Soil Thermal Diffusivity Research Articles

Photothermal Beam Deflection Spectroscopy for the Determination of Thermal Diffusivity of Soils and Soil Aggregates

Photothermal beam deflection spectroscopy (BDS) with a red He–Ne laser (632.8 nm, 35 mW) as an excitation beam source and a green He–Ne laser (543.1 nm, 2 mW) as a probe was used for estimating thermal diffusivity of several types of soil samples and individual soil aggregates with small surfaces (2 × 2 mm). It is shown that BDS can be used on demand for studies of changes in properties of soil entities of different hierarchical levels under the action of agrogenesis. It is presented that BDS clearly distinguishes between thermal diffusivities of different soil types: Sod-podzolic [Umbric Albeluvisols, Abruptic], 29 ± 3; Chernozem typical [Voronic Chernozems, Pachic], 9.9 ± 0.9; and Light Chestnut [Haplic Kastanozems, Chromic], 9.7 ± 0.9 cm2·h−1. Aggregates of chernozem soil show a significantly higher thermal diffusivity compared to the bulk soil. Thermal diffusivities of aggregates of Chernozem for virgin and bare fallow samples differ, 53 ± 4 cm2·h−1 and 45 ± 4 cm2·h−1, respectively. Micromonoliths of different Sod-podzolic soil horizons within the same profile (topsoil, depth 10–14 cm, and a parent rock with Fe illuviation, depth 180–185 cm) also show a significant difference, thermal diffusivities are 9.5 ± 0.8 cm2·h−1 and 27 ± 2 cm2·h−1, respectively. For soil micromonoliths, BDS is capable to distinguish the difference in thermal diffusivity resulting from the changes in the structure of aggregates.

Study of functioning of heat exchanger in soils with different thermal diffusivity

It was found with the help of mathematical model of the process of heat exchange between the air moving in vertical heat exchanger and the massif of soil, which connects energetic factors of the soil heat exchanger with its parameters as well as natural-climatic conditions that effective thermal energy during the term of heat exchanger functioning depends linearly on thermal diffusivity of soil both for separate heat exchanger and for two heat exchangers located at 4m between axes. Calculative experiment was conducted with application of the packet of calculative hydrodynamics ANSYS Fluent. Temperature field of the air being cooled and of the massif of soil has been detected for the soils with different thermal diffusivity. It has been found that temperature diffusivity of the soil is a determinative factor of energy potential of soil and has a dramatic effect on the effective thermal capacity especially for long-term functioning of soil heat exchanger. From the soil with temperature diffusivity 2,68 m 2 /s we can obtain approximately 3,6 times as more effective thermal energy while heat exchanger is functioning than from the soil with temperature diffusivity 0,83 m 2 /s.

Mechanisms of biochar effects on thermal properties of red soil in south China

Soil thermal properties play crucial roles in governing heat storage and conduction across soil profiles and affect various soil processes by determining soil microclimate. Biochar has gained wide attention as a soil amendment to affect a series of soil physiochemical properties. However, little information is available on the integrated effects of biochar application on soil thermal properties. Disturbed soil columns with consistent bulk density (1.3 g cm−3) were packed using clayey red soil and wheat straw biochar at application rates (w/w) of 0%, 0.5%, 1.0%, 1.5%, 2.0% and 2.5%. Besides, a 2-year field experiment of biochar application at the same application rates with crop rotation was performed in a red soil region in south China. Soil thermal properties, i.e. thermal capacity, conductivity and diffusivity, were measured with heat pulse method for disturbed soil columns and undisturbed soil cores from the field at controlled soil water contents ranging from 0% to 40% at an interval of 5%. Furthermore, soil thermal properties were measured in situ for different biochar treatments under field conditions. For the disturbed soil columns, no significant effect of biochar application on soil thermal properties was detected at most of the soil water content levels. Additionally, it indicated that biochar application cannot directly affect soil thermal properties by changing soil solid substances composition at application rates up to 2.5% w/w. The results from undisturbed soil cores showed significant decreasing effects of biochar application on soil thermal capacity and diffusivity at most of the soil water content levels. The results from in situ measurement showed significant decreasing effect of biochar application on soil thermal capacity, conductivity and diffusivity. Two main underlying mechanisms were identified for the effects of biochar application on soil thermal properties. One is the negative effect of biochar application on soil thermal capacity and conductivity by increasing the soil total porosity, mainly by increase in the meso- and macro-porosity. The other is the positive effects of biochar application on soil thermal properties by increasing the soil water content through improved soil water retention ability. The negative effects through change in the soil structure were the dominant effect under field condition.

