Emission of green house gases for spring maize on different fertilizer treatments

Abstract: Maize production inevitably generates greenhouse gas (GHG) emissions which contribute to global warming. The greenhouse gas intensity (GHGI) of maize production was controlled by various management techniques. Fuel, fertilizer production, herbicide production, seed consumption, transportation, and on-farm energy consumption all result in GHG emissions. Life cycle assessment (LCA) methodology was adopted in this study to calculate GHG emissions under different fertilization treatments aiming at comprehensively evaluating the effects of different fertilization treatments on GHG emissions and selecting the options with both economic benefits and GHG mitigation. Four different fertilization treatments are: local traditional fertilization; urea treatment; sulfur coated urea; and urea added with dicyandiamide treatment. Static chamber and gas chromatography (GC) systems were used to continuously monitor N2O emissions from maize cropland. N2O emissions under different fertilization treatments were calculated. Data on the amount and type of fertilizer applied, energy consumption for the tillage, herbicide consumption, irrigation area and Diesel consumption, for tillage, electricity consumption for irrigation, and seed consumption were collected. Total GHG emissions from fertilizer production, energy consumption, seed production were estimated. GHG emission intensity based on grain yield and economic benefit were also calculated. The result showed that N2O emissions from fertilization, total GHG emission of the whole life cycle, emission intensities based on yield and output were all ranked as local traditional fertilization＞urea treatment＞urea added with dicyandiamide treatment＞sulfur coated urea treatment. N2O emissions from the local traditional fertilization treatment was very significantly higher than that from the other three treatments (P＜0.01). N2O emissions from the sulfur coated urea treatment was significantly lower than that from the urea treatment (P＜0.05) and was not significantly different from that in the urea added with dicyandiamide treatment (P＞0.05). Total GHG emissions from the treatments of local traditional fertilization, urea, sulfur coated urea, and urea added with dicyandiamide were 4.11, 2.71, 2.56, and 2.61 t/(hm2·a) respectively. Emission per unit of yield for the treatments of local traditional fertilization, urea, sulfur coated urea, and urea added with dicyandiamide were 364.1, 238.3, 216.6, and 223.4 kg/t maize, respectively. Emission per 10 000 yuan for the treatments of local traditional fertilization, urea, sulfur coated urea, and urea added with dicyandiamide were 2.19, 1.32, 1.15, and 1.18 t /10 000 yuan respectively. Compared with a traditional fertilization treatment, sulfur coated urea could reduce total GHG emissions, GHG emission per unit of yield and per 10 000 yuan net output by 37.8%, 40.5%, and 47.3% respectively, while the urea added with dicyandiamide treatment could reduce total GHG emissions, GHG emission per unit of yield, and per 10 000 yuan by 36.5%, 38.6%, and 45.9% respectively. Production of fertilizers, especially nitrogen fertilizer, makes the greatest contribution to total GHG emissions for maize cultivation, accounting for 42.4%-55.0% of the total GHG emissions from the four treatments, followed by fertilizer application, accounting for 20.8%-26.1% of the total GHG emissions from the four treatments. In order to ensure grain output and economic benefits, two fertilization treatments, sulfur coated urea treatment and urea added with dicyandiamide treatment, resulted in relatively low total emissions and emission intensity. They can be recommended as options to mitigate GHG emissions from maize production.