Soil structure and soil organic matter : II. A normalized stability index and the effect of mineralogy

Soil aggregate distribution and stability measurements have been proposed as soil quality indicators. However, pretreatment of soil, antecedent water content and differences in sand size distribution among soils can confound interpretation of these measurements. We propose a normalized stability index (NSI) which (i) compares aggregate distribution after slaking and rewetting to characterize whole soil stability and eliminate confounding effects of pretreatment and antecedent water content, (ii) corrects for the confounding effect of differences in sand size distribution among soils, aggregate size classes and pretreatments, and (iii) normalizes the level of disruption imposed by slaking by using a maximum level of disruption. The NSI was tested on three soils dominated by a 2:1 clay mineralogy and one soil characterized by a mixed (2:1 and 1:1) clay mineralogy. Each site had native vegetation (NV), no-tillage (NT), and conventional tillage (CT) treatments. In soils dominated by 2:1 clays, NSI decreased with increasing cultivation intensity (NV > NT > CT). However, NSI was higher in the soil with mixed clays compared to the other soils and was not different along the cultivation gradient. These observations are hypothesized to be related to the presence of Fe- and Al-oxides and kaolinite. In conclusion, NSI appears to be a good indicator for soil structural quality since it is sensitive to changes in agricultural practices and it minimizes confounding effects. A decrease of SOM levels results in a smaller decrease of soil stability in soils dominated by oxides and 1:1 minerals compared to soils dominated by 2:1 minerals.

[1]  Ramesh P. Rudra,et al.  SEASONAL VARIATION OF ERODIBILITY INDICES BASED ON SHEAR STRENGTH AND AGGREGATE STABILITY IN SOME ONTARIO SOILS , 1988 .

[2]  Ag Waters,et al.  Aggregate hierarchy in soils , 1991 .

[3]  B. D. Kay,et al.  Rates of Change of Soil Structure Under Different Cropping Systems , 1990 .

[4]  R. R. Bruce,et al.  A comparison of methods for measuring water-stable aggregates: implications for determining environmental effects on soil structure , 1993 .

[5]  N. Bissonnette,et al.  Microbial and biochemical changes induced by rotation and tillage in a soil under barley production , 1993 .

[6]  R. K. Schofield,et al.  Flocculation of kaolinite due to the attraction of oppositely charged crystal faces , 1954 .

[7]  Roel Merckx,et al.  Two simple indexes for distributions of soil components among size classes , 1991 .

[8]  B. Warren,et al.  X-Ray Diffraction , 2014 .

[9]  W. D. Kemper,et al.  Soil Cohesion as Affected by Time and Water Content , 1984 .

[10]  K. Paustian,et al.  Soil structure and organic matter: I. Distribution of aggregate-size classes and aggregate-associated carbon. , 2000 .

[11]  K. Norrish,et al.  The nature of soil particles particularly those reacting with arsenate in a series of chemically treated samples , 1983 .

[12]  J. Torrent,et al.  Relationships between aggregation and iron oxides in Terra Rossa soils from southern Italy , 1991 .

[13]  J. Torrent,et al.  Citrate-Ascorbate as a Highly Selective Extractant for Poorly Crystalline Iron Oxides , 1997 .

[14]  S. El‐Swaify,et al.  Changes in the Physical Properties of Soil Clays Due to Precipitated Aluminum and Iron Hydroxides: I. Swelling and Aggregate Stability After Drying 1 , 1975 .

[15]  U. Schwertmann,et al.  Microaggregates from Oxisols and Inceptisols: dispersion through selective dissolutions and physicochemical treatments , 1996 .

[16]  C. Monz,et al.  Organic matter contained in soil aggregates from a tropical chronosequence: correction for sand and light fraction. , 1991 .

[17]  G. Stirk.  EXPRESSION OF SOIL AGGREGATE DISTRIBUTIONS , 1958 .

[18]  M. Jackson,et al.  Quantitative Determination of Vermiculite in Soils1 , 1965 .

[19]  Y. Kitagawa.  Goethite and hematite in some solls from the amazon region , 1983 .

[20]  G. S. Francis,et al.  Changes in microbial biomass C, soil carbohydrate composition and aggregate stability induced by growth of selected crop and forage species under field conditions , 1993 .

[21]  A. Karathanasis,et al.  Water dispersible colloids and factors influencing their dispersibility from soil aggregates , 1996 .

[22]  E. T. Elliott.  Aggregate structure and carbon, nitrogen, and phosphorus in native and cultivated soils , 1986 .

[23]  E. Barberis,et al.  Iron oxides and particle aggregation in B horizons of some Italian soils , 1989 .

[24]  D. Angers,et al.  Early changes in water-stable aggregation induced by rotation and tillage in a soil under barley production , 1993 .

[25]  Jean Caron,et al.  Improvement of structural stability of a clay loam with drying , 1992 .

[26]  R. W. Sheard,et al.  Factors Influencing Soil Structural Stability within a Growing Season , 1990 .

[27]  Ky Chan,et al.  Surface physical properties of a sandy loam soil under different tillage practices , 1988 .

[28]  Johan Six,et al.  Aggregate and Soil Organic Matter Dynamics under Conventional and No-Tillage Systems , 1999 .

[29]  B. Theng.  Soils with Variable Change , 1982 .

[30]  H. Gollany,et al.  AGGREGATE STABILITY OF AN ERODED AND DESURFACED TYPIC ARGIUSTOLL , 1991 .

[31]  J. Tisdall,et al.  Organic matter and water‐stable aggregates in soils , 1982 .