GASEOUS REACTIVE NITROGEN LOSSES FROM ORCHARDS,VEGETABLES AND TEA PLANTATIONS

Nitrogen fertilizer application has accelerated the agricultural soil N cycle while ensuring food security.Gaseous reactive N emissions from orchards,vegetables and tea plantations(OVT)are less understood than those from cereal crops.This paper presents a compilation of data on soil ammonia,nitrous oxide,and nitric oxide emissions from 1454 OVT systems at 184 unique experimental locations worldwide aiming to investigate their emission characteristics,emission factors(EF),and contribution to total farmland emissions.NH_(3)and N_(2)O emissions from orchards and N_(2)O and NO emissions from vegetable production were significantly higher in China than in the rest of the world,regardless of fertilizer application,while N_(2)O emissions from tea plantations were lower than for vegetables.The EF of NH_(3)for vegetables was close to the global mean value with urea application but significantly higher than that of orchards.The EF of N_(2)O in orchards and vegetables was comparable to the global median value,while in tea plantations,the value was 2.3 times higher than the global median value.Current estimates suggest that direct emissions of NH_(3),N_(2)O,and NO from OVT systems are equivalent to approximately a quarter,two thirds and a half of the total farmland in China,respectively.Future research needs to strengthen observational field studies in establishing standard sampling methods for gaseous N emissions and implementing knowledge-based management measures to help achieve the green development of agriculture.