Penetrometer Resistance Measurements Research Articles

Structure liming reduces draught requirement on clay soil

Liming with ‘structure lime’, comprising approximately 80–85% ground limestone and 15–20% slaked lime, has been promoted in subsidised environmental schemes in Sweden since 2010 to increase clay aggregate stability and mitigate particulate phosphorus losses to surface waters. To date, approximately 65,000 ha have been structure-limed. Apart from stabilising aggregates, liming may also improve other physical properties, such as soil strength. This study examined the effect of increasing application rate (0–16 t ha-1) of structure lime on soil strength, approximated by horizontal (draught requirement) and vertical (penetrometer resistance) measurements, in eight field soils (clay content 26–38%) to which structure lime had been applied two, three, four or six years previously. Draught requirement when cultivating with a multipurpose cultivator significantly decreased (by 11%) with the highest application rate of structure lime (16 t ha-1) compared with an unlimed control. This reduced the wheel power requirement by 7.1 kW and diesel consumption by 1.2–1.4 L ha-1, and lowered CO2 emissions by 3–4 kg ha-1. To clarify the general effect of structure liming, the mean value of all limed treatments was compared with that of the unlimed control. This showed that structure liming in general significantly reduced the draught requirement (by 7%). However, penetrometer resistance measurements revealed no significant effects of structure liming and no relation between draught requirement and penetrometer resistance measurements. Overall, the results indicate that structure liming can reduce fuel consumption, due to easier soil tillage, and thus lower CO2 emissions.

A Field Study on the Influence of M1A1 Abrams Tank Traffic on Soil Compaction

Military training exercises using heavy-tracked vehicles is an intensive land-use activity that may result in vegetation disturbances and soil compaction. In this study, the focus was on soil compaction as a result of M1A1 Abrams battle tank traffic. For this purpose, two main treatments were investigated: tank trafficking rates at the time of tank training maneuvers and moisture content of the soil profile. The influence of Abrams tank traffic on soil bulk density and mechanical impedance was measured immediately after the tank passes on plots having three different soil moisture levels. We found increased soil bulk density as a result of tank traffic regardless of the number of tank passes. Overall soil bulk density increases throughout the soil profile were 0.04, 0.07, and 0.04 g/cm3 for the low-, medium-, and high-moisture plots, respectively. After three, six, and nine tank passes, consistent increases in penetrometer resistance measurements were observed. However, the effects of the number of passes appear somewhat inconsistent when low-moisture contents were dominant in the soil profile (0.12–0.17 cm3/cm3). For plots with the highest moisture level (0.37–0.38 cm3/cm3 ), the impact of tank traffic was concentrated in the surface 15 cm, with an average increase of 1 MPa regardless of the number of tank passes. We conclude that the effects of different tank passes on soil compaction did not follow a clear trend. Moreover, based on the residual impact of tank traffic, we conclude that efforts should be made to avoid tank exercises when the moisture content in the soil profile is 0.26 cm3/cm3. We further conclude that tank traffic should be restricted when possible when the soil moisture content is in the 0.40- to 0.46-cm3/cm3 range.

The analysis of ranked observations of soil structure using indicator geostatistics

