|COLLIER, SARAH - University Of Wisconsin|
|RUARK, MATTHEW - University Of Wisconsin|
|NABER, MACK - University Of Wisconsin|
|ANDRASKI, TODD - University Of Wisconsin|
Submitted to: Soil Science Society of America Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/5/2016
Publication Date: 4/20/2017
Citation: Collier, S., Ruark, M., Naber, M., Andraski, T., Casler, M.D. 2017. Apparent stability and subtle change in soil carbon and nitrogen under a long-term fertilizer gradient. Soil Science Society of America Journal. 81:310-321.
Interpretive Summary: Long-term tillage, cropping, and fertilization can have profound impacts on soil quality. Long-term studies that measure the impact of fertilization on soil health are very rare. This study examines the impact of 53 years of continuous corn receiving varying rates of chemical nitrogen (N) fertilizer on soil properties including soil organic carbon, total nitrogen, and bulk density to a depth of 1 meter. The study had four highlights: (1) long-term fertilizer rate affected soil properties to a depth of 1 meter under continuous corn, (2) inorganic N fertilization was a benefit rather than a detriment to soil carbon and nitrogen, (3) the most productive treatments maintained but did not build soil carbon and nitrogen, and (4) all fertilizer rate treatments experienced topsoil loss. The results of this study will impact fertilization recommendations for continuous corn cropping systems on similar soils throughout the central USA.
Technical Abstract: Uncertainty exists regarding the depth and extent to which agricultural practices affect soil properties, in particular soil organic C (SOC). This study examines the impact of 53 years of continuous corn (Zea mays L.) receiving varying rates of chemical N fertilizer with complete stover return on soil properties including SOC, total N, and bulk density (BD) to a depth of 1 m. The treatment receiving virtually no applied N saw a significant reduction in soil N content at 0 to 30 cm over the study period, while the treatment receiving N well in excess of recommended application levels was nearly indistinguishable from the treatment receiving recommended rates of N fertilizer. Trends in SOC content were similar to those for total N, but a significant treatment effect was detectable throughout the entire 1 m soil profile sampled. Over the course of the study, all experimental fields appear to have lost approximately 6 cm of topsoil through erosion, with the lowest N rate treatment sinking a further 2 cm due to compaction. The experimental system employs harsh physical (moldboard plow) and chemical (anhydrous ammonia) management practices. Despite this aggressive management, declines in soil C and N content were not apparent for this soil type under conditions of low slope and the linear gains in productivity realized under the two higher N rate treatments. Thus N fertilizer was a benefit to this cropping system, rather than a detriment, and was sufficient to allow maintenance – but not building – of SOC.