Modelling oxygen transport in soil with plant root and microbial oxygen consumption: depth of oxygen penetration

A set of equations governing oxygen diffusion and consumption in soils has been developed to include microbial and plant-root sinks. The dependent variable is the transformed oxygen concentration, which is the difference between the gaseous concentration and a scaled value of the aqueous oxygen concentration at the root–soil interface. The results show how, as the air-filled porosity decreases, the reduced oxygen flux causes the depth of extinction to decrease. The results also show how the depth of extinction at a particular value of soil water content decreases with increasing temperature, due to increased microbial respiration. The critical value of water content at which the oxygen concentration goes to extinction at a finite depth was compared with alternative calculations with only a microbial sink. By ignoring the feedback of oxygen concentration on root uptake, the alternative calculations yielded substantially higher critical values of water content at all temperatures. Two soil oxygen diffusion coefficient functions from the literature were compared and shown to give significantly different critical values of water content for fine-textured soils, one more realistic than the other. A single relationship between the extinction depth and the ratio of the water content to the critical value was shown to apply for all temperatures and soil textures. The oxygen profiles were used along with a function relating redox potential to oxygen concentration to generate redox potential profiles. This application of the model could be useful in explaining soil biochemical processes in soils. For one such process, denitrification, the depth at which a critical oxygen concentration is reached was calculated as a function of the air-filled porosity and temperature of the soil. The implications of the critical value of soil water content in terms of water-filled pore space and matric potential are discussed in relation to the diffusion coefficient functions and recent literature.

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Relationship of Soil Respiration to Crop and Landscape in the Walnut Creek Watershed

Journal of Hydrometeorology ◽

10.1175/jhm459.1 ◽

2005 ◽

Vol 6 (6) ◽

pp. 812-824 ◽

Cited By ~ 17

Author(s):

T. B. Parkin ◽

T. C. Kaspar ◽

Z. Senwo ◽

J. H. Prueger ◽

J. L. Hatfield

Keyword(s):

Microbial Biomass ◽

Soil Respiration ◽

Water Content ◽

Soil Water ◽

Soil Water Content ◽

Net Primary Production ◽

Plant Root ◽

System Effect ◽

Organic C ◽

Creek Watershed

Abstract Soil respiration is an important component of the carbon dynamics of terrestrial ecosystems. Many factors exert controls on soil respiration, including temperature, soil water content, organic matter, soil texture, and plant root activity. This study was conducted to quantify soil respiration in the Walnut Creek watershed in central Iowa, and to investigate the factors controlling this process. Six agricultural fields were identified for this investigation: three of the fields were cropped with soybean [Glycine max (L.) Merr.] and three were cropped with corn (Zea mays L.). Within each field, soil respiration was measured at nine locations, with each location corresponding to one of three general landscape positions (summit, side slope, and depression). Soil respiration was measured using a portable vented chamber connected to an infrared gas analyzer. Soil samples were collected at each location for the measurement of soil water content, pH, texture, microbial biomass, and respiration potential. Field respiration rates did not show a significant landscape effect. However, there was a significant crop effect, with respiration from cornfields averaging 37.5 g CO2 m−2 day−1 versus an average respiration of 13.1 g CO2 m−2 day−1 in soybean fields. In contrast, laboratory measurements of soil respiration potential, which did not include plant roots, showed a significant landscape effect and an insignificant cropping system effect. Similar relationships were observed for soil organic C and microbial biomass. Additional analyses indicate that corn roots may be more important than soybean roots in their contribution to surface CO2 flux, and that root respiration masked landscape effects on total soil respiration. Also, the failure to account for soil respiration may lead to biased estimates of net primary production measured by eddy covariance.

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Spatiotemporal variability of soil penetration resistance in a field cultivated with sugarcane under conventional tillage system in northeast Brazil

10.5194/egusphere-egu2020-5718 ◽

2020 ◽

Author(s):

Brivaldo Gomes de Almeida ◽

Ceres Duarte Guedes Cabral de Almeida ◽

Thaís Fernandes de Assunção ◽

Bruno Campos Mantovanelli ◽

José Coelho de Araújo Filho ◽

...

