EFFECT OF ROOT EXUDATES FROM CORN AND BROMEGRASS ON SOIL STRUCTURAL STABILITY

1990 ◽  
Vol 70 (3) ◽  
pp. 351-362 ◽  
Author(s):  
T. POJASOK ◽  
B. D. KAY
Keyword(s):  
Structural Stability ◽  
Root Exudates ◽  
Soil Structure ◽  
Aggregate Stability ◽  
Clay Content ◽  
Flash Evaporation ◽  
Metal Organic ◽  
Loam Soil ◽  
Wet Aggregate Stability ◽  
Dispersible Clay

The effect of root exudates on structural stability and the hypothesis that the growing roots of corn (Zea mays L.) can destabilize soil structure by chelating Fe and Al involved in mineral-metal-organic matter linkages were investigated. Exudates were removed from 14C-labelled corn and bromegrass (Bromus inermis Leyss.) plants grown in sand using sequential leaching with water and acetone. The exudates were concentrated by flash evaporation and incubated with 1–2 mm aggregates of a calcareous silt loam soil for up to 240 h. Aggregates to which exudates from bromegrass were added had a higher wet aggregate stability (WAS) and lower dispersible clay content (DC) than aggregates to which exudates from corn were added. The greatest increase in stability occurred on addition of the water-extracted exudates (9.6% for WAS, 27.1% for DC). The increase in stability correlated positively with a release into solution of Ca and Mg from the soil solids. Addition of CaCl2 to the aggregates, to give corresponding amounts of Ca and Mg in solution, had similar effects on stability suggesting that the ions released by the exudates were not in a chelated form. The quantity of carbon added in the exudates and the mineralization of this carbon were positively and negatively correlated with stability, respectively. There was little evidence that corn exudates caused a destabilization of structure. Key words: Wet aggregate stability, dispersible clay, corn, bromegrass, flocculation, calcium

ASSESSMENT OF A COMBINATION OF WET SIEVING AND TURBIDIMETRY TO CHARACTERIZE THE STRUCTURAL STABILITY OF MOIST AGGREGATES

1990 ◽  
Vol 70 (1) ◽  
pp. 33-42 ◽  
Author(s):  
T. POJASOK ◽  
B. D. KAY
Keyword(s):  
Organic Matter ◽  
Structural Stability ◽  
Organic Matter Content ◽  
Aggregate Stability ◽  
Clay Content ◽  
Matter Content ◽  
Wet Aggregate Stability ◽  
Large Investment ◽  
Dispersible Clay ◽  
Wet Sieving

A method of measuring the structural stability of moist soils using a combination of turbidimetry and wet sieving has been developed and assessed. Aggregates of 1–2 mm in diameter are shaken end-over-end in test tubes and dispersed clay and stable aggregates greater than 0.25 mm diameter measured. Stabilities determined using this method were compared to stabilities determined using a modification of the Yoder wet-sieving method on 20 soils of different textures, organic-matter content, and recent cropping history. Wet aggregate stabilities determined by the two methods were correlated although the two measurements exhibited different sensitivities to clay content, organic-matter content and moisture content at the time of sampling. Dispersible clay was found to be a function of total clay content, organic-matter content and water content at the time of sampling. The new method offers the advantage of stability measurements of structural units of much different size using the same energy input and can be readily adapted to the routine analysis of a large number of samples without a large investment in equipment or space. Key words: Wet aggregate stability, dispersible clay, cropping history, soil structure

INFLUENCE OF ICE SEGREGATION AND SOLUTES ON SOIL STRUCTURAL STABILITY

1990 ◽  
Vol 70 (4) ◽  
pp. 571-581 ◽  
Author(s):  
E. PERFECT ◽  
W. K. P. van LOON ◽  
B. D. KAY ◽  
P. H. GROENEVELT
Keyword(s):  
Water Content ◽  
Structural Stability ◽  
Aggregate Stability ◽  
Frost Heave ◽  
Unfrozen Water Content ◽  
Soil Structural Stability ◽  
Frost Penetration ◽  
Wet Aggregate Stability ◽  
Dispersible Clay ◽  
Ice Segregation

