|DOLD, CHRISTIAN - Orise Fellow|
|Sauer, Thomas - Tom|
|WACHA, KENNETH - Orise Fellow|
Submitted to: Agrosystems, Geosciences & Environment
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/30/2018
Publication Date: 3/17/2019
Publication URL: https://handle.nal.usda.gov/10113/6550429
Citation: Dold, C., Hatfield, J.L., Prueger, J.H., Sauer, T.J., Moorman, T.B., Wacha, K.M. 2019. Impact of management practices on carbon and water fluxes in corn-soybean rotations. Agrosystems, Geosciences & Environment. 2(1). https://doi.org/10.2134/age2018.08.0032.
Interpretive Summary: Corn and soybean are important crops in Iowa, and crop management typically comprises tillage activities, yet, improvements in management practices may have substantial impact on available water and soil organic carbon. Four eddy covariance stations monitored water and carbon gains and losses in 2016/2017 in two corn-soybean rotation systems – a conventional and a reduced till and cover crop (i.e., aspirational) system. The amount of carbon stored on the aspirational site was higher than on the conventional site for both crops because less carbon was respired from soil and plants. In spring before planting, carbon was mineralized faster on the conventional than on the aspirational site, probably because the plant residues were tilled into the soil, which enhanced mineralization. The soybean-years were a carbon source (that is, carbon is lost from the system) in both management systems. The amount of water transpired by plants and evaporated from soils was similar at all sites. The efficiency to use one unit of water to produce one unit of carbon was higher in the conventional systems. Since the cover crop development was poor, the impact in the aspirational system was probably due to soil management. This research is important for scientist, farmers, and extensionists, who want to know which corn-soybean production system is more efficient in storing carbon and in water use.
Technical Abstract: Corn [Zea mays L.] and soybean [Glycine max (Merr.) L] are important crops in Iowa, and crop management typically comprises tillage activities, yet improvements in management practices may have substantial impact on carbon and water dynamics. Four eddy covariance stations monitored evapotranspiration (ET) and net ecosystem production (NEP) in 2016/2017 in two corn-soybean rotation systems – a conventional and a reduced till and cover crop (i.e., aspirational) system. Net biome production (NBP), gross primary production (GPP), ecosystem respiration (RE), and water use efficiency (IWUE*) were calculated. Total NEP on the aspirational site was higher than the conventional site with 565 versus 421 g C m-2 in corn, and 108 versus -64 g C m-2 in soybean, respectively. The aspirational system RE was lower than under conventional management for both corn and soybean. Thus, GPP was lower in aspirational than conventional corn with 1285 and 1405 g C m-2, and higher in soybean with 750 and 742 g C m-2. Linear regression analysis (p < 0.05) also showed higher NEP slopes in spring in conventional than the aspirational system with -0.016 and -0.004 in soybean, and -0.012 and -0.005 in corn, respectively. The soybean-years were a carbon source in both management systems. While annual ET was similar among crops and management with 589 – 610 mm, the growing season IWUE* was higher in the conventional system in both crops. Since the cover crop development was poor, the impact in the aspirational system was probably due to soil management.