The availability of nitrogen and pheephorous from undigested liquid domestic sewage sludge and their behavior in envi-ronment

One year s lysimeter experiment with soil column cultivated for rice and rye grass was conducted to compare the impact of sludge and common fertilizer（urea, superphosphate ） on crop growth and groundwater qualitv,The results showed that N and P from sludge had a pronounced reidual effect as compared to that from the fertilizer. In the oerid of rice growth,the N and P contamination in groundwater was not discovered,but NO leaching through soil profile was noticeable in period of rye grass growth due to applicatlon of sludge and fertilizer,in which the later would produce much more NO₃ than the foimer. It is concluded that the undigested liquid domestic sewage sludge could be applied to paddy soil in certain conditions and by certain amounts with no harm of N,P pollution to groundwater. On the basis of the de-mands of crop for N and P without impairing the groundvvater quality.