Thermal design of Earth-to-Air Heat Exchanger. Part I a new transient semi-analytical model for determining soil temperature

Abstract This article is the first in a series about the thermal design of Earth-to-Air Heat Exchanger, EAHE, using a new developed semi-analytical method. The temperature distribution in the soil surrounding the EAHE is studied in the goal to determine the soil radius as a function of the operation duration. This radius is the first distance from the pipe axis where there is no effect of heat from EAHE. For that, a new transient semi-analytical model is developed in particular to facilitate the thermal design of EAHEs. The main application of the developed model is to predict the deterioration in EAHE's thermal performance as a function of the duration operation. This deterioration can be caused by soil thermal saturation where the nearby subsoil temperature becomes almost equal to the inlet air temperature resulting in minimum heat transfer between air and soil. The analytical solution of the proposed model has been integrated by means of the Bessel function method, for a constant heat flux per unit of length at the pipe surface in the radial dimension and constant inlet air temperature. The model has been verified with several results obtained from the literature. In addition, an investigation of continuous operation of an EAHE is made on thermal performance of the EAHE in the soil of the region of Biskra (Southern Algeria) (34°47′N - 005°43′E) by applying extreme ambient air temperature (57 °C). Results show that the deterioration in thermal performance of EAHE is observed for longer duration in hot and dry climate. In the case of 6 h of continuous operation, the soil radius can reach 0.55 m from the pipe surface. The model proposed in this paper can be considered as the first of its kind which gives a formula for calculating the soil radius (thickness) as a function of the: i) duration of operation, ii) soil thermal diffusivity, iii) pipe diameter and iv) air temperature.

An Empirical Model for Estimating Soil Thermal Diffusivity from Texture, Bulk Density, and Degree of Saturation

Abstract Soil thermal diffusivity κ is an essential parameter for studying surface and subsurface heat transfer and temperature changes. It is well understood that κ mainly varies with soil texture, water content θ, and bulk density ρb, but few models are available to accurately quantify the relationship. In this study, an empirical model is developed for estimating κ from soil particle size distribution, ρb, and degree of water saturation Sr. The model parameters are determined by fitting the proposed equations to heat-pulse κ data for eight soils covering wide ranges of texture, ρb, and Sr. Independent evaluations with published κ data show that the new model describes the κ(Sr) relationship accurately, with root-mean-square errors less than 0.75 × 10−7 m2 s−1. The proposed κ(Sr) model also describes the responses of κ to ρb changes accurately in both laboratory and field conditions. The new model is also used successfully for predicting near-surface soil temperature dynamics using the harmonic method. The results suggest that this model provides useful estimates of κ from Sr, ρb, and soil texture.

Flood effects on soil thermal regimes in contrasting cold‐desert river floodplains (Yampa and Green rivers, Colorado)

AbstractHeat transfer theory suggests that floodplain soils in dryland riverine ecosystems can be cooled by hyporheic flows generated during spring floods. I compared soil temperature cycles and associated hydrologic factors on a free‐flowing river to those on a river where flows and surface water temperatures are now regulated. Spring surface water temperatures were comparable on the 2 rivers, as was apparent diffusivity of the soil under mature Populus fremontii in a year when severe drought produced similar soil moisture regimes. Over 9 years of monitoring, mean annual maximum soil temperature was higher on the regulated river than on the free‐flowing river (10 cm depth: 33 vs. 23 °C; 40 cm depth: 30 vs. 20°C, respectively), and sinusoidal models of the annual temperature cycle at each depth indicated higher means and greater amplitudes on the regulated river. The annual maximum soil temperature was inversely related to peak flood discharge on the free‐flowing river but not on the regulated river. Temporal shifts in the lag between diel cycles at 40 and 10 cm depths—an index of soil thermal diffusivity—suggested that the capillary fringe is strongly involved in heat exchange. An increase in the lag during some water table declines suggested that shallow soils may undergo flood‐induced evaporative cooling. Hyporheic recharge can be an ecologically important determinant of growing‐season soil temperatures at plant rooting depth in dryland river floodplains. Reductions in spring flood magnitude due to river regulation, water abstraction, or climate change can increase these temperatures and thereby alter ecosystem structure and functioning.