Structure is an important physical feature of the soil that is associated with water movement, the soil atmosphere, microorganism activity and nutrient uptake. A soil without any obvious organisation of its components is known as apedal and this state can have marked effects on several soil processes. Accurate maps of topsoil and subsoil structure are desirable for a wide range of models that aim to predict erosion, solute transport, or flow of water through the soil. Also such maps would be useful to precision farmers when deciding how to apply nutrients and pesticides in a site-specific way, and to target subsoiling and soil structure stabilization procedures. Typically, soil structure is inferred from bulk density or penetrometer resistance measurements and more recently from soil resistivity and conductivity surveys. To measure the former is both time-consuming and costly, whereas observations made by the latter methods can be made automatically and swiftly using a vehicle-mounted penetrometer or resistivity and conductivity sensors. The results of each of these methods, however, are affected by other soil properties, in particular moisture content at the time of sampling, texture, and the presence of stones. Traditional methods of observing soil structure identify the type of ped and its degree of development. Methods of ranking such observations from good to poor for different soil textures have been developed. Indicator variograms can be computed for each category or rank of structure and these can be summed to give the sum of indicator variograms (SIV). Observations of the topsoil and subsoil structure were made at four field sites where the soil had developed on different parent materials. The observations were ranked by four methods and indicator and the sum of indicator variograms were computed and modelled for each method of ranking. The individual indicators were then kriged with the parameters of the appropriate indicator variogram model to map the probability of encountering soil with the structure represented by that indicator. The model parameters of the SIVs for each ranking system were used with the data to krige the soil structure classes, and the results are compared with those for the individual indicators. The relations between maps of soil structure and selected wavebands from aerial photographs are examined as basis for planning surveys of soil structure.

Soil penetrometer resistance spatial variability in a Ferralsol at several soil moisture conditions

The penetrometer resistance (PR) spatial variability in a Ferralsol under different soil moisture conditions was characterized through statistical and geostatistical methods. PR measurements were made in a 10-row, 10-columns, 3-m spacing grid at 20–30 cm depth using a hand-pushing penetrometer. Measurements were made for dry soil conditions (before irrigation) as well as 2 and 24 h after irrigation. The soil bulk density (BD) and the relative topographical altitudes (RT) were measured at the same locations. The PR spatial variability is normally distributed for dry soil conditions and after irrigation-water redistribution. A normal distribution fits also to the BD spatial variability. PR mean and coefficients of variations are lower for wet soil conditions and vary notably according to the soil moisture condition. The PR semivariance values are much higher for dry soil conditions than those found for wet soil conditions. However, the semivariogram of PR before irrigation shows almost a pure nugget effect. Irrigation yields a spatial structure in PR measurements. Despite the differences in the shown spatial structure, the range of the PR semivariograms before and 24 h after irrigation is about 8–10 m, which is very similar to the range of the BD semivariogram. The correlation coefficients between PR and the other measured variables are very small before and after irrigation, which could lead to the conclusion that those variables are not related at all. However, according to the co-dispersion coefficients plotted as a function of the separation lag, the correlation between those variables changes according to the separation distance. Particularly, PR and the RT show correlation 24 h after irrigation only for lags between 5 and 12 m. The results pointed out that PR spatial variability depends on soil moisture condition, soil BD and on several local features as microtopography.

Influence of single passes with high wheel load on a structured, unploughed sandy loam soil

In a field experiment, a sandy loam was subjected to single passes with a sugar beet harvester at two different soil water potentials. Different hopper fillings resulted in ground contact pressures of 130 kPa (partial load) and 160 kPa (full load) underneath the tyre. Bulk density, macroporosity (equivalent pore radius >100 μm), penetrometer resistance, air permeability and pre-consolidation pressure were measured within and next to the wheel tracks at depths of 0.12–0.17, 0.32–0.37 and 0.52–0.57 m. Furthermore, the soil structure at two horizons (Ahp 7–24 cm, B(C) 24–38 cm) was visually assessed and classified. The moist plot responded to a wheel load of 11.23 mg (160 kPa) with an increase in bulk density and pre-consolidation pressure as well as with a decrease in air permeability and macroporosity at a depth of 0.12–0.17 m. With a wheel load of 7.47 mg (130 kPa) on the moist plot and with both wheel load levels on the dry plot, only slight changes of the soil structure were detected. At a depth of 0.32–0.37 and 0.52–0.57 m, the measurements did not indicate any compaction. An ANOVA indicates that the factor “soil water potential” and the factor “wheel load” significantly influence the bulk density at a depth of 0.12–0.17 m. No interactions occurred between these two factors. The wheel traffic on the test plot had no effect on the yield of winter wheat planted after the experimental treatment. Bulk density, macroporosity and pre-consolidation pressure proved to be sensitive to detect compaction because they varied only slightly and are easy to measure. In contrast, the standard deviation of air permeability is large. The soil structure determined visually in the field confirms the values measured in the laboratory. The results of the penetrometer resistance measurements were not explainable.

