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- Aboulila, Tarek Selim, et al.
(author)
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Soil water and salinity distribution under different treatments of drip irrigation.
- 2013
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In: Soil Science Society of America Journal. - : Wiley. - 0361-5995. ; 77:4, s. 1144-1156
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Journal article (pop. science, debate, etc.)abstract
- In this study, field experiments and numerical simulations for different drip irrigation treatments in a sandy loam soil were conducted to investigate soil water and salinity distribution as well as dye infiltration patterns. Three treatments, surface drip irrigation without and with plastic mulch (T1 and T2, respectively); and subsurface drip irrigation (T3), were used. In addition, daily and bi-weekly irrigation regimes were considered during performing each treatment. After ceasing the designed irrigation schedule of each treatment, horizontal soil sections were dug with 10 cm intervals. Then, dye patterns were captured using a digital camera and soil water and pore water electric conductivity were measured by a WET-sensor. Experiments results revealed that maximum dye infiltration depth and maximum dye coverage volume occurred during the bi-weekly irrigation regime and in T3. Daily irrigation regime kept the top soil layer moist with adequate amount of soil water as compared to bi-weekly regime. Moreover, T2 provided higher soil water content within the soil domain as compared to other treatments. The simulation results also demonstrated that model prediction for soil moisture distribution within the flow domain was excellent. Furthermore, T2 and daily irrigation showed lower salinity levels in the flow domain as compared to other irrigation treatments and regimes. In sum, mulching treatment with daily irrigation regime is recommended for arid areas over other drip irrigation treatments and regimes. In addition, HYDRUS-2D/3D can be used as a fast and cost effective assessment tool for water flow and salt movement for specific sites having similar soil conditions.
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| 5. |
- Blombäck, Karin
(author)
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Evaluating the effectiveness of the phosphorus sorption index for estimating maximum phosphorus sorption capacity
- 2020
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In: Soil Science Society of America Journal. - : Wiley. - 0361-5995 .- 1435-0661. ; 84, s. 994-1005
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Journal article (peer-reviewed)abstract
- The single‐point P sorption index (PSI), which is defined as the ratio of sorbed P (S) to the log P concentration in soil solution following a single P addition, is often used to estimate maximum soil P sorption capacity (Smax). Although studies have found good correlations between PSI and Smax as determined from fitting the Langmuir model to complete sorption isotherm data, a thorough analysis of the role of added P concentration on this relationship is needed. Our first objective was to investigate the effect of added P concentration on the correlation between PSI and Smax as determined by the Langmuir equation. Our second objective was to determine if S was better than PSI for predicting Smax. Using numerical simulations, we tested the correlation between Smax and PSI for added P concentrations of 75, 100, 150, and 200 mg P L−1. Results of the simulations show that the strength of the correlation between Smax and PSI increases with increasing P concentration. Our results also show that PSI was a better predictor of Smax than S for added concentrations of 75 and 100 mg P L−1, whereas at the higher rates S was a slightly better predictor of Smax and gave a direct estimate of Smax rather than the relative estimate obtained from PSI. Results from P sorption data measured on soils from Maryland and Sweden were consistent with our results from the numerical simulations. Our findings highlight important limitations of using PSI for estimating Smax.
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| 6. |
- Getahun, Gizachew Tarekegn
(author)
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Eleven Years' Effect of Conservation Practices for Temperate Sandy Loams: I. Soil Physical Properties and Topsoil Carbon Content
- 2017
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In: Soil Science Society of America Journal. - : Wiley. - 0361-5995 .- 1435-0661. ; 81, s. 380-391
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Journal article (peer-reviewed)abstract
- Conservation agriculture (CA) has been suggested as a means of making intensification of agriculture sustainable. The purpose of this study was to understand and quantify long-term individual and combined effects of key conservation practices on soil physical properties and topsoil C content. Field experiments were conducted in 11- to 12-yr-old experiments on two Danish sandy loams at Foulum and Flakkebjerg. Three crop rotations/residue management treatments were compared and tillage was included as a split-plot factor. The tillage systems were moldboard plowing to a depth of 20 cm (MP), direct drilling (D) and harrowing to a depth of 8 to 10 cm (H). Soil sampling and in-field measurements were performed in autumn 2013 and spring 2014. In the field, soil structure was visually evaluated and penetration resistance (PR) measured. Soil C, wet stability (clay dispersion and wet aggregate stability), and soil strength were determined in the laboratory. The MP soil had a uniform soil organic carbon (SOC) content in the 0- to 20-cm depth of topsoil, whereas H and D resulted in SOC accumulation near the soil surface. Plowing resulted in the best visually assessed topsoil structure and had the lowest PR. However, H and D in combination with residue retention gave the best structural stability. Residue retention alleviated negative effects of reduced tillage on PR and improved wet stability in the MP treatment at the Foulum site. Clay and SOC correlated well with soil physical parameters, confirming their important role in soil structure formation and stabilization. Our study showed benefits of combining key CA elements, although longer-term studies are most likely needed to reveal the full potential.
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| 7. |
- Griffiths, Natalie A., et al.
