Lower Water Use Research Articles

Arbuscular mycorrhiza influences carbon-use efficiency and grain yield of wheat grown under pre- and post-anthesis salinity stress.

Soil salinity severely affects and constrains crop production worldwide. Salinity causes osmotic and ionic stress, inhibiting gas exchange and photosynthesis, ultimately impairing plant growth and development. Arbuscular mycorrhiza (AM) have been shown to maintain light and carbon use efficiency under stress, possibly providing a tool to improve salinity tolerance of the host plants. Thus, it was hypothesized that AM will contribute to improved growth and yield under stress conditions. Wheat plants (Triticum aestivum L.) were grown with (AMF+) or without (AMF-) arbuscular mycorrhizal fungi (AMF) inoculation. Plants were subjected to salinity stress (200mm NaCl) either at pre- or post-anthesis or at both stages. Growth and yield components, leaf chlorophyll content as well as gas exchange parameters and AMF colonization were analysed. AM plants exhibited a higher rate of net photosynthesis and stomatal conductance and lower intrinsic water use efficiency. Furthermore, AM wheat plants subjected to salinity stress at both pre-anthesis and post-anthesis maintained higher grain yield than non-AM salinity-stressed plants. These results suggest that AMF inoculation mitigates the negative effects of salinity stress by influencing carbon use efficiency and maintaining higher grain yield under stress.

Challenges and Opportunities for Sustainable Management of Water Resources in the Island of Crete, Greece

Crete, located in the South Mediterranean Sea, is characterized by long coastal areas, varied terrain relief and geology, and great spatial and inter-annual variations in precipitation. Under average meteorological conditions, the island is water-sufficient (967 mm precipitation; theoretical water potential 3425.89 hm3; and total water use 610 hm3). Agriculture is by far the greatest user of water (78% of total water use), followed by domestic use (21%). Despite the high average water availability, water scarcity events commonly occur, particularly in the eastern-south part of the island, driven by local climatic conditions and seasonal or geographical mismatches between water availability and demand. Other critical issues in water management include the over-exploitation of groundwater, accounting for 93% of the water used in agriculture; low water use efficiencies in the farms; limited use of non-conventional water sources (effluent reuse); lack of modern frameworks of control and monitoring; and inadequate cooperation among stakeholders. These deficiencies impact adversely water use efficiency, deteriorate quality of water resources, increase competition for water and water pricing, and impair agriculture and environment. Moreover, the water-limited areas may display low adaptation potential to climate variability and face increased risks for the human-managed and natural ecosystems. The development of appropriate water governance frameworks that promote the development of integrated water management plans and allow concurrently flexibility to account for local differentiations in social-economic favors is urgently needed to achieve efficient water management and to improve the adaptation to the changing climatic conditions. Specific corrective actions may include use of alternative water sources (e.g., treated effluent and brackish water), implementation of efficient water use practices, re-formation of pricing policy, efficient control and monitoring, and investment in research and innovation to support the above actions. It is necessary to strengthen the links across stakeholders (e.g., farmers, enterprises, corporations, institutes, universities, agencies, and public authorities), along with an effective and updated governance framework to address the critical issues in water management, facilitate knowledge transfer, and promote the efficient use of non-conventional water resources.

Regulation of soil water threshold on tomato plant growth and fruit quality under alternate partial root-zone drip irrigation

