Plant Water Demand Research Articles

Experimental and mathematical modeling of water regime and nitrate dynamics on zero tension plate lysimeters in soil influenced by high groundwater table

Unlike laboratory experiments, which are mostly performed under controlled conditions, lysimeter experiments generally simulate actual field conditions. This paper focuses on an efficiency of the zero tension plate lysimeters, which were implanted in silty-clay soils influenced by a high groundwater table. Measurements and following numerical simulations using the HYDRUS-2D model were performed separately for each of 4 years (2007–2010) to assess water flow and nitrate fluxes (applied as NPK or UREA fertilizer). Low efficiency of lysimeters during the vegetation period was mostly caused by high plant water demand and possible water diversion to the sides when the groundwater table was low. The HYDRUS-2D model was able in some degree to reproduce observed water and nitrate outflows. The water outflow through the lysimeter occurred when the groundwater table was high and greater rainfall events occurred. Water and solute diverged from the plate towards the dryer surrounding soil when groundwater table was low. Pressure head, water velocity and nitrate concentration distributions simulated around the lysimeter plate illustrated that the lysimeter plate had a significant impact on the water regime and nitrate behavior within the soil profile. The lysimeter plate also acted as a barrier for water flow and solute transport also.

Opencast mine restoration in a Mediterranean semi-arid environment: Failure of some common practices

Restoration works in opencast mining are mostly done with fast-growing herbaceous species to control the erosion of embankments during rainfall, especially immediately after their construction. Such species often exhibit a high demand for water and their survival is therefore associated to an adequate hydric supply. If this fails, these species can rapidly disappear when water is scarce. This paper shows the results of a restoration experiment where two stony mineral substrates were used in a quarry area (NE Spain). The experiment was carried out at lysimeter scale and the aim was to evaluate the short time vegetation response to common restoration practices in semiarid areas with two types of substrates and two types of irrigation practices. Lysimeter results were used to indirectly draw implications for the usual irrigation practices in the area.During periods of the first year after sowing, irrigated and non-irrigated lysimeters were monitored for substrate humidity, water leachates and plant development. The population cover of sown plants fluctuated according to the water availability in the substrate before drought. Density of total basal shoots decreased dramatically during the period of water stress, reaching negligible cover values on both types of substrates.Water content in the top substrate (0–20cm) was dramatically reduced in June, just after the maximum plant cover and water demand were reached (May).According with our results, it is not advisable to aim at a continuous and dense herbaceous cover composed of species that are not drought tolerant in restoration works, especially if embankments are constructed with spoil mine substrates. The restoration of opencast areas should include the use of water stress-resistant plants and careful irrigation plans.

Changes in the power spectrum of electrical signals in maize leaf induced by osmotic stress

To quantify the characteristics of the power spectrum of plant electrical signals, we defined the following concepts: spectral edge frequency (SEF), spectral center frequency (SCF), power index (PI) and power spectral entropy (PSE). These parameters were used to examine and quantify changes in the power spectrum of electrical signals in maize leaves under osmotic stress. In the absence of osmotic stress, the SEF of the electrical signal in maize leaves was approx. 0.2 Hz and the SCF was approx. 0.1 Hz. The electrical signal in maize leaves was mainly a slow wave signal with a frequency of 0–0.1 Hz. After 2 h osmotic stress, the SEF and SCF of the electrical signal increased to higher frequencies. The proportion of the fast wave frequency also increased to 0.1–0.2 Hz, resulting in a dramatic increase in PSE. We also found that the changes in PSE and SCF were significantly correlated during osmotic stress. We propose that the changes in the PSE and SCF in maize leaves can be used as a sensitive signal indicating water deficit in leaf cells under osmotic stress. Thus, measurement of SCF or PSE of electrical signals in maize leaves could be used to develop early warning and rapid diagnosis techniques for the water demands of plants.

