The assessment of environmental effect and economic benefit for apple orchard under different stand ages in the Loess Plateau, China

This study continuously monitored the greenhouse gas (GHG) emissions from different stand ages apple orchards, estimated the carbon footprint (CF) based on the life cycle assessment (LCA) method, and evaluated the net ecosystem carbon budget (NECB) and net ecosystem economic benefit (NEEB).

The CO₂ emissions from soil respiration increased with the stand ages. The N₂O emission in 15-year fertilized orchard (N15) was higher than that in 5-year fertilized orchard (N5) and 25-year fertilized orchard (N25) by 119.5% and 53.7%, respectively. Compared to non-fertilized plots, fertilization significantly increased the soil CO₂ emissions, N₂O emissions, soil organic carbon (SOC), dissolved organic carbon (DOC), microbial biomass carbon (MBC) contents and soil organic carbon sequestration rate (SOCSR). Meanwhile, SOC, MBC, SOCSR increased with the stand ages. The total CF in different stand ages apple orchards ranged from –786.8 to 8768.1 kg CO₂-eq ha^–1yr^–1, and the CF was positively correlated with fertilizer application rates and N₂O emissions. For the fertilized plots, fertilizer (38.6%-49.1%) and N₂O emissions (12.0%-14.9%) were the top two contributors to total CF. N₂O emissions and pesticides were essential contributors to total CF for the non-fertilized plots. The NECB was negatively correlated with yield and CO₂ emissions, and the NEEB was positively correlated with yield, excessive fertilizer input decreased the NEEB.

The optimizing fertilizer management and increasing apple yield should be the efficiency strategies employed to increase economic benefit and decrease environmental effects, which would be beneficial to the sustainable development of apple orchards in Loess Plateau, China.