The Effect of Soil Strength on the Growth of Young Wheat Plants

Wheat seedlings were grown in soil of various strengths, obtained by changing the bulk density or the water content of the soil. Leaf expansion and transpiration rate were monitored from emergence until the main stem had 5-7 leaves. Leaf area, and shoot and root dry weights, were negatively correlated with soil strength as measured by penetrometer resistance. The growth of roots was less affected than that of shoots. Leaf expansion was reduced before the first leaf was fully expanded. Relative rates of leaf expansion thereafter were consistently lower at high soil strength, although not always significantly. High soil strength also produced substantially smaller stomatal conductances. All effects were the same whether variations of soil strength were brought about by changes in water content or in bulk density. Three possible causes of reduced shoot growth were examined: (1) a limiting supply of nutrients; or (2) of water, because of a restricted root system; or (3) a reduced carbon supply because of a higher carbon demand from the roots, or because of the low stomatal conductance. We conclude that these are all unlikely explanations for the onset of the effects of soil strength, which were independent of soil phosphorus content, of leaf water potential, and of the amount of carbon reserves in the seed. We suggest that growth of the shoot is primarily reduced in response to some hormonal message induced in the roots when they experience high soil strength.

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Profile Soil Property Estimation Using a VIS-NIR-EC-Force Probe

Transactions of the ASABE ◽

10.13031/trans.12049 ◽

2017 ◽

Vol 60 (3) ◽

pp. 683-692 ◽

Cited By ~ 5

Author(s):

Yongjin Cho ◽

Kenneth A. Sudduth ◽

Scott T. Drummond

Keyword(s):

Soil Properties ◽

Water Content ◽

Bulk Density ◽

Soil Property ◽

Soil Strength ◽

Reflectance Spectra ◽

Land Resource ◽

Strength Data ◽

Soil Sensors ◽

Combining Data

Abstract. Combining data collected in-field from multiple soil sensors has the potential to improve the efficiency and accuracy of soil property estimates. Optical diffuse reflectance spectroscopy (DRS) has been used to estimate many important soil properties, such as soil carbon, water content, and texture. Other common soil sensors include penetrometers that measure soil strength and apparent electrical conductivity (ECa) sensors. Previous field research has related these sensor measurements to soil properties such as bulk density, water content, and texture. A commercial instrument that can simultaneously collect reflectance spectra, ECa, and soil strength data is now available. The objective of this research was to relate laboratory-measured soil properties, including bulk density (BD), total organic carbon (TOC), water content (WC), and texture fractions to sensor data from this instrument. At four field sites in mid-Missouri, profile sensor measurements were obtained to 0.9 m depth, followed by collection of soil cores at each site for laboratory measurements. Using only DRS data, BD, TOC, and WC were not well-estimated (R2 = 0.32, 0.67, and 0.40, respectively). Adding ECa and soil strength data provided only a slight improvement in WC estimation (R2 = 0.47) and little to no improvement in BD and TOC estimation. When data were analyzed separately by major land resource area (MLRA), fusion of data from all sensors improved soil texture fraction estimates. The largest improvement compared to reflectance alone was for MLRA 115B, where estimation errors for the various soil properties were reduced by approximately 14% to 26%. This study showed promise for in-field sensor measurement of some soil properties. Additional field data collection and model development are needed for those soil properties for which a combination of data from multiple sensors is required. Keywords: NIR spectroscopy, Precision agriculture, Reflectance spectra, Soil properties, Soil sensing.

