Influence of winter wheat on soil thermal properties of a Paleudalf (original) (raw)
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Comparison of thermal properties of three texturally different soils under two compaction levels
African Journal of Agricultural Research, 2013
The range of thermal conductivity (K) for was highest for black soil followed by alluvial sandy loam and red loamy sand soil. Thermal properties were the highest for black clay soil followed by alluvial sandy loam soil and were the lowest in red loamy sand soil. In all soil types, C v and K were higher in compacted soil as compare to loose soil. Hence, downward heat flux was more in compacted soil. The black color of the clay soil might have exerted added effects on the increase in the temperature because of more heat absorption whereas the moderating effect of higher moisture on ST was not prominent. Whereas in lighter colour alluvial soil due to moderating effect of soil water on ST would lead to the reduction evaporational losses and improvement in water use efficiency of crop.
Dry matter productivity and soil physical properties after winter cover crops cultivation
Scientia Agraria Paranaensis, 2020
The present study aimed to evaluate the dry matter yield of cover crops cultivated in monoculture and intercropped in a no-till system and its effects on the soil physical properties. The experimental design was of randomized blocks, with four replicates. Treatments used were black oat, black oat + forage radish, forage radish, black oat + field pea, field pea and the control (fallow). After 100 days after sowing the cover crops, the dry matter yield was evaluated, with the highest values found in the intercropped crops. After desiccation, undeformed soil samples were collected for the determination of macroporosity, microporosity, total porosity and soil bulk density in the 0-0,10; 0,10-0,20; 0,20-0,30 and 0,30-0,40 m layers. Soil penetration resistance was evaluated with a digital penetrometer. The intercrop of black oat with field pea and with forage radish provided the highest dry matter yield, showing the potential of dry matter accumulation in relation to monoculture. The cover crops were capable of improving the macroporosity, bulk density and soil penetration resistance when compared to the fallow area (control); however, they had no influence in soil aggregation due to the high compaction degree in the area.
Thermal properties of soils as affected by density and water content
Biosystems engineering, 2003
Thermal properties dictate the storage and movement of heat in soils and as such influence the temperature and heat flux in soils as a function of time and depth. The ability to monitor soil heat capacity is an important tool in managing the soil temperature regime to affect seed germination and crop growth. The effect of water content and bulk density on the specific heat, volumetric heat capacity, and thermal diffusivity of some sieved and repacked soils was investigated through laboratory studies. These laboratory experiments used the calorimetric method to determine specific heat of soils. The soils used were classified as sand and clay. For the type of soils studied, specific heat increased with increased moisture content. Also, volumetric heat capacity increased with increased moisture content and soil density. Volumetric heat capacity ranged from 1Á48 to 3Á54 MJ m À3 8C À1 for clay and from 1Á09 to 3Á04 MJ m À3 8C À1 for sand at moisture contents from 0 to 0Á25 (kg kg À1 ) and densities from 1200 to 1400 kg m À3 . Specific heat ranged from 1Á17 to 2Á25 kJ kg À1 8C À1 for clay and from 0Á83 to 1Á67 kJ kg À1 8C À1 for sand at moisture contents from 0Á02 to 0Á25 (kg kg À1 ) and soil density of 1300 kg m À3 . The volumetric heat capacity and specific heat of soils observed in this study under varying moisture content and soil density were compared with independent estimates made using derived theoretical relations. The differences between the observed and predicted results were very small. Clay soil generally had higher specific heat and volumetric heat capacity than sandy soil for the same moisture content and soil density. The results also show that thermal diffusivity vary with moisture content and soil texture. Sandy soil exhibited a thermal diffusivity peak at a definite moisture content range. Clay soil, however, did not exhibit a sharp thermal diffusivity peak.