Most Canadian soils contain dissolved salts and are subject to freezing. However, the structural consequences of freezing in the presence of solutes are unknown. The effects of ice segregation and solutes on soil structural stability were investigated in a laboratory experiment. Nine 27-cm-diameter by 19-cm-high columns were used. These were packed with air-dry Conestogo silt loam soil (Gleyed Melanic Brunisol or Aquic Eutrochrept) and wetted with CaCl2 solutions at 1, 2, and 4 g L−1. Slow freezing took place from the top down in an environmental chamber maintained at −3.4 ± 0.4 °C. Depth of frost penetration, temperature, frost heave, and unfrozen water content were monitored within each column. After 20 d, the mean frost penetration was 107 ± 18 mm and the soil surface had heaved 9 ± 4 mm, indicating ice segregation. At the end of the experiment, the frozen and unfrozen zones of each column were sampled destructively. Samples were equilibrated at 4 °C and analyzed for wet-aggregate stability (WAS), dispersible clay (DC), gravimetric water content, and CaCl2 concentration. Samples which had been frozen had significantly more water and CaCl2 in the thawed state than those which had remained unfrozen. These increases were attributed to a freezing-induced redistribution of the saturating solutions. DC decreased with increasing CaCl2 concentration, indicating an electrical double-layer effect. Soil that had been frozen and thawed had a more stable structure (in terms of both DC and WAS) than the unfrozen soil. No interaction was found between solutes and freezing. In contrast, there was a significant interaction between water content and freezing. WAS increased with decreasing water content for those aggregates which had been frozen and thawed, but not for those which had remained unfrozen. Key words: Soil structure, wet-aggregate stability, dispersible clay, frost heave, soil solution, bulk electrical conductivity

Structural stability of sodic soils in sugarcane production as influenced by gypsum and molasses

2002 ◽  
Vol 42 (3) ◽  
pp. 315 ◽  
Author(s):  
A. Suriadi ◽  
R. S. Murray ◽  
C. D. Grant ◽  
P. N. Nelson
Keyword(s):  
Structural Stability ◽  
Aggregate Stability ◽  
Clay Loam ◽  
Exchangeable Sodium ◽  
Sodic Soils ◽  
Clay Dispersion ◽  
Sugarcane Production ◽  
Mechanical Dispersion ◽  
Wet Aggregate Stability ◽  
Dispersible Clay

The aim of this work was to determine whether molasses, a by-product of sugar manufacture, alone or combined with gypsum, could improve the structural stability of sodic soils used for sugarcane production. A Burdekin sandy clay loam with an exchangeable sodium percentage (ESP) of 7.9, and a Proserpine loamy sand with an ESP of 18.8 were incubated with molasses (0 and 10 t/ha) and gypsum (0 and 10 t/ha) for 12 weeks, during which time they were leached 5 times with water (0.5 pore volumes each time). In the Burdekin soil, molasses and gypsum, either alone or combined, decreased spontaneous clay dispersion from 2.6 to <0.2 g/kg soil. Mechanical dispersion was reduced from 21.2 to <0.2 g/kg soil by gypsum alone, and to 14.9 g/kg soil by molasses alone. Molasses and gypsum both increased wet aggregate stability, with the combined effect being greatest; the proportion of aggregates >250 μm was 31% in the control and 71% with molasses + gypsum. Electrical conductivity (EC 1:5) was 0.1 and 1.9 dS/m, pH1:5 in water was 7.7 and 7.1, and ESP was 4.1 and 0.2 in the control and molasses + gypsum treatments respectively. In the Proserpine soil, the amounts of dispersible clay were much less than in the Burdekin soil. The effects of molasses and gypsum in decreasing spontaneous and mechanical clay dispersion were similar to those in the Burdekin soil, but less pronounced. Molasses and gypsum, either alone or combined, improved the structural stability of both soils by decreasing dispersion and/or slaking. An implication of this work is that molasses may be a useful ameliorant for sodic soils, either alone or combined with gypsum.

scholarly journals Quantitative and qualitative comparison of three wet aggregate stability methods using a long-term tillage system and crop rotation experiment

2018 ◽  
Vol 98 (4) ◽  
pp. 738-742 ◽  
Author(s):  
L.L. Van Eerd ◽  
A.H. DeBruyn ◽  
L. Ouellette ◽  
D.C. Hooker ◽  
D.E. Robinson
Keyword(s):  
Capital Investment ◽  
Surface Soil ◽  
Aggregate Stability ◽  
Clay Loam Soil ◽  
Qualitative Comparison ◽  
No Till ◽  
Tillage System ◽  
Loam Soil ◽  
Wet Aggregate Stability

