A carbon-based method for estimating the wetness of forest surface soil horizons

2007 ◽  
Vol 37 (4) ◽  
pp. 846-852 ◽  
Author(s):  
Donald S. Ross

The degree of wetness in forest surface soils has an effect on chemical and biological processes but is not easily measured. The high spatial variability in carbon (C) concentration creates high variability in water-holding capacity, and gravimetric water content is not informative. Local hydrology can create patchiness in soil moisture, with saturated soils often found near well-drained ones. When sampling to measure such factors as nitrification potential, it would be advantageous to have a simple metric that reflects the relative wetness of the soil. The relationship between C concentration (range 51.5–520.8 g·kg–1) and gravimetric water content was found to be linear for a set of 113 H- and A-horizon samples assumed to be at field capacity. The wetness ratio is defined as the actual water content of a sample divided by the water content predicted by the least squares regression equation based on C concentration (soil water content (kg·kg–1) = 0.080 + 0.0057 soil C concentration (g·kg–1)). Soil moisture retention curves were developed for a small number of samples in the range of 0 to about –10 kPa and showed that the equation predicted that water would be held at relatively high potential. In samples taken from 10 watersheds in the northeastern USA, wetness ratios between 1.25 and 3.1 were associated with soils identified in the field as ranging from wet to boglike. A median ratio of 0.49 was found in a watershed sampled after an extended dry period. At the Sleepers River Research Watershed, high wetness ratios were associated with a high soil calcium concentration, presumably from enriched groundwater. The ratio should be a useful measurement in watershed studies.

2015 ◽  
Vol 10 (4) ◽  
pp. 208 ◽  
Author(s):  
Lorenzo Barbanti ◽  
Ahmad Sher ◽  
Giuseppe Di Girolamo ◽  
Elio Cirillo ◽  
Muhammad Ansar

A better understanding of plant mechanisms in response to drought is a strong premise to achieving high yields while saving unnecessary water. This is especially true in the case of biomass crops for non-food uses (energy, fibre and forage), grown with limited water supply. In this frame, we investigated growth and physiological response of two genotypes of biomass sorghum (<em>Sorghum bicolor</em> (L.) Moench) to contrasting levels of soil moisture in a pot experiment carried out in a greenhouse. Two water regimes (high and low water, corresponding to 70% and 30% field capacity) were applied to JS-2002 and Trudan-8 sorghum genotypes, respectively bred for dry sub-tropical and mild temperate conditions. Two harvests were carried out at 73 and 105 days after seeding. Physiological traits (transpiration, photosynthesis and stomatal conductance) were assessed in four dates during growth. Leaf water potential, its components and relative water content were determined at the two harvests. Low watering curbed plant height and aboveground biomass to a similar extent (ca. 􀀀70%) in both genotypes. JS-2002 exhibited a higher proportion of belowground to aboveground biomass, <em>i.e</em>., a morphology better suited to withstand drought. Despite this, JS-2002 was more affected by low water in terms of physiology: during the growing season, the average ratio in transpiration, photosynthesis and stomatal conductance between droughty and well watered plants was, respectively, 0.82, 0.80 and 0.79 in JS-2002; 1.05, 1.08 and 1.03 in Trudan-8. Hence Trudan-8 evidenced a ca. 20% advantage in the three traits. In addition, Trudan-8 could better exploit abundant moisture (70% field capacity), increasing aboveground biomass and water use efficiency. In both genotypes, drought led to very low levels of leaf water potential and relative water content, still supporting photosynthesis. Hence, both morphological and physiological characteristics of sorghum were involved in plant adaptation to drought, in accordance with previous results. Conversely, the common assumption that genotypes best performing under wet conditions are less suited to face drought was contradicted by the results of the two genotypes in our experiment. This discloses a potential to be further exploited in programmes of biomass utilization for various end uses, although further evidence at greenhouse and field level is needed to corroborate this finding.


2002 ◽  
Vol 82 (4) ◽  
pp. 855-859 ◽  
Author(s):  
M. L. Leblanc ◽  
D. C. Cloutier ◽  
C. Hamel

A 2-year field study was conducted in corn to determine the influence of rainfall, irrigation and soil water content on common lambsquarters and barnyardgrass emergence. Rainfall or irrigation had no influence on the final weed density and little on the pattern of weed emergence because the soil water content was at or greater than field capacity during the main weed emergence period. Irrigation may hasten the first weed emergence by warming the soil when temperature is limiting for germination. In southwestern Quebec, temperature appears to be the most important factor regulating germination in the spring since soil moisture is normally at field capacity for a long period, in part because of the melting of snow. Key words: Irrigation, weed emergence, soil moisture


2019 ◽  
Vol 62 (2) ◽  
pp. 289-301
Author(s):  
Amjad T. Assi ◽  
Rabi H. Mohtar ◽  
Erik F. Braudeau ◽  
Cristine L. S. Morgan

