Submitted to: Soil Science Society of America Journal
Publication Type: Peer reviewed journal
Publication Acceptance Date: 10/9/2003
Publication Date: 5/1/2004
Citation: Mikha, M.M., Rice, C.W. 2004. Tillage and manure effects on soil and aggregate-associated carbon and nitrogen. Soil Science Society of America Journal. 68:809-816. Interpretive Summary: This study showed that no-tillage had significantly improved soil total C and N, water-stable aggregates, and labile C and N associated with macroaggregates compared with CT. Conventional tillage likely enhanced disruption of soil aggregates resulting in loss of SOM. On the other hand, manure significantly increased total C and N through the formation of water-stable macroaggregates and aggregate-associated C and N. The combination of NT and M further improved soil aggregation and aggregate-associated C and N.
Technical Abstract: In agricultural systems, maintenance of soil organic matter (SOM) has long been recognized as a strategy to reduce soil degradation. No-tillage and manure are management practices that can restore (SOM) and improve soil aggregatation. We investigated effect of tillage system and N source on aggregate size distribution and aggregate-associated C and N over 10-y period. The study was a split plot design replicated 4 times. The main plot was tillage (no-tillage, NT; conventional tillage, CT), subplot was N source (manure, M; NH4NO3 fertilizer, F). The experiment was established in 1990 on a moderately well-drained Kennebec silt loam (fine-silty, mixed, mesic cumulic Hapludoll) with continuous corn (Zea mays L.). Samples were collected (0-5 cm depth) from four replicated NT and CT with M and F treatments and separated into four aggregate size classes (> 2000, 250-2000, 53-250, and 20-53 mm) by wet sieving. Manure significantly improved total C and N. Labile C and N from all aggregate size fractions were measured from 28-d laboratory incubations of intact and crushed aggregate. Aggregate labile C and N were significantly greater with macroaggregates (> 2000, 250-2000 mm) than microaggregates (53-250, and 20-53 mm) and with M than F. Aggregate-associated C and N were significantly greater with the 250-2000 mm size fraction than any other size fraction. The flush of C due to aggregate crushing was significantly pronounced in macroaggregates at 7-d of incubation We observed a significant reduction in macroaggregates and a significant redistribution of aggregates into microaggregate size fractions with CT compared with NT. Either NT or M significantly improved soil aggregation and aggregate-associated C and N, however, NT and M further improved soil aggregation and aggregate-protected C and N.