Nitrogen loss factors of nitrogen trace gas emissions and leaching from excreta patches in grassland ecosystems: A summary of available data

Yanjiang Cai; Hiroko Akiyama

doi:10.1016/j.scitotenv.2016.07.222

Nitrogen loss factors of nitrogen trace gas emissions and leaching from excreta patches in grassland ecosystems: A summary of available data

Sci Total Environ. 2016 Dec 1:572:185-195. doi: 10.1016/j.scitotenv.2016.07.222. Epub 2016 Aug 4.

Authors

Yanjiang Cai¹, Hiroko Akiyama²

Affiliations

¹ Institute for Agro-Environmental Sciences, National Agriculture and Food Research Organization, 3-1-3, Kannondai, Tsukuba, Ibaraki 305-8604, Japan; Key Laboratory of Mountain Environment Evolvement and Regulation, Institute of Mountain Hazards and Environment, Chinese Academy of Sciences, Chengdu 610041, China; State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, Nanjing 210008, China.
² Institute for Agro-Environmental Sciences, National Agriculture and Food Research Organization, 3-1-3, Kannondai, Tsukuba, Ibaraki 305-8604, Japan. Electronic address: ahiroko@affrc.go.jp.

PMID: 27498380
DOI: 10.1016/j.scitotenv.2016.07.222

Abstract

Patches of excreta voided by grazing animals are nitrogen (N) transformation hotspots in grassland ecosystems and an important source of N trace gas emissions and leaching. Previous studies have focused on individual N losses from excreta, but no quantitative analysis has been performed on all the N losses via N trace gas emissions and leaching. To better understand the fate of N in excreta patches, we summarized 418, 15, 65, 22, 54, 11, and 81 measurements of nitrous oxide (N₂O), nitric oxide (NO), ammonia (NH₃), and ammonium (NH₄⁺) leaching, nitrate (NO₃^-) leaching, dissolved organic nitrogen (DON) leaching, and aboveground plant N uptake, respectively. The results based on field studies indicated that the average fractions of N lost via N₂O were 0.28%, 0.76%, 0.08%, and 0.35% for cattle dung, cattle urine, sheep dung, and sheep urine, respectively. Only 0.01-0.12% of excreta N was lost via NO, whereas 1.69-12.7%, 0-4.58%, 16.4-24.6%, and 1.43-5.91% were lost by NH₃ and NH₄⁺, NO₃^-, and DON leaching, respectively. Aboveground plant parts assimilated 10.4-31.4% of the excreta N. The N lost via N₂O from urine patches decreased as NH₃ losses increased, and greater NO₃^- leaching occurred with lower plant N uptake. The combined N₂O emission factors for dung and urine from cattle and sheep were 0.59% and 0.26%, respectively. Each N loss factor was much higher in urine patches than in dung patches, irrespective of animal type. This study provides general estimates of N losses and plant N uptake from excreta patches on grazed grassland based on currently available field data. More field studies are needed in the future with longer measurement periods from a wide range of climate zones to refine these N loss factors.

Keywords: Ammonia volatilization; Global warming; Greenhouse gas; Livestock; Nitrous oxide; Nutrient cycling.