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Biochemical Processes Controlling Soil Nitrogen Mineralization under Waterlogged Conditions
Author(s) -
Haddad S. A.,
Tabatabai M. A.,
Loynachan T. E.
Publication year - 2013
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/sssaj2012.0231
Subject(s) - soil water , chemistry , mineralization (soil science) , nitrogen , zoology , environmental chemistry , soil science , environmental science , biology , organic chemistry
Changes in precipitation patterns in recent years have resulted in flooding or ponding of many farmlands in the North Central region of the United States. In this work, 11 field‐moist surface soils (0–15 cm) and their air‐dried counterparts were incubated at 30°C under waterlogged conditions for times ranging from 3 to 15 d, and the amounts of NH 4 –N released were determined. Results showed that, presumably because of slaking effects, the rates of NH 4 –N release were greater in air‐dried than in field‐moist soils. The mineralization rates of the field‐moist soils were significantly correlated with organic C ( r = 0.59, P < 0.05), organic N ( r = 0.69, P < 0.05), and microbial biomass C ( r = 0.62, P < 0.05) and N ( r = 0.63, P < 0.05). The corresponding r values for the air‐dried soils were 0.76 ( P < 0.01), 0.87 ( P < 0.01), 0.84 ( P < 0.01), and 0.85 ( P < 0.001), respectively. Estimation of the amounts of N mineralized per hectare of field‐moist soils in 1 d ranged from 2.2 to 4.9 kg (average = 3.3). Those values for air‐dried soils ranged from 5.2 to 26.2 kg (average = 15.5). The rates of hydrolysis of six enzyme substrates studied were significantly correlated with the rates of NH 4 –N release in the field‐moist soils. The relationships were amidase ( r = 0.82, P < 0.01), arginase ( r = 0.90, P < 0.001), asparaginase ( r = 0.86, P < 0.001), glutaminase ( r = 0.88, P < 0.001), β‐glucosidase ( r = 0.83, P < 0.01), and β‐glucosaminidase ( r = 0.84, P < 0.01). Temperature coefficient ( Q 10 ) values ranged from 1.2 to 1.4 (average = 1.3) for the field‐moist soils and from 1.0 to 1.3 (average = 1.1) for their air‐dried counterparts. This study showed that microbial biomass, a number of hydrolases, and slaking seem to play a significant role in hydrolysis of N in temporarily flooded soils.