Abstract: This study quantified the effect of controlled release nitrogen fertilizer (CRNF) on dynamics of electrical conductivity (EC), pH, TN、NH4+-N and NO3--N concentration in rice surface water and TN losses from runoff in alluvial sandy loamy paddy soil (ASP) and Purple calcareous clayed paddy soil (PCP). After applying urea, the surface water TN and NH4+-N concentration reached peak at the 1st day and the 3rd day respectively, then it went down rapidly; though the floodwater NO3--N in PCP at the 3rd to 7th arose to some extent, it showed very low level as a whole; The surface water pH from early rice within 15d (late rice within 3d) after receiving urea rose gradually, and EC kept the pace with dynamics of NH4+. Compared with urea application, the peak of floodwater TN、NH4+ concentration fallen significantly after applying CRNF, and the peak of EC and pH also fallen distinctly, but NO3- concentration raised a little. The effect of raining event occurred within 20d after applying fertilizer on TN losses from runoff was significant. Compared with applying urea, the TN concentration in runoff water caused by raining event within 10d after receiving CRNF declined significantly, as result, the TN losses from runoff in rice field during whole rice growing season decreased significantly.

Key words: controlled release nitrogen fertilizer, rice field, surface water, nitrogen, losses from runoff