Abstract. The purpose of this study was to evaluate the use of the pedostructure concept to determine the soil available water capacity, specifically the field capacity (FC). Pedostructure describes the soil aggregate structure and its thermodynamic interaction with water. Specifically, this work compared the calculation of soil water-holding properties based on the pedostructure concept with other standard methods for determining FC and permanent wilting point (PWP). The standard methods evaluated were the FAO texture estimate (FAO method), the Saxton-Rawls pedotransfer functions (PTFs method), and the water content at predefined soil suction (330 and 15,000 hPa) as measured with a pressure plate apparatus (PP method). Additionally, two pedostructure methods were assessed: the thermodynamic water retention curve (TWRC method) and the thermodynamic pedostructure (TPC method). Undisturbed loamy fine sand soil from a field in Millican, Texas, was analyzed at both the Ap and E horizons. The results showed that the estimated water content at FC and PWP for the three standard methods and for the TWRC method were in relative agreement. However, the TPC method used characteristic transition points in the modeled contents of different water pools in the soil aggregate and was higher for the Ap horizon, but in agreement with the other methods for the E horizon. For example, for the Ap horizon of the soil analyzed in this study, the FC estimated with the standard and TWRC methods ranged from 0.073 to 0.150 m3H2O m-3soil, while the TPC method estimate was 0.221 m3H2O m-3soil. Overall, the different methods showed good agreement in estimating the available water; however, the results also showed some variations in these estimates. It is clear that the TPC method has advantages over the other methods in considering the soil aggregate structure and modeling the soil water content within the aggregate structure. The thermodynamic nature of the TPC method enabled the use of both the soil shrinkage curve and the water retention curve in a weakly structured soil. It is expected that the TPC method would provide more comprehensive advances in understanding the soil water-holding properties of structured soils with higher clay contents. Keywords: Available water, Field capacity, Pedostructure, Pedotransfer functions, Permanent wilting point.


Koedoe ◽  
2014 ◽  
Vol 56 (1) ◽  
Author(s):  
Robert Buitenwerf ◽  
Andrew Kulmatiski ◽  
Steven I. Higgins

Soil water potential is crucial to plant transpiration and thus to carbon cycling and biosphere–atmosphere interactions, yet it is difficult to measure in the field. Volumetric and gravimetric water contents are easy and cheap to measure in the field, but can be a poor proxy of plant-available water. Soil water content can be transformed to water potential using soil moisture retention curves. We provide empirically derived soil moisture retention curves for seven soil types in the Kruger National Park, South Africa. Site-specific curves produced excellent estimates of soil water potential from soil water content values. Curves from soils derived from the same geological substrate were similar, potentially allowing for the use of one curve for basalt soils and another for granite soils. It is anticipated that this dataset will help hydrologists and ecophysiologists understand water dynamics, carbon cycling and biosphere–atmosphere interactions under current and changing climatic conditions in the region.


Koedoe ◽  
2014 ◽  
Vol 56 (1) ◽  
Author(s):  
Robert Buitenwerf ◽  
Andrew Kulmatiski ◽  
Steven I. Higgins

Soil water potential is crucial to plant transpiration and thus to carbon cycling and biosphere–atmosphere interactions, yet it is difficult to measure in the field. Volumetric and gravimetric water contents are easy and cheap to measure in the field, but can be a poor proxy of plant-available water. Soil water content can be transformed to water potential using soil moisture retention curves. We provide empirically derived soil moisture retention curves for seven soil types in the Kruger National Park, South Africa. Site-specific curves produced excellent estimates of soil water potential from soil water content values. Curves from soils derived from the same geological substrate were similar, potentially allowing for the use of one curve for basalt soils and another for granite soils. It is anticipated that this dataset will help hydrologists and ecophysiologists understand water dynamics, carbon cycling and biosphere–atmosphere interactions under current and changing climatic conditions in the region.


HortScience ◽  
2008 ◽  
Vol 43 (7) ◽  
pp. 2143-2150 ◽  
Author(s):  
Craig Cogger ◽  
Rita Hummel ◽  
Jennifer Hart ◽  
Andy Bary