Increasingly limited global freshwater resources coupled with low water use efficiency (WUE) increases the need for water-saving irrigation technologies in agricultural production. Numerous studies have investigated the emerging water-saving irrigation technology of alternate partial root-zone drip irrigation (APDI) on crop yield and WUE. This study investigated the effects of lower soil water thresholds for alteration of the irrigation (LTAI) to the previously dry root-zone on tomato plant growth, yield, and irrigation water use efficiency (IWUE) under APDI in year 2016 with field plot area of 6.48 m2. There were six APDI treatments coded as AS80, AS70, AS60 and AD80, AD70, AD60, indicating APDI under sufficient irrigation (S) or deficit irrigation (D) with LTAI controlled at 80 %, 70 % and 60 % field water capacity (FC) in the previously dry root-zone, respectively. In addition, conventional sufficient (CSD) and deficit (CDD) drip irrigation treatments were added as the controls. The results showed that lowering the irrigation amount significantly reduced tomato plant growth, yield and harvest index, but improved fruit quality in terms of reducing sugar, soluble sugar, vitamin C, and sugar-acid ratio. Compared with that of conventional drip irrigation, the promotion effect of APDI, especially with LTAI at 70 % FC, on root growth was observed in the 0−20 cm top soil layer where more than 90 % of the plant roots were distributed irrespective of irrigation amounts. Under sufficient irrigation, tomato shoot growth and the harvest index showed no significant difference among treatments, but tomato yield and the root to shoot ratio increased significantly in AS70, while fruit quality was improved in AS70 and AS60. Under APDI with deficit irrigation, when LTAI decreased from 80 % FC to 70 % FC in the previously drying root-zone, the yield and IWUE in AD80 and AD70 increased by 8.6 % and 17.4 %, respectively, and thus increased the harvest index compared with CDD. The AD70 treatment saved 31.2 % irrigation water without significant yield reduction, but increased IWUE by 44.9 % compared with the CSD. However, the harvest index and the yield decreased significantly when LTAI decreased from 70 % FC to 60 % FC (AD70 Vs. AD60). In addition, the yield showed no significant difference between AD60 and CDD. Fruit quality increased under APDI as compared with CDD under deficit irrigation, with the best quality appeared in the AD70 and AD60 treatments. These results indicated that the effects of APDI on tomato growth and fruit quality were modulated by LTAI and irrigation amount. APDI with LTAI controlled at 70 % FC was the optimal choice for better yield and fruit quality, especially under deficit irrigation. Unfavorable LTAI could diminish and even eliminate the beneficial effects of APDI on yield and IWUE as compared with conventional drip irrigation.

Biochar and its impact on soil properties, growth and yield of okra plants

Applying biochar to the soil can mitigate problems that hinder agricultural production, such as water scarcity and low fertility soils. The objective of this research was to evaluate the impact of dry coconut husk biochar and sewage sludge combinations on soil chemical characteristics, growth, yield and water productivity of okra crop. The experiment was arranged in randomized blocks, with 6 treatments (CHB+BSS -coconut husk biochar + biochar of sewage sludge, CHB+RSS-coconut husk biochar + raw sewage sludge, BSS+RSS -biochar of sewage sludge + raw sewage sludge, CHB -coconut husk biochar, BSS -biochar of sewage sludge, WB -without biochar (control)). Plant height, number of fruits per plant, yield and water use productivity were evaluated. To evaluate the effect of biochar on soil, soil samples weretaken to determine pH, CEC, P, K, Ca, Mg concentrations after incorporation of biochar into the soil. The BSS + RSS and BSS treatments provided better results on okra production and growth characteristics with a 421.15% and 419% productivity increase, respectively, compared to the control treatment. The BSS and BSS + RSS treatments provided better water productivity,with values of 14.5 and 13.3kilogramproduced for each cubic meter of water applied, respectively.All soil chemical characteristics analyzed were modified when the biochar was incorporated into the soil. The results provide valuable insight that okra growers can embrace the use of the combination BSS+RSS and BSS, providing better yields and lower water use in growing this plant.

Competition and Drought Alter Optimal Stomatal Strategy in Tree Seedlings.

