Mechanical dispersion of clay from soil into water: readily-dispersed and spontaneously-dispersed clay

Abstract

A method for the experimental determination of the amount of clay dispersed from soil into water is described. The method was evaluated using soil samples from agricultural fields in 18 locations in Poland. Soil particle size distributions, contents of organic matter and exchangeable cations were measured by standard methods. Sub-samples were placed in distilled water and were subjected to four different energy inputs obtained by different numbers of inversions (end-over-end movements). The amounts of clay that dispersed into suspension were measured by light scattering (turbidimetry). An empirical equation was developed that provided an approximate fit to the experimental data for turbidity as a function of number of inversions. It is suggested that extrapolation of the fitted equation to zero inversions enables the amount of spontaneously-dispersed clay to be estimated. This method introduces the possibility of replacing the existing subjective, qualitative method of determining spontaneously-dispersed clay with a quantitative, objective method. Even though the dispersed clay is measured under saturated conditions, soil samples retain a ‘memory’ of the water contents at which they have been stored.

Effects of different soil management practices on soil properties and microbial diversity

“…What is more, the higher concentration of SOM in soil under RT induced a decrease in RDC content, in comparison to that of the CT system. According to Czyż et al (2002), Czyż and Dexter (2015), Dexter et al (2008), and Gajda et al (2016), the total organic C controls mostly the RDC and then RDC shows a similar outcome to that induced by organic matter, but since it is a complex-bound C, a similar outcome cannot be expected for RDC. As Czyż and Dexter (2015) reported, an increase of SOM has been found to reduce the amount of RDC, in a Polish soil (Dexter and Czyż, 2000), in Romanian soils (Watts et al, 1996), and for a UK soil (Watts and Dexter, 1997).…”

“…The role and importance of soil quality for sustainable agricultural development under environmental protection conditions is receiving increasing attention from both farm ers and researchers. In order to have soil with high physical quality, it is necessary to have two main structural features: firstly, the soil must be stable in water, and, secondly, the soil must have a suitable pore size distribution that will enable the soil to absorb, store and release water for plant use (Czyż and Dexter, 2015;Gaţe et al, 2004). Such soils will also have a good aeration status and will be more easily penetrable by plant roots.…”

“…Soil is usually assumed to have 'good' physical quality when it is friable, does not produce clods when tilled, is not hard-setting, is penetrable by plants, is permeable and is stable in water (Dexter, 2002;Gaţe et al, 2004;Keller et al, 2007). Clay and organic matter contents play significant roles in the structural stability of soils , 2015. Soil organic matter (SOM) is a key attribute of soil quality and affects soil physical, chemical and microbiological properties (Franzluebbers, 2002;Gajda et al, 2017;Gregorich et al, 1994;Six et al, 2002).…”

Methodological aspects of the quantification of dispersible clay and their relations with soil properties along a catena under no-till system

“…The indicators of structural stability can be used to contribute to the monitoring of possible modifications, indicating improvements or deteriorations in the structure of the soil (Arshad and Martin, 2002;Nunes et al, 2017). Dispersible clay represents the portion of the total clay which has the ability to disperse easily in the presence of water (Dexter and Czyż, 2000;Dexter et al, 2011); it is an important indicator of structural stability (Igwe and Udegbunam, 2008;Nunes et al, 2017) in catena soils which have been influenced by intensive fertilization, constant soil tillage and the absence of organic carbon (Azevedo and Bonumá, 2004;Dexter et al, 2011;Czyż and Dexter, 2015).…”

Impact of tillage intensity on clay loam soil structure

“…This dispersion further reduces soil permeability and tends to inhibit the infiltration of water and the exchange of gases between soil and atmosphere. Clogging and slow infiltration may lead to surface runoff, water erosion and pollution of surface waters (Czyż & Dexter, ; Dong, Wang, Zhou, & Shan, ; Mironenko & Pachepsky, ; Petersen et al., ). Miller and Bahruddin () reported strong correlations between infiltration, water erosion and clay dispersibility.…”