Moisture Potential Research Articles

Minimize water deficit in wheat crop to ameliorate groundwater decline in rice-wheat cropping system

There is a notion that more withdrawal of groundwater for irrigating the rice crop in rice-wheat cropping system is responsible for water table decline in central Punjab of India. Any reduction in irrigation water by the improved irrigation schedules in rice like alternate wetting and drying, and based on soil moisture potential; shifting planting date, crop diversification of higher irrigation requirement to lower, direct seeded rice, laser levelling etc.; and appropriate tillage system to reduce percolation losses save water and increase water productivity. However, the present study showed that water deficit [evapotranspiration – (rainfall + surface water)] can approximate the water table decline/rise rather than groundwater withdrawal alone. In rice-wheat system though irrigation water requirement of wheat crop is less (300–400 mm) than rice (1500–2000 mm) yet the water deficit, responsible for water table decline, is more in wheat crop than rice. In rice transplanted at recommended time, evapotranspiration (ET) is almost equal to the rainfall, while in wheat ET is 3.9 times that of rainfall. It warrants the ET reduction in wheat, overlooked so far, for supplementary amelioration of water table decline in rice-wheat cropping system. Reduction in ET and saving of energy by different technologies in wheat crop has also been discussed.

Effects of differential hillslope‐scale water retention characteristics on rainfall–runoff response at the Landscape Evolution Observatory

AbstractHillslopes turn precipitation into runoff and thus exert important controls on various Earth system processes. It remains difficult to collect reliable data necessary for understanding and modeling these Earth system processes in real catchments. To overcome this problem, controlled experiments are being conducted at the Landscape Evolution Observatory at Biosphere 2, The University of Arizona. Previous experiments have revealed differences in hydrological response between 2 landscapes within Landscape Evolution Observatory, even though both landscapes were designed to be identical. In an attempt to discover where the observed differences stem from, we use a fully 3‐dimensional hydrological model (CATchment HYdrology) to show the effect of soil water retention characteristics and saturated hydraulic conductivity on the hydrological response of these 2 hillslopes. We also show that soil water retention characteristics can be derived at hillslope scale from experimental observations of soil moisture and matric potential. It is found that differences in soil packing between the 2 landscapes may be responsible for the observed differences in hydrological response. This modeling study also suggests that soil water retention characteristics and saturated hydraulic conductivity have a profound effect on rainfall–runoff processes at hillslope scale and that parametrization of a single hillslope may be a promising step in modeling rainfall–runoff response in real catchments.

LEAF WATER POTENTIAL OF THE PURPLE ELEPHANT GRASS, PENNISETUM PURPUREUM SCHUMACH. (POACEAE) AND IT�S RELATIONSHIP WITH SOIL MOISTURE

Objectives: To investigate how the time of day affects the water potential values of the purple elephant grass (Pennisetum purpureum) in areas with and without irrigation during the dry season and the relation with soil moisture, in order to establish a good performance of the crop. Method: Water potential was measured with the Scholander pressure chamber and humidity was measured with a Moisture Soil Kit. Four demonstration plots of 3 m × 3 m (three with irrigation and one without irrigation) were select and the determination was made at: 08:00, 13:00 and 17:00, for 10 weeks two days a week. Findings: The crop under irrigation maintained values of water potential between 0.02 to 0.05 MPa, and crop without irrigation between 0.02 and 0.25 MPa. Additionally, a higher yield was obtained for the irrigated crop of 22 t/ha/year in dry matter. The purple elephant grass maintains a good yield with humidity between 20% and 30% and water potential between 0.03 and 0.05 MPa. Novelty /Improvement: Obtaining the equation (Y = 0.493 * X- 0.775) that relates soil moisture and leaf water potential of purple elephant grass Pennisetum purpureum Schumach. (Poaceae), which can be used to find the water potential (Y) in a soil with a sandy clay loam texture. Keywords: Availability of Water in the Plant, Pennisetum purpureum, Performance, Soil Moisture, Time, Water Potential