Keyword(s):

Water Content ◽

Soil Water ◽

Soil Water Content ◽

Penetration Resistance ◽

Conventional Tillage ◽

Critical Value ◽

Spatiotemporal Variability ◽

Spatial And Temporal Variability ◽

Soil Penetration Resistance ◽

Tillage System

Soil management, although intended to create favorable structural conditions for crop growth and development, without prior assessment of potential and limitations, has been one of the reasons for the degradation of natural resources. The effects on soil degradation and respective structural quality are generally evaluated by some physical soil attributes such as bulk density (BD), total porosity (TP) and soil penetration resistance (PR). The PR is recognized as a physical parameter that supports the identification of areas with different stages of compaction and thus can be used to define appropriate management for soil remediation. Besides, this parameter depends on intrinsic soil factors (texture, structure, and mineralogy) and soil water content (SWC). Therefore, PR increases with BD and decreases with SWC (gravimetric or volumetric). Thus, it is possible to establish the critical limit of PR (PRCL) associated with the value of SWC that limits the growth of plant roots. PRCL varies according to soil type and plant species, but 2.0 MPa is the value scientifically accepted as the critical value to limit the root growth. Thus, the paper aimed to evaluate the spatial and temporal variability of PR in a field cultivated with sugarcane, under the conventional tillage system. The research was carried out in the Carpina Sugarcane Experimental Station, Pernambuco, Brazil. A grid of 70 x 70 m was delineated at intervals of 10 m and in each point soil samples were collected in the layers 0 - 0.30 m and 0.30 - 0.60 m depth. Three samplings were done to determine gravimetric soil water content; the first after six months of subsoiling (Time 6) before harrowing and planting, the second after 12 months of subsoiling (Time 12, six months after harrowing and planting) and the last after 18 months of subsoiling, before harvesting (Time 18). In each sampling time, in situ PR tests were carried out with the Solo Track equipment (Falker&#174; - Model PLG 5300) and the simultaneous values of gravimetric soil water content were determined and associated with the PR data. The results showed that soil water content had a weak degree of spatial dependence, indicating the need to increase the number of samples. On the other hand, the PR values showed that the subsoiling did not promote a positive effect on the soil physical quality, with values above the PRCL for root development in Time 6 (2.42 MPa), even if after one year the sugarcane root system acted positively, by reducing PR in Time 18 (1.04 MPa) below the critical value.

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Soil moisture heterogeneity during deficit irrigation alters root-to-shoot signalling of abscisic acid

Functional Plant Biology ◽

10.1071/fp07009 ◽

2007 ◽

Vol 34 (5) ◽

pp. 439 ◽

Cited By ~ 60

Author(s):

Ian C. Dodd

Keyword(s):

Water Content ◽

Root System ◽

Soil Water ◽

Soil Water Content ◽

Deficit Irrigation ◽

Plant Root ◽

Arithmetic Mean ◽

Similar Amount ◽

Graft Union ◽

Plant Root System

The effects of different irrigation techniques on leaf xylem ABA concentration ([X-ABA]leaf) were compared in tomato (Lycopersicon esculentum Mill.). During partial rootzone drying (PRD), water was distributed unevenly to the root system such that part was irrigated while the remainder was allowed to dry the soil. During conventional deficit irrigation (DI), plants received the same volume of water as PRD plants, but water was distributed evenly to the entire root system. When the plant root system was allowed to explore two separate soil compartments, DI plants had a higher [X-ABA]leaf than PRD plants with moderate soil drying, but PRD plants had a higher [X-ABA]leaf than DI plants as the soil dried further. The difference in [X-ABA]leaf between the two sets of plants was not because of differences in either whole pot soil water content (θpot) or leaf water potential (Ψleaf). To investigate the contribution of different parts of the root system to [X-ABA]leaf, individual shoots were grafted onto the root systems of two plants grown in two separate pots, so that the graft union had the appearance of an inverted ‘Y’. After sap collection from detached leaves, removal of the shoot below the graft union allowed sap collection from each root system. Again, DI plants had a higher [X-ABA]leaf than PRD plants when the soil was relatively wet, but the opposite occurred as the soil dried. Root xylem ABA concentration ([X-ABA]root) increased exponentially as soil water content (θ) declined. In DI plants, [X-ABA]root from either pot (or the arithmetic mean of [X-ABA]root) accounted for a similar amount of the variation in [X-ABA]leaf. In PRD plants, [X-ABA]root from the watered side underestimated [X-ABA]leaf, whereas [X-ABA]root from the dry side overestimated [X-ABA]leaf. The arithmetic mean of [X-ABA]root best explained the variation in [X-ABA]leaf, implying continued sap flow from the dry part of the root system (Jdry) at soil water potentials (Ψsoil) at which Jdry had ceased in previous studies of PRD plants (Yao et al. 2001). Evaluating the relationship between Jdry and Ψsoil may assist in maintaining export of ABA (and other growth regulators) from the drying part of the root system, to achieve desirable horticultural outcomes during PRD.

