Effect of Spray Irrigation of Municipal Wastewater on Nitrogen Transformations in Soil.

摘要

Nitrogen transformations on soils of the Pennsylvania State University Wastewater Management Study were investigated for Reed Canarygrass,Old Field, Hardwood Forest and Gameland sites. Nitrogen mineralization rates,plotted as N mineralized versus to the 1/2power for the 26week mineralization period were linear for 0-7.5cm soil depths for all sites but only for eight weeks at the 7.5-15cm depth,reflecting the depletion of mineralizable N compounds at lower depths. N mineralization was higher for wastewater treated sites on Hublersberg soil and represented 3.0-3.5% of the soil N;rates were 5-9times greater on the coarse-textured Morrison soil,indicating a greater danger of NO3(-) leaching with wastewater treatment of this type of soil. Nitrification was rapid on all treated soils,absent on Old Field and Gameland control sites and slow on Hardwood Forest sites due to low soil pH. Denitrifying activity was low on all sites even in surface layers;glucose-amended soils,however,gave rapid denitrification,indicating a lack of available carbon. This was supported by measurements of soluble and mineralizable carbon in soil. Plant residues taken from the site supplied available carbon for denitrification for 2-4weeks only.