Estimation of bare soil evaporation for different depths of water table in the wind-blown sand area of the Ordos Basin, China

Soil surface evaporation is a significant component of the hydrological cycle, occurring at the interface between the atmosphere and vadose zone, but it is affected by factors such as groundwater level, soil properties, solar radiation and others. In order to understand the soil evaporation characteristics in arid regions, a field experiment was conducted in the Ordos Basin, central China, and high accuracy sensors of soil moisture, moisture potential and temperature were installed in three field soil profiles with water-table depths (WTDs) of about 0.4, 1.4 and 2.2 m. Soil-surface-evaporation values were estimated by observed data combined with Darcy’s law. Results showed that: (1) soil-surface-evaporation rate is linked to moisture content and it is also affected by air temperature. When there is sufficient moisture in the soil profile, soil evaporation increases with rising air temperature. For a WTD larger than the height of capillary rise, the soil evaporation is related to soil moisture content, and when air temperature is above 25 °C, the soil moisture content reduces quickly and the evaporation rate lowers; (2) phreatic water contributes to soil surface evaporation under conditions in which the WTD is within the capillary fringe. This indicates that phreatic water would not participate in soil evaporation for a WTD larger than the height of capillary rise. This finding developed further the understanding of phreatic evaporation, and this study provides valuable information on recognized soil evaporation processes in the arid environment.

Patterns of vegetation and soil properties in a beaver-created wetland located on the Coastal Plain of Virginia

This study investigated vegetation and soil properties in a beaver-created freshwater wetland located on the Coastal Plain of Virginia near Washington, DC. We focused on the associations among floristic quality, soil physicochemistry, denitrification, and hydrologic conditions of the wetland to understand links between the effects of beaver engineering and ecosystem function. The floristic quality assessment index (FQI) and denitrification are two important indicators often used to examine overall habitat quality and ecosystem functioning of a wetland. Samples were collected from ten plots (10 m × 10 m each) in August 2014. Vegetation attributes included total percent cover, species richness (S), diversity, FQI, and prevalence index (PI). Soil attributes included organic matter (OM), total carbon, total nitrogen, gravimetric moisture (GM), pH, bulk density (Db), and denitrification potential (DP). FQI was greater in the higher of the two standing water level categories, where Db was lower, and was negatively associated with Db but no other soil nutrient properties. DP was positively associated with soil nutrients, OM, and GM, but not with measured vegetation attributes nor standing water levels. We found higher soil GM, lower plant community PI, and lower plot S in this study compared to our previous study, with no changes to other vegetation or soil attributes, indicating enduring beaver activity and a resilient plant community. The outcome of the study includes regression models that best explain the association between structural and functional attributes of the ecosystem, which can be applicable to the study of other beaver-created wetlands. The study also provides partial evidence for the notion that low-lying areas dug out by beaver positively impact the FQI of wetlands.

Assessment of enclosing structure moisture regime using moisture potential theory

The paper describes principal development directions of mathematical models of enclosing structure moisture regime. Benefits of mathematical models based on moisture potential theory are demonstrated. Moisture regime calculation by means of moisture potential, taking liquid and vapor moisture transfer into consideration, and using discrete-continual approach is proposed. New formulas for single-layer and multi-layer enclosing structures allowing for numerical analytic determination of moisture potential value in any enclosing structure section, at any moment of time, under continuous control of temperature distribution, have been derived. Moisture distribution has been studied for a number of enclosing structures using different methods of moisture potential theory: unsteady-state method, quasi-stationary method, the proposed discrete-continual method. Moisture regime has been determined for single-layer enclosing structure with ceramic brick basement and lime brick cladding in Moscow. It is shown that the greatest moisture value is achieved in enclosing structure calculation by means of steady-state method. Unsteady-state method gives more accurate moisture distribution. The proposed discrete-continual method gives quantitative and qualitative result of moisture distribution similar to results obtained by unsteady-state method. The benefit of discrete-continual method is a distribution obtained analytically, which allows to use solution results without numerical method application.