A better understanding of plant stomatal strategies holds strong promise for improving predictions of vegetation responses to drought because stomata are the primary mechanism through which plants mitigate water stress. It has been assumed that plants regulate stomata to maintain a constant marginal water use efficiency and forego carbon gain when water is scarce. However, recent hypotheses pose that plants maximize carbon assimilation while also accounting for the risk of hydraulic damage via cavitation and hydraulic failure. This “gain-risk” framework incorporates competition in stomatal regulation because it takes into account that neighboring plants can “steal” unused water. This study utilizes stomatal models representing both the water use efficiency and carbon-maximization frameworks, and empirical data from three species in a potted growth chamber experiment, to investigate the effects of drought and competition on seedling stomatal strategy. We found that drought and competition responses in the empirical data were best explained by the carbon-maximization hypothesis and that both drought and competition affected stomatal strategy. Interestingly, stomatal responses differed substantially by species, with seedlings employing a riskier strategy when planted with a high water use competitor, and seedlings employing a more conservative strategy when planted with a low water use competitor. Lower water users in general had less stomatal sensitivity to decreasing ΨL compared to moderate to high water users. Repeated water stress also resulted in legacy effects on plant stomatal behavior, increasing stomatal sensitivity (i.e., conservative behavior) even when the seedling was returned to well-watered conditions. These results indicate that stomatal strategies are dynamic and change with climate and competition stressors. Therefore, incorporating mechanisms that allow for stomatal behavioral changes in response to water limitation may be an important step to improving carbon cycle projections in coupled climate-Earth system models.

Influence of stand density on growth and water use efficiency in Eucalyptus clones

We examined the influence of stand density and genotype on transpiration and water use efficiency in high productivity plantations. Three widely planted Eucalyptus clones that differ in drought tolerance and productivity (E. urophylla, E. urophylla × E. grandis and E. grandis × E. camaldulensis, clones IP, B2 and C3, respectively) were measured at four densities (590, 1030, 1420, and 2950 trees ha−1). Over the 1-year study period (1.5–2.5 years after planting), individual biomass increment decreased with increasing density, from 21 kg tree−1 at 590 trees ha−1 to 6 kg tree−1 at 2950 trees ha−1. Stand increment typically follows the reverse pattern, increasing as density increases. This was the case for two clones (IP and B2), but stand increment was consistent across tree spacings for C3. Transpiration increased with density, from a low of 622 mm yr−1 to a high of 879 mm y−1. Some of the increased water use resulted from higher leaf area index at higher densities. The B2 clone transpired the most water on average, produced the greatest increment (23 Mg ha−1 yr−1 for 1030 trees ha−1), and produced the most wood L−1 transpiration (water use efficiency, 2.3 g biomass L−1). The clone C3 had the lowest increment (only 12 Mg ha−1 yr−1) because of the combination of low transpiration and low water use efficiency (only 1.5 g biomass L−1). Optimizing clone selection and silviculture for the combination of high yield and high water use efficiency may help reduce risks from drought as well as water conservation.

Efficiency and sustainability of inter-provincial crop-related virtual water transfers in China

The phenomenon of virtual water flows (VWFs) reveals the remote pressure on local water resources on one hand, and provides the possibility of global water saving if VWFs from water-rich places of higher water use efficiencies to water-poor or lower water use efficiencies regions on the other hand. A VWF is marked as efficient when at least half of the water footprint (WF) in producing the traded products is below the corresponding WF benchmark. Whereas the VWF is marked as sustainable when flowing from the places where the water consumption did not exceed local sustainable renewable water availability. However, most attention has been taken to the sustainability of VWFs, ignoring their efficiency and spatial-temporal variations. Here we, taking inter-provincial crop-related VWFs of twenty major crops in the mainland China over 2004–2013 as a study case, analysing the efficiency of VWFs and the sustainability of blue VWFs, as well as their mutual relationship. Results show that over the study period, although inter-provincial crop-related VWFs increased slightly by 2%, the North to South VWFs and blue VWFs increased by 41% and 2.5 times, respectively. The weight of inefficient inter-provincial VWFs reduced to 75% in 2013 from 94% in 2004, whereas the unsustainable blue VWFs increased by 8%. Trade-offs between the efficiency and sustainability of VWFs existed in five provinces. Wheat, rice, maize, and cotton were the main contributors to inefficient and unsustainable VWFs. Assessments in VWFs should account for local water resources conditions, considering both efficiency and sustainability to determine hotspots and critical products and allow appropriate management of crop production and water allocation.