Biomass Productivity of Different Winter Cover Crops and Their Effect on Soil Physical Properties
Journal of Agricultural Science, 2020
The cultivation of cover crops is a vegetative practice considered an alternative for sustainable soil management, due to its beneficial action in different aspects of soil properties. Thus, the present work aimed to evaluate the effect of cultivation of different species of cover crops on soil density, porosity and diameter of soil aggregates. The experimental design was in randomized blocks, with four replications. The treatments consisted of four species of winter green manure: black oat, forage turnip, forage pea, and common vetch, a consortium of black oat + forage turnip and area kept fallow (control). The following evaluations were performed: dry matter production of cover crops, macroporosity, microporosity, total porosity, soil density, geometric mean diameter and weighted average diameter. The cultivation with forage turnip and the consortium of black oat + forage turnip presented higher dry matter productivity, decreased soil density, increased soil porosity, improved the...
European Journal of Soil Science, 2019
Soil thermal properties play important roles in dynamic heat and mass transfer processes, and they vary with soil water content (θ) and bulk density (ρ b). Both θ and ρ bchange with time, particularly in recently tilled soil. However, few studies have addressed the full extent of soil thermal property changes with θ and ρ b. The objective of this study is to examine how changes in ρ b with time after tillage impact soil thermal properties (volumetric heat capacity, C v, thermal diffusivity, k, and thermal conductivity, λ). The study provides thermal property values as functions of θ and ρ b and of air content (n air) on undisturbed soil cores obtained at selected times following tillage. Heat pulse probe measurements of thermal properties were obtained on each soil core at saturated, partially saturated (θ at pressure head of −50 kPa) and oven-dry conditions. Generally, kand λ increased with increasing ρ b at the three water conditions. The C v increased as ρ bincreased in the oven-dry and unsaturated conditions and decreased as ρ b increased in the saturated condition. For a given θ, a larger ρ b was associated with larger thermal property values, especially for λ. The figures of C v, k and λ versus θ and ρ b, as well as C v, k and λ versus n air, represented the range of soil conditions following tillage. Trends in the relationships of thermal property values with θ and ρ b were described by 3-D surfaces, whereas each thermal property had a linear relationship with n air. Clearly, recently tilled soil thermal property values were quite dynamic temporally due to varying θ and ρ b. The dynamic soil thermal property values should be considered in soil heat and mass transfer models either as 3-D functions of θ and ρ b or as linear functions of n air.
Advances in Water Resources, 2012
Diffusive heat flux at the soil surface is commonly determined as a mean value over a time period using heat flux plates buried at some depth (e.g., 5-8 cm) below the surface with a correction to surface flux based on the change in heat storage during the corresponding time period in the soil layer above the plates. The change in heat storage is based on the soil temperature change in the layer over the time period and an estimate of the soil thermal heat capacity that is based on soil water content, bulk density and organic matter content. One-or multiple-layer corrections using some measure of mean soil temperature over the layer depth are common; and in some cases the soil water content has been determined, although rarely. Several problems with the heat flux plate method limit the accuracy of soil heat flux values. An alternative method is presented and this flux gradient method is compared with soil heat flux plate measurements. The method is based on periodic (e.g., half-hourly) water content and temperature sensing at multiple depths within the soil profile and a solution of the Fourier heat flux equation. A Fourier sine series is fit to the temperature at each depth and the temperature at the next depth below is simulated with a sine series solution of the differential heat flux equation using successive approximation of the best fit based on changing the thermal diffusivity value. The best fit thermal diffusivity value is converted to a thermal conductivity value using the soil heat capacity, which is based on the measured water content and bulk density. A statistical analysis of the many data resulting from repeated application of this method is applied to describe the thermal conductivity as a function of water content and bulk density. The soil heat flux between each pair of temperature measurement depths is computed using the thermal conductivity function and measured water contents. The thermal gradient method of heat flux calculation compared well to values determined using heat flux plates and calorimetric correction to the soil surface; and it provided better representation of the surface spatiotemporal variation of heat flux and more accurate heat flux values. The overall method resulted in additional important knowledge including the water content dynamics in the near-surface soil profile and a soil-specific function relating thermal conductivity to soil water content and bulk density.
