Junxiang Jia Liying Sun Xianwang Kong Xiaoyuan Yan Zhengqin Xiong. Annual N2O and CH4 emissions from intensively managed vegetable fields in Nanjing China. Soil Science and Plant Nutrition 2012 58: 91—103.

Abstract

Nitrous oxide (N2O) and methane (CH4) emissions were monitored from an intensive vegetable production region with four typical consecutive rotations and a bare fallow in Nanjing China from 2009 to 2010. The four consecutive rotations were established as follows: Celery (Apium graveolens dulce L.)—Tung choy (Ipomoea aquatica Forsk L.)—Baby bok choy (Brassica rapa Chinensis L.)—Amaranth (Amaranthus mangostanus L.) (C-T-Bb-A) Choy sum (Brassica rapa Chinensis L.)—Celery—Tung choy—Bok choy (Brassica rapa Chinensis L.) (Cs-C-T-Bc) Garland chrysanthemum (Chrysanthemum coronarium L.)—Tung choy—Bok choy (G-T-Bc) and Celery—Choy sum—Lettuce (Lactuca sativa L.)—Bok choy (C-Cs-L-Bc). Annual cumulative N2O emissions were 237.7_x0002_18.3 137.2_x0002_8.5 100.9_x0002_7.5 56.4_x0002_10.6 and 29.2_x0002_3.7 kgNha_x0003_1 from the G-T-Bc C-T-Bb-A Cs-C-T-Bc C-Cs-L-Bc rotation fields and the bare fallow respectively. Cumulative N2O emissions from the rotation fields except the C-Cs-L-Bc rotation were significantly higher than that from the bare fallow. Annual cumulative CH4 emissions were 9.0_x0002_3.5 13.9_x0002_1.5 18.8_x0002_1.2 12.1_x0002_3.8 and 16.1_x0002_3.5 kgCha_x0003_1 from the bare fallow C-T-Bb-A Cs-C-T-Bc G-TBc and C-Cs-L-Bc respectively and they did not show significant differences among systems. The annual N2O emission factor averaged 2.6% ranging from 1.2% to 5.0% and was higher than the current IPCC default value (1.0%). Total N fertilizer application rate explained 35.5% of annual N2O emissions. N2O emissions from intensively managed vegetable fields were characterized by high fluxes and emission factors that varied with cropping systems. Frequent year-round monitoring of N2O fluxes from intensively managed vegetable fields is essential for better constraint of the national N2O budget.