Trends in water demand and water availability for power plants—scenario analyses for the German capital Berlin

The availability of electric power is an important prerequisite for the development or maintenance of high living standards. Global change, including socio-economic change and climate change, is a challenge for those who have to deal with the long-term management of thermoelectric power plants. Power plants have lifetimes of several decades. Their water demand changes with climate parameters in the short and medium term. In the long term, the water demand will change as old units are retired and new generating units are built. The present paper analyses the effects of global change and options for adapting to water shortages for power plants in the German capital Berlin in the short and long term. The interconnection between power plants, i.e. water demand, and water resources management, i.e. water availability, is described. Using different models, scenarios of socio-economic and climate change are analysed. One finding is that by changing the cooling system of power plants from a once-through system to a closed-circuit cooling system the vulnerability of power plants can be reduced considerably. Such modified cooling systems also are much more robust with respect to the effects of climate change and declining streamflows due to human activities in the basin under study. Notwithstanding the possible adaptations analysed for power plants in Berlin, increased economic costs are expected due to declining streamflows and higher water temperatures.

Changes in the potential distribution of humid tropical forests on a warmer planet

The future of tropical forests has become one of the iconic issues in climate-change science. A number of studies that have explored this subject have tended to focus on the output from one or a few climate models, which work at low spatial resolution, whereas society and conservation-relevant assessment of potential impacts requires a finer scale. This study focuses on the role of climate on the current and future distribution of humid tropical forests (HTFs). We first characterize their contemporary climatological niche using annual rainfall and maximum climatological water stress, which also adequately describe the current distribution of other biomes within the tropics. As a first-order approximation of the potential extent of HTFs in future climate regimes defined by global warming of 2°C and 4°C, we investigate changes in the niche through a combination of climate-change anomaly patterns and higher resolution (5 km) maps of current climatology. The climate anomalies are derived using data from 17 coupled Atmosphere-Ocean General Circulation Models (AOGCMs) used in the Fourth Assessment of the Intergovernmental Panel for Climate Change. Our results confirm some risk of forest retreat, especially in eastern Amazonia, Central America and parts of Africa, but also indicate a potential for expansion in other regions, for example around the Congo Basin. The finer spatial scale enabled the depiction of potential resilient and vulnerable zones with practically useful detail. We further refine these estimates by considering the impact of new environmental regimes on plant water demand using the UK Met Office land-surface scheme (of the HadCM3 AOGCM). The CO(2)-related reduction in plant water demand lowers the risk of die-back and can lead to possible niche expansion in many regions. The analysis presented here focuses primarily on hydrological determinants of HTF extent. We conclude by discussing the role of other factors, notably the physiological effects of higher temperature.

Tendências recentes nos elementos do clima e suas implicações na evapotranspiração da cultura do milho em Viçosa - MG

A mudança nas condições climáticas tem gerado grandes preocupações em nível mundial, sendo que uma das grandes questões, neste contexto, é o aquecimento global. As alterações ocorridas nas condições climáticas podem afetar a demanda de água das plantas, porque a evapotranspiração é afetada por mudanças nos elementos climáticos. O objetivo deste trabalho foi analisar os efeitos das possíveis mudanças dos elementos do clima na evapotranspiração de referência e na evapotranspiração da cultura do milho para a região de Viçosa - MG. Mediante análise de tendência pelo teste de Mann-Kendall e da estatística do teste t da regressão linear, verificou-se o comportamento dos seguintes elementos climáticos: temperaturas máxima e mínima, insolação, velocidade do vento e umidade relativa. Observou-se uma redução na evapotranspiração de referência e da cultura do milho ao longo dos últimos 41 anos, principalmente em razão da redução da insolação e da velocidade do vento. A evapotranspiração de referência apresentou redução da ordem de 4,2 mm por ano.

Effects of temperature changes on maize production in Mozambique

We examined intraseasonal changes in maize phenology and heat stress exposure over the 1979-2008 period, using Mozambique meteorological station data and maize growth require- ments in a growing degree-day model. Identifying historical effects of warming on maize growth is particularly important in Mozambique because national food security is highly dependent on domes- tic food production, most of which is grown in already warm to hot environments. Warming temper- atures speed plant development, shortening the length of growth periods necessary for optimum plant and grain size. This faster phenological development also alters the timing of maximum plant water demand. In hot growing environments, temperature increases during maize pollination threaten to make midseason crop failure the norm. In addition to creating a harsher thermal environ- ment, we find that early season temperature increases have caused the maize reproductive period to start earlier, increasing the risk of heat and water stress. Declines in time to maize maturation suggest that, independent of effects to water availability, yield potential is becoming increasingly limited by warming itself. Regional variations in effects are a function of the timing and magnitude of tempera- ture increases and growing season characteristics. Continuation of current climatic trends could induce substantial yield losses in some locations. Farmers could avoid some losses through simple changes to planting dates and maize varietal types.