Although compost can improve soil properties related to plant growth and water quality, the value of amending landscape beds for trees and shrubs has been questioned. This research assesses short and midterm effects of compost application and bark mulch on soils and plants in landscape beds and compares the effects of compost applied to the surface or incorporated. Trees and shrubs were established in 2001 in a replicated field experiment with the following treatments: 1) unamended control; 2) compost (7.6-cm depth) applied to the surface; 3) 7.6 cm compost incorporated by rototilling to a depth of 20 cm; 4) bark mulch (7.6 cm); 5) compost surface-applied (7.6 cm) + bark mulch (7.6 cm); and 6) compost incorporated + bark mulch. Soil measurements were made one or more times between 2001 and 2007, including bulk density, compaction, infiltration, aggregate stability, soil moisture tension, total carbon (C) and nitrogen (N), nitrate-N, Bray-phosphorus, exchangeable potassium, and pH. Bark and compost mulch depths were determined three times and plant growth measured annually. Half the depth of surface-applied compost and 26% to 41% of the initial soil C increase from incorporated compost remained 5 years after application; and significant changes in bulk density, compaction, infiltration, and nutrients were apparent. Compost incorporation had a greater effect than surface application on soil C, N, and bulk density. Infiltration was similar in incorporated and surface treatments, and nutrient availability was similar except for N. Soil moisture retention was improved with surface-applied compost. Bark had similar effects as surface-applied compost on bulk density, soil moisture retention, and infiltration. During the first 4 years after transplanting, dogwoods in the compost incorporated + bark mulch treatment typically had larger shoot growth indices. By Year 5, treatment no longer influenced shoot growth. Plants in compost-treated plots had darker green leaves. Surface application of compost could provide significant benefits where incorporation is not feasible.


Koedoe ◽  
2014 ◽  
Vol 56 (1) ◽  
Author(s):  
Robert Buitenwerf ◽  
Andrew Kulmatiski ◽  
Steven I. Higgins

Soil water potential is crucial to plant transpiration and thus to carbon cycling and biosphere–atmosphere interactions, yet it is difficult to measure in the field. Volumetric and gravimetric water contents are easy and cheap to measure in the field, but can be a poor proxy of plant-available water. Soil water content can be transformed to water potential using soil moisture retention curves. We provide empirically derived soil moisture retention curves for seven soil types in the Kruger National Park, South Africa. Site-specific curves produced excellent estimates of soil water potential from soil water content values. Curves from soils derived from the same geological substrate were similar, potentially allowing for the use of one curve for basalt soils and another for granite soils. It is anticipated that this dataset will help hydrologists and ecophysiologists understand water dynamics, carbon cycling and biosphere–atmosphere interactions under current and changing climatic conditions in the region.


2019 ◽  
Vol 1 (3) ◽  
pp. 230-240
Author(s):  
Ling Zeng ◽  
Fan Li ◽  
Jie Liu ◽  
Qianfeng Gao ◽  
Hanbing Bian

Abstract The soil-water characteristic curve (SWCC) is often used to estimate unsaturated soil properties (e.g. strength, permeability, volume change, solute and thermal diffusivity). The SWCC of soil samples is significantly affected by cyclic wetting-drying. To examine how water content and cyclic wetting-drying affect the SWCC of disintegrated carbonaceous mudstone (DCM), SWCC tests were implemented using a pressure-plate apparatus. In addition, SWCC models for DCM considering the initial gravimetric water content and cyclic wetting-drying were developed. The test results showed that the volumetric water content (θ) of the DCM first decreased rapidly and then became stable as matric suction (s) increased. The initial water content affected the SWCC by altering the pore structure of the DCM. For a given number of wetting-drying cycles, the higher the initial water content, the higher the stabilized θ. At a given s value, θ decreased as the number of wetting-drying cycles increased, which suggests that cyclic wetting-drying reduces the water-holding capacity of DCM. The Gardner model for DCM was constructed considering initial water content and cyclic wetting-drying, and was effective at describing and predicting the SWCC model for DCM.


1990 ◽  
Vol 70 (3) ◽  
pp. 667-675 ◽  
Author(s):  
YVES CLOUTIER ◽  
ANDRÉ COMEAU ◽  
MICHÈLE BERNIER-CARDOU ◽  
DENIS A. ANGERS

A field study was conducted to determine the effect of soil moisture on the survival of three winter cereal species. Treatments were applied by watering and weighing the soil to the desired water content. Plants were overwintered in a plastic greenhouse in 1988 and in 1989, in which the air was not heated, but the soil was slightly heated on cold days to avoid very low temperatures. Soil temperature did not fall below −16 °C. Soil temperature rate of change was dependent on moisture content. Puma winter rye and Otrastajuskaja 38 winter wheat were the hardiest, followed by Wintri winter triticale and Norstar winter wheat. Harus winter wheat was less hardy, and Champlein winter wheat was totally winter killed. The highest survival rate was obtained at moderate to high soil moisture content. The soil contained 44% water at field capacity and 19% at the wilting point. The drier the soil in the range 13–23%, the greater the mortality indicating a negative effect of long-term drought on plant survival. By contrast, the wettest treatments: 58% and partial ice encasement, did not reduce survival. However, total ice encasement killed 50–75% of the plants depending on the cultivar. There was an interaction between cultivar and moisture treatment. The data suggest that a moisture level intermediate between the wilting point and field capacity should be sought in studies of cold hardiness.Key words: Moisture, winterkill, ice encasement, wheat, rye, triticale


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