Methane emissions as affected by crop rotation and rice cultivar in the Lower Mississippi River Valley, USA

The objective of this field study was to evaluate the effects of crop rotation (rice-rice and soybean-rice) and rice cultivar selection (one hybrid and two pure-line cultivars) across two consecutive growing seasons (2012 and 2013) on methane (CH4) fluxes and emissions from rice grown in the drill-seeded, delayed-flood production system on a silt-loam soil. Weekly CH4 fluxes were measured from flooding to harvest from 30-cm-diameter, enclosed-headspace chambers at the Rice Research and Extension Center near Stuttgart, Arkansas. Averaged over years, area-scaled season-long CH4 emissions were greater (P < 0.05) from two pure-line cultivars following rice (192.5 and 167.5 kg CH4-C ha− 1 from Taggart and Cheniere, respectively), which did not differ, than from the hybrid CLXL745 following soybean (72.2 kg CH4-C ha− 1). Averaged across years and cultivars, yield-scaled season-long CH4 emissions were greater (P < 0.05) following rice than soybean (18.4 and 13.3 kg CH4-C [Mg grain]− 1, respectively). Averaged across years and crop rotation, yield-scaled season-long CH4 emissions were 77% greater (P < 0.05) from the two pure-line cultivars than from the hybrid. Emission did not vary between the two years and thus, season-long CH4 emissions provide valuable data for future estimates of CH4 emissions from the drill-seeded, delayed-flood production system on a silt-loam soil among crop rotation-cultivar combinations to refine greenhouse gas emissions estimates and evaluate anticipated climate change.