Evaluation of a Capillary-Irrigation System for Better Yield and Quality of Hot Pepper (Capsicum annuum)

A capillary-irrigation system using porous membrane with different negative pressures was successfully developed and tested by growing jalapeno hot peppers. The water drawn into the root zone from this irrigation system was controlled exclusively by the plant water demand. In order to find a moderately negative pressure that is suitable for jalapeno peppers, three different negative pressure irrigations namely -0.2, -0.4, and -0.6 m were tested and compared against a conventional manual irrigation. There was no significant difference in number of leaves, plant height, and leaf area between -0.2 m negative pressure and the manual irrigation treatment, but they were significantly lower in the -0.4 m and -0.6 m treatments. A similar trend was also observed for pepper biomass yield. Moreover, pepper fruits were qualitatively analyzed for their hotness or pungency level using high-performance liquid chromatography (HPLC). The results showed that the hotness of fruits in water-starved plants were greater than in the plants receiving sufficient water. A 35% reduction in water consumption was observed in the -0.2 m treatment compared to manual irrigation. Overall, the -0.2 m capillary-irrigation had better performance in terms of growth and yield parameters when compared to manual irrigation while saving a substantial amount of water. The capillary-irrigation technique offers a precise water delivery with minimal labor requirement which is suitable for use in greenhouse pepper production and in areas with limited water supply and scarce labor.

Water uptake and nutrient concentrations under a floodplain oak savanna during a non‐flood period, lower Cedar River, Iowa

AbstractFloodplains during non‐flood periods are less well documented than when flooding occurs, but non‐flood periods offer opportunities to investigate vegetation controls on water and nutrient cycling. In this study, we characterized water uptake and nutrient concentration patterns from 2005 to 2007 under an oak savanna located on the floodplain of the Cedar River in Muscatine County, Iowa. The water table ranged from 0·5 to 2·5 m below ground surface and fluctuated in response to stream stage, plant water demand and rainfall inputs. Applying the White method to diurnal water table fluctuations, daily ET from groundwater averaged more than 3·5 mm/day in June and July and approximately 2 mm/day in May and August. Total annual ET averaged 404 mm for a growing season from mid‐May to mid‐October. Savanna groundwater concentrations of nitrate‐N, ammonium‐N, and phosphate‐P were very low (mean <0·18, <0·14, <0·08 mg/l, respectively), whereas DOC concentrations were high (7·1 mg/l). Low concentrations of N and P were in contrast to high nutrient concentrations in the nearby Cedar River, where N and P averaged 7·5 mg/l and 0·13, respectively. In regions dominated by intensive agriculture, study results document valuable ecosystem services for native floodplain ecosystems in reducing watershed‐scale nutrient losses and providing an oasis for biological complexity. Improved understanding of the environmental conditions of regionally significant habitats, including major controls on water table elevations and water quality, offers promise for better management aimed at preserving the ecology of these important habitats. Copyright © 2009 John Wiley & Sons, Ltd.

Dynamic modelling of water demand, water availability and adaptation strategies for power plants to global change

According to the latest IPCC reports, the frequency of hot and dry periods will increase in many regions of the world in the future. For power plant operators, the increasing possibility of water shortages is an important challenge that they have to face. Shortages of electricity due to water shortages could have an influence on industries as well as on private households. Climate change impact analyses must analyse the climate effects on power plants and possible adaptation strategies for the power generation sector. Power plants have lifetimes of several decades. Their water demand changes with climate parameters in the short- and medium-term. In the long-term, the water demand will change as old units are phased out and new generating units appear in their place. In this paper, we describe the integration of functions for the calculation of the water demand of power plants into a water resources management model. Also included are both short-term reactive and long-term planned adaptation. This integration allows us to simulate the interconnection between the water demand of power plants and water resources management, i.e. water availability. Economic evaluation functions for water shortages are also integrated into the water resources management model. This coupled model enables us to analyse scenarios of socio-economic and climate change, as well as the effects of water management actions.

