Nitrogen mineralization potentials in three tropical soils treated with biosolids

This study attained anaerobic biosolids (DS) and aerobic biosolids (MS) from the wastewater treatment plants in Kaohsiung and Taipei, Taiwan. Three tropical soils (Lt, Cp and Ca) were selected for incubation with the two biosolids at application rates of 10, 50 and 100 Mg ha−1 for 48 weeks. This study aims to characterize the influence of the application of biosolids on the soil potential for N mineralization (N0) and also to elucidate the kinetics of N mineralization in tropical soils treated with different biosolids. Experimental results indicate that the amounts of N mineralized accumulated in the biosolids-treated soils during the incubation period tended to match the first-order kinetics calculated by the nonlinear least squares equation. The N0 values of the MS biosolids-treated soils greatly exceeded those of the DS soils. The rates of N mineralization (k) of the DS biosolids-treated soils varied greatly from 0.047 to 0.075 week−1 and that of the MS soils varied from 0.047 to 0.105 week−1. Little of the organic N fraction in the biosolids remained available for further mineralization following 48 weeks of incubation. Based on the demand of N uptake by vegetables grown in Taiwanese soils, the rates of biosolids application to the soils are safe, as determined by the amount of N mineralization that does not cause nitrate accumulation.