Guilin is a typical karst area where the hydraulic proximitv between surfaca water and ground water is close From the point of environ-mental conservation,karst aquifers are more vul-nerable than non-karst aquifers because their underground conduits provide no filtration There-tore, it 1s necessary to pay close attention to con-tamination from heavy metals in the groundwater if a sludge fertilizer. which USUaUv contains relatively large amount of heavy metals. is applied to the land surfaca in this area To determine the effect of sludge fertilizer and the possible toxicitv of heavy metals when the sludge of municipal wastewater is used in agriculture, a series of experiments was undertaken Firsfly, sludge was extracted from the sewage treat-ment plant of Guilin and the plant nutrient and heavy metal was than analyzed Secondlv'a complexorganic fertilizer of sludge (OCFS) was produced This OCFS was applied to rice land to determine itseffect as a ferilizer Lastlv. the heavy metal contents of agricultural products after application of OCFS were studied It ws shown that (1)there were large amounts of plant nutrients in the sludge: on average it contained 396%organic matter The content of total nitrogen, phosphorus, and potassium was 48 3, 21 1, and 85g/kg on average, respectively The heavy metal contents ofthe sludge are in accordance with the National Standard and, basicalh the sludge is suitable for agricultural application f2 The fertilizer of sludge was effective The output of rice was increased by 1819% when OCFS was used The effect of sludge fertilizer was better than that of a complex fertilizer sold on the market When sludge fertilizer was tested against others on the market, no difference could be found in the heavy metal content ofthe rice and rice stems Therefore. sludge fertilizer can be assumed to be safe and effective for agricul-ture f3 The extraction rate of heavy metals ranged from 23 to 60% when the sludge was extracted by O 1mol ofEDTA,i e, 23 to 60% ofmetals maybe absorbed by plants