Net global warming potential and greenhouse gas intensity in a double cropping cereal rotation as affected by nitrogen and straw management

Abstract

The effects of nitrogen and straw management on global warming potential (GWP) and greenhouse gas intensity (GHGI) in a winter wheat–summer maize double-cropping system on the North China Plain were investigated. We measured nitrous oxide (N_2O) emissions and studied net GWP (NGWP) and GHGI by calculating the net exchange of CO₂ equivalent (CO₂-eq) from greenhouse gas emissions, agricultural inputs and management practices, and changes in soil organic carbon (SOC), based on a long-term field experiment established in 2006. The field experiment includes six treatments with three fertilizer N levels (zero-N control, optimum and conventional N) and straw removal (i.e. N₀, N_opt and N_con) or return (i.e. N₀, N_opt and SN_con). Optimum N management (N_opt, SN_opt) saved roughly half of the fertilizer N compared to conventional agricultural practice (N_con, SN_con) with no significant effect on grain yields. Annual mean N_2O emissions reached 3.90 kg N₂O-N ha^−1 in N_con and SN_con, and N_2O emissions were reduced by 46.9% by optimizing N management of N_opt and SN_opt. Straw return increased annual mean N_2O emissions by 27.9%. Annual SOC sequestration was 0.40–1.44 Mg C ha^−1 yr^−1 in plots with N application and/or straw return. Compared to the conventional N treatments the optimum N treatments reduced NGWP by 51%, comprising 25% from decreasing N_2O emissions and 75% from reducing N fertilizer application rates. Straw return treatments reduced NGWP by 30% compared to no straw return because the GWP from increments of SOC offset the GWP from higher emissions of N_2O, N fertilizer and fuel after straw return. The GHGI trends from the different nitrogen and straw management practices were similar to the NGWP. In conclusion, optimum N and straw return significantly reduced NGWP and GHGI and concomitantly achieved relatively high grain yields in this important winter wheat–summer maize double-cropping system

Long‐term no‐till and stover retention each decrease the global warming potential of irrigated continuous corn

“…Thus, similar to SOC losses observed under continuous corn, residue removal in a rainfed corn–soybean system also resulted in SOC losses (Lehman & Osborne, ). Other corn rotational systems (e.g., corn–wheat Triticum aestivum L.) have shown numerical but not statistically significant SOC losses after crop residue removal (Lemke et al ., ; Huang et al ., ). In some rainfed no‐till corn studies, however, surface soils gained SOC over time regardless of stover removal level, with slower accrual when stover was removed (Follett et al ., ; Jin et al ., ; Stewart et al ., ).…”

“…Area‐scaled and yield‐scaled (GHGI) annual N 2 O emissions reported here were within the range of measured or modeled values for other irrigated corn production systems (Adviento‐Borbe et al ., ; Liu et al ., ; Cui et al ., ; Grassini & Cassman, ; Aguilera et al ., ; Huang et al ., ; Jin et al ., ; Zhang et al ., ). Further, both area‐scaled and yield‐scaled emissions showed similar responses to management treatments, which have also been noted in other irrigated and nonirrigated studies (Drury et al ., ; Huang et al ., ; van Kessel et al ., ). For area‐scaled N 2 O and CH 4 emissions, mean annual fluxes were relatively stable across the five crop‐years under NT, but more variable under CT such that CT soils were stronger GHG emitters in some years (2013, 2014 for N 2 O; 2012, 2013, 2015 for CH 4 ).…”

“…Warmer soil temperatures associated with stover removal likely provided more favorable conditions for corn germination, growth, and grain production (Kaspar et al, 1990;Sims et al, 1998;Blanco-Canqui & Lal, 2007;Sindelar et al, 2013;Halvorson & Stewart, 2015). In contrast, some irrigated corn studies have reported that stover removal did not affect yield (Biau et al, 2013;Huang et al, 2013;Kenney et al, 2013), and progressive yield declines have been found in rainfed corn production sites when stover was removed (Wilhelm et al, 2004;Blanco-Canqui & Lal, 2007).…”

Can knowledge‐based N management produce more staple grain with lower greenhouse gas emission and reactive nitrogen pollution? A meta‐analysis

“…Traditional N application rate (control) was compared with optimal N rate (treatment). The optimal N rate refers to the N application rate determined based on the soil N test, which was calculated by the difference between crop N demand and soil N supply, that is the target crop N demand minus the soil NH 4 + and NO 3 À present in the root zone (Ju et al, 2009;Huang et al, 2013). On average, the optimal N rate was 28% lower than the traditional N rate of the studies included in this meta-analysis.…”

Impacts of natural factors and farming practices on greenhouse gas emissions in the North China Plain: A meta‐analysis

“…Natural factors also affect or interact with farming practices, thereby influence N 2 O and CH 4 emissions (Chatskikh, Olesen, Berntsen, Regina, & Yamulki, ; Čuhel et al., ; Gu et al., ; Jansen, ; Smith, ; Vidon, Marchese, Welsh, & Mcmillan, ). In recent decades, many site‐specific studies have been conducted to explore the impacts of fertilization (Tan et al., ; Yan, Yao, Zheng, & Liu, ), tillage (Tian et al., ; Wei et al., ), and crop residues (Hu et al., ; Huang, Gao, Christie, & Ju, ) on GHG emission and crop yield in the NCP. However, these individual studies were not able to provide a generalized understanding across this large region.…”