Economic feasibility of conversion to mobile drip irrigation in the Central Ogallala region

As groundwater levels continue to decline in the Ogallala Aquifer, stakeholders, policymakers, and producers encourage the adoption of new irrigation technology in an effort to conserve groundwater, extend the economic life of the aquifer, and enhance profitability. One such technology currently receiving attention in the Central Ogallala region is the mobile drip irrigation (MDI) application system. This study compares MDI to low elevation spray application irrigation by evaluating the changes in variable cost per hectare to calculate the payback period for a MDI system under three levels of investment cost for grain and fiber crops representing three levels of water use while holding yield constant. Using a 3% discount rate, under the medium level of investment cost ($371 per hectare), a discounted payback period of 4.9, 9.0, and 6.3 years is required for corn, cotton, and sorghum/wheat, respectively. As the cost per hectare to convert an existing center pivot drops to $185 per hectare, the payback period also drops to 2.3, 4.2, and 3.0 years, respectively. Thus, producers growing higher water use crops are able to recover the costs of the conversion to MDI through increased water use efficiency quicker than producers growing medium and lower water use crops.

Effects of optimal nitrogen fertilizer management on water and fertilizer utilization efficiency and yield under double-ridge-furrow sowing with the whole plastic film mulching in maize in a semi-arid area

Improper fertilization style is one of the main reasons for low water and fertilizer use efficiency of double-ridge-furrow sowing with the whole plastic film mulching in maize production in the semi-arid area. Understanding the effects of reduction, postponing, and organic fertilizer substitution of nitrogen fertilizer on water and fertilizer use efficiency and yield of maize can provide theore-tical basis for effective management of water and fertilizer in maize production. Based on a 4-year field experiment with three treatments: all fertilizers as base fertilizer under double-ridge-furrow sowing with the whole plastic film mulching (CK), nitrogen fertilizer reduced by 15% and topdres-sing in tasseling stage (RN), 30% of the chemical fertilizer replaced by organic fertilizer and topdressing in tasseling stage (RNM), we measured water consumption characteristics, growth and development, water and fertilizer utilization efficiency of maize. The results showed that fertilization pattern significantly affected water and fertilizer utilization efficiency and yield of maize, which was dependent on annual rainfall. In dry and normal rainfall year, water consumption in pre-flowering stage of RN was decreased by 16.1%-18.8% and that in post-flowering stage was increased by 18.0%-22.2%, while water consumption in pre-flowering and post-flowering stages of RNM did not differ from that in CK. In wet year, water consumption in pre-flowering stage of RN and RNM was decreased by 16.7% and 6.3%, while that in post-flowering stage was increased by 11.4% and 29.7%, respectively. Compared with CK, RN significantly increased the relative content of chlorophyll (SPAD) of maize leaves after topdressing, the biomass in post-flowering stage was increased by 15.6%-44.9%, the ear length, the number and weight of grains per spike and the 100-grain weight were increased significantly, yield was increased by 9.8%-17.0%, and water use efficiency (WUE) was increased by 6.3%-21.4%, with the partial productivities of fertilizer (PEPT), N (PEPTN), P (PEPTP) and K (PEPTK) were all increased significantly. In conclusion, RN could improve water consumption and the SPAD value in post-flowering stage of maize in different precipitation years, increase post-flowering biomass, and optimize the ear character, obviously improve yield, water and fertilizer use efficiency. It was a effective fertilizer management mode with high-efficiency utilization of water and fertilizer under double-ridge-furrow sowing with the whole plastic film mulching in maize in the semi-arid area.

Leaf Gas Exchange Performance of Ten Quinoa Genotypes under a Simulated Heat Wave.