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Properties and Management of Allophanic Soils

Tropical Soils ◽

10.1093/oso/9780195115987.003.0017 ◽

2003 ◽

Author(s):

Anthony S. R. Juo ◽

Kathrin Franzluebbers

Keyword(s):

Water Content ◽

Bulk Density ◽

Water Retention ◽

Field Capacity ◽

High Water ◽

Soil Porosity ◽

Water Retention Capacity ◽

Soil Taxonomy ◽

Retention Capacity ◽

High Soil

Allophanic soils are dark-colored young soils derived mainly from volcanic ash. These soils typically have a low bulk density (< 0.9 Mg/m3), a high water retention capacity (100% by weight at field capacity), and contain predominantly allophanes, imogolite, halloysite, and amorphous Al silicates in the clay fraction. These soils are found in small, restricted areas with volcanic activity. Worldwide, there are about 120 million ha of allophanic soils, which is about 1% of the Earth's ice-free land surface. In tropical regions, allophanic soils are among the most productive and intensively used agricultural soils. They occur in the Philippines, Indonesia, Papua New Guinea, the Caribbean and South Pacific islands, East Africa, Central America, and the Andean rim of South America. Allophanic soils are primarily Andisols and andic Inceptisols, Entisols, Mollisols, and Alfisols according to the Soil Taxonomy classification. Allophanic soils generally have a dark-colored surface soil, slippery or greasy consistency, a predominantly crumb and granular structure, and a low bulk density ranging from 0.3 to 0.8 Mg/m3. Although allophanic soils are apparently well-drained, they still have a very high water content many days after rain. When the soil is pressed between fingers, it gives a plastic, greasy, but non-sticky sensation of a silty or loamy texture. When dry, the soil loses its greasiness and becomes friable and powdery. The low bulk density of allophanic soils is closely related to the high soil porosity. For example, moderately weathered allophanic soils typically have a total porosity of 78%, with macro-, meso-, and micropores occupying 13%, 33%, and 32%, respectively. Water retained in the mesopores is readily available for plant uptake. Water retained in the micropores is held strongly by soil particles and is not readily available for plant use. The macropores provide soil aeration and facilitate water infiltration. The high water retention capacity is also associated with the high soil porosity. In allophanic soils formed under a humid climate, especially those containing large amounts of allophane, the moisture content at field capacity can be as high as 300%, calculated on a weight basis. Such extremely high values of water content seem misleading.

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A novel approach to estimate soil penetrometer resistance from water content, bulk density, and shear wave velocity: A laboratory study on a loamy sand soil

Geoderma ◽

10.1016/j.geoderma.2020.114276 ◽

2020 ◽

Vol 368 ◽

pp. 114276 ◽

Cited By ~ 2

Author(s):

Wencan Zhang ◽

Weida Gao ◽

Tusheng Ren ◽

W. Richard Whalley

Keyword(s):

Water Content ◽

Bulk Density ◽

Shear Wave ◽

Wave Velocity ◽

Laboratory Study ◽

Shear Wave Velocity ◽

Sand Soil ◽

Penetrometer Resistance ◽

Loamy Sand Soil ◽

Novel Approach

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The Response of Various Soil Strength Indices to Changing Water Content and Bulk Density

Transactions of the ASAE ◽

10.13031/2013.35401 ◽

1978 ◽

Vol 21 (5) ◽

pp. 0854-0861 ◽

Cited By ~ 16

Author(s):

L. G. Wells ◽

O. Treesuwan

Keyword(s):

Water Content ◽

Bulk Density ◽

Soil Strength

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Variation in soil strength, bulk density and gravel concentration along a toposequence in Abeokuta, south-western Nigeria

Soil Research ◽

10.1071/sr07057 ◽

2007 ◽

Vol 45 (8) ◽

pp. 643 ◽

Cited By ~ 1

Author(s):

F. K. Salako ◽

P. O. Dada ◽

J. K. Adesodun ◽

F. A. Olowokere ◽

I. O. Adekunle

Keyword(s):

