Porous Suction Research Articles

Impact of split nitrogen applications on nitrate leaching and maize yield in irrigated loamy sand soils of Northeast Nebraska

AbstractLittle information is available on optimizing the number of nitrogen (N) splits based on nitrate (NO3‐N) leaching and maize yield in sandy soils. To address this gap, we evaluated the impact of multiple N splits (2‐, 3‐, 4‐, and 5‐N splits) on NO3‐N leaching and maize (Zea mays L.) grain yield in irrigated loamy sand soil at a producer site in the Bazile Groundwater Management Area of Northeast Nebraska. Porous suction cup lysimeters were installed at a depth of 120 cm to collect pore water samples from 23 leaching events in 2021, a dry year. Increasing the number of N‐splits did not affect the pore‐water NO3‐N concentration; however, it was 169%, 152%, 150%, and 129% higher in 2‐, 3‐, 4‐, and 5‐N split treatments compared to control, that is, without N application. Though the 2‐, 3‐, 4‐, and 5‐N splits had 110%, 71%, 120%, and 91% higher area‐based NO3‐N leaching than the control, less deep percolation and more evapotranspiration in control led to no significant differences in area‐based NO3‐N leaching among all treatments. All N‐splits resulted in higher maize yield, nitrogen use efficiency, plant N uptake, harvest index, and aboveground biomass than control; however, the number of N‐splits did not affect these parameters. The inclusion of environmental cost reduced the return to nitrogen by 92–143 $ ha−1 across all N‐split treatments but did not significantly affect the differences among the splits. Overall, the results indicate that increasing the number of N‐splits does not provide agronomic, economic, and environmental benefits in irrigated maize fields during a dry year.

Colloids facilitate transport of cadmium and uranium in arable soils, which is undetected by suction cups in the field

AbstractColloids can facilitate the transport of trace elements in soil, but earlier studies fell short either because of sampling artefacts or because no contrasting soils were used; both factors hamper a better understanding of where this occurs. Here, leaching in undisturbed and unsaturated soil columns was observed to identify colloidal transport of cadmium (Cd) and uranium (U) in soils with contrasting properties. Crucially, it was examined how such column data relate to more traditional in situ data obtained with porous suction cups. Soils were collected from three agricultural fields in Switzerland (soil pH 5.1–7.3), leached during 36 days (0.6 pore volumes, ~1.6 mm day−1), and elements trapped in the PTFE suction plates were recovered and were ascribed to colloids. Of the total mobile mass (sum percolate and plate), 18%–53% (Cd) or 8–89% (U) was retained by plates, the range depending on the field where soil was sampled and that fraction depends on soil pH and for U also on dissolved inorganic carbon. The total mobile Cd or U mass divided by the percolated volume indicates the metal concentration in the average leachate and was logically highest for Cd in the most acidic soil and for U in the most alkaline soil. The concentrations of Cd and U in these column leachates were >10‐fold higher than corresponding concentrations in the suction cups in the field for those soils and elements where colloids dominated leaching. In contrast, they were within a factor of two where colloids are <20% of the mobile mass. Flow Field‐Flow Fractionation (FlFFF) analyses showed an association of colloidal U with oxyhydroxides, clays and organic matter and, for colloidal Cd, an association with organic matter. These data show that suction cups or filtered percolates can underestimate the leaching of Cd and U by up to an order of magnitude.

Immediate Effects of Prescribed Fire on Sub-Surface Water Quality in a Managed Yellow Pine Forest

