ELEVATED TEMPERATURE INDUCED CHANGE OF NONPOINT SOURCE POLLUTANTS IN PADDY WATER

Higher temperature could induce biological effects in many areas of agriculture. The objective of this study is to investigate the effects of elevated temperature on nutrients and non-point source pollutants in paddy water and soil. Nitrogen and phosphorus were applied based on the recommended application amounts for rice cultivation and there was an unfertilized plot as a control. Paddy soils were flooded with distilled water in an incubator for eight weeks. Temperature treatments included ambient as a control, ambient plus 2 degrees C, and ambient plus 4 degrees C. Soil NH4-N content after elevated temperature treatment was high in sandy loam soil and soil NO3-N content after elevated temperature treatment was high in clay loam soil. Elevated temperatures induced increments of water total nitrogen (T-N) concentration for no chemical fertilization, standard fertilization, and standard fertilization + 100% in sandy loam soil. T-N concentration dissolved in distilled water in rice straw of ambient + 2 degrees C temperature increased by 24% more than that of the control temperature treatment, and total phosphorus (T-P) concentration of ambient + 4 degrees C temperature increased by 16%. Thus, it was considered that water soluble T-N and T-P of rice residue could be released easily by rain from agricultural fields.