Soil organic C affected by dry-season management of no-till soybean crop rotations in the tropics

Authors: GONSIORKIWICZ-RIGON, JOAO PAULO - Sao Paulo State University (UNESP); CALONEGO, JULIANO CARLOS - Sao Paulo State University (UNESP); CAPUANI, SILVIA - Sao Paulo State University (UNESP); Franzluebbers, Alan

Submitted to: Plant and Soil
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/3/2021
Publication Date: 5/20/2021
Citation: Gonsiorkiwicz-Rigon, J., Calonego, J., Capuani, S., Franzluebbers, A.J. 2021. Soil organic C affected by dry-season management of no-till soybean crop rotations in the tropics. Plant and Soil. 462:577-590. https://doi.org/10.1007/s11104-021-04878-0.
DOI: https://doi.org/10.1007/s11104-021-04878-0

Interpretive Summary: Winter soil management in the tropical regions of Brazil could be improved with better cover crops to promote soil organic matter accumulation. A scientist with USDA Agricultural Research Service in Raleigh NC collaborated with scientists from São Paulo State University to determine the best combination of fall cropping and early spring cover cropping to promote soil improvement in a long-term soybean cropping system. Soil organic carbon accumulated with fall planting of ruzigrass (Urochloa ruziziensis) following soybean harvest and cover cropping in early spring with sunn hemp (Crotolaria juncea). Both quality and quantity of crop residues were considered important for sequestering soil organic carbon and improving soil health. These results can be used to better understand how soil health can be improved with different cover crops in the US as well.

Technical Abstract: Cover crop species selection for soybean (Glycine max) production under no-tillage (NT) management may affect soil organic C sequestration by altering the quantity and quality of C inputs, thereby affecting cropping system sustainability. We assessed changes in soil organic C stock and soil C and N fractions during the last three years of dry-season cover cropping in a soybean production system managed with NT for 9 years on a Rhodic Hapludox in Sao Paulo, Brazil. Dry-season management treatments were repeated yearly in a split-plot scheme. Main plots during the fall-winter were (1) ruzigrass (Urochloa ruziziensis), (2) grain sorghum (Sorghum bicolor), and (3) the intercropped mixture of ruzigrass and sorghum. Subplots during spring prior to planting soybean were (a) millet (Pennisetum glaucum), (b) sunn hemp (Crotolaria juncea), and (c) forage sorghum (Sorghum bicolor). Soil C and N fractions were affected according to crop residue characteristics of the rotations. Ruzigrass increased soil organic C stock by an average of 7% at 0.2-0.4 m soil depth from 2012 to 2015. High straw input with ruzigrass in the fall-winter sequestered 0.61 Mg C/ha/yr at 0-0.1 m soil depth compared with lower C sequestration using grain sorghum (0.29 Mg C/ha/yr). Our results suggest that the quantity and quality of crop residues in cropping systems can be considered relevant for soil C retention and sequestration. These aspects could contribute to the mitigation of atmospheric CO2 in crop production systems.