Abstract
Physical and mechanical stresses induced changes in clay dispersion is a major sustainability and environmental issue, particularly in large-scale intensive agricultural production systems. However, the dispersed clay may re-stabilize when the stresses are reduced or minimized/ removed. The objectives of this study are to (i) quantify the maximum potentially dispersible (DCmax) and stabilizable clay (SCmax) in soils with textural differences when the stresses were introduced and reduced, respectively, and (ii) identify the role of inherent soil variable(s) on DCmax and SCmax- Dispersible clay measurements were conducted at monthly intervals for 3 years on seven soil types under different cropping treatments. The cropping treatments used in this study were conventionally tilled continuous corn (CTCC) and forages, which were established in 1989 on plot that were previously under CTCC for more than 10 years. The CTCC represents stress imposed and the forages the stress reduced system. The DCmax in the stress imposed system across soils ranged from 3.2 to 16.6 % compared to 6.4 to 33.8 %, the total clay (TC) content. The DCmax increased with increasing TC and decreasing soil organic matter (SOM) content. The SCmax in the stress reduced system across soils ranged from 1.2 to 4.5 % and it increased with increasing TC and SOM. Eleven to 37 % of the DCmax was re-stabilized during the 3-year period under forages, i.e. stress reduced system. The amount of SOM in the soil at the time of switchover from CTCC played a significant role in the re-stabilization of dispersed clay, particularly in soils with similar TC. The results show the stabilization of dispersed clay under reduced stresses depended on DCmax and SOM.
