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Soil Science Society of America Journal Abstract - DIVISION S-6-SOIL & WATER MANAGEMENT & CONSERVATION

Role of Hydrophobic Components of Soil Organic Matter in Soil Aggregate Stability


This article in SSSAJ

  1. Vol. 63 No. 6, p. 1801-1810
    Received: June 15, 1998

    * Corresponding author(s): alpiccol@unina.it
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  1. Alessandro Piccolo *a and
  2. Joe S. C. Mbagwub
  1. a Dipartimento di Scienze Chimico-Agrarie, Università di Napoli “Federico II”, Via Università 100, 80055 Portici (NA), Italy
    b Dep. of Soil Science, Univ. of Nigeria, Nsukka, Nigeria


Little is known about the effects of the individual components of organic matter (OM) on aggregate stability (AS). We hypothesized that AS of a Typic Haplustalf from which native OM was either removed or retained would be affected by incubation periods and application rates of a hydrophilic polysaccharide gum (G) and a hydrophobic stearic acid (S) with or without pretreatment with a hydrophobic humic acid (HA). Removal of OM reduced AS of unmodified soil by ≈40 and 20% after soil incubation for 7 and 40 d, respectively. In both soil samples, AS was best at the highest rate of G (5.0 g kg−1). Its effect was better on Soil A (where OM was removed) than Soil B (where OM was retained) but diminished rapidly during 40 d. At this rate, G increased AS by 750% in Soil A and by 335% in Soil B compared with no addition. With S, aggregate stability increased more with time in Soil B than in Soil A. Its maximum effect was also at the highest application rate (5.0 g kg−1), where AS increased 100% on Soil A and 131% on Soil B. At the highest rate (0.2 g kg−1), HA increased AS by 73% on Soil B and 27% on Soil A. The effect of HA alone did not vary with time. Soil pretreatment with HA before addition of G reduced significantly both the state of aggregation and AS of both soils. The reverse occurred when HA was applied before S. After 40 d, S+HA increased AS in Soil B by 34%, whereas G and G+HA decreased AS by 14 and 4%, respectively. We found that soil AS was improved and maintained with time more by hydrophobic than by hydrophilic components of organic matter. Long-lasting aggregate stability of soils can be thus achieved by addition of hydrophobic humic material with hydrophobic organic wastes.

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