Quinoa (Chenopodium quinoa Willd.) is a highly nutritious crop that is resilient to a wide range of abiotic stresses; however, sensitivity to high temperatures is regarded as an impediment to adoption in regions prone to heat waves. Heat stress is usually associated with a decrease in crop reproductive capacity (e.g., pollen viability), yet little is known about how leaf physiological performance of quinoa is affected by high temperatures. Several trials were conducted to understand the effect of high temperatures, without confounding stressors such as drought, on ten selected quinoa genotypes considered to encompass heat sensitive and heat tolerant plant material. Plants were grown under favorable temperatures and exposed to two temperature treatments over four consecutive days. The heat treatment simulated heat waves with maximum and minimum temperatures higher during the day and night, while the control treatment was maintained under favorable temperatures (maximum and minimum temperatures for ‘Heat’: 45/30 °C and ‘Control’: 20/14 °C). Leaf gas exchange (day), chlorophyll fluorescence (predawn and day) and dark respiration (night) were measured. Results show that most quinoa genotypes under the heat treatment increased their photosynthetic rates and stomatal conductance, resulting in a lower intrinsic water use efficiency. This was partly corroborated by an increase in the maximum quantum yield of photosystem II (Fv/Fm). Dark respiration decreased under the heat treatment in most genotypes, and temperature treatment did not affect aboveground biomass by harvest (shoot and seeds). These results suggest that heat stress alone favors increases in leaf carbon assimilation capacity although the tradeoff is higher plant water demand, which may lead to plant water stress and lower yields under non-irrigated field conditions.

Performance Evaluation of Sanko Small Scale Irrigation Scheme at Basketo Special Woreda in SNNPR, Ethiopia

This study conducted to evaluate the performance of Sanko small-scale irrigation scheme at Basketo Special Woreda, South Nation Nationalities Peoples Regional states. The irrigation scheme includes command area of 120 ha and 600 beneficiaries. The scheme was evaluated using internal and productivity performance indicators. From the analyses of the internal performance indicators, the conveyance efficiency of the main canal was found to be 69.3% and application efficiencies at head (61.6%), middle (63.4%) and tail (46.5%) with average application efficiency of 57.2%. A light soil with high infiltration rates favors deep percolation losses at the top of the fields, resulting in low field application efficiency in tail end part of the scheme. A deep percolation ratio and storage efficiency of the scheme was found to be 42.8% and of 78.5% respectively. Generally overall scheme efficiency of scheme was 39.6%. From the evaluation of productivity indicators, the outputs per cropped area found as at head (84,706 Birr ha-1), middle (220,690 Birr ha-1) and tail (69,686.4 Birr ha-1) and the value of the outputs per command area of scheme was 15,003,276 Birr per command area. The output per unit irrigation supply of irrigation scheme was at head (13.5 Birr m-3), middle (33.95 Birr m-3) and tail (22.12 Birr m-3). Relative water supply and relative irrigation supply; found to be 1.28, which was the same for both since there was no rainfall during study period. From the analysis result, there was lower water use efficiency (WUE) at upper head (23.37 ton/m3) as compared to middle (48.78 ton/m3) and tail (60.22 (ton/ m3) part of the scheme in relation to yield obtained. Based on the evaluation result, highest yield was obtained from at middle part of irrigation scheme and lower yield was obtained from both upper and tail end part of the scheme. The yield reduction in upper and tail part of the scheme was due to over and under irrigation. However, there is still a room for improvement at all system levels. Therefore to reduce over and under irrigate; farmers should get awareness how to use, when to use and how much water used on their fields.

A multilevel analysis of the drivers of household water consumption in a semi-arid region

