Management Systems Impact On Soil Aggregate Protected Carbon and Nitrogen Accumulation.

Continuous no-till with cover crops is important to support sustainable agriculture. A field study was established at Piketon, Ohio to determine the long-term effects (2005 to 2013) of tillage and cover crops on soil aggregate size distribution, aggregate stability and C and N protection. Treatments included corn-soybean rotation with conventional tillage (CT-CS), corn-soybean rotation with continuous no-till (NT-CS), and corn-soybean-wheat-cover crop rotation with continuous no-till (NT-CSW-CC) and replicated three times. Composite soil samples were collected from 0 to 90 cm depth at 15 cm increments, processed and analyzed for bulk density, aggregate size distribution from <0.053, 0.053 to 0.125, 0.250, 0.50, 1.0, 2.0 and 5.0 mm, macro- and microaggregate stability, mean weight diameter (MWD), geometric mean diameter (GMD), and total C and N content of various aggregate size distribution. Results showed that NT significantly increased macroaggregates, MWD and GMD, and aggregate stability and decreased bulk density as compared with CT. Likewise, higher content of total C and N was measured in macroaggregates of NT. The effect of NT with cover crops was more pronounced on soil aggregate properties and C and N protection than on CT-CS and NT-CS. Irrespective of treatments, soil aggregate stability and C and N protection decreased with depth.