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A Possible Source of Serious Error in the Determination of Nitrate Production in Soils
Author(s) -
Timmons D. R.,
Kilmer V. J.,
Stahly V. F.
Publication year - 1961
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj1961.03615995002500040030x
Subject(s) - soil water , division (mathematics) , soil conservation , environmental science , geography , soil science , archaeology , mathematics , arithmetic , agriculture
OEVERAL YEARS AGO, during the course of nitrate forma»̂ tion studies, abnormall y high nitrate production was obtained with incubated soil-vermiculite mixtures. 2 Upon further investigation, the vermiculite used in the study as a soil amendmen t was found to contai n 0.02% nitrogen. A possibl e source of this nitrogen appeare d to be the laborator y atmosphere . In order to gain additional information on this point, the study reported herei n was undertaken. Samples of Sassafra s sandy loam and Beltsville silt loam were collected, air-dried, and passed through a 2mm. sieve. Sufficient quantities of Perlite and Terra-lite (vermiculite) were obtained and heated at 800° C. for 1 hour in order to remove possibl e traces of nitrogen. Some pertinent characteristic s of the two soils, Perlite and vermiculite, are given in table 1. The soils, along with the heat-treate d Perlite and vermiculite, were placed separatel y in two types of containers : (1) covered, in screw-cap glass jars, and (2) uncovered, in open-top paper cartons. Each storage condition for each sampl e of soil and amendmen t was replicated four times. Each paper carton contained approximatel y 2 pounds of soil. The jars and cartons were randoml y located in the Soil and Plant Analysis Laborator y for a period of about 8 months. At 2-month intervals, 20-g. samples of the covered and uncovered soils were mixed with weighed amount s of covered and uncovered vermiculite and Perlite, (8 combinations in all). The mixtures were transferred to leaching tubes fitted with a basal layer of Perlite, leached with water and incubated at 30° C. and 55% relative humidity for a 2-week period. This technique is fully described by Stanford and Hanway. 3 The nitrate produced during the 2-week incubation period was measured by the phenoldisulfoni c acid procedure. Ammonia in various forms is used routinely in the Soil and Plant Analysis Laboratory, as well as in other laboratories located in the same building. Thus, the level of ammoni a contamination indicated in table 2 is representa Table 1—Some characteristics of the two soils and amendments.