Although prescribed fire is a forest management tool annually applied to nearly one million hectares across the southeastern United States, little is known about how prescribed fire influences soil water quality in the region. Sub-surface pools of nitrogen (N) and phosphorous (P) are important indicators of ecosystem response to disturbance and are likely modified, at least temporarily, by fire. We undertook a five-month study to examine sub-surface nutrient concentrations and pH in a managed yellow pine (Pinus sp.) forest before and after a low-severity dormant season prescribed fire in the Southern Blue Ridge Mountains of South Carolina. Between February and July 2019, soil solution was collected weekly from a 30 cm porous cup suction lysimeters and analyzed for ammonium (NH4+), nitrate (NO3-), and orthophosphate (PO43-), as well as pH. We compared the five-month mean and maximum nutrient concentrations and pH to quantify the immediate effects of prescribed fire. The prescribed fire caused significant pH buffering towards neutrality in burned transects relative to the control. There was no change in soil solution NO3-. The prescribed fire caused a significant increase in maximum NH4+ (18.0 mg/L) and PO43- (6.6 mg/L) concentrations. Post-fire NH4+ concentrations reached a maximum of 18.0 mg/L before declining three weeks post-fire. PO43- concentrations in burned stands reached a maximum of 6.6 mg/L and remained elevated for four weeks post-fire. Nutrient leaching was minimal due to complexion to soil cations and ground water uptake from regenerating vegetation at the onset of the growing season. The PO43- and NH4+ pulses in this study are likely influenced by fire-induced changes to soil chemistry and future studies should examine the homogeneity of pH buffering and nutrient pulses across the burned landscape.

Leaching behavior of nitrogen in a long-term experiment on rice under different N management systems

The leaching behavior of nitrogen was studied in single rice paddy production ecosystems in Tsukuba, Japan after 75 years of consistent fertilization regimes (no fertilizer, ammonium sulfate, a combination of composted rice straw with soybean cake, and fresh clover). During the 75-year period, management was unchanged with respect to rice planting density, irrigation, and net N fertilization for each field to which an N-source was added. Percolation water was collected, from May 2001 to April 2002, using porous suction cups installed in the fields at depths of 15, 40, and 60 cm. All water samples were taken to the laboratory for the measurement of both NH(4) ( + )-N and NO(3) ( - )-N concentrations using a continuous-flow nitrogen analyzer. The result indicated that there were significant differences in N leaching losses between treatments during the rice growing season. Total N leaching was significantly lower with the application of composted rice straw plus soybean cake (0.58 kg N ha( - 1)) than with ammonium sulfate (2.41 kg N ha( - 1)), which resulted in N leaching at a similar level to that with the fresh clover treatment (no significant difference). The majority of this N leaching was not due to NO(3) ( - )-N loss, but to that of NH(4) ( + )-N. The mean N leaching for all fertilizer treatments during the entire rice growing season was 1.58 kg N ha( - 1). Composted rice straw plus soybean cake produced leaching losses which were 65-75% lower than those with the application of fresh clover and ammonium sulfate. N accumulation resulting from nitrification in the fallow season could be a key source of nitrate-N leaching when fields become re-flooded before rice transplanting in the following year; particular attention should be paid to this phenomenon.

MHD mixed convection for viscoelastic fluid past a porous wedge

A magnetic hydrodynamic (MHD) mixed convective heat transfer problem of a second-grade viscoelastic fluid past a wedge with porous suction or injection has been studied. Governing equations include continuity equation, momentum equation and energy equation of the fluid. It has been analyzed by a combination of a series expansion method, the similarity transformation and a second-order accurate finite-difference method. Solutions of wedge flow on the wedge surface have been obtained by a generalized Falkner–Skan flow derivation. Some important parameters have been discussed by this study, which include the Prandtl number (Pr), the elastic number (E), the free convection parameter (G) and the magnetic parameter (M), the porous suction and injection parameter (C) and the wedge shape factor (β). Results indicated that elastic effect (E) in the flow could increase the local heat transfer coefficient and enhance the heat transfer of a wedge. In addition, similar to the results from Newtonian fluid flow and conduction analysis of a wedge, better heat transfer is obtained with a larger G and Pr.

Sampling VOCs with Porous Suction Samplers in the Presence of Ethanol: How Much Are We Losing?