Hourly, Daily, and Monthly Soil Temperature Fluctuations in a Drought Tolerant Crop

ABSTRACT Soil temperature is a physical property of great agricultural importance in the soil-plant relationship and in energy exchange with the atmosphere. This study was conducted in a degraded Cambissolo Haplico Ta Eutrofico (Cambisol; Inceptisol) in the Irece Identity Territory, Bahia, Brazil, aiming to evaluate the hourly, daily, and monthly fluctuations of soil temperature at depth, and soil thermal diffusivity in the castor bean crop. Hourly soil temperature data from February 4, 2014, to September 30, 2015, were obtained by [...]

The insensitivity of thermal diffusivity of natural sediments to saturation

This extended abstract presents a ground-breaking study of thermal properties of soils and their dependency on saturation. The paper tries to prove that thermal diffusivity is not significantly dependent on saturation due to its close relationship with saturation-independent parameters such as thermal conductivity and volumetric heat capacity. The investigation is divided into two main scopes of work: the first is to build statistical analysis using the Monte Carlo technique by means of random sampling certain soil thermal properties; and the second is to experimentally validate the statistical models. The experimental framework of the study encompasses the measurement of thermal properties of different soil samples. These samples varied in terms of grain size, percentage clay content, and level of saturation. The experiments were carried out using a KD2-Pro Dual Needle Probe Thermal Properties Analyser. The results demonstrate that saturation has a negligible effect on thermal diffusivity of soils but an inverse relationship exists between diffusivity and clay content. Furthermore, the variation in grain size effect on diffusivity is within 5%. The study shows a correlation between lithology, porosity, and thermal properties. The implications are numerous: from the determination of unwanted heat diffusion of pipelines to the estimation of reservoir properties such as porosity and permeability.

Estimating soil thermal diffusivity at different water contents from easily available data on soil texture, bulk density, and organic carbon content

This study provides an algorithm to estimate soil thermal diffusivity at any water content from data on soil texture, bulk density, and percentage of organic carbon. Models were trained on the dataset of 77 soil samples including silty clays, silty clay loams, silt loams, clay loams, loams, sandy clay loams, sandy loams, loamy sands, and sands. The ranges of sand, silt, and clay within the dataset were 1 – 97, 2 – 80, and 1 – 52%; wet bulk density varied from 860 to 1820 kg m −3 , organic carbon ranged from 0.1 to 6.5%. Thermal diffusivity of the undisturbed soil cores measured by the unsteady-state method was from 0.77 to 10.09 × 10 −7 m 2 s −1 . The dataset was split randomly into the training set of 67 samples and the test set of 10 samples; the procedure was repeated three times. Models were developed from the measured thermal diffusivity vs. water content curves. The experimental data points for each sample were described by a 4-parameter function. Parameters of average curves for different textural classes were also determined. Then regression equations were obtained to estimate the parameters of the thermal diffusivity vs. water content function for different soils: (i) from soil texture; (ii) from soil texture and bulk density; (iii) from soil texture and organic carbon; (iv) from soil texture, bulk density, and organic carbon. The test set data were used to evaluate the model performance. The normalised root mean square errors of the best-performing models were from 20 to 33% depending on soil information available.

