Soil Carbon Accumulation under Switchgrass Barriers

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 (Panicum virgatum 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 [Sorghum bicolor (L.) Moench]–soybean [Glycine max (L.) Merr.]–corn (Zea mays L.) rotation. Compared with the cropped area, switchgrass barriers accumulated about 0.85 Mg ha-1 yr-1 of SOC and 80 kg ha-1 yr-1 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 (r = 0.89***) and porosity (r = 0.47*). Overall, switchgrass barriers integrated with intensively managed agroecosystems can increase the SOC pool and improve soil structural properties