Drought deaths in Eucalyptus globulus (Labill.) plantations in relation to soils, geomorphology and climate

The occurrence of tree deaths in young, 3 to 6 year old Eucalyptus globulus plantations established on farmland in south-western Australia was found to be strongly related to factors indicative of poor soil water storage capacity. Seven years after planting tree survival was significantly less on soils 2 m deep (22% vs 70%). This is due to the limited ability of some soils to store a sufficient proportion of the annual rainfall within the root-zone to meet the plant water demand in a region with a recurrent annual summer drought. There are practical difficulties in routinely surveying soils to depths in excess of 2 m over broad areas, to predict the likelihood of tree death. On the granitic basement rocks of south-west Western Australia, the occurrence of ferricrete gravels provides a useful surrogate indicator for the presence of deeper soils. In this region the distribution of soil depth and soil fertility has a geomorphic basis, being related to previous patterns of deep weathering and regolith stripping. Soils have developed on various horizons of deeply weathered profiles, formed from granites and gneisses. These materials have been stripped to a variable extent by erosion, leading to a range of soil depths. The original weathered profiles, which correspond to the soils with ferricrete gravels, comprise the deepest soil/regolith materials (~30-50 m deep); whereas along drainage lines the regolith has been completely stripped, the soils are shallow and plantations are most susceptible to drought. Knowledge of the relationship between soil depth and plantation performance allows regional indications of drought risk to be developed from regional soil mapping and the production of more efficient sampling designs for site assessment.

Wireless Mesh Network for Irrigation Control and Sensing

Variations in plant water and nutrient demand and environmental regulations to protect water quality provide significant justification for site-specific irrigation and fertigation systems. We have developed wireless valve controllers that self-assemble into a mesh network. Mesh networking means that controllers pass messages to extend the effective communication range without using high-power radios. Solar energy is collected with a 200 mW panel to operate each controller node without yearly battery replacement. Nine nodes were tested in a mesh network, and each properly responded to commands. Measurements of battery voltage, solar panel voltage, enclosure temperature, and external sensors were transmitted every 10 min. Irrigation schedules were stored locally on each node and executed automatically. Schedules for each node were unique, based on the needs of the particular area being irrigated. Internal clock drift was an average 6.3 s per day. Clock offset was removed using daily time stamps. One-hop transmission range using 916 MHz radios varied from 20.9 m with a whip antenna at ground level to 241.1 m with a dipole antenna at 3 m. Node commands were acknowledged after an average of 2.7 s per hop. Charge consumption was approximately 7.03 mAh per day for the node circuit and 1 mAh per day for battery self-discharge. The solar panel produced 26.0 to 81.3 mAh in direct sunlight and 6.5 to 13.7 mAh in shade. Node operation is expected to be continuous with occasional sunlight exposure. Soil moisture, pressure, temperature, and other environmental sensors will be used for feedback control and detection of problems. Such a network of intelligent valve controllers will allow growers in orchards, vineyards, nurseries, greenhouses, and landscapes to develop management practices that improve water- and fertilizer-use efficiency.

Water table fluctuations under three riparian land covers, Iowa (USA)

AbstractWater table depth is known to play an important role in nitrogen cycling in riparian zones, but little detailed monitoring of water table fluctuations has been reported. In this study, results of high‐resolution water table monitoring under three common riparian land covers (forest, cool season grass, corn) were analysed to gain a better understanding of the relation of vegetation cover to water table depth. Three riparian wells located at the Neal Smith National Wildlife Refuge in Jasper County, Iowa, were instrumented with data loggers to record hourly water table behaviour from July to December 2004. Water table depth under the forest showed a diurnal pattern of rising and falling water levels, whereas the grass and corn exhibited a stepped pattern of greater drawdown during the day and less drainage at night. Clear daytime and night‐time water table signals were related to daily plant water demands and lateral groundwater flow. Using two estimates of specific yield, hourly and daily ET rates were estimated to be higher under the forest cover than the grass and corn, with peak ET rates in July ranging from 5·02 to 6·32 mm day−1 for forest and from 1·81 to 4·13 mm day−1 for corn and grass. Following plant senescence in October, water table declines were associated with lateral flow to Walnut Creek. The results from this study suggest that consideration should be given to monitoring water table behaviour more frequently to capture daily and seasonal patterns related to riparian vegetation type. Copyright © 2007 John Wiley & Sons, Ltd.