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Disentangling temporal and population variability in plant root water uptake from stable isotopic analysis: a labeling study

10.5194/hess-2019-543 ◽

2019 ◽

Author(s):

Valentin Couvreur ◽

Youri Rothfuss ◽

Félicien Meunier ◽

Thierry Bariac ◽

Philippe Biron ◽

...

Keyword(s):

Water Content ◽

Soil Water ◽

Physical Model ◽

Soil Water Content ◽

Water Uptake ◽

Temporal Dynamics ◽

Plant Root ◽

Root Water Uptake ◽

Leaf Water ◽

Stable Isotopic

Abstract. Isotopic labeling techniques have the potential to minimize the uncertainty of plant root water uptake (RWU) profiles estimated through multi-source (statistical) modeling, by artificially enhancing soil water isotopic gradient. Furthermore, physical models can account for hydrodynamic constraints to RWU if simultaneous soil and plant water status data is available. In this study, a population of tall fescue (Festuca arundinacae cv Soni) was grown in a macro-rhizotron setup under semi-controlled conditions to monitor such variables for a 34-hours long period following the oxygen stable isotopic (18O) labeling of deep soil water. Aboveground variables included tiller and leaf water oxygen isotopic compositions as well as leaf water potential (ψleaf), relative humidity, and transpiration rate. Belowground profiles of root length density (RLD), soil water content and isotopic composition were also sampled. While there were strong correlations between hydraulic variables as well as between isotopic variables, the experimental results underlined the discrepancy between variations of hydraulic and isotopic variables. In order to dissect the problem, we reproduced both types of observations with a one-dimensional physical model of water flow in the soil-plant domain, for 60 different realistic RLD profiles. While simulated ψleaf followed clear temporal variations with little differences across plants as if they were “on board of the same rollercoaster”, simulated δtiller values within the plant population were rather heterogeneous (“swarm-like”) with relatively little temporal variation and a strong sensitivity to rooting depth. The physical model thus suggested that the discrepancy between isotopic and hydraulic observations was logical, as the variability captured by the former was spatial and may not correlate with the temporal dynamics of the latter. For comparison purposes a Bayesian statistical model was also used to simulate RWU. While they predicted relatively similar cumulative RWU profiles, the physical model could differentiate spatial from temporal dynamics of the isotopic signature, and supported that the local increase of soil water content and formation of a peak of labelled water observed overnight were due to hydraulic lift.

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The use of computer assisted tomography to determine spatial distribution of soil water content

Soil Research ◽

10.1071/sr9830435 ◽

1983 ◽

Vol 21 (4) ◽

pp. 435 ◽

Cited By ~ 110

Author(s):

JM Hainsworth ◽

LAG Aylmore

Keyword(s):

Water Content ◽

Soil Water ◽

Soil Water Content ◽

Plant Root ◽

Computer Assisted ◽

X Ray ◽

Computer Assisted Tomography ◽

Spatial Changes ◽

Exciting Possibility ◽

Non Destructive

To date no experimental technique has been capable of directly and repetitively measuring spatial distributions of soil water content in a non-destructive manner. The potential of computer assisted tomography (CAT) to overcome this problem has been examined in this paper. The results obtained from a commercially-produced X-ray CAT scanner and a conventional gamma scanner suggest that CAT scanning can be used to determine spatial changes in soil water content with adequate resolution for soil-plant studies. The technique can clearly be used to resolve spatial changes in soil water content with time. Application of the technique to water uptake by a single plant root shows that CAT scanning presents an extremely exciting possibility for studies of soil-plant water relations.

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CONTEÚDO DE ÁGUA NO SOLO E PRODUÇÃO DE RABANETE EM FUNÇÃO DE DIFERENTES DOSES DE CONDICIONADOR ORGÂNICO DE SOLO

Irriga ◽

10.15809/irriga.2009v14n2p135-144 ◽

2009 ◽

Vol 14 (2) ◽

pp. 135-144

Author(s):

Dolores Wolschick ◽

Joaquim Basso

Keyword(s):