Communities across the Western United States face the growing challenge of managing water resources in the face of rapid population growth and climate change. There are two contrasting approaches to understanding and managing residential water demand in this context. Many scientists and water managers see water use as a reflection of individual attitudes and decisions where people are assumed to have the agency to act independently of structural constraints. Conversely, other scientists and policymakers focus on the importance of the built environment and the broader social, economic, and policy contexts within which households make water decisions. Using multilevel models, we compared attitudinal, demographic, and structural drivers of indoor and outdoor residential water use for a sample of households in Northern Utah. We estimated multilevel mixed-effect Poisson models with robust standard errors using matched household survey data with metered residential water use records. Outdoor water use had a substantially greater amount of neighborhood-level variation than indoor water use. Structural factors generally eclipsed individual agency in our analysis. While indoor use was most strongly predicted by household size, tenure status, and length of residence, outdoor water use was most associated with the built environment (lot size and the presence of vegetable gardens and underground sprinklers), socioeconomic status (household income, rental status), and residents' sensitivity to lawn watering norms. Higher water prices were associated with lower water use, with lower-income households being more responsive to prices than higher-income households. Our findings have important implications for water managers and policymakers.

A putative tomato inositol polyphosphate 5-phosphatase, Le5PT1, is involved in plant growth and abiotic stress responses.

Based on sequence similarity to Arabidopsis inositol polyphosphate 5-phosphatases (5PTases) involved in abiotic stress responses and development, four tomato cDNAs (Le5PT1-4) encoding putative 5PTase proteins were identified. The predicted protein sequences of the Le5PTs include conserved catalytic domains required for 5PTase enzyme activity. Le5PT1, 2, and 3 showed high amino acid sequence identity with At5PTase2, At5PTase1 and At5PTase3, and At5PTase5 and At5PTase6, respectively. The expression of Le5PT1 was downregulated soon after initiation of dehydration and salt stress as well as exposure to polyethylene glycol (PEG) and NaCl, but not by exogenous ABA treatment. On the other hand, the expression of Le5PT2 gradually increased with time in all treatments. Transgenic tobacco plants overexpressing Le5PT1 exhibited reduced growth in height, leaf area, and dry weight compared to wild type plants. Transgenic plants also had lower water use efficiency (WUE) than wild type and the downregulation of the drought-responsive gene, NtERD10B. Together these results suggest that Le5PT1 may have a negative role in response to water deficit through the repression of drought-inducible genes that in turn affects plant growth and development.

Efficacy of drip irrigation on Melia composita Willd. (Malabar Neem)

Irrigation water requirements and irrigation schedules are available for most of the crops grown in different agro climatic regions of the country; however, there is negligible literature on irrigation and water management aspects on forest tree species. Therefore, an experiment was conducted to study the effects of irrigation scheduling and irrigation methods on Melia composita grown in the farm of College of Agricultural Engineering and Technology, Dediapada during year 2017–18. Irrigation schedules of drip irrigation were based on IW/CPE ratio of 0.6, 0.8, 1.0 and 1.2 in the present study. The depth of water applied for the first year was 832 mm, 1109 mm, 1389 mm and 1665 mm barring the rainfall depth and the total time of irrigation was 83, 111, 138 and 169 hours for IW/CPE ratio of 0.6, 0.8, 1.0 and 1.2 IW/CPE, respectively. The tree height and collar diameter of 4.81 m and 8.27 cm, respectively were found to be statistically significant in IW/CPE = 1.2 while the highest specific leaf weight of 0.34 g/cm2 was found in treatment IW/CPE = 0.6 which was significantly higher than all the other treatments. When the data was extrapolated for 4 years, it was found that the highest and lowest water use efficiency would be 16.32 kg/ha-mm and 14.16 kg/ha-mm under T4 (IW/CPE = 1.2) and T1 (IW/CPE = 0.6) treatments after 4 years while the highest biomass of 154 tonne/ha would be obtained in IW/CPE = 1.20 and the lowest biomass of 99 tonne/ha would be obtained in IW/CPE = 0.6 after 4 years. The highest benefit cost ratio of 9.6 would be obtained in IW/CPE = 1.20 and the lowest benefit cost ratio of 6.7 would be obtained in IW/CPE = 0.6 after 4 years.