Seven years of enhanced water availability influences the physiological, structural, and functional attributes of a soil microbial community

Water availability is known to influence many aspects of microbial growth and physiology, but less is known about how complex soil microbial communities respond to changing water status. To understand how long-term enhancement of soil water availability (without flooding) influences microbial communities, we measured the seasonal dynamics of several community-level traits following >7 years of irrigation in a drought-prone tallgrass prairie soil. From late May to mid-September, water was supplied to the irrigated treatments based on calculated plant water demand. Phospholipid fatty acids (PLFA) were used to assess changes in microbial community structure and physiology. To assess the community-level physiological profile, microbial utilization of BIOLOG substrates was determined. After incubation for 2 days, the distribution of added 13C-glucose in microbial and respired pools was used as an index of substrate utilization efficiency. We also measured the relative contribution of fungi and bacteria to soil microbial biomass via substrate-induced respiration (SIR). Multivariate analysis of mol% PLFA and BIOLOG substrate utilization indicated that both water availability and sampling time influenced both the physiological and structural characteristics of the soil microbial community. Specific change in biomarker PLFA revealed a decreased ratio of cyclopropyl to ω7-precursors due to water addition, suggesting community-level stresses were reduced. Over the growing season, continuously greater water availability resulted in a 53% greater ratio of fungal to bacterial biomass using SIR, and a 65% increase in fungal PLFA. The number of substrates utilized by the cultivable microbial community tended to be greater in continuously wetted soil, especially during periods of low rainfall. While water dynamics appeared to be associated with some of the shifts in microbial community activity, structural and functional changes in the community appeared to be more closely linked to the cumulative effects of water regime on ecosystem properties. Seasonality strongly influenced microbial communities. The environmental factors associated with seasonal change need to be more closely probed to better understand the drivers of community structure and function.

Hydrologic processes at the urban residential scale

AbstractIn the face of increasing urbanization, there is growing interest in application of microscale hydrologic solutions to minimize storm runoff and conserve water at the source. In this study, a physically based numerical model was developed to understand hydrologic processes better at the urban residential scale and the interaction of these processes among different best management practices (BMPs). This model simulates hydrologic processes using an hourly interval for over a full year or for specific storm events. The model was applied to treatment and control single‐family residential parcels in Los Angeles, California. Data collected from the control and treatment sites over 2 years were used to calibrate and validate the model. Annual storm runoff to the street was eliminated by 97% with installation of rain gutters, a driveway interceptor, and lawn retention basin. Evaluated individually, the driveway interceptor was the most effective BMP for storm runoff reduction (65%), followed by the rain gutter installation (28%), and lawn converted to retention basin (12%). An 11 m3 cistern did not substantially reduce runoff, but provided 9% of annual landscape irrigation demand. Simulated landscape irrigation water use was reduced 53% by increasing irrigation system efficiency, and adjusting application rates monthly based on plant water demand. The model showed that infiltration and surface runoff processes were particularly sensitive to the soil's physical properties and its effective depth. Replacing the existing loam soil with clay soil increased annual runoff discharge to the street by 63% when climate and landscape features remained unchanged. Copyright © 2006 John Wiley & Sons, Ltd.

Analysing industrial water demand in India: An input distance function approach

This study investigates the water demand of Indian manufacturing plants. It adopts an input distance function approach and approximates it by a translog form. Duality between cost function and input distance function is exploited to retrieve information concerning substitutability and the shadow price of water. The model is estimated using a linear programming approach on a sample of 92 firms over three years. The results show that the average shadow price of water is 7.21 Rupees per kilolitre (Rupees/kl) and the price elasticity of derived demand for water is high, −1.11 on average, a value similar to that found by other researchers working in developing countries (for example, China and Brazil). This indicates that water charges may be an effective instrument for water conservation.

