The Effects of Soil Pollution Originated from Irrigation on Nitrogen Mineralization in Sludge Amended Soils

Abstract

In this research, three wastewater sludges which were different in origin were amended to soil samples taken from Bursa-Ozluce region at rates equivalent to 100t/ha and an incubation study was performed during a period of 12 months. Soil samples which have similar physical properties were taken from two agricultural lands: nonirrigated and irrigated from polluted Nilufer-Ayvalý stream. Total and anorganic nitrogen forms and nitrogen mineralization ratios in sludge amended soils were compared and probable differences which might occur due to irrigation were studied. The results of the study indicated that wastewater sludge amendments apparently increased the total nitrogen contents of both soil samples. The nitrogen mineralization occurred during the first three months were significantly differentiated with respect to the origin of wastewater sludge (p<0.05). At the end of the total incubation period, 48- 66% of the sludge organic nitrogen was mineralized in all amended pots. When the results of the study were evaluated with respect to irrigated and nonirrigated soil samples, it was determined that the nitrate nitrogen concentrations in nonirrigated soils were significantly higher than those in irrigated soils for all sludge amendments (p<0.001). The calculated percentages of organic nitrogen mineralization at the end of 12 months in irrigated and polluted soils (average 54%) were significantly (p<0.05) different from calculated values in nonirrigated soils (average 64%) for all sludge amendments.