Cultivation and Nitrogen Management Practices Effect on Soil Carbon Fractions, Greenhouse Gas Emissions, and Maize Production under Dry-Land Farming System

Effective nitrogen management practices by using two cultivation techniques can improve corn productivity and soil carbon components such as soil carbon storage, microbial biomass carbon (MBC), carbon management index (CMI), and water-soluble carbon (WSC). It is essential to ensure the long-term protection of dry-land agricultural systems. However, excessive application of nitrogen fertilizer reduces the efficiency of nitrogen use and also leads to increased greenhouse gas emissions from farming soil and several other ecological problems. Therefore, we conducted field trials under two planting methods during 2019–2020: P: plastic mulching ridges; F: traditional flat planting with nitrogen management practices, i.e., 0: no nitrogen fertilizer; FN: a common nitrogen fertilizer rate for farmers of 290 kg ha−1; ON: optimal nitrogen application rate of 230 kg ha−1; ON75%+DCD: 25% reduction in optimal nitrogen fertilizer rate + dicyandiamide; ON75%+NC: 25% reduction in optimal nitrogen rate + nano-carbon. The results showed that compared to other treatments, the PON75%+DCD treatment significantly increased soil water storage, water use efficiency (WUE), and nitrogen use efficiency (NUE) because total evapotranspiration (ET) and GHG were reduced. Under the PON75%+DCD or PON75%+NC, the soil carbon storage significantly (50% or 47%) increased. The PON75%+DCD treatment is more effective in improving MBC, CMI, and WSC, although it increases gaseous carbon emissions more than all other treatments. Compared with FFN, under the PON75%+DCD treatment, the overall CH4, N2O, and CO2 emissions are all reduced. Under the PON75%+DCD treatment, the area scale GWP (52.7%), yield scale GWP (90.3%), biomass yield (22.7%), WUE (42.6%), NUE (80.0%), and grain yield (32.1%) significantly increased compared with FFN, which might offset the negative ecological impacts connected with climate change. The PON75%+DCD treatment can have obvious benefits in terms of increasing yield and reducing emissions. It can be recommended to ensure future food security and optimal planting and nitrogen management practices in response to climate change.