Land Use ◽

Water Content ◽

Bulk Density ◽

Extreme Values ◽

Soil Depth ◽

Density Measurement ◽

Soil Strength ◽

Slope Position ◽

Fine Earth ◽

Wet Season

This study was carried out at Abeokuta, south-western Nigeria, to understand the variation in soil strength, gravel distribution, and bulk density along a toposequence. In 2003, a 120-m transect on a fallowed land was sampled at every 1 m for topsoil bulk density measurement by excavation (3278 cm3 pits), while soil strength was measured at every soil depth increment of 25 mm to 0.50 m depth. Total dry (ρt) and fine earth (<2 mm) (ρf) bulk densities were determined. Soil water content was also determined. Gravel was divided into classes of 2–4, 4–8, 8–16, and >16 mm. In 2006, four 100-m transects were considered; two each on adjacent fallowed and cultivated lands. Soil strength and water content were measured. The fine earth fraction of topsoil ranged from 62 to 90.6%. Gravel in the 2–4 mm class was dominant with a range of 0.8–35.7%. Thus, cores ≥50 mm could be used in the topsoil to obtain reliable estimates of bulk density. Total bulk density (ρt) was reduced by 4–19% when corrected for gravel to obtain ρf. Soil strength of the lower slope was highest in 2003 (1981–4482 kPa) and lowest in 2006 (1546 kPa). In spite of the apparent significant influence of water content on soil strength, the relationship was weakly expressed by regression analysis, as only 35% of variation in soil strength was explained by water content at 0.10–0.15 m soil depth in 2003. No relationship was found in 2006; the cultivated segment had higher soil strength (2045 kPa) than the fallowed segment (1970 kPa) even though the water contents were similar. Also, only the 2–4 mm gravel significantly influenced ρt. Land use, soil depth, and slope position significantly affected soil strength. Root-limiting soil strength (>2000 kPa) would certainly be encountered below 0.20 m soil depth in the wet season irrespective of land use. Management of this gravelly landscape must be based on the heterogeneous nature of soil physical properties along the toposequence, and this could be made effective by grouping the soils according to slope position and taking interest in the few portions of the landscape with extreme values of gravel distribution and high soil strength.

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Use of the neutron method in assessing the changes in soil strength of undisturbed and ameliorated transitional red-brown earths during soil drying cycles

Soil Research ◽

10.1071/sr9900167 ◽

1990 ◽

Vol 28 (2) ◽

pp. 167

Author(s):

NS Jayawardane ◽

J Blackwell

Keyword(s):

Bulk Density ◽

Soil Strength ◽

Wheat Crop ◽

Regression Equations ◽

Experimental Site ◽

Undisturbed Soil ◽

Soil Matrix ◽

Penetrometer Resistance ◽

Neutron Count ◽

Neutron Method

The relationships between penetrometer resistance (qp) and volumetric moisture content (�v) measured using the neutron method in an undisturbed transitional red-brown earth and after an~elioration by application of surface gypsum and slotted gypsum were examined. A very highly significant (P < 0.001) negative correlation was obtained between qp and �v in all treatments. The low r2 values of the regressions were attributed to heterogeneity in strength characteristics of the soil matrix, due to presence of cracks and macropores and the associated wetting patterns. The qp at any given e, was significantly reduced in the slots with lower bulk density compared to the undisturbed soil. The differences in qp- �v relationship of the undisturbed part of the soil under different ameliorative practices were attributed to changes in the swelling characteristic, and hence in the bulk density at any given �v of the undisturbed soil, caused by the presence of gypsum and the slots. Regression equations between qp and neutron count rate (n) for the undisturbed soil and for the slots were developed by combining the qp on �v relationships with the neutron meter calibration for �v measurements. The use of these regression equations and measured n values to predict changes in soil strength profiles during a wheat crop drying cycle in an undisturbed and ameliorated transitional red-brown earth was evaluated on another experimental site. There were no significant differences between the predicted and measured qp values in the non-ameliorated soil and the gypsum-slotted soil. Significant differences were observed between the predicted and measured qp values in the surface gypsum applied soil. The study shows the potential for using the neutron method as a convenient in-situ field technique to predict qp profile changes, preferably using qp on n relationships developed at the experimental site.

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