Experimental Investigation of Thermo-Physical Properties of Soil Using Solarisation Technology

Soil Thermo-Physical Properties (TPP) depend on heat transfer in the soil. This paper presents a study on different soil solarisation technologies influenced by soil TPP. This study evaluates three factors: The tillage depth for soil at three levels (15, 25 and 45 cm), the number of plastic film at three levels (single, double and without plastic film) and three cases of fertilizers (chemical fertilizer, organic fertilizer and without fertilizer). The parameters explored in this study include soil bulk density (Mg/cm3), soil porosity (%), soil volumetric moisture content (cm3/cm3) and soil thermal diffusivity (m2/sec). Data management and analysis were performed using SAS 9.1 statistical software and the spilt-plot under Randomized Complete Block Design (RCBD). The results show that soil Tillage Depth (TD) strongly influences TPP, as well as a significant effect on soil bulk density (ρb), porosity (Φ), volumetric moisture content (θ) and thermal diffusivity (D). The results also reveal that a tillage depth of 15 cm produces lower values of ρb, θ and D (1.25 Mg/cm3, 0.131 cm3/cm3 and 1.24×10-6 m2/sec, respectively) and a higher value of Φ (52.78%). In addition, the finding indicates that ρb is increased by increasing TD. There was a significant positive correlation between the number of plastic film and parameters studied. The soil double plastic film produced lower values of ρb and D for soil (1.253 Mg/cm3, 7.76×10-7m2/sec). However, it recorded higher values for Φ and θ for soil (52.70% and 0.231 cm3/cm3, respectively). Furthermore, the current study shows significant differences between the types of fertilizers on ρb. Organic Fertilizer (OF) obtained a lower value of ρb (1.2 Mg/m3), compared with chemical fertilizer and without fertilizer (1.28 and 1.31 Mg/m3, respectively). In contrast, contrary to expectations, this study did not find significant differences between the types of fertilizer on D and θ for soil. A positive correlation was found in the interaction between the studied factors in the parameters. Furthermore, D increased with increasing soil bulk density (pb) and tillage depth.

Deriving pedotransfer functions for soil quartz fraction in southern France from reverse modeling

Abstract. The quartz fraction in soils is a key parameter of soil thermal conductivity models. Because it is difficult to measure the quartz fraction in soils, this information is usually unavailable. This source of uncertainty impacts the simulation of sensible heat flux, evapotranspiration and land surface temperature in numerical simulations of the Earth system. Improving the estimation of soil quartz fraction is needed for practical applications in meteorology, hydrology and climate modeling. This paper investigates the use of long time series of routine ground observations made in weather stations to retrieve the soil quartz fraction. Profile soil temperature and water content were monitored at 21 weather stations in southern France. Soil thermal diffusivity was derived from the temperature profiles. Using observations of bulk density, soil texture, and fractions of gravel and soil organic matter, soil heat capacity and thermal conductivity were estimated. The quartz fraction was inversely estimated using an empirical geometric mean thermal conductivity model. Several pedotransfer functions for estimating quartz content from gravimetric or volumetric fractions of soil particles (e.g., sand) were analyzed. The soil volumetric fraction of quartz (fq) was systematically better correlated with soil characteristics than the gravimetric fraction of quartz. More than 60 % of the variance of fq could be explained using indicators based on the sand fraction. It was shown that soil organic matter and/or gravels may have a marked impact on thermal conductivity values depending on which predictor of fq is used. For the grassland soils examined in this study, the ratio of sand-to-soil organic matter fractions was the best predictor of fq, followed by the gravimetric fraction of sand. An error propagation analysis and a comparison with independent data from other tested models showed that the gravimetric fraction of sand is the best predictor of fq when a larger variety of soil types is considered.

