Balancing soil carbon emissions and productivity in maize agroecosystems through nitrogen, biochar, and straw regulation
Pingan Zhang, Li Lü, Qiang Fu, Changzheng Du, Aizheng Yang, Nan Sun, Lihong Wang, Mo Li
Abstract
Straw return is an important measure for improving soil quality and maize yield, and biochar application is recognized as an effective countermeasure for reducing greenhouse gas (GHG) emissions and improving agroecosystem benefits. This study focused on the effects of nitrogen, biochar, and straw application on maize yield under rain-fed conditions. Orthogonal experiments on the coupled application of nitrogen, biochar, and straw were conducted during the maize growing seasons in 2021 and 2022, including three nitrogen treatments (N 1 : 50 % CF, N 2 : 100 % CF, N 3 : 150 % CF, where CF is the recommended local nitrogen application rate, 270 kg ha −1 ), three biochar treatments (B 1 : 0 kg ha −1 , B 2 : 4000 kg ha −1 , B 3 : 8000 kg ha −1 ) and three straw treatments (S 1 : 50 % S, S 2 : 100 % S, S 3 : 150 % S, where S is the amount of local straw returned to the field, 6000 kg ha −1 ). A dynamic control model of the multidimensional target synergy of maize yield, net economic benefits (NEBs) and net carbon emissions (NCEs) based on the comprehensive regulation framework of experiment–simulation–optimization was constructed to explore the optimal nitrogen–straw–biochar application mode and its synergistic effects on yield, NEBs and NCEs. The results revealed that during 2021 and 2022, the addition of nitrogen (N 2 ) to the same biochar combined with straw significantly increased the soil moisture content (+2.95 %), soil organic carbon content (+2.27 %), soil respiration rate (+30.32 %), yield (+16.74 %) and greenhouse gas emissions (CO 2 : +18.64 %; N 2 O: +12.32 %; CH 4 : −23.41 %). Under the same nitrogen application conditions, biochar combined with straw application had no significant effect on the NEBs compared with straw alone but significantly reduced the NCEs (30.5 %) while increasing the soil respiration rate (16.07 %) and yield (16.61 %). The multiobjective optimization model revealed that rainfall, nitrogen fertilizer and biochar were the main components affecting both yield and NEBs (54.34 %), and biochar was the main component affecting the NCEs (36.92 %). Under the conditions of future climate change in SSP1–2.6, SSP2–4.5 and SSP3–7.0, rainfall could significantly promote the coordinated development of maize agroecosystems (16.19 %). In this study, the amounts of nitrogen, biochar and straw were dynamically regulated by a combination of experiment-simulation-optimization, which provided a scientific basis for the sustainable development of maize agroecosystems and the refinement of resource inputs. • Benefits of farmland measures on soil quality, crop yield, and the environment were assessed. • Biochar and straw reduced the adverse effects of nitrogen on soil carbon sinks and GHGs. • A combined experimental-simulation framework for resource regulation was developed. • The strategies for obtaining optimal fertilization under future climate scenarios were identified.