|DOLD, CHRISTIAN - Orise Fellow|
|WACHA, KENNETH - Orise Fellow|
|Sauer, Thomas - Tom|
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 10/25/2017
Publication Date: 10/25/2017
Citation: Dold, C., Hatfield, J.L., Prueger, J.H., Wacha, K.M., Sauer, T.J. 2017. Changes in soil carbon in a continuous corn-soybean rotation in the Midwest, 2005–2016. In: Proceedings of ASA-CSSA-SSSA Annual Meeting, October 22-25, 2017, Tampa, Florida.
Technical Abstract: Comprehensive carbon budgets are essential to improve understanding of the changes in carbon pools and fluxes in agricultural soils, and to assess the sustainability of agricultural production with respect to carbon sequestration. However, this requires long-term experimental setups, due to the slow response and high variability of soil carbon affected by land management. We investigated the impact of a continuous corn-soybean rotation (conventional tillage without catch crops) on carbon pools and fluxes in Central Iowa from 2005 to 2016. Soil samples in 0–120 cm depths were taken at 42 locations in a 50x50 m grid in 2005 and 2016. The carbon flux was continuously measured with an eddy-flux station during the same period, and net ecosystem production (NEP, as the sum of carbon respired and taken up by plants and soil) was calculated. In addition, carbon loss by yield removal was recorded. Preliminary results show that mean total carbon concentration in the 0–15 cm depth decreased from 3.50% to 3.00% at similar bulk densities of 1.36 and 1.34 g/cm3 in 2005 and 2016, respectively. The mean carbon stock (0–15 cm) decreased from 70.1 metric tons/ha to 58.2 metric tons/ha, indicating an average loss of soil carbon of 11.9 metric tons/ha in an eleven year period of continuous corn-soybean production. The average loss in 0–120 cm was 9.9 metric tons/ha, showing that the bulk of soil carbon reduction was due to mineralization and not translocation to deeper strata. The calculated NEP was 16.7 metric tons/ha with positive NEP for corn and near-neutral and negative NEP for soybean-years. The carbon removed as corn grain and beans summed to 33.1 metric tons/ha, which indicates a net loss of 16.4 metric tons/ha of carbon. The presented carbon budget stresses the unsustainability of conventional corn-soybean rotation systems in the Midwest.