Irreversible Thermodynamics for Stress, Strain and Other Soil Physical Property Description

RHEOLOGIC models used to describe the mechanical behavior of soil have recently been reviewed and summarized in detail by Scott and Ko (1969). Their review (274 references) is a "state of the art" report which describes theoretical and experimental application to soils of rate process theory, granular models, and the continuum models of elasticity, plasticity, and viscoelasticity. Applications of the various models were primarily for engineering rather than agricultural purposes. Continuum models have received far more intensive recent application than granular models. Also, the application of rate process theory to soils has intensified with attempts to link particle surface properties to macroscopic soil stress-strain behavior. One subject area with nearly a complete lack of information was the effect of temperature on soil stress-strain properties

Soil Structure Evaluation with Audio- frequency Vibrations

Young's moduli for soils measured with a vibrational technique varied with soil aggregate size, water content, texture, sensor-to-sample contact, and column handling. The magnitude of a Young's modulus varied from 10? dynes/cm² (147 psi) for nearly saturated columns to over 10? dynes/cm² for an air-dried, Na-saturated silt. The accuracy of the moduli measurements is in the order of 15% to 20%. The measured values compare favorably with others previously reported in the literature for undisturbed and reworked soil samples. The range of measured soil moduli, the repeatability of the measurements, the lack of restriction on sample size and the nondestructive nature of the technique indicate that this procedure may provide a useful measure for soil structure evaluatio

CQESTR Simulation of Management Practice Effects on Long-Term Soil Organic Carbon

Management of soil organic matter (SOM) is important for soil productivity and responsible utilization of crop residues for additional uses. CQESTR, pronounced “sequester,” a contraction of “C sequestration” (meaning C storage), is a C balance model that relates organic residue additions, crop management, and soil tillage to SOM accretion or loss. Our objective was to simulate SOM changes in agricultural soils under a range of climate and management systems using the CQESTR model. Four long-term experiments (Champaign, IL, \u3e100 yr; Columbia, MO, \u3e100 yr; Lincoln, NE, 20 yr; Sidney, NE, 20 yr) in the United States under various crop rotations, tillage practices, organic amendments, and crop residue removal treatments were selected for their documented history of the long-term effects of management practice on SOM dynamics. CQESTR successfully simulated a substantial decline in SOM with 50 yr of crop residue removal under various rotations at Columbia and Champaign. The increase in SOM following addition of manure was simulated well; however, the model underestimated SOM for a fertilized treatment at Columbia. Predicted and observed values from the four sites were signifi cantly related (r2 = 0.94, n = 113, P \u3c 0.001), with slope not signifi cantly different from 1. Given the high correlation of simulated and observed SOM changes, CQESTR can be used as a reliable tool to predict SOM changes from management practices and offers the potential for estimating soil C storage required for C credits. It can also be an important tool to estimate the impacts of crop residue removal for bioenergy production on SOM level and soil production capacity

Row Cropping Sandy Soils Under Sprinklers Using a Winter Grain Cover to Control Wind Erosion

One of the most effective ways to prevent the wind erosion of sandy soils is to maintain a continuous crop cover. Summer row cropping following a winter grain cover offers several attractive features, although it does present management problems. The grain cover must be established in the fall after harvesting the row crop, and the transition back to a row crop in the spring must be made without leaving the soil surface unprotected from the wind. This report summarizes 4 years of observations and exploratory studies in which a variety of cover-row cropping management systems were tested with emphasis on methods for establishing row crops directly in the winter cover. Pertinent literature and observations of other field trials are also discussed

Irreversible Thermodynamics for Stress, Strain and Other Soil Physical Property Description

RHEOLOGIC models used to describe the mechanical behavior of soil have recently been reviewed and summarized in detail by Scott and Ko (1969). Their review (274 references) is a "state of the art" report which describes theoretical and experimental application to soils of rate process theory, granular models, and the continuum models of elasticity, plasticity, and viscoelasticity. Applications of the various models were primarily for engineering rather than agricultural purposes. Continuum models have received far more intensive recent application than granular models. Also, the application of rate process theory to soils has intensified with attempts to link particle surface properties to macroscopic soil stress-strain behavior. One subject area with nearly a complete lack of information was the effect of temperature on soil stress-strain properties

Soil Structure Evaluation with Audio- frequency Vibrations

Young's moduli for soils measured with a vibrational technique varied with soil aggregate size, water content, texture, sensor-to-sample contact, and column handling. The magnitude of a Young's modulus varied from 10? dynes/cm² (147 psi) for nearly saturated columns to over 10? dynes/cm² for an air-dried, Na-saturated silt. The accuracy of the moduli measurements is in the order of 15% to 20%. The measured values compare favorably with others previously reported in the literature for undisturbed and reworked soil samples. The range of measured soil moduli, the repeatability of the measurements, the lack of restriction on sample size and the nondestructive nature of the technique indicate that this procedure may provide a useful measure for soil structure evaluatio

Row Cropping Sandy Soils Under Sprinklers Using a Winter Grain Cover to Control Wind Erosion

One of the most effective ways to prevent the wind erosion of sandy soils is to maintain a continuous crop cover. Summer row cropping following a winter grain cover offers several attractive features, although it does present management problems. The grain cover must be established in the fall after harvesting the row crop, and the transition back to a row crop in the spring must be made without leaving the soil surface unprotected from the wind. This report summarizes 4 years of observations and exploratory studies in which a variety of cover-row cropping management systems were tested with emphasis on methods for establishing row crops directly in the winter cover. Pertinent literature and observations of other field trials are also discussed