Moisture behavior calculation of single-layer enclosing structure by means of discrete-continuous method

The paper proposes mathematical model for unsteady-state moisture behaviour calculation of single-layer enclosing structures by means of moisture potential and discrete-continuous method. A formula for moisture potential value calculation for single-layer enclosing structure in any enclosing structure section, at any moment of time, under continuous control for temperature distribution, has been derived. Moisture transfer between the enclosing structure and ambient air is taken into account by means of third-kind boundary conditions. Temperature distribution is taken as constant during a month. The proposed method allows for moisture potential determination according to the proposed formula for every month. Calculation results obtained by the proposed method, well-known unsteady-state method and engineering method developed by V.G. Gagarin and V.V.Kozlov have been compared for single-layer enclosing structure made of aerated concrete. It was shown that average value calculation results disagreement does not exceed 7% for the proposed method and unsteady-state method. However, the proposed approach allows for moisture distribution determination using analytical expression, which is convenient for use in engineering practice.

The moisture potential in conditions of phase transition of soil solution in sod-podzolic soil

The moisture potential in conditions of phase transition of soil solution in sod-podzolic soil

Landau–Deryagin law and hydration energy of soils of different genesis

Linear regression equations between the logarithm of the total soil moisture potential and soil moisture content in the hygroscopic moisture range (Landau–Deryagin law) were derived for typical soils from different natural zones of European Russia. From these equations, a compact algorithm was developed for calculating the hydration energy of soils, which increases from 1280 to 10600 J/kg in the following soil series: heavy loamy soddy podzolic soil–heavy loamy gray forest soil–medium loamy light chestnut soil–heavy loamy brown semidesert soil–light clayey solonchak–light clayey chernozem–medium clayey krasnozem. Relationships were revealed between the hydration energy of soils, the specific surface of soils, the content of physical clay in soils, and the concentration of hydrated exchangeably adsorbed ions.

The Effect of Various Supplementary Irrigation Treatments on Plant and Soil Moisture Relationships in a Vineyard (Vitis Vinif era var. Chenin Blanc)

In a field plot trial with grape vines planted on a high potential soil, the soil moisture status on different irrigation treatment plots was compared with that of a dryland control. Soil moisture budgeting was based on physical soil properties and root distribution patterns before treatments commenced. A maximum concentration of roots occurred at the 300-450 mm depth zone, while approximately 90 per cent of the total number of roots was found above 900 mm. Tensiometric readings of soil moisture potential, supplemented by electrometric resistance readings from gypsum blocks, indicated complete depletion between veraison and harvesting of the total available moisture on dryland plots. Despite this severe moisture stress as illustrated by chrono-isopletes, a reasonably good grape yield was still produced by the dryland vines, indicating either exceptional drought resistance or the uptake of water from extraneous sources. Supplementary irrigations greatly improved soil moisture conditions during the important growth stages of (a) flowering and fruit set, (b) green berry stage and (c) veraison. Moisture depletion patterns changed markedly as the season progressed from November to January, and as naturally stored rain water became depleted. In contrast to the absorption pattern in November, the fastest rate of water loss occurred in the deepest root zones during January, because of unsaturated moisture flow into the dry partly decomposed parent material. The apparently unproductive subsoil might act as a large natural reservoir for superfluous winter rain, which in summer becomes available to the vines through unsaturated upward flow into the root zone. Determination of leaf water potential showed unexpectedly high values at night (minima of -283kPa) in plants growing in soil of which the major part was dried below wilting point. Vines were thus able to regain turgidity at night. Crop factors for use with the American Class A-pan for scheduling irrigations were calculated. Crop factors were low (November to February = 0,20-0,30), and again emphasised the ability of vines to use water frugally. Crop factors were strongly dependent upon soil moisture conditions. Empirical coefficients for use in the Blaney-Criddle formula are also presented.

