Animal manure, together with synthetic fertilizer such as urea, is commonly used in agricultural systems to boost crop production. However, a recent study by Chinese scientists found that it also shows potential risk of nitrous oxide (N₂O) emission increase, especially under dry climate.

Nitrous oxide, a major scavenger of stratospheric ozone, is a key member of the greenhouse gas family. It is estimated that 30% of nitrous oxide in the atmosphere is the result of human activity, chiefly agriculture.

"About 66 per cent of human-related nitrous oxide emission comes from agro-ecological system, mainly from chemical fertilizer and manure application," said GAO Xiaopeng, leading researcher of the study, from the Xinjiang Institute of Ecology and Geography (XIEG) of the Chinese Academy of Sciences.

GAO and his team from XIEG, after a field experiment in 2015 and 2016 in arid region of northwestern China, found that Manure increased cumulative N₂O emission by 30-188%, compared with urea-only and 50/50 mix of urea and manure applications in the test cotton fields.

"These results suggest a potential risk of manure application to increase N₂O emission for irrigated crop production in soils with low soil organic matter and under dry climate," said GAO.

Greater N₂O emission with manure application was mainly attributed to the increased rates of nitrification and denitrification through the manure’s increased supply of carbon for associated microbes, according to the study.

Results of the study entitled "Effects of fertilizer and irrigation management on nitrous oxide emission from cotton fields in an extremely arid region of northwestern China" were published in Field Crops Research.