English

Soil thermal parameters are mainly inputs for models of soil heat flux. Mathematical models are important tool for predicting the soil heat and water transfer, depending on some fundamentals of soil physical properties. Soil moisture is one of the soil physical properties that have a great effect on thermal parameters. The aim of the work is to describe the behavior of soil thermal parameters under different values of soil moisture, and is to investigate the effect of some fundamentals of soil physical properties on thermal parameters. We could describe the relationship between thermal diffusivity and soil moisture by ∩ shaped curve using a quadratic equation and evaluate the efficiency of this equation, statistically. Experimental thermal diffusivity (Kexp) by direct method and mathematical models were measured. Mathematical models were Chung and Horton model (1987) (Kcal-2), the model of Arkhangel’skaya (2004) (Kcal-3) and the suggested quadratic equation (Kcal-1). Efficiency of the quadratic equation and mathematical models were estimated using the correlation coefficient (R2), Root Mean Square Error (RMSE), and the Nash-Sutcliffe Efficiency (NSE). The values of R2, RMSR and NSE for the quadratic equation were 0.978, 0.24 and 0.95, respectively, for sod-podzolic soil under the study. The quadratic equation is a simple and faster equation for forecasting soil thermal diffusivity. Key words: Soil thermal parameters, thermal diffusivity, thermal conductivity, soil heat capacity, soil moisture, soil bulk density, organic matter, quadratic equation and mathematical models.

Structural-functional concept of thermophysical condition of the soils of Altai Region

The goal of this study was to reveal the quantitative interrelations between the thermophysical indices (thermal conductivity and thermal diffusivity) and physical soil properties such as; moisture content, density and detachability. According to the research targets, the soil samples including different genesis and soil particle size distribution were taken in different soil and climatic zones of the Altai Region. These were the sod-podzolic sandy loam soils of the dry steppes, chernozems and chestnut soils of light and medium loamy particle size distribution of temperately arid zone, and the heavy loamy gray forest soils and clayey chernozems of the Altai foothills and low mountains. The samples of undisturbed structures in different soil horizons were studied. To measure the thermophysical properties in laboratory setting, a pulse method of a two-dimensional heat source was used. The method takes into account the patterns of temperature field equalization in an unbounded medium after the heat source termination. A feature of this process is the occurrence of peak temperature at the investigated point of the medium at a given instant. The knowledge of this temperature and time enables to determine the soil thermal capacity, thermal conductivity and thermal diffusivity.

Effects of Biochar Amendment on Soil Thermal Properties in the North China Plain

Core Ideas Biochar may change the surface soil heat balance. Biochar significantly decreased soil thermal conductivity and thermal diffusivity. Changes were mainly attributed to soil bulk density and the biochar itself. Few studies have examined the effects of biochar amendment on soil thermal properties. Soil thermal properties dominate the storage and conduction of heat in soil, affect soil temperature and water and heat movement, and consequently influence plant growth and soil biochemical processes. A 7‐yr field experiment was performed to investigate the effects on soil thermal properties of biochar amendment at three application rates: 0 (control), 4.5 t ha−1 yr−1 (B4.5), and 9.0 t ha−1 yr−1 (B9.0). Soil heat capacity (C), thermal conductivity (λ), and thermal diffusivity (α) of the 0‐ to 5‐cm‐depth topsoil were determined throughout a corn (Zea mays L.)–wheat (Triticum aestivum L.) growing period using a heat pulse method. The results showed that soil bulk density was decreased significantly by biochar (P < 0.05). There was no significant difference in soil water content between the control and biochar treatments. There was no significant difference in the soil volumetric heat capacity between the control and biochar treatments. Soil thermal conductivity and thermal diffusivity were decreased significantly by biochar (P < 0.05). There was a strong positive relationship between soil thermal conductivity and bulk density, and between soil thermal conductivity and water content (P < 0.001, n = 99). In contrast, there was a strong negative relationship between soil thermal conductivity and biochar amount (P < 0.001, n = 99). The reduction in soil thermal diffusivity may be attributed largely to the low thermal diffusivity of biochar and the decrease in soil bulk density caused by biochar.

