Abstract
Intensive fertilization of grasslands with cattle slurry can cause high environmental nitrogen (N) losses in form of ammonia (NH(3)), nitrous oxide (N(2)O), and nitrate (NO(3) (-)) leaching. Still, knowledge on short-term fertilizer N partitioning between plants and dinitrogen (N(2)) emissions is lacking. Therefore, we applied highly (15)N-enriched cattle slurry (97 kg N ha(-1)) to pre-alpine grassland field mesocosms. We traced the slurry (15)N in the plant-soil system and to denitrification losses (N(2), N(2)O) over 29 days in high temporal resolution. Gaseous ammonia (NH(3)), N(2) as well N(2)O losses at about 20 kg N ha(-1) were observed only within the first 3 days after fertilization and were dominated by NH(3). Nitrous oxide emissions (0.1 kg N ha(-1)) were negligible, while N(2) emissions accounted for 3 kg of fertilizer N ha(-1). The relatively low denitrification losses can be explained by the rapid plant uptake of fertilizer N, particularly from 0-4 cm depth, with plant N uptake exceeding denitrification N losses by an order of magnitude already after 3 days. After 17 days, total aboveground plant N uptake reached 100 kg N ha(-1), with 33% of N derived from the applied N fertilizer. Half of the fertilizer N was found in above and belowground biomass, while at about 25% was recovered in the soil and 25% was lost, mainly in form of gaseous emissions, with minor N leaching. Overall, this study shows that plant N uptake plays a dominant role in controlling denitrification losses at high N application rates in pre-alpine grassland soils. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s00374-024-01826-9.