Site effects in Mexico City: Constraints from surface wave inversion of shallow refraction data

In order to understand and simulate site effects on strong ground motion records of recent earthquakes in Mexico City, it is fundamental to determine the in situ elastic and anelastic properties of the shallow stratigraphy of the basin. The main properties of interest are the shear wave velocities and Q-quality factors and their correlation with similar parameters in zones of the city. Despite population density and paved surfaces, it is feasible to gather shallow refraction data to obtain laterally homogeneous subsoil structures at some locations. We focused our analysis in the Texcoco Lake region of the northeastern Mexico City basin. This area consists of unconsolidated clay sediments, similar to those of the lake bed zone in Mexico City, where ground motion amplification and long duration disturbances are commonly observed. We recorded Rayleigh and Love waves using explosive and sledgehammer sources and 4.5 Hz vertical and horizontal geophones, respectively. Additionally, for the explosive source, we recorded three-component seismograms using 1 Hz seismometers. We obtained phase velocity dispersion curves from ray parameter-frequency domain analyses and inverted them for vertical distribution of S wave velocity. The initial model was obtained from a standard first-break refraction analysis. We also obtained an estimation of the Q S shear wave quality factor for the uppermost stratigraphy. Results compare well with tilt and cone penetrometer resistance measurements at the same test site, emphasizing the importance of these studies for engineering purposes.

Evaluation of shallow tillage for spring cereals on a fine sandy loam. 2. Soil physical, chemical and biological properties

Changes in the soil condition were determined over a 4-year period, to assess the use of shallow tillage for the low-input production of spring cereals in Prince Edward Island. The soil was a Charlottetown fine sandy loam (Orthic Podzol) which has a low resistance to compaction. Shallow tillage (rotary harrow, disc harrow) was conducted to the 10 cm soil depth and compared with mouldboard ploughing (20 cm) and direct-drilling. Shallow tillage caused excessive compaction in the middle portion of the Ap horizon (8–16 cm) as characterized by reduced macroporosity (<12%, v/v) and increased relative compaction (>85%). Penetrometer resistance measurements indicated that both shallow tillage and direct-drilling reduced the depth of loose soil (<1.5 MPa) to 10–15 cm, compared with 20–25 cm under ploughing. Shallow tillage improved the size distribution of macro-aggregates and increased the stability of 1–9 mm aggregates at the soil surface (0–3 cm). Differences in placement and incorporation of crop residues and amendments caused a redistribution of organic matter, microbial biomass, and extractable P and Ca within the Ap horizon. An acidic, lower Ap horizon developed over time in the shallow-tillage system. The tillage requirement for acidic, fine sandy loams would necessitate a periodic increase in tillage depth for long-term shallow-tillage systems to remove middle Ap horizon compaction and to provide deeper soil mixing of lime amendments to neutralize soil acidity.

4648492 Mechanism to engage part time drive system in a moving vehicle

The tractive performance of a two-wheel drive tractor, a four-wheel drive tractor with front wheels smaller than rear and a four-wheel drive tractor with equal-sized wheels, each having the same 63 p.t.o. kW (84 hp) engine, was measured in 13 different field conditions. The average maximum drawbar power of the four-wheel drive tractor with equal-sized wheels in all fields was 14% higher than that of the two-wheel drive tractor and that of the four-wheel tractor with unequal sized wheels was 7% higher than that of the two-wheel drive tractor. All measurements were made on level ground and in fairly good tractive conditions. The results were compared with predictions of tractive performance from cone penetrometer resistance measurements by methods derived from single wheel test results. Fairly good agreement was obtained for the four-wheel drive tractors but not for the two-wheel drive tractor. Maximum D.B. hp was generally obtained with a coefficient of traction of 0·4 and a wheel slip of 10% with the four-wheel drive tractors but at a higher coefficient of traction and slip for the two-wheel drive tractor. It is suggested that this was due to practical difficulties in operating the two-wheel drive tractors at a high enough speed to use the full engine power available at a coefficient of traction of 0·4. This in turn may have led to the lower maximum D.B. powers.

