Sediment and runoff losses from rainfall simulation: Effects of elevated atmospheric CO2 and tillage practice

There is a lack of information regarding how rising atmospheric CO₂ concentration will affect runoff aspects in cropping systems. Following a 10-year study, a rainfall simulation examined the impacts of atmospheric CO₂ level (ambient and twice ambient) and tillage system (conventional tillage and no-till) on a Decatur silt loam (clayey, kaolinitic, thermic Rhodic Paleudults). Conventional tillage was a sorghum [Sorghum bicolor (L.) Moench.] and soybean [Glycine max (L.) Merr.] rotation using spring tillage and winter fallow, while the no-till system used this same rotation with three rotated cover crops [crimson clover (Trifolium incarnatum L.), sunn hemp (Crotalaria juncea L.), and wheat (Triticum aestivum L.)]. Elevated atmospheric CO₂ led to more residue production in both tillage systems; this effect was greater under no-till conditions. More residue improved water infiltration only in the no-till system. Regardless of CO₂ level, sediment loss was lower under no-till, and elevated CO₂ reduced sediment loss in the conventional tillage system. No-till reduced sediment loss in addition to C, N, and P lost in sediment. No-till also reduced runoff water volume and N and P losses in this runoff. Results indicated that both high CO₂ and no-till management increased surface residues that could improve water infiltration, reduce sediment and runoff losses as well as nutrients lost in sediment and runoff water. This study suggests that farmers who practice conservation agriculture are likely to lose less soil and nutrients to rain-induced erosion and that these improvements could be enhanced as the CO₂ concentration in the atmosphere continues to rise.