AbstractPorous suction samplers have been widely used to obtain ground water samples from the vadose zone. However, previous studies identified different mechanisms that may compromise the sample’s representativeness, such as volatilization and sorption. This issue is particularly important when dealing with volatile organic compounds (VOCs) as in gasoline spills. Ethanol is common in modern fuels and so may be present in ground water contamination from fuel releases. The objective of this work was to evaluate the losses of VOCs in the presence of ethanol when using porous suction samplers. Laboratory experiments were performed using a ceramic porous suction sampler to sample test solution containing benzene, toluene, xylenes, trimethylbenzenes, naphthalene, and different volumetric fractions of ethanol. Significant losses were found up to 30% for ethylbenzene. Ethanol was found to affect the accuracy of the readings by two main mechanisms: first, negatively, by increasing the headspace in the sampling tube, and second, positively, increasing partition to the aqueous phase due to the cosolvent effect and therefore decreasing the mass loss by volatilization. As a consequence, the highest losses of VOCs were found at intermediate ethanol volume fractions: 10% and 20% (v/v). The losses can be anticipated by measuring the ratio of gas to water in the sampling line and then by applying simple partition models considering cosolvency by ethanol. The importance of adequate purging when using porous suction samplers was also shown.

Friction and Heat Transfer in a Laminar Separated Flow behind a Rectangular Step with Porous Injection or Suction

Results of a numerical study of a laminar separated flow behind a rectangular step on a porous surface with uniform injection or suction are described. Two cases are considered: an unconfined flow past a step and flow evolution in a confined channel (duct). It is shown that mass transfer on the surface causes strong changes in the flow structure and substantially affects the position of the reattachment point, as well as friction and heat transfer. More intense injection leads first to an increase in the separation-zone length and then to its rapid vanishing due to boundary-layer displacement. Vice versa, suction at high Reynolds numbers Res > 100 reduces the separation-zone length. The duct flow has a complicated distribution of friction and heat-transfer coefficients along the porous surface owing to the coupled effect of the transverse flow of the substance and changes in the main flow velocity due to mass transfer.

Changes in the microbial community in a forest soil amended with aluminium in situ

Considerable knowledge exists about the effect of aluminium (Al) on root vitality, but whether elevated levels of Al affect soil microorganisms is largely unknown. We thus compared soils from Al-treated and control plots of a field experiment with respect to microbial and chemical parameters, as well as root growth and vitality. The field experiment was established in a 50-year-old Norway spruce (Picea abies L.) stand where no Al or low concentrations of Al had been added every 7–10 days during the growth season for 7 years. Analysis of soil solutions collected using zero tension lysimeters and porous suction cups showed that Al treatment lead to increased concentrations of Al, Ca and Mg and lower pH and [Ca + Mg + K/Al] molar ratio. Corresponding soil analyses showed that soil pH remained unaffected (pH 3.8), that exchangeable Al increased, while exchangeable Ca and Mg decreased due to the Al treatment. Root in-growth into cores placed in the upper 20 cm of the soil during three growth seasons was not affected by Al additions, neither was nutrient concentration or mortality of these roots. The biomass of some taxonomic groups of soil microorganisms, analyzed using specific membrane components (phospholipid fatty acids; PLFAs), was clearly affected by the imposed Al treatment, both in the organic soil horizon and in the underlying mineral soil. Microbial community structure in both horizons was also clearly modified by the Al treatment. Shifts in PLFA trans/cis ratios indicative of short term physiological stress were not observed. Yet, aluminium stress was indicated both by changes in community structure and in ratios of single PLFAs for treated/untreated plots. Thus, soil microorganisms were more sensitive indicators of subtle chemical changes in soil than chemical composition and vitality of roots.

Mobilidade de metais pesados em um Latossolo Amarelo distrófico tratado com lodo de esgoto e cultivado com cana-de-açúcar