4651784 Plain weave shedding mechanism

The tractive performance of a two-wheel drive tractor, a four-wheel drive tractor with front wheels smaller than rear and a four-wheel drive tractor with equal-sized wheels, each having the same 63 p.t.o. kW (84 hp) engine, was measured in 13 different field conditions. The average maximum drawbar power of the four-wheel drive tractor with equal-sized wheels in all fields was 14% higher than that of the two-wheel drive tractor and that of the four-wheel tractor with unequal sized wheels was 7% higher than that of the two-wheel drive tractor. All measurements were made on level ground and in fairly good tractive conditions. The results were compared with predictions of tractive performance from cone penetrometer resistance measurements by methods derived from single wheel test results. Fairly good agreement was obtained for the four-wheel drive tractors but not for the two-wheel drive tractor. Maximum D.B. hp was generally obtained with a coefficient of traction of 0·4 and a wheel slip of 10% with the four-wheel drive tractors but at a higher coefficient of traction and slip for the two-wheel drive tractor. It is suggested that this was due to practical difficulties in operating the two-wheel drive tractors at a high enough speed to use the full engine power available at a coefficient of traction of 0·4. This in turn may have led to the lower maximum D.B. powers.

EFFECTS OF SUBSOIL BULK DENSITY, NUTRIENT AVAILABILITY AND SOIL MOISTURE ON CORN ROOT GROWTH IN THE FIELD

In a 4-yr study, root growth in the upper 50 cm of a silt loam soil (Gleyed Melanic Brunisol) was equal to or greater than that in a low-density artificial medium (soil:peat:perlite) in spite of a high bulk density in the soil (1.5 Mg m−3 in the 15-to 45-cm depth). We suggest that, due to the natural structure of the Bm horizon, the resistance to root growth is much less than would be expected from bulk density or penetrometer resistance measurements. Marked increases in P and K fertility in the surface soil had only minor effects on either the total length or distribution of roots although the shoot growth was markedly increased. Neither total root length nor root distribution were altered by irrigation during 1981, the only year a moisture variable was included. During a 2-wk dry period in July, prior to anthesis, soil water potential on the nonirrigated plots decreased to −1.5 MPa in the upper 15 cm and to −0.5 MPa in the 15- to 30-cm layer. Leaf water potential, stomatal conductance and rate of growth during the period were lower on the nonirrigated treatment although final dry matter production was not. The results indicate that corn root growth and distribution in the field are not as sensitive to environmental factors as one would expect from short-term laboratory studies. Key words: Corn, root growth, soil bulk density, fertility, soil water

Sucrose yield of sugar beet as affected by chiseling and plowing compacted soils

Sugar beet ( Beta vulgaris L.) growers in Nebraska, U.S.A. have been convinced by equipment manufacturers in the past 10 years that chisel tillage is needed on their soils to remove compaction zones. No data were available to assess the reality of their conviction that chiseling was an essential part of their tillage systems. The experiments discussed here were designed to test the impact and need for chiseling to depths up to 30 cm in systems where moldboard plowing to a depth of 20 cm is the most common primary tillage. Various degrees of soil compactness were created artificially in soil of the same type (Typic Haplustoll) in 3 different fields. Combinations of moldboard plowing and chiseling were then imposed on them. The relationships of water infiltration rates and resistance to penetration as measured by a penetrometer to the tillage treatments and to ultimate sucrose yield were determined. In all but the severest compaction treatment, either chiseling or moldboard plowing had equivalent impacts on yield restoration. In the most severely compacted soil chiseling was totally ineffective in 1 year and equal to plowing in another year. Combination plowing and chiselinng did not have an additive effect beyond plowing or chiseling along under any compaction condition. Even though the implements were equally effective in restoring yield potential, neither of them, alone nor in combination restored yields to levels achieved on non-compacted soil. Penetrometer resistance measurements indicated that compacted soil below 30 cm was the problem. The data indicated that it may be possible for a given soil type, to relate penetrometer resistance to the need for tillage to remove compaction. On these experiments each increase in resistance of 700 kPa over a range of 4000–8000 kPa resulted in a 10% reduction in sucrose yield.