Comparison of different soil temperature algorithms in permafrost regions of Qinghai-Xizang (Tibet) Plateau of China

Soil thermal diffusivity is a crucial physical parameter that affects soil temperature. By applying sinusoidal boundary conditions, an analytical solution using separated variables for the heat conduction-convection equation was developed. The thermal diffusivity and liquid water flux density were calculated with data collected at field observation sites in permafrost regions of Qinghai-Xizang (Tibet) Plateau (QXP). By taking the soil layer at the depth of 5cm as the upper boundary, the soil temperature at a depth of 10cm was modeled by the thermal conduction-convection method, amplitude method and phase method. The statistical analysis of the standard error of the estimate (SEE), the normalized standard error (NSEE) and the root mean square error (RMSE) demonstrated that the thermal conduction-convection method provided the most accurate prediction of soil temperature, with average SEE, NSEE, and RMSE of 0.72°C, 9.26% and 0.72°C, respectively. The thermal conduction-convection method provides a useful tool for calculating soil thermal parameters, simulating soil temperature and land surface processes parameterization for permafrost changes modelling under global warming.

Thermal conductivity and diffusivity estimations for shallow geothermal systems

Horizontal closed-loop ground collectors for ground source heat pumps are located within the soil and the top of the underlying superficial deposits. Estimating thermal properties for this zone is difficult as it is heterogeneous and is subject to seasonal water content variations. Soil thermal diffusivity values have been calculated at 56 sites using temperature data from UK Met Office weather stations. The technique utilizes the decrease in amplitude and increase in phase shift with depth of a transmitted heat pulse in the ground, the magnitudes of which are determined by thermal diffusivity. The weather stations are located throughout Great Britain and incorporate different soil types. The apparent thermal diffusivities derived from seasonal temperature cycles spanning several years generate seasonally averaged site-specific estimates that can be considered alongside diffusivity values determined in the laboratory or obtained by point measurements using field needle probes. Associated thermal conductivities have been estimated from the thermal diffusivities from knowledge of soil texture. Median thermal conductivities for the sand, loam and clay soil types have been estimated as 1.56, 1.15 and 1.81 W m −1 K −1 respectively with corresponding thermal diffusivities of 0.9961 × 10 −6 , 0.7173 × 10 −6 and 1.0295 × 10 −6 m 2 s −1 respectively.

New Fourier-series-based analytical solution to the conduction–convection equation to calculate soil temperature, determine soil thermal properties, or estimate water flux

Temperature is an important physical variable of soil. Heat transfer in soils predominantly occurs due to conduction and convection. In this paper, we present a new analytical solution, based upon the Fourier series boundary conditions for soil surface temperature, in which the separation of variables for the heat conduction–convection equation was established. Data that had been collected from the Qinghai-Xizang (Tibet) Plateau (QXP) were used to calculate the thermal diffusivity and the liquid water flux density using different methods. The results of the soil thermal diffusivity using 5cm as the upper boundary for the soil depth were used to calculate the soil temperature using both the single sine wave conduction and conduction–convection model and the Fourier series conduction–convection model. These results were then compared with the values for the temperature of the field soil measured at a depth of 10cm. The average standard error of the estimate (SEE), the normalized standard error (NSEE) and Bias were 0.16°C, 2.70% and 0.11°C for the Fourier series conduction–convection method. The results indicate that the Fourier series model provides a better estimate of observed field temperatures than the sine wave model. This method provides a useful tool for determining soil thermal parameters, simulating soil temperature and the parameterization of land surface processes for modeling permafrost changes under global warming conditions.

Estimation from Soil Temperature of Soil Thermal Diffusivity and Heat Flux in Sub-surface Layers

Soil thermal parameters are important for calculating the surface energy balance and mass transfer. Previous studies have proposed methods to estimate thermal parameters using field data; however, the application of these methods lacks validation and comprehensive evaluation under different climatic conditions. Here, we evaluate four methods (amplitude, phase shift, conduction–convection and harmonic) to estimate thermal diffusivity (k) under different climatic conditions. Heat flux was simulated and compared with data from heat-flux plates to validate the application of the four methods. The results indicated that, under clear-sky conditions, the harmonic method had the greatest accuracy in estimating k, though it generated large errors on rainy days or under overcast conditions. The conduction–convection method (CCM) provided a reliable estimate of k on rainy days, or under overcast skies, coinciding with increased water movement in the soil profile. The amplitude method, although a simple calculation, had poor accuracy for rainy and overcast conditions. Finally, the phase shift method was shown to be a suitable alternative for CCM to estimate k under overcast conditions, though only when soil moisture content was high.