Effects of crop residue cover and architecture on heat and water transfer at the soil surface
Geoderma, 2003
Different residue types and standing stubble versus distributed flat residues affect heat and water transfer at the soil surface to varying degrees. Understanding the effects of various residue configurations can assist in better residue management decisions, but this is complex due to various interacting influences. Therefore, modeling the effects of crop residues on heat and water movement can be an effective tool to assess the benefits of differing residues types and architectures for various climates. The purpose of this study was to test the ability of the Simultaneous Heat And Water (SHAW) model for simulating the effects of residue type and architecture on heat and water transfer at the surface and to evaluate the impacts of differing residue types and architectures on heat and water transfer in significantly different climates. The model was tested on bare tilled soils and corn, wheat and millet residues having varying amounts of standing and distributed flat residues for three separate locations: Ames, IA, Akron, CO and Pullman, WA. Modifications to the model were necessary to correctly simulate the effect of wind on convective transfer through a flat corn residue layer. Model efficiencies for simulated soil temperature approached or exceeded 0.90 for nearly all residue treatments and locations. The root mean square deviation for simulated water content compared to measured values was typically around 0.04 m 3 m À 3 . Satisfied that the model could reasonably simulate the effect of residue type and architecture, the model was applied to simulate the effects of differing residue architectures to 30 years of generated weather conditions for four diverse climate stations: Boise, ID; Spokane, WA; Des Moines, IA; Minneapolis, MN. Simulated frost depths for bare and standing residues were typically deeper than for flat residues. Bare soil had the highest evaporation at all sites, and flat wheat residue generally had the lowest evaporation. The wetter climates (Des Moines and Minneapolis) tended to favor flat residues for reducing evaporation more so than the drier climates. Near-surface soil temperature under standing residues warmed to 5 jC in the spring by as much as 5 -9 days earlier compared to bare and flat residue cover depending 0016-7061/03/$ -see front matter D
Soil and Tillage Research, 2000
Soil thermal conductivity determines how a soil warms or cools with exchange of energy by conduction, convection, and radiation. The ability to monitor soil thermal conductivity is an important tool in managing the soil temperature regime to affect seed germination and crop growth. In this study, the temperature-by-time data was obtained using a single probe device to determine the soil thermal conductivity. The device was used in the ®eld in some Jordanian clay loam and loam soils to estimate their thermal conductivities under three different tillage treatments to a depth of 20 cm. Tillage treatments were: notillage, rotary tillage, and chisel tillage. For the same soil type, the results showed that rotary tillage decreased soil thermal conductivity more than chisel tillage, compared to no-tillage plots. For the clay loam, thermal conductivity ranged from 0.33 to 0.72 W m À1 K À1 in chisel plowed treatments, from 0.30 to 0.48 W m À1 K À1 in rotary plowed treatments, and from 0.45 to 0.78 W m À1 K À1 in no-till treatments. For the loam, thermal conductivity ranged from 0.40 to 0.75 W m À1 K À1 in chisel plowed treatments, from 0.34 to 0.57 W m À1 K À1 in rotary plowed treatments, and from 0.50 to 0.79 W m À1 K À1 in no-till treatments. The clay loam generally had lower thermal conductivity than loam in all similar tillage treatments. The thermal conductivity measured in this study for each tillage system, in each soil type, was compared with independent estimates based on standard procedures where soil properties are used to model thermal conductivity. The results of this study showed that thermal conductivity varied with soil texture and tillage treatment used and that differences between the modeled and measured thermal conductivities were very small. #
Knowledge of the thermal properties of the soil top layer is of great importance in agricultural meteorology where problems of heat exchange at the soil surface are encountered. The availability of these data is important because of the improvements in wider applications of soil heat and water transport models as well as seed germination and crop growth. This research work therefore intends to determine the variability of soil thermal properties of a seasonally cultivated Agricultural Teaching and Research Farm located within the University of Ibadan campus, South-western Nigeria with a view to have understanding of how different soils warm up in order to allow better planning of planting of crops and have knowledge for the control of thermal-moisture regime of soil in the field and greenhouse. Forty-five points were located for the measurements of thermal properties in cultivated fields of maize, pineapple, cowpea, Okro and vegetables. A KD-2 Pro thermal analyzer was used for the measurements of these thermal properties such as thermal conductivity, thermal resistivity, volumetric specific heat and thermal diffusivity. Keywords : variability, thermal properties, moisture content, bulk density, agricultural farm, seed germination.