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Soil Carbon Accumulation under Switchgrass Barriers

Blanco-Canqui, Humberto, Gilley, John E., Eisenhauer, Dean E., Jasa, Paul J., Boldt, Alan
Agronomy journal 2014 v.106 no.6 pp. 2185-2192
Argiudolls, Glycine max, Panicum virgatum, Sorghum bicolor, Zea mays, aggregate stability, agricultural soils, agroecosystems, carbon, conventional tillage, corn, crop rotation, cropland, filter strips, grain sorghum, grasses, nitrogen, no-tillage, organic matter, porosity, silty clay soils, soil aggregates, soil aggregation, soil depth, soil organic carbon, soybeans, topographic slope, Nebraska
The benefits of grass barriers or hedges for reducing offsite transport of non-point-source water pollutants from croplands are well recognized, but their ancillary benefits on soil properties have received less attention. We studied the 15-yr cumulative effects of narrow and perennial switchgrass (L.) barriers on soil organic C (SOC), total N, particulate organic matter (POM), and associated soil structural properties as compared with the cropped area on an Aksarben silty clay loam (fine, smectitic, mesic Typic Argiudoll) with 5.4% slope in eastern Nebraska. Five switchgrass barriers were established in 1998 at ∼38-m intervals parallel to the crop rows in a field under a conventional tillage and no-till grain sorghum [ (L.) Moench]–soybean [ (L.) Merr.]–corn (L.) rotation. Compared with the cropped area, switchgrass barriers accumulated about 0.85 Mg ha yr of SOC and 80 kg ha yr of total soil N at the 0 to 15 cm soil depth. Switchgrass barriers also increased coarse POM by 60%. Mean weight diameter of water-stable aggregates increased by 70% at 0 to 15 cm and by 40% at 15 to 60 cm, indicating that switchgrass barriers improved soil aggregation at deeper depths. Large (4.75–8 mm) macroaggregates under switchgrass barriers contained 30% more SOC than those under the cropped area. Switchgrass-induced changes in SOC concentration were positively associated with aggregate stability (= 0.89***) and porosity (= 0.47*). Overall, switchgrass barriers integrated with intensively managed agroecosystems can increase the SOC pool and improve soil structural properties.