Estimating apparent thermal diffusivity of soil using field temperature time series

Reliable estimates of soil thermal properties such as heat capacity, thermal conductivity, and diffusivity are important in analysis of heat transmission through soils in applications such as shallow geothermal applications, buried electrical conduits, and in general heat/fluid flow analyses. A number of analytical, numerical and experimental methods are available to determine the soil thermal properties. In this paper, the analytical and numerical methods developed on the basis of one-dimensional heat conduction equation are used to estimate the apparent thermal diffusivity of soil. Three of the four analytical methods, Amplitude, Phase, and Arctangent provide explicit equations for the apparent thermal diffusivity. Two methods, Harmonic and Numerical, make use of large number of temperature measurements to implicitly solve for the apparent thermal diffusivity. The temperature time series data monitored at different depths in two field sites in Melbourne, Australia for more than 2 year period were used to estimate the apparent thermal diffusivity of soil down to 2 m depth. The apparent thermal diffusivity was calculated using all five methods and compared with laboratory experimental results. The effectiveness of each method in predicting the thermal diffusivity was compared and observed discrepancies were discussed. Finally, the observed soil temperature data for a 12 month period are used to model the temperature variation in the ground analytically using Harmonic method and the model prediction for the following 12 month was compared independently with the field measurements. The analytical model prediction is found to be in good agreement with the field monitored data.

The determination of soil temperature and thermal diffusivity

Topraklardaki sicaklik degisimi ve isisal yayinim toprak mikro klimasinin olusumuna, toprak ozelliklerinin degisimi ve bitki gelisimi sureclerine onemli duzeyde etki yapmaktadir. Bu calisma, Samsun ili Carsamba ilcesinde cim ortusu ile kapli acik (I. deneme alani) ve seftali bahcesinde agaclarin golgeleme yaptigi (II. deneme alani) alanlarda yurutulmustur. Deneme alanlarinda topraklarin yuzeyinden 100 cm’ye kadar her 10 cm derinliginde 700, 1200, 1800 saatlerindeki gunluk toprak sicakliklari 21 agustos 19 eylul 2011 tarihleri arasinda olculmustur. Olculen toprak sicaklik degerlerinden faydalanarak; gunluk sicaklik degisimi ve bu degisime bagli olarak amplitut, isisal yayinim katsayisi gibi isisal ozellikler, topragin temel isi tasinim denkleminin cozume gore elde edilen teorik gunluk sicaklik degerleri ile olcum degerlerinin karsilastirilmasi irdelenmistir. I. ve II. deneme alanlarinin 0-50 cm katmanlarindaki 700, 1200 ve 1800 saatlerinde olculen gunluk sicaklik degerleri sirasiyla 16.5-24.0; 21.0-34.0; 19.5-27.0°C ve 16.5-23.0; 19.0-27.5; 19.0-24.8°C ve 50-100 cm katmanlarinda ise sirasiyla 19.1-23.0; 21.0- 25.5; 19.2-25.0°C ve 18.9-22.0; 19.2-24.5; 19.0-24.0°C arasinda degismektedir. Genel olarak her iki deneme alaninda da topraklari yuzeye yakin katmanlarindaki sicaklik degisimleri az olup, asagi katmanlara dogru ( > 50 cm) inildikce bu degisimler daha da azalmaktadir. Amplitut degerleri I. deneme alaninda toprak yuzeyinde 2.03-5.60oC, 10 cm’den derin katmanlarda ise 0.93-3.07oC arasinda, II. deneme alaninda ise sirasiyla 1.97-2.77oC ve 0.94-2.46oC arasinda belirlenmistir. Ortalama isisal yayinim I. deneme alaninda 10-100 cm toprak derinliginde 0.0835-0.8830 cm2 sn-1; II. deneme alaninda ise 0.2578-1.9692 cm2 sn-1 araliklarinda bulunmustur. Topragin isi tasinim denklemine gore hesaplanan sicaklik degerleri ile olculen sicaklik degerleri arasindaki ortalama nispi hata 0.015 - 0.089 araliginda belirlenmistir.