Effect of calcium silicate on growth and dry matter yield of Chloris gayana and Sorghum sudanense under two soil water regimes

AbstractThe effects of five rates [0 (control), 1, 2, 4 and 6 Mg ha−1] of calcium silicate on the growth and water consumption by rhodes grass (Chloris gayana Kunth) and sudan grass (Sorghum sudanense Piper) under wet and dry soil water regimes (60 g and 30 g H2O kg−1 soil respectively) were evaluated in a pot experiment. The effect of the application of silicate on plant biomass was similar to that of the control. However, the shoot and root dry mass varied significantly (P < 0.001) according to the soil water regime and plant species. During the first cut, the shoot dry mass was 5.7 g per pot under the wet soil moisture regime, significantly exceeding that under the dry soil water regime proportionately by 0.68. For sudan grass, the shoot dry mass varied from 3.6 g per pot in the control to 4.3 g per pot in the treatment that received 6 Mg ha−1 of calcium silicate. Plant water demand decreased as the rate of calcium silicate application increased, suggesting that an application of calcium silicate could reduce drought stress and enhance water economy. For the soil under study, the reduction in plant water demand represents a water saving ranging from 0.076 to nearly 0.20.

Wood anatomical variation of Neobuxbaumia tetetzo: A columnar Cactaceae

Anatomical variation in radial and longitudinal wood in Neobuxbaumia tetetzo was studied in four monopodic individuals. Vascular bundles in the radial direction from the pith to the vascular cambium and in the longitudinal direction from the base to the stem apex were analysed. Except for vessel density in the radial direction, the anatomical characters studied showed a pattern of cambial maturation similar to those reported for other angiosperms. The patterns of fiber anatomical variation show higher mechanical strength in the lower part of the stem, while the increase in vessel diameter towards the vascular cambium produces a positive relationship between plant water demands and larger size.

The effect of water management based on soil redox potential on methane emission from two kinds of paddy soils in Japan

Abstract Paddy fields are major sources of the global methane (CH4) emission. Water management of paddy fields affects rice yield and CH4 emission. There is need for improvement in the management to achieve a balance between them. We suggest the water management based on soil redox potential (Eh), which was named Eh control. The effects of Eh control on rice yield and CH4 emission, and applicability to field conditions were considered by pot experiments. This study was carried out at a plastic film house in the Agricultural and Forestry Research Center, University of Tsukuba, Japan, in 2002. The effects of Eh control (EH) were compared with conventional management methods (continuous flooding [CF], midseason drainage [MD], and MD plus intermittent irrigation [IM]) for two kinds of soils. The drainage for Eh control, aim of which was not to reach −200 mV, was carried out when the soil Eh decreased to −150 mV. Then one or two days later, the soil was reflooded. The CH4 emissions of MD, IM, and EH were 64, 26, and 17% of CF, respectively. However, the order of brown rice yield was as follows: IM > MD > CF > EH. With the drainage for Eh control, soil Eh increased to higher than 400 mV several times, and this condition was maintained for up to one day. This excessive drying of the soil affected rice growth and yield of EH. To apply Eh control to field conditions, the upper limit of soil Eh must be controlled to avoid the excessive drying. Moreover, water demand of rice plants is necessary to be considered.

Analyzing Industrial Water Demand in India: An Input Distance Function Approach

This study investigates the water demand of Indian manufacturing plants. It adopts an input distance function approach and approximates it by a translog form. Duality between cost function and input distance function is exploited to retrieve information concerning substitutability and the shadow price of water. The model is estimated, using linear programming approach, on a sample of 92 firms over the three years. The results show that the average shadow price of water is rupees 7.21 per kilolitre and the price elasticity of derived demand for water is high, -1.11 on average, a value similar to what has been found by other researchers working on developing countries (for example, China and Brazil). This indicates that water charges may be an effective instrument for water conservation.