Cone Index Profiles Research Articles

Finite Element Modeling and Simulations to Investigate the Relationship between the Cone Index Profile and Draft Requirements of a Compaction Profile Sensor with Depth

Abstract. Previous research conducted using a compaction profile sensor and a standard cone penetrometer over a wide range of soil types and conditions found that the unit pressure acting on the cutting edge, defined as the cone index equivalent (CIE), at a specific depth (d) was related to the cone index (CI) value at that depth, the depth of the cutting edge (d), and the interaction between CI and the depth of the cutting edge (i.e., CI × d) with a very high coefficient of multiple determination irrespective of the soil type and conditions. The objective of this study was to provide an analytical basis for the relationship between CIE and CI. A two-dimensional axisymmetric model for soil-cone interaction and a three-dimensional model for soil-tine interaction were developed using a finite element method (FEM). A non-linear elasto-plastic constitutive behavior along with the Drucker-Prager yield criterion were used to represent the soil cutting process. Simulations studies were conducted in 25 distinct soil types and conditions, and the results indicated a similar relationship between CIE and CI, as observed in the previous research. These results support the existence of a strong theoretical basis for the empirical relationship observed in the previous research. Keywords: Cone index, Compaction profile sensor, Finite element modeling, Soil penetration resistance.

Estimating Sample Size of Soil Cone Index Profiles by Bootstrapping

ABSTRACT Measurements of the soil cone index are widely used to assess soil resistance to root penetration (SR) and to monitor the soil compaction status of agricultural fields. However, soil sampling for SR estimation is a rather challenging task in view of the high spatial and temporal variability of the soil. This study proposed a bootstrapping method to determine the minimum sample size required to estimate the vertical profile of mean soil cone index (CI) values at different levels of [...]

Potato Yield and Quality Response to Subsoil Tillage and Compaction

Compacted soils have been found in intensively cultivated vegetable crop regions of Central Wisconsin, resulting in the wide scale use of subsoil tillage by growers. The goal of this project was to assess potato (Solanum tuberosum L.) yield and quality response to soil compaction and subsoil tillage. Potato quality factors evaluated were marketable yield, tuber size distribution, internal quality, and sugar concentration. A controlled small plot experiment and several field scale experiments located in collaborating grower fields were conducted to assess potato and soil responses to subsoil tillage. Cone index profiles showed the potential for limited root growth below the compacted soil layer with values >2.0 MPa. Subsoil tillage reduced cone index values to <1.0 MPa below 33 cm in 2 of 3 yr. Total and U.S. no. 1 yields were not influenced by subsoil tillage. Likewise, no consistent differences were seen in the size distributions of U.S. no. 1 tubers across treatments, but subsoil tillage tended to decrease proportion of tubers 113 to 170 g. Subsoil tillage did not affect tuber glucose or sucrose concentrations at harvest or following storage for 120 d. Internal tuber defects were not affected by either compaction or subsoil tillage. The lack of consistent effects of subsoil tillage on potato yield raises questions regarding the validity of this practice. The recommendation that potato growers use subsoil tillage may be linked to increased tuber size distribution or factors other than yield such as water, nutrient, or disease management.

Use of an instrumented disc coulter for mapping soil mechanical resistance

A soil mechanical resistance sensor with a large-diameter disc coulter was developed to delineate areas of differing soil strength across agricultural fields. The instrumented disc coulter consisted of a 76.2 cm disc with two depth-measuring sensors (rotary potentiometer and ultrasonic proximity sensor) along with a global positioning system (GPS) receiver to georeference operating depth measurements. The consistency and repeatability of the system response were evaluated by making six passes across long-term tillage comparison plots with different degrees of soil disturbance, including: 20 cm plowing, 15 cm disking, 30 cm chiseling, and no-till in several combinations. At the time of testing, standard soil cone penetrometer measurements were taken. The relationship between the average cone index in the 0–30 cm soil profile (CI 0–30 cm ) and the disc operating depth was evaluated. In addition, the cumulative energy density of the given depth of penetration defined as specific cone penetration energy (J m −2 or N cm −1) for each tillage plot was calculated using the cone index profiles. The average measured depth in each tillage plot was compared to the average predicted depth ( d ci) of a fixed specific cone penetration energy ( P ci). Static calibration tests on the depth sensors showed excellent linearity with coefficients of determination ( R 2) greater than 0.99. The results showed that, on the average, the changes in the depth measured with the rotary potentiometer were 44 and 68% of the changes in the depth measured with the ultrasonic proximity sensor while the disc coulter was passing across, or along, the tillage plots. This difference was primarily due to the sinkage of the tractor wheels. The depth measured with the ultrasonic sensor had significant correlation with both CI 0–30 cm and d ci. This was partially due to the fact that a significantly high correlation ( R 2 = 0.97) between the CI 0–30 cm and d ci was observed, which was not expected and originated from the type of soil profiles present. The instrumented disc coulter is a low soil disturbance system and could be used as an inexpensive and simple sensor to obtain information about the mechanical condition of the soil for spot tillage or other management decisions.

Development, Construction, and Field Evaluation of a Soil Compaction Profile Sensor

Studies have shown that an increased level of soil compaction leads to a reduction in infiltration characteristics of soil, which in turn leads to low soil moisture. Conventional methods of measuring soil compaction are tedious, time consuming, and expensive. The objective of this study was to develop and evaluate a soil compaction profile sensor (SCPS) that could assist in the assessment of the state of compactness of the soil profile in real-time. The device developed in this study consisted of eight cutting elements, designed to provide information on soil resistance to cutting for every 7.5 cm layer down to a total depth of 60 cm. The design produced a sensor with a backward-sloping rake angle and a total thickness of 5.1 cm. Extensive field tests were conducted during summer and fall of 2001 and spring of 2002 in loamy, clayey, and sandy fields. Within each soil type, three different moisture conditions were included in the test (low, medium, and high). Analysis of the test data revealed that the soil cutting force was a function of soil bulk density, moisture content, and the location of the cutting element within the soil profile. Additional analyses were conducted to relate soil cutting force profile to the cone index profile. The empirical relationship between predicted and measured profile sensor output had a coefficient of multiple determination (R2) of 0.977, indicating that the SCPS can potentially be used to make real-time measurements of soil strength profile.