Comparison of Soil Water Potential Sensors: A Drying Experiment

Core Ideas In situ water retention curve is key to capture the dynamics of root zone functions. Some of the water potential probes can cover a wide range of water potential levels. The potential probes ability to capture an in situ retention curve is tested. The soil water retention curve (WRC) plays a major role in a soil's hydrodynamic behavior. Many measurement techniques are currently available for determining the WRC in the laboratory. Direct in situ WRC can be obtained from simultaneous soil moisture and water potential readings covering a wide tension range, from saturation to the wilting point. There are many widely used soil moisture probes. Whereas near‐saturation tension can be measured using water‐filled tensiometers, wider ranges of water potential require new, more expensive, and less widely used probes. We compared three types of soil water potential sensors that could allow us to measure water potential in the field, with a range relevant to water uptake by plants. Polymer tensiometers (POTs), MPS‐2 probes, and pF meters were compared in a controlled drying experiment. The study showed that the POTs and MPS‐2 probes had good reliability in their respective ranges. Combined with a soil moisture probe, these two sensors can provide observed WRCs. The pF meters below −30 kPa were inaccurate, and their response was sensitive to measurement interval, with greater estimated suction at shorter measurement intervals. In situ WRC can provide supplementary information, particularly with regard to its spatial and temporal variability. It could also improve the results of other measurement techniques, such as geophysical observations.

A Networked Sensor System for the Analysis of Plot-Scale Hydrology.

This study presents the latest updates to the Audubon Society of Western Pennsylvania (ASWP) testbed, a $50,000 USD, 104-node outdoor multi-hop wireless sensor network (WSN). The network collects environmental data from over 240 sensors, including the EC-5, MPS-1 and MPS-2 soil moisture and soil water potential sensors and self-made sap flow sensors, across a heterogeneous deployment comprised of MICAz, IRIS and TelosB wireless motes. A low-cost sensor board and software driver was developed for communicating with the analog and digital sensors. Innovative techniques (e.g., balanced energy efficient routing and heterogeneous over-the-air mote reprogramming) maintained high success rates (>96%) and enabled effective software updating, throughout the large-scale heterogeneous WSN. The edaphic properties monitored by the network showed strong agreement with data logger measurements and were fitted to pedotransfer functions for estimating local soil hydraulic properties. Furthermore, sap flow measurements, scaled to tree stand transpiration, were found to be at or below potential evapotranspiration estimates. While outdoor WSNs still present numerous challenges, the ASWP testbed proves to be an effective and (relatively) low-cost environmental monitoring solution and represents a step towards developing a platform for monitoring and quantifying statistically relevant environmental parameters from large-scale network deployments.

Effect of Artificially Induced Drought Stress on Seedlings of Pinus roxburghii Sarg

ABSTRACT Water relation and growth parameters of drought stressed seedlings of Chir pine (Pinus roxburghii Sarg.) were studied over a one year period. The seedlings were subjected to three drought cycles of 9, 18, 27 days and one control level (watered every alternate day) in a polyhouse. Pre-dawn (5.30-6.30 AM) and Mid-day water potential was estimated using a pressure chamber. The bench drying method was followed for developing P-V curves for estimating components of water potential. Osmotic adjustment was estimated as the difference between the osmotic potential at zero and full turgor of seedlings kept at control and those given 27 days drought. Across drought cycles the pre- dawn water potential ranged between -0.59 MPa and -2.12 MPa and the mid-day water potentials were always lower than pre-dawn water potentials. The Osmotic adjustment was – 1.17 MPa at full turgor and -2.0 MPa at zero turgor. The seedlings growth was positively related to soil moisture and water potential. The daily change in water potential (difference between pre-dawn and mid-day water potential) declined with increasing drought and was nominal (less than -0.2 MPa) in seedlings subjected to 18 and 27 days drought cycle. Needle characteristics were severely affected by water stress. In Pinus roxburghii Sarg seedlings osmotic adjustment may be an important adaptive mechanism that assists it to invade and grow on dry inhospitable sites.