Mediterranean Diet and Its Environmental Footprints Amid Nutrition Transition: The Case of Lebanon

Many Mediterranean countries, including Lebanon, are experiencing a shift in food consumption away from the traditional Mediterranean diet (MD), concomitant with the escalating burden of non-communicable diseases and dwindling environmental resources. Objective: to examine the adherence to the MD and its association with environmental footprints (EFPs), including water use, energy use, and greenhouse gas (GHG) emissions, among Lebanese adults. Data of Lebanese adults were drawn from the national food consumption survey (n = 2610). Assessment of dietary intake was conducted using a food-frequency questionnaire. Adherence to the MD was examined using four published MD scores. Metrics for the EFPs were calculated using a review of existing life cycle assessments (LCAs). For all MD scores, less than 13% of participants were in the highest tertile. After adjustments for covariates, two of the MD scores were associated with lower water use. For GHG, significant inverse associations were observed with all MD scores. Energy use was not associated with MD scores. Overall, low adherence to the MD among Lebanese adults was observed, together with an inverse association between adherence to the MD and water use and GHG emissions. These findings support and enforce ongoing efforts that aim to increase adherence to the MD in order to address health issues, as well as tackle environmental sustainability.

Climate-Water Adaptation for Future US Electricity Infrastructure.

Future climate-water conditions are anticipated to increase electricity demand, reduce transmission capacity, and limit power production. Yet, typical electricity capacity expansion planning does not consider climate-water constraints. We project four alternative U.S. power system configurations using an iterative modeling and data exchange platform that integrates climate-driven hydrological, thermal power plant, and capacity expansion models. Through a comparison with traditional modeling approaches, we show that this novel approach provides greater confidence in electricity capacity projections by incorporating feasibility checks that adjust infrastructure development to reach grid reliability thresholds under climate-water constraints. Initial projections without climate-water impacts on electricity generation show future power systems become less vulnerable, independent of climate-water adaptation, as economic drivers increase renewable and natural gas-based capacity, while water-intensive coal and nuclear plants retire. However, power systems may face reliability challenges without climate-water adaptation, revealing the significance of incorporating climate-water impacts into power system planning. Climate-adjusted (Iterative approach) projections require a 5.3-12.0% increase in national-level capacity, relative to Initial projections, leading to an additional $125-143 billion (5.0-7.0%) in infrastructure costs. Variable renewable and natural gas technologies account for nearly all the additional capacity and, together with regional trade-offs in electricity generation, enhance grid performance to reach reliability thresholds. These adaptation transitions also lower water use and emissions, contributing to climate change mitigation, and highlight the trade-offs and impacts of both near and long-term electricity generation planning decisions.

Characterization of small-scale dairy farms and its relation to water use efficiency in the Mexicali Valley, Mexico.

A survey was completed to determine water use by small-scale dairy farms in Mexicali Valley of Mexico and to associate it with dairy production parameters. Mexicali Valley surrounds the capital city of the state Baja California, Mexicali. Sixty-one smallholders were interviewed in person in this rural area of northwestern Mexico. On average, small dairy holders had more than 20 years of experience and were ~ 55 years of age; people working on their farms are especially relatives. A low percentage was literate (20%), and they belong to a local dairy association. Milk yield/cow/year does not reach 4000 kg of milk and 75% of producers do not follow a defined management program for their cattle. Hand-milking is still practiced by 27% of the producers, and there is a general lack of infrastructure to maintain milk in a refrigerated state so that there is a very high risk of zoonotic diseases. Water use efficiency (WUE) was linearly correlated (P < 0.05) with total irrigated area, but not with animal production parameters. Regression equations constructed to explain WUE exhibited low adjustment, and WUE was not associated (P > 0.05) with milk yield. Small dairy producers in Mexicali Valley are in a generally poor situation with low water use practices; however, required more government support to increase their benefits from this livestock activity.

