a Modified "Ball-Berry" Model

Stomatal conductance (g_s) and water use efficiency (WUE) of tomato leaves exposed to different irrigation regimes and at ambient CO₂ (a[CO₂], 400 ppm) and elevated CO₂ (e[CO₂], 800 ppm) environments were simulated using the "Ball-Berry" model (BB-model). Data obtained from a preliminary experiment (Exp. I) was used for model parameterization, where measurements of leaf gas exchange of potted tomatoes were done during progressive soil drying for 5 days. The measured photosynthetic rate (P_n) was used as an input for the model. Considering the effect of soil water deficits on g_s, an equation modifying the slope (m) based on the mean soil water potential (Ψ_s) in the whole root zone was introduced. Compared to the original BB-model, the modified model showed greater predictability for both g_s and WUE of tomato leaves at each [CO₂] growth environment. The models were further validated with data obtained from an independent experiment (Exp. II) where plants were subjected to three irrigation regimes: full irrigation (FI), deficit irrigation (DI), and alternative partial root-zone irrigation (PRI) for 40 days at both a[CO₂] and e[CO₂] environment. The simulation results indicated that g_s was independently acclimated to e[CO₂] from P_n. The modified BB-model performed better in estimating g_s and WUE, especially for PRI strategy at both [CO₂] environments. A greater WUE could be seen in plants grown under e[CO₂] associated with PRI regime. Conclusively, the modified BB-model was capable of predicting g_s and WUE of tomato leaves in various irrigation regimes at both a[CO₂] and e[CO₂] environments. This study could provide valuable information for better predicting plant WUE adapted to the future water-limited and CO₂ enriched environment.

Interactive Effects of Elevated CO2 and N Fertilization on Yield and Quality of Tomato Grown Under Reduced Irrigation Regimes

The interactive effects of CO₂ elevation, N fertilization, and reduced irrigation regimes on fruit yield (FY) and quality in tomato (Solanum lycopersicum L.) were investigated in a split-root pot experiment. The plants were grown in two separate climate-controlled greenhouse cells at atmospheric [CO₂] of 400 and 800 ppm, respectively. In each cell, the plants were fertilized at either 100 or 200 mg N kg^-1 soil and were either irrigated to full water holding capacity [i.e., a volumetric soil water content of 18%; full irrigation (FI)], or using 70% water of FI to the whole pot [deficit irrigation (DI)] or alternately to only half of the pot [partial root-zone irrigation (PRI)]. The yield and fruit quality attributes mainly from sugars (sucrose, fructose, and glucose) and organic acids (OAs; citric acid and malic acid) to various ionic (NH₄⁺, K⁺, Mg²⁺, Ca²⁺, NO₃^-, SO₄^2-, and PO₄^3-) concentrations in fruit juice were determined. The results indicated that lower N supply reduced fruit number and yield, whereas it enhanced some of the quality attributes of fruit as indicated by greater firmness and higher concentrations of sugars and OAs. Elevated [CO₂] (e[CO₂]) attenuated the negative influence of reduced irrigation (DI and PRI) on FY. Principal component analysis revealed that the reduced irrigation regimes, especially PRI, in combination with e[CO₂] could synergistically improve the comprehensive quality of tomato fruits at high N supply. These findings provide useful knowledge for sustaining tomato FY and quality in a future drier and CO₂-enriched environment.

Proteomic analysis of Camellia sinensis (L.) reveals a synergistic network in the response to drought stress and recovery

Drought is a crucial limiting factor for tea yield and quality. To systematically characterize the molecular response of tea plants to drought stress and its capacity to recover, we used iTRAQ-based comparative proteomic approach to investigate the effects of drought on protein expression profiles in tea seedlings subjected to different drought treatments. A total of 3274 proteins were identified, of which 2169 and 2300 showed differential expressions during drought and recovery, respectively. Functional annotation showed that multiple biological processes were regulated, suggesting that tea plants probably employed multiple and synergistic resistance mechanisms in dealing with drought stress. Hierarchical clustering showed that chlorophyll a/b-binding proteins were up-regulated in DB and RE, suggesting that tea plants might regulate expression of chlorophyll a/b-binding proteins to maintain the photosystem II function during drought stress. Abundant proteins involved in sulfur-containing metabolite pathways, such as glutathione, taurine, hypotaurine, methionine, and cysteine, changed significantly during drought stress. Among them, TL29 interacted with LHCb6 to connect S-containing metabolites with chlorophyll a/b-binding proteins. This suggests that sulfur-containing compounds play important roles in the response to drought stress in tea plants. In addition, the expression of PAL was up-regulated in DA and down-regulated in DB. Cinnamyl alcohol dehydrogenase, caffeic acid O-methyltransferase, and 4-coumarate-CoA ligase also showed significant changes in expression levels, which regulated the biosynthesis of polyphenols. The results indicate that slight drought stress might promote polyphenol biosynthesis, while serious drought stress leads to inhibition. The expression of lipoxygenase and short-chain dehydrogenase increased during slight drought stress and some volatile metabolite pathways were enriched, indicating that drought stress might affect the tea aroma. The study provides valuable information that will lay the foundation for studies investigating the functions of drought response genes in tea leaves.