Study on the Dehumidification and Indoor Air Cleaning Performance of Rotary Desiccant Rotor

With the improvements of living standards, people’s demand for indoor environment is not only confined to thermal comfort, but also spread to health-oriented aspects. However, the indoor environment in major parts of China face challenges of atmospheric pollutions and building energy consumptions. In the present paper, a novel adsorption ventilation system which combines air thermal conditioning and indoor air cleaning was proposed. The proposed system utilizes the moisture and gaseous pollution adsorption potential of desiccant material to realize indoor air dehumidification and cleaning, and aims at improving indoor air quality and reducing energy consumption of building ventilation. Literature review study on the performance of desiccant rotor commonly used as adsorption equipment was conducted. An experimental system was designed and developed to validate the performance of desiccant rotor and investigate the key influence parameters. A system which combine the desiccant rotor with heat pump was discussed.

Within canopy temperature differences and cooling ability of Tilia cordata trees grown in urban conditions

Urban trees regulate their thermal environment mostly through the canopies. With multilayered complex canopies trees prevent solar radiation (reaching the ground) thus reduce the heat storage underneath. More importantly the intercepted energy rather increases the latent heat flux, hence reduces the air temperature during the daytime. However, there is little information on within canopy temperature of urban trees and inter-relationships between latent heat flux exchanges to identify thermal impact of vegetation. The present study continuously measured sapflow and within the canopy air temperature of Tilia cordata trees along with meteorological variables at two different street canyons in Munich, Germany over the summer, 2015. Within the canopy radius of 4.5 m, daytime temperature reduced up to 3.5 °C with energy loss of 75 W m−2 during warm and dry August when the soil moisture potential was below 1.5 MPa and vapour pressure deficit was 4 kPa, but the nighttime temperature went up to 0.5 °C. Deeper underneath the tree canopy, 1.5 m above the ground the average temperature fell by up to 0.85 °C on hot sunny days. The regression equation showed better agreement of this air temperature reduction with the sap flow of trees (R2 = 0.61) rather than the differences between shaded and unshaded, paved and grass surface temperatures. Although the research is at an early stage, the results showed the potential of using canopy air temperature differences as a tool to better understand the transpiration response to within and below canopy temperature and also to be used in climate models.

Diacyl Disulfide: A Reagent for Chemoselective Acylation of Phenols Enabled by 4-(N,N-Dimethylamino)pyridine Catalysis.

A general and excellent acylation reagent, diacyl disulfide, was uncovered for efficient ester formation enabled by DMAP (4-(N,N-dimethylamino)pyridine) catalysis. This protocol offered a promising synthetic platform on site-selective acylation of phenolic and primary aliphatic hydroxyl groups, which greatly expanded the realm of protecting group chemistry. The importance of the reagent was also reflected by its excellent moisture tolerance, high efficiency, and potential in synthetic chemistry and biologically meaningful natural product modification.

Microclimatic differences and their influence on transpirational cooling of Tilia cordata in two contrasting street canyons in Munich, Germany

Urban trees can help to mitigate the urban heat island through evapotranspiration. However, growing conditions in cities are heterogeneous and micrometeorological conditions in street canyons can have a large impact on a tree’s transpiration. Here we investigated a common urban street tree species Tilia cordata of different ages and sizes, planted in two contrasting street canyons in a densely built neighbourhood within the centre of Munich, Germany: Bordeaux Platz, an open green square (OGS), and Pariser Platz, a circular paved square (CPS) with similar aspect ratio≈0.5. The experiment was carried out during the exceptionally hot and dry summer of 2015. The open green square showed significantly higher wind speed and vapour pressure deficit but lower soil temperature, less negative soil moisture potential and also a smaller wind tunneling effect compared to the circular paved square. All these variables showed strong relationship with the sapflux density (Js) of trees grown at these two sites. They explain almost 78% of the variation in Js. On average Js values of the trees at Bordeaux Platz peaked to 0.30–0.35mlcm−2min−1 during the day compared to the peak values of 0.20–0.23mlcm−2min−1 for trees at Pariser Platz. Consequently, trees grown at the open green square showed higher peak cooling of 2.3kWtree−1 or 82wm−2 than at the circular paved square (1.9kWtree−1). Interestingly, nocturnal cooling was higher for trees at the circular paved square with 18% of daytime transpiration compared to 2% for trees at the open green square. The study gave new insights into the cooling benefits of urban trees planted in open green squares compared to closed and paved squares and its temporal variation.