Water Content ◽

Soil Water ◽

Soil Water Content ◽

Raphanus Sativus ◽

Plant Root ◽

Field Capacity ◽

Organic Soil ◽

Mato Grosso ◽

Soil Conditioner ◽

Raphanus Sativus L

CONTEÚDO DE ÁGUA No SOLO e produção DE RABANETEem função de diferentesDOSES de condicionador ORGÂNICO de solo Dolores Wolschick; Joaquim BassoUniversidade para o Desenvolvimento da Região e do Pantanal (UNIDERP), Campo Grande, Mato Grosso do Sul, [email protected] 1 RESUMO Condicionadores de solo são materiais adicionados ao solo para otimizar suas propriedades físico-hídricas. O objetivo deste trabalho foi avaliar a influência de doses de condicionador orgânico de solo no conteúdo de água no solo e na produção de rabanete (Raphanus sativus L.). O experimento foi conduzido em casa de vegetação com 30 vasos plásticos, contendo2,6 kg de solo e 5 doses de condicionador de solo orgânico (0,0; 0,035; 0,070; 0,105;0,140 Kg por vaso) e 6 repetições. Metade dos vasos foi mantida na umidade da capacidade de campo e a outra metade, a partir do desbaste, sem irrigação até o final do ciclo da cultura. Foram avaliados a massa de matéria fresca e seca de plantas, diâmetro de raiz e consumo de água durante o ciclo da cultura. A adição do condicionador de solo aumentou o conteúdo de água no solo na capacidade de campo e apresentou tendência de diminuição da necessidade de reposição de água. A dose de0,035 Kg demonstrou tendência de aumento na produção, enquanto a de0,140 Kg por vaso, de diminuição. UNITERMOS: capacidade de campo, turfa, irrigação. WOLSCHICK, D; BASSO , J. SOIL WATER CONTENT AND RADISH YIELD UNDER DIFFERENT DOSAGES OF ORGANIC SOIL CONDITIONER 2 ABSTRACT Soil conditioners are substances that are added to the soil in order to improve its physical-hydric properties. This work aimed to verify the influence of organic soil conditioner dosages on soil water content and on the radish production (Raphanus sativus L.). The experiment took place in a greenhouse with 30 plastic vases containing2.6 Kg of soil and five dosages (0.035; 0.070; 0.105;0.140 Kg a vase) of the organic soil conditioner and six replications. Half of them were kept in the humidity of field capacity, while the others were not irrigated after thinning until the end of the culture cycle. Fresh and dry matter of radish plant, root diameter and water consumption during growth were evaluated. The conditioner application increased soil water content at field capacity and presented a decreasing tendency in water reposition necessity. The0.035 Kg dosage showed an increasing tendency in production, while the0.140 Kg dosage showed a tendency to reduction. KEYWORDS: field capacity, peat, irrigation.

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SOIL WATER CONTENT AFFECTS THE AVAILABILITY OF PHOSPHATE

Proceedings of the New Zealand Grassland Association ◽

10.33584/jnzg.1985.46.1696 ◽

1985 ◽

pp. 185-189

Author(s):

M.C.H.Mouat Pieter Nes

Keyword(s):

Water Content ◽

Soil Water ◽

Soil Water Content ◽

Soil Solution ◽

Equivalent Reduction

Reduction in water content of a soil increased the concentration of ammonium and nitrate in solution, but had no effect on the concentration of phosphate. The corresponding reduction in the quantity of phosphate in solution caused an equivalent reduction in the response of ryegrass to applied phosphate. Keywords: soil solution, soil water content, phosphate, ryegrass, nutrition.

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Effect of inter-row cultivation on soil carbon dioxide emission in a peach plantation

Agrokémia és Talajtan ◽

10.1556/agrokem.59.2010.1.19 ◽

2010 ◽

Vol 59 (1) ◽

pp. 157-164 ◽

Cited By ~ 1

Author(s):

E. Tóth ◽

Cs. Farkas

Keyword(s):

Water Content ◽

Soil Water ◽

Soil Water Content ◽

Carbon Dioxide Emission ◽

Nutrient Content ◽

Soil Disturbance ◽

Biological Properties ◽

Soil Tillage ◽

Favourable Effect ◽

Volumetric Soil Water Content

Soil biological properties and CO2emission were compared in undisturbed grass and regularly disked rows of a peach plantation. Higher nutrient content and biological activity were found in the undisturbed, grass-covered rows. Significantly higher CO2fluxes were measured in this treatment at almost all the measurement times, in all the soil water content ranges, except the one in which the volumetric soil water content was higher than 45%. The obtained results indicated that in addition to the favourable effect of soil tillage on soil aeration, regular soil disturbance reduces soil microbial activity and soil CO2emission.

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