582-8 Agronomic and Environmental Implications of Soil Resource Heterogeneity at Small Scales.

See more from this Division: S03 Soil Biology & Biochemistry
See more from this Session: Soil Biology and Soil Nitrogen

Monday, 6 October 2008: 10:30 AM
George R. Brown Convention Center, 370C

Terry Loecke, Cary Institute of Ecosystem Studies, Millbrook, NY and G. Philip Robertson, Crop and Soil Sciences and Kellogg Biological Station, Michigan State University, Hickory Corners, MI
Abstract:
Soil resource spatial heterogeneity is a common property of most natural and managed soils; however, its functional influence over soil and plant processes is poorly known.  To understand how plant litter aggregation affects nitrogen cycle processes including N mineralization, plant N acquisition, nitrate leaching, and N2O and total N loss we distributed 15N-labeled Trifolium pratensis litter in soil across an aggregation gradient (from uniformly distributed to highly aggregated) into which we planted maize.  Under N-limited conditions maize was 14% more productive where litter was aggregated.  Litter aggregation did not affect root to shoot ratio; however, total belowground C allocation appeared to be greater in response to uniformly distributed than to aggregated litter.  Plant N acquisition was greater in response to aggregated than uniformly distributed litter.  Litter aggregation also increased litter-derived N mineralization by 20%, shoot N by 18% and root N by 33% relative to uniformly distributed litter.  Of the litter-N added to the soil, 15% on average was unaccounted for at the end of growing season regardless of litter aggregation.  Nitrate leaching was also similar across the litter aggregation gradient (1-2% of added litter-N); however, N2O emissions were significantly greater when the litter was aggregated than when uniformly distributed.  Results suggest that resource spatial heterogeneity alone can alter N cycling processes, and thus the management of sub-plant scale resource heterogeneity to optimize agronomic and environmental services in agricultural systems should be investigated further.

See more from this Division: S03 Soil Biology & Biochemistry
See more from this Session: Soil Biology and Soil Nitrogen