The influence of sorption hysteresis on diffusion coefficients represented with different moisture potentials

This paper continues the discussion in a previous paper [Saeidpour and Wadsö doi:10.1016/j.cemconres.2016.02.003] where a clear effect of sorption hysteresis was seen in moisture diffusion coefficients for cement-based materials. Coefficients with vapor content as potential (Dv) had different values depending on whether the sample was in absorption or in desorption. In this paper we recalculate these Dv coefficients into coefficients with other potentials and draw them as a function of different potentials. The aim is to see if the effect of hysteresis disappears with an optimal choice of representation. The best choice was to draw Dv is as a function of the degree of saturation (concentration, moisture content).

Research and Monitoring on Conservation State and Preservation Conditions in Unsaturated Archaeological Deposits of a Medieval Farm Mound in Troms and a Late Stone Age Midden in Finnmark, Northern Norway

This paper presents archaeological observations and results of palaeoecological and geo-chemical analyses of archaeological deposits from two rural sites in northernmost Norway. These are combined with climate data and the first period of continuous monitoring of soil temperature, moisture, and redox potential in sections. This data constitutes the basic research material for evaluations of conservation state and preservation conditions. The data has been collected in collaboration with the partners of a cross-disciplinary project: ‘Archaeological Deposits in a Changing Climate. In situ Preservation of Farm Mounds in Northern Norway’ funded by the Norwegian Council for Research (http://www.niku.no/en/archaeology/environmental_monitoring/archaeological_deposits_in_a_changing_climate_in_situ_preservation_of_farm_mounds/). This is an important Norwegian research initiative on monitoring of rural archaeological deposits, and the results have consequences for heritage management of a large number of sites from all periods. Palaeoecological analyses and redox measurements have revealed ongoing decay that might not otherwise have been detected. Decay studies indicate that both site types may be at risk with the predicted climate change. Some mitigating acts are suggested.

The In Situ Preservation in the Unsaturated Zone: Results from Environmental Investigations at the ‘Schultz Gate’ Case Study in the Medieval Town of Trondheim, Norway

Medieval Trondheim is located on the eastern part of Nidarneset, a small peninsula formed by the river plain at the mouth of the River Nid on the southern shore of Trondheimsfjord. The topographic conditions for medieval Trondheim differ from those of the other Norwegian medieval towns (notably Bergen, Oslo, and Tønsberg), and the protected, historic part of Trondheim contains anthropogenic sediments which lie entirely within an unsaturated environment. A large proportion of these sediments contain wood and other types of organic material. The thickness of the anthropogenic sediments varies greatly from more than 4 m to less than 0.5 m, and they overlie well-drained alluvial sands and gravels. The Directorate for Cultural Heritage (Riksantikvaren) and the Norwegian Institute for Cultural Heritage Research (NIKU) have different roles in the management of cultural heritage sites. However, they cooperate in developing sustainable management and a scientific approach to research, as well as finding practical solutions aimed at securing stable preservation conditions for anthropogenic sediments that are vulnerable and sensitive to environmental changes, both chemical and mechanical. In this paper we present results from environmental investigations conducted in 2007 and 2012 at a location in the central part of medieval Trondheim where an in situ preservation project has been established on the site of new construction work. The project is cross-interdisciplinary, combining archaeological retrieval methods with the sampling and analysis of soil chemical parameters and the monitoring of present basic parameters such as temperature, moisture and redox potential. The monitoring has been ongoing since the beginning of 2013 and will continue until 2017.