Effects of cover crops and nitrogen fertilizer on greenhouse gas emissions and net global warming potential in a potato cropping system

The study was conducted to investigate the effects of cover crops and different nitrogen levels on greenhouse gas emissions and net global warming potential in a potato production system during the 2018–2019 and 2019–2020 growing seasons at the Agricultural Research Farm of Razi University, Kermanshah, Iran. The experiment was arranged as a split plot based on a randomized complete block design with three replications. The main factor was cover crop including hairy vetch, rye, mixed (rye + hairy vetch), and control (no cover crop), and the sub factor was nitrogen fertilizer (as urea) at four levels consisted of 0 (control), 33, 66 and 100 % of the recommended nitrogen fertilizer based on the soil test. Results showed that the use of cover crops as green manures increased net ecosystem carbon balance (NECB) and the highest NECB was observed in the mixed treatment (rye + hairy vetch) along with the 66 % of nitrogen fertilizer. The mixed cover crops (hairy vetch + rye) along with the 100 % of nitrogen fertilizer showed higher CO₂ emission and, while hairy vetch along with the 100 % of nitrogen fertilizer had higher emissions of N₂O and CH₄ during the potato growing season. It can be concluded that the use of cover crops as green manures before the planting of potato can notably increase greenhouse gas emissions and the net global warming.