Short-duration mungbean (Vigna radiata (L.) R. Wilczek) genotypes differ in performance, water use and apparent water-use efficiency in southern Lao PDR

Improving nutrition-sensitive food security is important in low-income, food-deficit nations like Lao PDR, where subsistence farmers rely on a single rainfed lowland rice crop in the wet season. Access to resource conservation technologies, small on-farm water storages and electricity are starting to allow farmers to consider post-rice crops. With water availability still limited, short-duration pulse crops may be viable. This paper examined grain yield and water use during grain filling of eight short-duration mungbean genotypes after rainfed lowland rice at Champhone and Pakse in southern Lao PDR in the 2013 dry season. Two supplementary watering regimes were used, watered every 15 days (at 15, 30 and 45 days), and watered as needed at the first sign of visible wilting (at 23 and 45 days), with three replicates. Soil volumetric water content was measured by time-domain reflectometer. Over two drying cycles, VC1913A, VC3890A and VC7118A used significantly less water than other genotypes at both sites. Genotypes VC7118A and NM94 were higher yielding at Champhone, and VC6310 was higher yielding at Pakse. The relationship between grain yield and water use during grain filling was less straight forward, as it applied within apparent water-use efficiency categories. Overall, VC7118A was superior, due to its effective combination of higher apparent water-use efficiency during grain filling, lower water use in grain filling, and higher grain yield. NM94 also performed well, but required more water for similar yield performance. Drill sowing would allow timely establishment of the post-rice crop to utilize residual soil water in the dry season. These results suggest that mungbeans have a role as a post-rice crop with supplementary irrigation in Lao PDR and comparable environments, to improve nutrition-sensitive food security.

English

To evaluate the effect of water stress at different crop growth stages on yield, yield components and water use efficiency, a field experiment was carried out in 2015/2016, 2016/2017 and 2017/2018 for bread wheat (Gambo variety) at Werer Agricultural Research Center. The experiment was laid out in Randomized Complete Block Design (RCBD) with three replications having 15 experimental treatments. Combination of water stress with crop growth stages was applied in the major investigation of the experiment. The highest grain yield was obtained from the control treatment irrigation at all stages (no stress). Stressing irrigation water at initial stages and maturity stages gave second highest yield (29.23 and 28.57 qt/ha) and lower water use efficiency (0.43 and 0.35 kg/m3) respectively. While irrigating only at the initial stage gave highest water use efficiency (0.79 kg/m3) and lowest grain yield. Application of irrigation water at all stages except initial and maturity gives optimum grain yield (26.73 qt/ha) and water use efficiency (0.62 kg/m3) for the study area. Therefore, wheat should not be stressed at development and mid stage to obtain optimum water use efficiency (WUE) without a significant grain yield reduction. Key words: Grain yield, growth stages, water use efficiency, irrigation. &nbsp

Water-conserving and biomass-allocation traits are associated with higher yields in modern cultivars compared to landraces of soybean [Glycine max (L.) Merr.] in rainfed water-limited environments

Drought is one of the main factors restricting the productivity of soybean (Glycine max L.), especially in arid and semi-arid areas where the crop may suffer from frequent and severe drought events unless irrigated. The aim of the present study was to determine the plant responses to water deficits in four landraces and four modern soybean cultivars that differed in yield in rainfed water-limited environments to determine the characteristics associated with yield under drought in the field and under a rainout shelter. During a slow progressive soil drying cycle, the stomata began to close at higher soil water contents (SWC) of 65–67% vs 61–63%, photosynthesis began to decrease at higher SWC of 60–62% vs 52–54% and leaf hydraulic conductance fell by 20% at higher SWC of 50–67% vs 36–48%, while the leaf relative water content began to decrease at lower SWC of 30–35% vs 38–39% in modern cultivars than landraces, respectively, indicating that the modern cultivars exhibited greater isohydric behaviour than the landraces. Water use after flowering was lower in the modern cultivars, consistent with the conservative leaf physiology, but yield was not correlated or negatively correlated with water use so the higher yield and water use efficiency for grain in the modern cultivars was associated with lower water use and higher distribution of biomass to grain, i.e., a higher harvest index. We conclude that breeders of modern high-yielding cultivars of soybean for rainfed semiarid environments have selected for lower biomass and leaf area, larger grain size and higher harvest index, while also selecting for stronger isohydric behaviour and water-conserving traits.