Aggregate size distribution and associated carbon and nitrogen in mulched winter wheat and spring corn

Authors: FU, XIN - Northwest University; WANG, JUN - Northwest University; Sainju, Upendra; LIU, WENZHAO - Northwest University

Submitted to: Canadian Journal of Soil Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/1/2019
Publication Date: 7/12/2019
Citation: Fu, X., Wang, J., Sainju, U.M., Liu, W. 2019. Aggregate size distribution and associated carbon and nitrogen in mulched winter wheat and spring corn. Canadian Journal of Soil Science. https://doi.org/10.1139/cjss-2019-0015.
DOI: https://doi.org/10.1139/cjss-2019-0015

Interpretive Summary: Soil aggregation reduces erosion, improves water filtration capacity, and enhances root growth compared with no aggregation. Aggregates protect the mineralization of soil organic carbon (C) and nitrogen (N) by reducing access to the substrates for microbes. In the Loess Plateau of China, straw and plastic film mulches are commonly applied at the soil surface to conserve soil water and reduce evaporation and soil erosion, especially in dryland cropping systems. Little is known about the effects of these mulching practices on soil aggregation and associated C and N storage in this region. The effects of 6 yr of three mulching treatments (no mulching [CK], straw mulching [SM], and plastic film mulching [PM]) on water-stable soil aggregates and associated C and N storage under winter wheat and corn were studied in 2014 in the Loess Plateau of China. Soil samples were collected from the 0-20 cm depth, separated into 10.00-5.00 mm, 5.00-2.00 mm, 2.00-1.00 mm, 1.00-0.50 mm, 0.50-0.25 mm and <0.25 mm aggregate-size classes by wet sieving, and analyzed for soil organic C (SOC) and total N (STN). Aggregate proportion was greater with mulching than without in the 10.00-2.00 size class, but the trend reversed in the <0.50 mm size class. The SOC and STN concentrations were greater with SM than CK and PM in all size classes, except the <0.25 mm class. The SOC and STN stocks were greater with mulching than without in the 5.00-2.00 mm class, but the trends reversed in the 0.50-0.25 mm class under winter wheat. Under corn, SOC and STN stocks varied among treatments and aggregate-size classes. The SOC and STN stocks in the whole-soil were not affected by treatments. Mean corn grain and biomass yields were greater with PM than CK, but winter wheat grain and biomass yields were greater with CK than SM and PM. Plastic film mulching enhanced soil aggregation, C and N stocks in aggregates, and corn yield compared with no mulching. Both plastic film and straw mulching also enhanced soil aggregation and associated C and N stocks under winter wheat, but their benefits on wheat yield were not realized.

Technical Abstract: Mulching may influence soil aggregation and associated C and N by reducing soil erosion and conserving water compared with no mulching. The effects of 6 yr of three mulching treatments (no mulching [CK], straw mulching [SM], and plastic film mulching [PM]) on water-stable soil aggregates and associated C and N storage under winter wheat (Triticum aestivum L.) and corn (Zea mays L.) were studied in 2014 in the Loess Plateau of China. Soil samples were collected from the 0-20 cm depth, separated into 10.00-5.00 mm, 5.00-2.00 mm, 2.00-1.00 mm, 1.00-0.50 mm, 0.50-0.25 mm and <0.25 mm aggregate-size classes by wet sieving, and analyzed for soil organic C (SOC) and total N (STN). Aggregate proportion was greater with mulching than without in the 10.00-2.00 size class, but the trend reversed in the <0.50 mm size class. The SOC and STN concentrations were greater with SM than CK and PM in all size classes, except the <0.25 mm class. The SOC and STN stocks were greater with mulching than without in the 5.00-2.00 mm class, but the trends reversed in the 0.50-0.25 mm class under winter wheat. Under corn, SOC and STN stocks varied among treatments and aggregate-size classes. The SOC and STN stocks in the whole-soil were not affected by treatments. Mean corn grain and biomass yields were greater with PM than CK, but winter wheat grain and biomass yields were greater with CK than SM and PM. Plastic film mulching enhanced soil aggregation, C and N stocks in aggregates, and corn yield compared with no mulching. Both plastic film and straw mulching also enhanced soil aggregation and associated C and N stocks under winter wheat, but their benefits on wheat yield were not realized.