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This article in SSSAJ

  1. Vol. 73 No. 3, p. 961-966
     
    Received: June 10, 2008
    Published: May, 2009


    * Corresponding author(s): sjfonte@ucdavis.edu
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doi:10.2136/sssaj2008.0204

Fertilizer and Residue Quality Effects on Organic Matter Stabilization in Soil Aggregates

  1. Steven J. Fonte *a,
  2. Edward Yeboahb,
  3. Patrick Oforib,
  4. Gabriel W. Quansahb,
  5. Bernard Vanlauwec and
  6. Johan Sixa
  1. a Dep. of Plant Sciences, Univ. of California, One Shields Avenue, Davis, CA 95616
    b Soil Research Institute, Academy Post Office, Kwadaso, Kumasi, Ghana
    c Tropical Soil Biology and Fertility Inst. of CIAT, P.O. Box 30677, Nairobi, Kenya

Abstract

This study examined the influence of organic residue quality and N fertilizer on aggregate-associated soil organic matter (SOM) in maize (Zea mays L.) cropping systems of southern Ghana. Six residue treatments of differing quality [Crotalaria juncea L., Leucaena leucocephala (Lam.) de Wit, maize stover, sawdust, cattle manure, and a control with no residues added] were applied at 4 Mg C ha−1 yr−1 both with and without fertilizer N additions (120 kg N ha−1 season−1). Soils (0–15 cm) were sampled 3 yr after study implementation and wet sieved into four aggregate size classes (8000–2000, 2000–250, 250–53, and <53 μm). Small macroaggregates (2000–250 μm) were further separated into coarse particulate organic matter (>250 μm), microaggregates within macroaggregates (53–250 μm), and macroaggregate-occluded silt and clay (<53 μm). Nitrogen fertilizer additions reduced aggregate stability, as was evident from a 40% increase in the weight of the silt and clay fraction (P = 0.014) as well as a decrease in microaggregates across all residue types (P = 0.019). Fertilizer similarly affected C and N storage within these aggregate fractions, while the effects of residue quality were largely insignificant. Our results suggest that fertilizer effects on soil aggregation may have important implications for long-term SOM dynamics.

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