Nitrogen mineralization of municipal solid wastes in soils during laboratory incubations.

摘要

Sustainable land application of organic wastes need sound knowledge of the chemical composition and N mineralization rates. This study was conducted to investigate the N mineralization of municipal solid wastes (MSW) in two different soils using a lab incubation experiment at NWFP Agricultural University, Peshawar (pakistan) during 2003-04. MSW in Peshawar were collected from four locations viz. vegetable market, Town-1, Town-3 and University. Field moist soil collected from two soil series (Pirsabak and Katti Khel) at 0-25 cm were amended with dried ground (<2 mm) MSW at three rates equivalent to 0, 200 or 400 kg N ha-1 and then incubated in ventilated plastic containers at 25 degrees C. Sub-soil samples were taken out at 0, 8, 24, 50, 64, 78 and 92 days and analyzed for mineral N. The results revealed that application of MSW significantly (P<0.05) increased total mineral N by 3 fold compared to the control. Mineral N productions and N mineralization rates exhibited temporal variations and varied significantly with waste locations and their application rates and soil types. During the first 50 days of incubation, net N mineralization rates were either negative (immobilization) or very low as evident from their low mineral N production. Immobilization could be attributed to the lack of readily mineralizable organic substrates in MSW at the time of their application or due to the fact that added MSW was fresh and was not stabilized. After 50 days incubation period, soils amended with MSW exhibited a clear phase of net N mineralization. At day 78 and 92, net N mineralization rates in MSW treated soils were significantly higher than those of the control. Net N mineralization rates increased from 0.16 mg N kg-1 soil day-1 in control to 3 mg N kg-1 soil day-1 in MSW treated soils representing 19 times increase over control. Over all MSW at 400 kg N ha-1 rates produced more mineral N than that at 200 kg. The N mineralization rate was relatively high in Katekhel than in Pirsabak soil series indicating that the presence of salts in Katekhel series had no adverse effect on the N mineralization process. These results suggested that dried and ground MSW can be used on agricultural lands as a source of N but need to be applied at least 50 days before sowing of a crop.