Automated wet-sieving is preferred for this clay loam soil due to better sensitivity and savings (time and disposables) despite a larger capital investment. Rotations with greater frequency of winter wheat and no-till compared with conventional plow system had greater wet aggregate stability values, indicating better surface soil quality.

scholarly journals Tillage Intensity Effects on Soil Structure Indicators—A US Meta-Analysis

2020 ◽  
Vol 12 (5) ◽  
pp. 2071 ◽  
Author(s):  
Márcio R. Nunes ◽  
Douglas L. Karlen ◽  
Thomas B. Moorman
Keyword(s):  
Crop Production ◽  
Soil Structure ◽  
Management Practices ◽  
Cropping Systems ◽  
Meta Analysis ◽  
Soil Health ◽  
Health Assessment ◽  
Aggregate Stability ◽  
Soil Penetration Resistance ◽  
Wet Aggregate Stability

Tillage intensity affects soil structure in many ways but the magnitude and type (+/−) of change depends on site-specific (e.g., soil type) and experimental details (crop rotation, study length, sampling depth, etc.). This meta-analysis examines published effects of chisel plowing (CP), no-tillage (NT) and perennial cropping systems (PER) relative to moldboard plowing (MP) on three soil structure indicators: wet aggregate stability (AS), bulk density (BD) and soil penetration resistance (PR). The data represents four depth increments (from 0 to >40-cm) in 295 studies from throughout the continental U.S. Overall, converting from MP to CP did not affect those soil structure indicators but reducing tillage intensity from MP to NT increased AS in the surface (<15-cm) and slightly decreased BD and PR below 25-cm. The largest positive effect of NT on AS was observed within Inceptisols and Entisols after a minimum of three years. Compared to MP, NT had a minimal effect on soil compaction indicators (BD and PR) but as expected, converting from MP to PER systems improved soil structure at all soil depths (0 to >40-cm). Among those three soil structure indicators, AS was the most sensitive to management practices; thus, it should be used as a physical indicator for overall soil health assessment. In addition, based on this national meta-analysis, we conclude that reducing tillage intensity improves soil structure, thus offering producers assurance those practices are feasible for crop production and that they will also help sustain soil resources.

scholarly journals From the study of the characteristics of the mountain dark kastanozem in the mouth of Shar Khad in Uvur Zaisan, Bogd Khan mountain

2021 ◽  
Vol 31 (3) ◽  
pp. 137-142
Author(s):  
Lkhamsuren Byambaja ◽  
Khishigsaikhan Adiyazar ◽  
Janchivdorj Baatarkhuu ◽  
Soronzongombo Byambaa ◽  
Namjilsuren Ganbaatar
Keyword(s):  
Structural Stability ◽  
Soil Structure ◽  
Humus Content ◽  
Chemical Properties ◽  
Clay Content ◽  
Physical And Chemical Properties ◽  
Control Parameters ◽  
Physical Clay ◽  
Physical And Chemical ◽  
And Chemical Properties

