Cohesion development in disrupted soils as affected by clay and organic matter content and temperature

Kemper, W.D. and Rosenau, R.C. and Dexter, A.R. (1987) Cohesion development in disrupted soils as affected by clay and organic matter content and temperature. Soil Science Society of America Journal. 51(4):860-867.

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Abstract

Soils were dispersed and separated into sand, silt, and clay fractions
that were reconstituted to give mixtures of each soil with 5 to
40% clay. In the range from 0 to 35% clay, higher clay contents
resulted in greater stability. Rate of cohesion recovery was over 10
times as fast at 90°C as it was at 23°C, showing that the processes
Involved are physical-chemical rather than biological. Maximum rates
of cohesion recovery occurred at moderate soil water tensions, probably
because some tension is needed to pull the particles into direct
contact, but a continuous water phase is also essential to allow diffusion
of bonding agents to the contact points. Since diffusion rates
in water increase 300%, while rate of cohesion recovery increased
1000% when temperature was raised from 23 to 90°C, other factors,
such as higher Mobilities at higher temperatures of compounds
contributing hooding ions to the solution. probably play a role In
the rate of cohesion recovery. Recovery of cohesion was more rapid
in the soil with organic C contents of 0.004 kg/kg than in the soil
with 0.012 kg/kg. When the organic matter was removed with H2O2
from the soil with 0.012 kg C/kg, its rate of cohesion recovery increased.
Rate of cohesion recovery of this high organic matter soil
was also increased by aging it at 0.1 kg H2O/kg soil compared to
0.2 kg/kg. A possible explanation is that organic coatings, tending
to prevent direct contact and bonding of adjacent projections of mineral
surfaces, are forced away from contact points by extremely strong
forces that pull the adjacent minerals together when soil water tensions
are high. When the higher organic matter soil had been consolidated
by air-drying and rehydrated, its rate of cohesion recovery
was just as rapid as that of the soil with low organic matter.

Item Type:	Article
NWISRL Publication Number:	0603
Subjects:	Soil Mass Import - autoclassified (may be erroneous)
Depositing User:	Dan Stieneke
Date Deposited:	20 Nov 2010 21:52
Last Modified:	13 Jan 2017 18:47
Item ID:	479
URI:	https://eprints.nwisrl.ars.usda.gov/id/eprint/479