Determination of Tillage Depth Based on Physical Properties of Soil for Rice Production in Korea

Compaction is becoming a great concern in crop production and the environment. Recently, three has been a need of field management based on site-specific conditions to improve sustainability of agriculture and reduce environmental damage. In the study, soil management or tillage depth was recommended nondestructively based on cone index profiles for typical Korean rice paddy fields. Field variables related to tillage, soil strength, rice growth, and other soil physical properties showed considerable spatial and vertical variations as well as significant (α<0.1) correlations among them. Cone index profiles observed also varied by field sites, and maximum cone index and depth to the maximum cone index showed significant (α<0.1) correlation with tilled depth as well as rice growth and other field variables. When soil management was recommended based on CI measurements, 13.4, 16.8, and 95.3% of the total surveyed areas, and 10.6, 18.9, and 51.6% of the total soil volume were chosen for management depth of 10, 20, 40 cm, respectively, indicating that soils of many field sites would not restrict rice growth. It was concluded that the concept of site-specific soil management based on soil conditions could save labor, time, machine use, and energy.

AN ALGORITHM TO DETERMINE THE OPTIMUM TILLAGE DEPTH FROM SOIL PENETROMETER DATA IN COASTAL PLAIN SOILS

Soil compaction is a significant problem in the southeastern Coastal Plain soils. Cone penetrometers are used widely for soil strength measurement and tillage decisions. However, there is no standard or comprehensive method for determining the optimum tillage depth from soil penetrometer data in Coastal Plain soils. Our objective was to develop an algorithm for determining the optimum tillage depth from soil cone penetrometer measurements to effectively remove the hardpan. Intensive geo-referenced soil cone penetrometer measurements were obtained and each cone index profile was graphically examined. The results showed six main patterns for penetrometer profiles in a Dothan loamy sand soil. An algorithm and computer program was developed to determine the optimum tillage depth from the penetrometer data taken in a two-year study (2000 and 2001). The results clearly indicated that the thickness and the location of the hardpan can be determined from the soil cone penetrometer data. A great amount of variation was observed in the depth and the thickness of the hardpan (4 to 25 cm) as well as in the optimum tillage depth (25 to 45 cm) in both years.

Measurement and variation of site-specific hardpans for silty upland soils in the Southeastern United States

Soil compaction in the form of a hardpan layer restricts root growth and reduces crop yield throughout the Southeastern United States. However, the depth of this compacted soil layer varies significantly over landscapes. A sampling procedure was developed and evaluated to determine the depth of the hardpan layer in upland soils of Grenada silt loam soil type in this region. Cone index profiles taken with a multiple-probe soil cone penetrometer in three fields were used to measure the hardpan depth and to predict their spatial variation. Continuous treatments of these fields for several years included conventional tillage, no-tillage, segregated traffic, and random traffic. Conventional tillage systems were found to bring the hardpan significantly closer to the soil surface as compared to no-till systems; in trafficked row middles by 0.144 m, directly beneath the rows by 0.165 m, and in no-trafficked row middles by 0.094 m. Little difference in depth of hardpan was found between a no-till field subjected to random traffic and a field where traffic was segregated. However, the effect of this random traffic was found to dramatically reduce the predicted range (which is a geo-statistical measure of field variability) from 43.2 m for the no-till field in the trafficked row middle as compared to 12.4 m for the randomly trafficked no-till field. This may indicate that the depth of the hardpan layer in these soils is brought uniformly closer to the soil surface by the effect of traffic, especially when annual tillage is not practiced which could alter this hardpan depth. This information about the variation of the hardpan layer will greatly assist researchers who are interested in developing site-specific tillage technologies to remedy this soil compaction condition.

Profile cone penetrometer data used to distinguish between soil materials

In young glaciated landscapes the variability of soil materials imparts a major control on crop growth and yield and environmental quality associated with production agriculture. Two common soil materials found on these glaciated landscapes are glacial till and reworked loess. Soil materials can be characterized by a combination of physical and morphological soil attributes. We hypothesized that penetration resistance is the response signal to a complex of multiple soil attributes and can be used as an integrating indicator to map soil materials. Our objective was to test the ability of a profile cone penetrometer to map soil materials at landscape-scale. The study site was located in southern Wisconsin, USA, on soils developed in reworked loess material overlying glacial till, which are classified as Typic or Mollic Hapludalfs and Typic Argiudolls. We collected a dense data set of cone index profiles from a 2.73 ha area on a 10 m grid up to depths of 1.3 m. Additionally, we collected soil cores randomly at 21 penetration locations and analyzed these by layer for texture, bulk density, and water content. We utilized point elevation data collected with a differential global positioning system to create a digital elevation model and derive slope and compound topographic index to subdivide the study area into landform element classes. We used expert knowledge to characterize soil materials and subsequently measured soil attributes to identify soil materials. A hierarchical cluster analysis was used to group cone index profiles. Combining the sparse soil material data with the dense cone index and landform element data resulted in soil material information covering the entire study area. The spatial distribution of soil materials was visualized using a three-dimensional soil layer model. The proposed method is associated with large uncertainties in some areas and can be recommended only for coarse mapping of contrasting soil materials such as glacial till and reworked loess at landscape-scale, when used in combination with landform element data.