We cut in 25.5 hectares of soil at the mouth of Shar Khad in Uvur Zaisan, Bogd Khan Uul, made morphological records, determined the soil structure, its stability, physical and chemical properties, and compared it with the soil properties of the fenced area selected as the main control parameters. In this study, we compared the structure, structural stability, physical and chemical properties of mountain dark kastanozem. For the soil structure of the study area, the proportion of 0.25-10 mm structure in the 0-8 cm layer is 5-18 %, and the structure size of less than 0.25 mm is 27 %, and the structural stability is 2-2.5 on average at 0-3 cm soil In terms of points and mechanical composition, light loam and sandy soils predominated in the 0-8 cm layer of soil, sand content increased by 48.2%, physical clay content decreased by 68.8%, and humus content decreased by 0.6% from the fenced area selected for control. As a result, the characteristics of the dark kastanozem degraded of the settled area. Богдхан уулын Өвөр Зайсангийн Шар хадны амны уулын хар хүрэн хөрсний шинж чанарыг судалсан дүн Бид Богд Хан уулын Өвөр Зайсангийн Шар хадны амны  25.5 га талбайн хөрсөнд зүсэлт хийж, морфологи бичиглэл үйлдэн, хөрсний бүтэц, түүний тогтвортой байдал, физик, химийн шинж чанарыг тодорхойлон голлох үзүүлэлтээр хяналт болгон сонгож авсан хашиж хамгаалсан талбайн хөрсний шинж чанартай харьцуулан уг судалгааг хийж гүйцэтгэв. Бид уг судалгаагаар уулын хар хүрэн хөрсний бүтэц, бүтцийн тогтвортой байдал, физик, химийн шинж чанарыг харьцуулан судлав. Судалгааны талбайн хөрсний бүтцийн хувьд 0-8 см үе давхаргад 0.25-10 мм хэмжээтэй бүтцийн эзлэх хувь 5-18 %, 0.25 мм-ээс бага хэмжээтэй бүтэц 27 %-ийг эзэлж, бүтцийн тогтвортой байдал хөрсний 0-3 см үед дунджаар 2-2.5 балл, механик бүрэлдэхүүний хувьд хөрсний 0-8 см үе давхаргад хөнгөн шавранцар механик бүрэлдэхүүн зонхилж, элсний агууламж 48.2 %-иар нэмэгдэж, физик шаврын агууламж 68.8 %-иар, ялзмагийн агууламж хяналт болгон сонгож авсан хашсан талбайнхаас 0.6 %-иар тус тус буурсан байна. Мөн хөрсний шим тэжээлийн элементүүд болох хөдөлгөөнт фосфор, солилцох калийн агууламжийн хувьд ч хашсан талбайнхаас бага байна. Дээрхи үр дүнгээс үзэхэд судалгааны талбайд тогтворжсон уулын хар хүрэн хөрсний шинж чанарт мэдэгдэхүйц өөрчлөлт орж талхагдал, доройтолд өртжээ гэж үзэх үндэстэй байна.  Түлхүүр үг: Хөрсний бүтэц, хөрсний бүтцийн тогтвортой байдал, хөрсний физик шинж, хими шинж, хөрсний доройтол

Persistent improvements in the structure and hydraulic conductivity of a Ferrosol due to liming

Soil Research ◽  
2007 ◽  
Vol 45 (3) ◽  
pp. 218 ◽  
Author(s):  
J. M. Kirkham ◽  
B. A. Rowe ◽  
R. B. Doyle
Keyword(s):  
Hydraulic Conductivity ◽  
Organic Carbon ◽  
Soil Structure ◽  
Aggregate Stability ◽  
Aggregate Size ◽  
Soil Surface ◽  
Penetration Resistance ◽  
Organic C ◽  
Soil Penetration Resistance ◽  
Wet Aggregate Stability

Changes in the soil structure and hydraulic conductivity of an Acidic Red Ferrosol were measured in a long-term (1968–2003) fertiliser experiment on pasture in north-western Tasmania, Australia. Studies were initiated following observations of both softer soil surface and cracking on plots that had received 15 t/ha of ground agricultural limestone. Liming decreased penetration resistance and increased hydraulic conductivity. These structural improvements were associated with increased mean dry aggregate size, a small increase in wet aggregate stability, higher exchangeable calcium levels, and increased plant growth, but a 9% decrease in total soil organic carbon in the surface 50 mm. This decrease in organic carbon was not associated with deterioration in soil structure, as may have been anticipated. This was probably because total organic C was still 82 g/kg on unlimed plots. Decreases in soil penetration resistance due to liming increased the likelihood of pugging from livestock but may improve ease of tillage. This research demonstrates that liming can improve the structure of a well-aggregated Ferrosol as well as its previously reported effects of increasing soil pH and yields of pasture and barley despite decreasing organic C.

scholarly journals Assessing of soil aggregate stability: the sand-correction and its relevance

2009 ◽  
pp. 29-47
Author(s):  
Andrea Huisz
Keyword(s):  
Wheat Straw ◽  
Soil Structure ◽  
Sandy Loam ◽  
Aggregate Stability ◽  
Index Formula ◽  
Soil Aggregate Stability ◽  
Mean Weight Diameter ◽  
Loam Soil ◽  
The Mean ◽  
Organic Matter Addition