A movimentação de metais pesados em profundidade, em solos tratados com lodo de esgoto, é uma das possibilidades que causam grandes preocupações no que diz respeito ao potencial poluente do resíduo, aos aqüíferos subterrâneos. O objetivo do presente trabalho foi estudar a movimentação de Cd, Cr, Cu, Ni, Pb e Zn num Latossolo Amarelo distrófico tratado com aplicações sucessivas de lodo de esgoto. O experimento foi conduzido nos anos agrícolas 1996/97 e 1997/98 sendo que, no primeiro ano, de acordo com os teores de metais do lodo, foram aplicadas em área total, doses equivalentes a 33, 66 e 99 Mg ha-1 (base seca) de lodo de esgoto. Em 1997/98 o lodo foi reaplicado em doses equivalentes a 37, 74 e 110 Mg ha-1. Os resultados para Cd, Ni e Pb não foram conclusivos, uma vez que seus teores no solo e na solução do solo estiveram abaixo do limite de determinação do método analítico utilizado. Para os metais Cu e Cr, não houve evidências de mobilidade ao final dos dois anos agrícolas. O Zn se mostrou um elemento móvel no perfil do solo, sendo encontrado, ao final de 1997/98, incrementos significativos até a camada 0,4 -- 0,6 m.

Developed turbulent flow in a plane channel with simultaneous injection through one porous wall and suction through the other

Results of a numerical-theoretical study of a developed turbulent flow of an incompressible fluid in a plane channel with simultaneous injection of mass through one porous wall and suction of the same mass through the other are presented. The system of equations of averaged motion is closed using a turbulent-stress model. The calculated data of the mean and fluctuational characteristics are in reasonable agreement with experimental results for two values of the Reynolds number of the main flow (Re=10,400 and34,000).

Nitrogen‐15 Tracers Combined with Tensio‐Neutronic Method to Estimate the Nitrogen Balance of Irrigated Maize

AbstractIn response to a very high increase of groundwater NO−3 pollution, largely connected with intensive agricultural practices, a long‐term experimentation has been set up close to Grenoble, France, with the following aims: first to characterize the response of maize (Zea mays L.), a predominant crop in the area, to fertilization, and second to quantify the N balance during and after the crop cycle. This study relates to results concerning the second issue; experiments were conducted on irrigated maize in 1991, 1992, and 1993 on the Experimental Farm at La Côte Saint‐André, France, in the heart of one of the most important agricultural zones between the French Alps and the Rhone Valley. The dynamics of soil and fertilizer N (NO−3 transport and N balance during cropping and intercropping periods) were continuously monitored using 15N isotopic tracing and the tensio‐neutronic method (i.e., continual measurement of soil water balance using a neutron moisture meter and tensiometers), together with porous suction cups installed at 0.3‐, 0.5‐, and 0.8‐m depths. Water drainage and leaching of NO−3‐N, with a partition between that derived from fertilizer and that produced by soil mineralization, were thus obtained during and after the crop cycle. The balance of the labeled fertilizer at harvest was also determined by conventional soil coring and plant sampling. The two methods were used successfully during the 3 yr in which there were different climatic conditions and different fertilizer application rates. The results show that the traditional fertilizer input in the area (260 kg N ha−1) could be reduced nearly 30% without any substantial loss in grain yield but with a considerable reduction of nonpoint source pollution due to NO−3 leaching. It is also shown that with the combined use of the two methods, it is possible to characterize separately fertilizer‐N uptake, fertilizer‐N leaching, and N immobilization and to estimate N‐gaseous losses.

Aluminium contamination of acid soil solution isolated by means of porcelain suction cups: a reply to a paper by Hughes & Reynolds (1990) and an interpretation of aluminium release

SUMMARY Possible aluminium contamination of acid soil solutions isolated by use of porous porcelain suction cups (‘P.80 type’) was reported by Raulund-Rasmussen (1989). The aluminium release was explained by a proton-induced dissolution of cup material. Hughes & Reynolds (1990) suggested that the aluminium release and proton consumption could be explained by an ion-exchange reaction. In an attempt to understand the mechanism and thereby also the usefulness of suction cups, laboratory experiments were carried out to define mineralogical and chemical composition, stability under acid conditions, cation exchange capacity, and reactivity under conditions relevant to the field. The cups consisted of mullite and corundum (65% Al2O3) as shown by X-ray diffraction analysis. The cation exchange capacity of the cups was too low (0.65 μmolc per cup) to explain the observed contamination of isolated soil solution. Ground cup material dissolved slowly in acid. Investigations on whole cups showed that aluminium release to acid test solutions depended on the time of exposure. It is concluded that porcelain suction cups may lead to contamination of isolated soil solution depending on: (i) the intake rate, (ii) the rinsing procedure before sampling, and (iii) the composition of the soil solution (pH and aluminium ion activity being important parameters).

