Abstract: Vertical and ‘T’ types of lysimeter were used to measure the concentrations of ammonia N, nitrate N, and total nitrogen (TN) in the leakage of paddy field in rice growth season under different N application levels. For ammonia N, its concentration measured with these two types of lysimeter all ranged in 0〖KG-*2〗-〖KG-*7〗8 mg·L-1 in 2007 and 0〖KG-*2〗-〖KG-*7〗4 mg·L-1 in 2006; for nitrate N, its concentration measured with vertical lysimeter was 0〖KG-*2〗-〖KG-*7〗4 mg·L-1 in 2007 and basically the same in 2006, while that measured with ‘T’ type lysimeter was 0〖KG-*2〗-〖KG-*7〗20 mg·L-1 in 2007 but lower in 2006. The TN concentration in the leakage was 0〖KG-*2〗-〖KG-*7〗60 mg·L-1 in 2007, much higher than that (0〖KG-*2〗-〖KG-*7〗16 mg·L-1) in 2006. In the leakage, nitrate N was the dominant N form. The total leakage loss of N in whole rice growth season in 2007 was 1581 kg·hm-2 of TN and 933 kg·hm-2 of nitrate N when measured with vertical lysimeter, and 721 kg·hm-2 of TN and 425 kg·hm-2 of nitrate N when measured with ‘T’ type lysimeter. Due to the difference in the pathways of ammonia-N and nitrate-N leakage, different methods for calculating N leakage should be employed when using the two types of lysimeter in measurement. The N leakage measured by vertical lysimeter was more close to that estimated by paddy plot-leaching measurement method.

Key words: land use change, readily oxidizable carbon, soil physical and chemical properties, coastal area of northern Jiangsu Province.