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Ammonia Emission from Soybean‐Amended Calcareous Soil with Various Soil Temperature and Moisture Levels
Author(s) -
O'Deen W. A.,
Follett R. F.
Publication year - 1992
Publication title -
agronomy journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.752
H-Index - 131
eISSN - 1435-0645
pISSN - 0002-1962
DOI - 10.2134/agronj1992.00021962008400050024x
Subject(s) - calcareous , water content , chemistry , ammonia , agronomy , moisture , residue (chemistry) , environmental chemistry , zoology , botany , biology , biochemistry , geotechnical engineering , organic chemistry , engineering
High soil temperature, moisture, and crop residue levels were found to combine for maximum volatilization of ammonia from calcareous soil amended with soybean [ Glycine max (L.) Merr.] tissue in this study. An unusually large amount of ammonia was liberated to the atmosphere and provided the opportunity to measure accurately isotope separation of 15 N and 14 N atoms resulting from the diffusion process. Soybean tissue (early reproductive stage) was mixed with a calcareous soil (Aridic Paleustoll) at two different levels (25 and 50 g kg −1 ). The two soil soybean‐tissue mixtures were wetted to the desired moisture content (20, 60, and 100% field capacity) and incubated 7 d at either 10, 20, or 30 °C. After incubation, ammonia evolution and moisture loss were determined during either a 4‐ or 7‐d dry‐down period in which dry NH 3 ‐free air was passed across the soil surface. We found more NH 3 volatilized at 100ɐ FC than at 20 or 60% FC, at 30 than at 10 or 20 °C, and at 50 than at 25 g kg −1 residue rate. Maximum loss of NH 3 was about 5% of soybean‐tissue N measured in an experiment in which four wet‐dry cycles were used. Maximum loss was directly related to water evaporation rate. These results indicate that soil temperature, moisture, and crop‐residue rates all influence NH 3 losses from soybean‐tissue amended soil. Isotopic ratios of the NH 3 −N evolved were measured and ammonia content of the first fraction of ammonia volatilized was lower in atom % 15 N than the last fraction. These results indicate that, for the conditions of this study, diffusion is an important process since the 14 N atoms volatilized more quickly as NH 3 than did the 15 N atoms.