Agricultural Water Productivity Oriented Water Resources Allocation Based on the Coordination of Multiple Factors

Agricultural water productivity (AWP), which is associated with multiple factors, is an important index for measuring the effectiveness of agricultural water management. The purpose of this study is to promote AWP through optimally allocating limited agricultural water resources with the coordination of related elements. Firstly, the coordination effects of multiple factors related to AWP are quantified as relative optimum membership degrees based on the fuzzy optimum selecting theory. Secondly, based on the relative optimum membership degrees for various crops, a linear fractional programming model is established to maximize AWP in agricultural water resources allocation. Thirdly, the impacts of the allocation schemes on the development of social-economy and ecological environment are discussed using the multi-dimensional regulation theory. The developed integrated system has advantages in increasing agricultural water productivity through the coordination of multiple factors with aspects of economy, society and resources. Moreover, the system is capable of screening schemes considering harmonious development of resources, economy, society and ecology based on optimization results, providing decision makers with more sustainable schemes for irrigation water allocation. The integrated system including the aforementioned three parts is applied to a real-world case study in China to demonstrate its feasibility and applicability. Different water allocation schemes for various crops under different scenarios were obtained. The average value of AWP is 1.85 kg/m3, which is 0.31 kg/m3 higher than the current value of AWP. An optimum scheme with 1.1405 × 108 m3 of water being allocated was also selected due to its highest level of coordination for resources, economy, society and ecology. The developed system can provide an effective method for AWP promotion. The obtained results can help local decision makers adjust water resources allocation schemes.

Growth, Water Use, and Nitrate-15N Uptake of Greenhouse Tomato as Influenced by Different Irrigation Patterns, 15N Labeled Depths, and Transplant Times

Increasing water use efficiency and reducing nitrogen pollutant discharge are important tasks for modern agriculture. To evaluate the effect of alternate partial root-zone irrigation (APRI) on tomato plant growth, water use efficiency and nitrate-15N uptake, an experiment was conducted from June to December in 2014 under greenhouse condition in northern China. The experiment contained two irrigation patterns [APRI and conventional irrigation (CI)], two 15N labeled depths in soil (10 and 50 cm) and two transplant time (early and late summer). Results showed that, compared to CI, APRI did not significantly (p > 0.05) impact the growth and biomass accumulation in aboveground part of tomato, while it enhanced the root, reflecting by greater length density, and more dry mass. APRI produced marginally lower yields, but saved 34.9% of irrigation water, and gave a 37.6-49.9% higher water use efficiency relative to CI. In addition, APRI improved fruit quality, mainly through increasing the contents of soluble solid (by 12.8-21.6%), and vitamin C (2.8-12.7%), and the sugar/acid ratio (3.5-8.5%). The 15N utilization efficiency (15NUE) in APRI was higher than that in CI, which was more evident when 15N was labeled at 50 cm depth. Significant (p < 0.05) 15N recovery increase of 10.2-13.2% and 15N loss decrease of 35.4-54.6% were found for APRI compared to CI. The overall results suggest that APRI under greenhouse could benefit the nitrate-N recovery and increase the water use efficiency in tomato.

Evaluation of the effects of irrigation and fertilization on tomato fruit yield and quality: a principal component analysis

Irrigation and fertilization are key practices for improving the fruit quality and yield of vegetables grown in greenhouses. We carried out an experiment in a solar greenhouse spanning three consecutive growing seasons to evaluate the effects of irrigation and fertilization on the fruit yield and quality, water use efficiency (WUE) and fertilizer partial factor productivity (PFP) of tomatoes. Interactions between irrigation and fertilization treatments and individual factors of irrigation and fertilization significantly (p < 0.01) affected fruit yield, WUE and PFP. WUE and fruit yield and quality were more sensitive to changes in irrigation than to changes in fertilizer, but PFP showed the opposite trend. Interestingly, the treatment with moderate irrigation (W2: 75% ET ₀ ) and high fertilizer level (F1: 240N-120P₂O₅-150K₂O kg ha^-1) was twice ranked first after a combinational evaluation. In conclusion, the proper application of drip fertigation (W2F1) may be a good compromise for solar greenhouse-grown tomatoes with regard to fruit yield and quality, WUE, and PFP. The present study sheds light on the contributions of these practices, clarifies their impacts, and provides a basis for evaluating and selecting better management practices for growing greenhouse vegetables.