S. D. KIMURA YAN Xiao-Yuan R. HATANO A. HAYAKAWA K. KOHYAMA TI Chao-Pu DENG Mei-Hua M. HOJITO S. ITAHASHI K. KURAMOCHI CAI Zu-Cong and M. SAITO. Influence of Agricultural Activity on Nitrogen Budget in Chinese and Japanese Watersheds. Pedosphere 2012 22(2): 137–151.
Abstract
To analyze the effect of agricultural activity on nitrogen (N) budget at the watershed scale a comparative study was conducted at two Japanese watersheds the Shibetsu River watershed (SRW) and Upper-Naka River watershed (UNRW) and one Chinese watershed the Jurong Reservoir watershed (JRW). The total area and the proportion of agricultural area (in parentheses) of the watersheds were 685 (51%) 1 299 (21%) and 46 km2 (55%) for SRW UNRW and JRW respectively. The main agricultural land use in SRW was forage grassland while paddy fields occupied the highest proportion of cropland in UNRW (11% of total area) and JRW (31% of total area). The farmland surplus N was 61 48 and 205 kg N ha−1 year−1 for SRW UNRW and JRW respectively. The total input and output for the whole watershed were 89 and 76 83 and 61 and 353 and 176 kg N ha−1 year−1 for SRW UNRW and JRW respectively. The proportion of discharged N to net anthropogenic N input was 31% 37% and 1.7% for SRW UNRW and JRW respectively. The two watersheds in Japan showed similar proportions of discharged N to those of previous reports while the watershed in China (JRW) showed a totally different characteristic compared to previous studies. The high N input in JRW did not increase the amount of discharged N at the outlet of the watershed due to high proportions of paddy fields and water bodies which was an underestimated N sink at the landscape scale.
