Impacts of crop rotational diversity and grazing under integrated crop-livestock system on soil surface greenhouse gas fluxes

Integrated crop-livestock (ICL) system is beneficial in enhancing soil organic carbon and nutrient cycling. However, the benefits of the ICL system on mitigation of GHG emissions are poorly understood. Thus, the present study was initiated in 2011 to assess the effect of crop rotation diversity and grazing managed under the ICL system on GHG emissions. The cropping system investigated here included spring wheat grown continuously for five years and a 5-yr crop rotation (spring wheat-cover crops-corn-pea/barley-sunflower). Each phase was present each year. Yearling steers grazed only the pea/barley, corn and cover crops plots in 2016 and 2017. Exclusion areas avoided the grazing in these crops to compare the GHG fluxes under grazed vs. non-grazed areas. The GHG fluxes were measured weekly from all crop phases during the growing season for both years using a static chamber. Cumulative CO(2) and CH(4) fluxes were similar from all crop phases over the study period. However, continuous spring wheat recorded higher cumulative N(2)O fluxes (671 g N ha(-1)) than that under spring wheat in rotation (571 g N ha(-1)). Grazing decreased cumulative CO(2) fluxes (359 kg C ha(-1)) compared to ungrazed (409 kg C ha(-1)), however, no effect from grazing on cumulative CH(4) and N(2)O fluxes over the study period were found. The present study shows that grazing and crop rotational diversity affected carbon and nitrogen inputs, which in turn affected soil CO(2) and N(2)O fluxes. Long-term monitoring is needed to evaluate the response of soil GHG emissions to grazing and crop rotation interactions under the ICL system.