Movement of xylene through unsaturated soils following simulated spills

A field study was conducted to determine the rapidity and extent of xylene movement after simulated spills on undisturbed soils of diverse texture and structure. To monitor xylene movement, porous ceramic suction cups and newly developed pan samplers were installed at a depth of 61 cm at two locations in each of three soils. A volume equivalent to a depth of 5 cm of dye labeled xylene was spilled on one plot of each soil contained in large lysimeters. Split applications of 1.25 cm depth equivalent were also made 21 days apart on one lysimeter of each of the soils.

Numerical-perturbation technique for stability of flat-plate boundary layers with suction

A numerical-perturbation scheme is proposed for determining the stability of flows over plates with suction through a finite number of porous suction strips. The basic flow is calculated as the sum of the Blasius flow and closed-form linearized triple-deck solutions of the flow due to the strips. A perturbation technique is used to determine the increment a(ij) in the complex wavenumber at a given location x(j) due to the presence of a strip centered at x(i). The end result is a set of influence coefficients that can be used to determine the growth rates and amplification factors for any suction levels without repeating the calculations. The numerical-perturbation results are verified by comparison with interacting boundary layers for the case of six strips and the experimental data of Reynolds and Saric for single- and multiple-strip configurations. The influence coefficient form of the solution suggests a scheme for optimizing the strip configuration. The results show that one should concentrate the suction near branch I of the neutral stability curve, a conclusion verified by the experiments.

Stability of flow over axisymmetric bodies with porous suction strips

A numerical-perturbation scheme is used to determine the stability of incompressible flows past axisymmetric bodies with porous strips. Linear triple deck, closed-form solutions are developed for the basic-flow quantities, which account for upstream influence. These solutions are linear superpositions of the flow past the body without suction plus the perturbations caused by the suction strips. The flow past the suctionless body is calculated using the Transition Analysis Program System (TAPS). A perturbation scheme is used to determine the increment aij in the complex wavenumber at a given location sj because of the presence of a strip centered at si. The end result is a set of influence coefficients that can be used to determine the growth rates and amplification factors for any suction levels without repeating the calculations. The influence coefficients are used to develop a simple linear optimization scheme to determine the number, spacing, and mass flow rate through the strips on an axisymmetric body.

Boundary layer with selective suction

The heat- and mass-transfer processes in a boundary layer with porous suction of one of the components of the gas mixture are analyzed. It is shown that for selective suction there is a limiting penetration parameter, and the asymptotic suction regime is not attained.

Effect of porous injection and suction on the operation of a stalled conical diffuser

The influence of porous injection and suction on the drag, pressure recovery, and efficiency of a conical diffuser in the stalled flow regime is studied experimentally.

Growth of Turbulent Boundary Layers over Nonsta tionary Boundaries

Wind tunnel data are presented which show that the velocity distribution in a turbulent boundary layer above a moving ground plane can be represented as a power law. The flows under consideration are encountered in studies of shock waves near solid boundaries and of the near-field drag of tube vehicles. The two wind tunnels used in the experiment were equipped with moving ground belts and employed porous suction plates to remove the normal tunnel boundary layer. The layers studied are, therefore, assumed to originate at the leading edge of the belt.

Experimental study of free convection with porous blowing and suction on a vertical surface

The paper presents the results of an experimental study of the heat transfer and the temperature field in a free-convection boundary layer on a vertical surface with uniform porous blowing and suction and Tw=const. The method of measurement is described and the experimental data are compared with the theoretical results obtained by the authors in an earlier work. The experiments were carried out on a Zender-Mach interferometer. The theoretical and experimental results are found to be in good agreement. Critical values of the parameters are found, which determine the beginning of the transient and developed turbulent regions as a function of the rate of blowing or suction.