(author)
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Temporal and Spatial Variation in Peatland Carbon Cycling and Implications for Interpreting Responses of an Ecosystem-Scale Warming Experiment
- 2017
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In: Soil Science Society of America Journal. - : ACSESS. - 0361-5995 .- 1435-0661. ; 81:6, s. 1668-1688
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Journal article (peer-reviewed)abstract
- We are conducting a large-scale, long-term climate change response experiment in an ombrotrophic peat bog in Minnesota to evaluate the effects of warming and elevated CO2 on ecosystem processes using empirical and modeling approaches. To better frame future assessments of peatland responses to climate change, we characterized and compared spatial vs. temporal variation in measured C cycle processes and their environmental drivers. We also conducted a sensitivity analysis of a peatland C model to identify how variation in ecosystem parameters contributes to model prediction uncertainty. High spatial variability in C cycle processes resulted in the inability to determine if the bog was a C source or sink, as the 95% confidence interval ranged from a source of 50 g C m(-2) yr(-1) to a sink of 67 g C m(-2) yr(-1). Model sensitivity analysis also identified that spatial variation in tree and shrub photosynthesis, allocation characteristics, and maintenance respiration all contributed to large variations in the pretreatment estimates of net C balance. Variation in ecosystem processes can be more thoroughly characterized if more measurements are collected for parameters that are highly variable over space and time, and especially if those measurements encompass environmental gradients that may be driving the spatial and temporal variation (e.g., hummock vs. hollow microtopographies, and wet vs. dry years). Together, the coupled modeling and empirical approaches indicate that variability in C cycle processes and their drivers must be taken into account when interpreting the significance of experimental warming and elevated CO2 treatments.
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| 8. |
- Hamed Abd El Mageed, Yasser, et al.
(author)
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Soil solution electrical conductivity measurements using different dielectric techniques
- 2003
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In: Soil Science Society of America Journal. - : Wiley. - 0361-5995. ; 67:4, s. 1071-1078
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Journal article (peer-reviewed)abstract
- Accurate measurements of soil solution electrical conductivity (or.) are needed in various applications. One recently developed technique that measures sigma(w) is the Sigma Probe (SP). The SP is supposed to give accurate readings only-slightly dependent on water content (theta) and soil type. To test the performance of the SP, it was compared with another dielectric technique, time domain reflectometry (TDR). Both techniques utilize the dielectric constant (K-a) and bulk electrical conductivity (sigma(a)) to estimate the sigma(w). Measurements of sigma(w) were obtained in a laboratory experiment using nine different soil types with theta in the range 0.05 to 0.50 m(3) m(-3). In each soil type, three different sigma(w) were used (approximately 0.3, 1.2, and 3.0 dS m(-1)). The linear sigma(w)-sigma(a)-theta model used by the SP contains only one soil specific parameter (K-0) Using this model, the SP readings were constant over the encountered range in 0, whereas the TDR estimation calculated by the same model typically increased at K-a values below the range of 10 to 15. Using the SP with a default K-0 value of 4.1 typically gave a sigma(w) that was 20% of the true sigma(w) when sigma(w) > 1 dS m(-1). The error in the sigma(w) estimation for or, lower than 1 dS m(-1) can be much larger except in sandy soils. The TDR measurements of sigma(w) using a conventional sigma(w)-sigma(a)-theta model were more accurate in all soil types at all theta, with root mean square errors that were lower by about 50% compared with the SP readings. However, this model requires soil specific parameters that have to be obtained during a calibration experiment.
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| 9. |
- Hansson, Linnea, et al.
(author)
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Soil Compaction Effects on Root-Zone Hydrology and Vegetation in Boreal Forest Clearcuts
- 2019
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In: Soil Science Society of America Journal. - : Wiley. - 0361-5995 .- 1435-0661. ; 83
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Journal article (peer-reviewed)abstract
- Soil compaction is a common consequence of forestry traffic traversing unprotected, moist soils; it decreases porosity and affects hydraulic conductivity even in coarse-textured soils. The aim here was to study root-zone hydrology and vegetation in three microsites (in, between, and beside wheel tracks) 4 to 5 yr after forwarder traffic, on stony and sandy till soils in two clearcuts in northern Sweden. Measurements of soil volumetric water content (VWC), vegetation indicators and one-dimensional hydrological modeling (Hydrus-1D) of wheel tracks and undisturbed soil were conducted. Soil VWC was monitored hourly during 2017 and 2018 in three or four plots along a slope on each site. Soil VWC was also measured once with a portable sensor in 117 plots along two slopes at each site, where the vegetation was recorded and analyzed using Ellenberg indicator indexes. Soil VWC was highest in wheel tracks and lowest between tracks; this was corroborated by the species composition in the wheel tracks (Ellenberg indicator for soil moisture). Bare soil was more frequent in wheel tracks and between tracks than in undisturbed soil. The model simulations indicated that the changed soil hydraulic properties influenced the VWC results in the wheel tracks. However, the differences in average pressure heads in the root zone were small between the microsites and only apparent during dry periods. In the wheel tracks, air-filled porosity was <0.10 m(3) m(-3), indicating insufficient soil aeration during 82% (Site T) and 23% (Site R) of the 2017 growing season. Insufficient aeration could be one explanation for the presence of some still unvegetated areas.
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| 10. |
- Hyvonen, R, et al.
(author)
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Predicting long-term soil carbon storage from short-term information
- 1998
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In: SOIL SCIENCE SOCIETY OF AMERICA JOURNAL. - : SOIL SCI SOC AMER. - 0361-5995. ; 62:4, s. 1000-1005
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Journal article (other academic/artistic)abstract
- Changes in land use and in climate may induce changes in soil organic matter storage in different ecosystems, Predictions of future soil organic matter storage are based on extrapolations from shortterm observations. Certain errors in the extrapolation pr
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