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Nitrogen Loss through Lateral Seepage in Near-Trench Paddy Fields

Dep. of Environmental Engineering, College of Natural Resources and Environmental Science, Zhejiang Univ., Hangzhou, 310029,China

View larger version (50K): [in this window] [in a new window]   Fig. 1. The collection system for water samples of lateral seepage. B is a gravel-packed buffer zone between the bund and the trench, C is a container for collecting lateral seepage, R is a bucket with a pipe for collecting runoff, and T is a 1-m-deep trench. Lateral seepage water is pumped out from tube 1 using a syringe, and tube 2 is for air connection.

View larger version (56K): [in this window] [in a new window]   Fig. 2. Dynamics of lateral seepage during three rice-growing seasons. Vertical bars above each data column indicate SE.

View larger version (59K): [in this window] [in a new window]   Fig. 3. Dynamics of rainfall, irrigation, and floodwater level during three rice-growing periods.

View larger version (16K): [in this window] [in a new window]   Fig. 4. Relationship between lateral seepage and floodwater level in flooded period of three rice seasons.

View larger version (40K): [in this window] [in a new window]   Fig. 5. Temporal variations of total-N, NH4+–N, and NO3––N concentrations in lateral seepage water during three rice seasons. Vertical bars above each data point indicate SE. Arrows represent N fertilizer application dates.

View larger version (31K): [in this window] [in a new window]   Fig. 6. Comparison of mean seasonal flux of total nitrogen in lateral seepage and surface runoff under a series of urea fertilizer application rates. *Significant differences (P = 0.05) between lateral seepage and surface runoff at each N rate. Error bars represent 1 SD.

View larger version (34K): [in this window] [in a new window]   Fig. 7. Mean rice grain yield at different urea application rates in 2003, 2004, and 2005. Vertical bars above each data column indicate SE. Yields labeled with the same letter are not significantly different (P = 0.05).