Soil structure and changes in its quality caused by Maize stem (1), Wheat straw (2) and Maize stem & wheat straw (3) addition were assessed by three aggregate-stability indices. We observed that the NSI index formula proposed by Six et al. (2000) was nonsensitive to the changes in soil structure caused by the investigated organic matter addition. Furthermore it overestimates the aggregate-stability of the investigated silty sandy loam soil. Therefore we proposed a new modified NSI formula which is sensitive to the questionable treatments and that resulted in a morerealistic NSI data. The most sensitive index to differences of the investigated treatments were the Mean weight diameter (MWD) proposed by van Bavel (1953, in Kemper és Rosneau, 1986).

Comparison of the effects of latex and poly(DADMAC) on structural stability and strength of soil aggregates

Soil Research ◽  
1995 ◽  
Vol 33 (2) ◽  
pp. 369 ◽  
Author(s):  
SM Bernas ◽  
JM Oades ◽  
GJ Churchman ◽  
CD Grant
Keyword(s):  
Structural Stability ◽  
Cropping Systems ◽  
Soil Aggregates ◽  
Aggregate Stability ◽  
Structural Condition ◽  
Mechanical Action ◽  
Water Stable Aggregates ◽  
The Face ◽  
Wet Aggregate Stability ◽  
Aromatic Oils

Two types of high molecular weight polymers having contrasting charge properties and molecular shapes [latex and poly(DADMAC)] were applied at different rates to three Alfisols and a Mollisol to examine the effects of these polymers on soil strength and structural stability, and to identify some of the mechanisms by which these polymers act to stabilize soils. Wet aggregate stability, mechanically dispersible clay, and soil friability tests were used to assess treatment effects, which were found to be greatest in soils having a poor structural condition. Each polymer acted differently. Latex, which acted like a coat of paint (because of its inability to penetrate beyond the surface of aggregates), dramatically increased the proportion of water stable aggregates >2 mm in all soils examined, and this was achieved without the traditional (expensive) use of aromatic oils and stabilizers. The latex coating produced a conglomeration of smaller soil aggregates, but did not extensively alter either the dispersibility of the aggregates in the face of mechanical action, or their strength and friability. Results indicate latex may be best suited to minimum tillage cropping systems. Poly(DADMAC), by contrast, was capable of entering most pores accessible to water. This enabled it to minimize clay dispersion, increase soil friability, and to modestly increase the size of water stable aggregates. In many ways, poly(DADMAC) would appear to be an ideal soil conditioner, although the economic suitability of this polymer and its effects on erosion control and plant growth have yet to be assessed.

Freezing cycle effects on water stability of soil aggregates

2013 ◽  
Vol 93 (4) ◽  
pp. 473-483 ◽  
Author(s):  
Daryl F. Dagesse
Keyword(s):  
Water Content ◽  
Structural Stability ◽  
Soil Aggregates ◽  
Aggregate Stability ◽  
Clay Content ◽  
Initial Water Content ◽  
Water Stability ◽  
Initial Water ◽  
Freeze Thaw ◽  
Freezing Cycle

Dagesse, D. F. 2013. Freezing cycle effects on water stability of soil aggregates. Can. J. Soil Sci. 93: 473–483. The freezing process is commonly implicated as a key factor in defining the state of soil structural stability following the winter months. Controversy exists, however, regarding the efficacy, and even the net effect, of this process. The objective of the study was to establish the separate effects of the freezing, freeze–thaw and freeze-drying processes in defining soil structural stability following the over-winter period. Aggregates from soils of varying clay content (0.11, 0.33, 0.44 kg kg−1) and initial water content (0.10, 0.20 or 0.30 kg kg−1) were subjected to freeze-only (F), freeze–thaw (FT) and freeze-dry (FD) treatments. Post-treatment aggregate stability determination was via wet aggregate stability (WAS) and dispersible clay (DC). Freezing alone and freeze-dry treatments generally resulted in greater aggregate stability, while the freeze–thaw generally resulted in lower aggregate stability as compared with a control, not frozen treatment (T). These data suggest the freezing-induced desiccation process improves aggregate stability, while the addition of a thaw component following freezing, with the attendant liquid water, is responsible for degradation of aggregate stability. Clay content and initial water content are important factors governing the magnitude of this process.

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