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Evaluation of Nitrogen Availability Indexes for a Sludge Compost Amended Soil
Author(s) -
O'Keefe Barry E.,
Axley J.,
Meisinger J. J.
Publication year - 1986
Publication title -
journal of environmental quality
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.888
H-Index - 171
eISSN - 1537-2537
pISSN - 0047-2425
DOI - 10.2134/jeq1986.00472425001500020007x
Subject(s) - loam , lime , soil water , chemistry , compost , soil test , nitrogen , agronomy , incubation , soil fertility , zoology , environmental science , soil science , biology , paleontology , biochemistry , organic chemistry
Several N availability methods were evaluated on a sludge amended soil, since sludge applications are usually based on N availability and a soil N evaluation to optimize loading rates. Yearly amendments of composted, lime‐stabilized, raw sludge were applied, at 0, 56, 112, and 224 Mg ha −1 , to an Elkton silt loam soil (Typic Ochraquults), in Beltsville, MD, as follows: whole plots (1975–1977), half plots (1978), and no plots (1979–1981). In 1978 and 1981, surface and subsurface soil samples were collected and maize ( Zea mays L.) total N uptake was determined. The biological method (73‐week aerobic incubation [NT]) of assessing soil N availability revealed an initial rapid miner. alization phase (NE) over the first 28 weeks and a constant phase thereafter. The chemical methods were total soil N (TN), acid KMnO 4 oxidizable N (P), autoclave extractable N (A), and 2 M KCl extractable NH + 4 ‐N (K). Curvilinear regression analyses relaling maize N uptake to these N indexes gave the following R 2 values: NE, 0.93; NT, 0.94; TN, 0.93; P, 0.92; A, 0.95; and K, 0.92. All methods were equally sensitive on sludge treated soils; however, the incubation procedure was best on untreated soil. Including second zone soil N and expressing the results on a root‐zone volume basis improved N uptake predictions with unfertilized controls, but was unnecessary for sludge treated plots. These results indicate that chemical N availability indexes can be used to assess soil N availability on sludge treated land; provided they are calibrated to local soil‐crop‐climate conditions.