Trafficability Factor in a Silty Clay Loam Soil

ABSTRACT SUBSURFACE drainage systems affect spring and fall trafficability, the timeliness of planting and subse-quent crop harvest and yield on a silty clay loam marine soil. Drainage effectiveness and trafficability response were evaluated by mercury tensiometers for soil moisture, a cone penetrometer for soil strength and by a subjective walk-on trafficability index (TI). Soil moisture and penetrometer resistance measurements were taken over the shallow drains spaced at 3, 6 and 12 m, at the mid-point between drains and at two comparable random locations in undrained plots. Trafficability was found to develop more rapidly in the spring on a slowly permeable representative silty clay loam soil with drainage than on undrained plots. However, we did not observe any clear differences be-tween any of the three drain spacing treatments. A good correlation existed between soil moisture tension and soil strength in the 0-15 cm soil depth which could be match-ed to soil readiness and thus to workday or trafficable conditions. Corn yields vs. drainage for 1980, a year characterized by a dry spring, showed no significant difference between drainage and no drainage. Alfalfa in 1981, when drained plots were ready for cultivation 3 wk earlier than un-drained plots, gave yields significantly greater for the drained over no drainage from two cuttings. There was no difference between drained treatments.

A field comparison of the tractive performance of two- and four-wheel drive tractors

The tractive performance of a two-wheel drive tractor, a four-wheel drive tractor with front wheels smaller than rear and a four-wheel drive tractor with equal-sized wheels, each having the same 63 p.t.o. kW (84 hp) engine, was measured in 13 different field conditions. The average maximum drawbar power of the four-wheel drive tractor with equal-sized wheels in all fields was 14% higher than that of the two-wheel drive tractor and that of the four-wheel tractor with unequal sized wheels was 7% higher than that of the two-wheel drive tractor. All measurements were made on level ground and in fairly good tractive conditions. The results were compared with predictions of tractive performance from cone penetrometer resistance measurements by methods derived from single wheel test results. Fairly good agreement was obtained for the four-wheel drive tractors but not for the two-wheel drive tractor. Maximum D.B. hp was generally obtained with a coefficient of traction of 0·4 and a wheel slip of 10% with the four-wheel drive tractors but at a higher coefficient of traction and slip for the two-wheel drive tractor. It is suggested that this was due to practical difficulties in operating the two-wheel drive tractors at a high enough speed to use the full engine power available at a coefficient of traction of 0·4. This in turn may have led to the lower maximum D.B. powers.

Advantages of anti-friction machinery

The tractive performance of a two-wheel drive tractor, a four-wheel drive tractor with front wheels smaller than rear and a four-wheel drive tractor with equal-sized wheels, each having the same 63 p.t.o. kW (84 hp) engine, was measured in 13 different field conditions. The average maximum drawbar power of the four-wheel drive tractor with equal-sized wheels in all fields was 14% higher than that of the two-wheel drive tractor and that of the four-wheel tractor with unequal sized wheels was 7% higher than that of the two-wheel drive tractor. All measurements were made on level ground and in fairly good tractive conditions. The results were compared with predictions of tractive performance from cone penetrometer resistance measurements by methods derived from single wheel test results. Fairly good agreement was obtained for the four-wheel drive tractors but not for the two-wheel drive tractor. Maximum D.B. hp was generally obtained with a coefficient of traction of 0·4 and a wheel slip of 10% with the four-wheel drive tractors but at a higher coefficient of traction and slip for the two-wheel drive tractor. It is suggested that this was due to practical difficulties in operating the two-wheel drive tractors at a high enough speed to use the full engine power available at a coefficient of traction of 0·4. This in turn may have led to the lower maximum D.B. powers.