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Mineralization and nitrification potentials of grassland soils at shallow depth during laboratory incubation
Author(s) -
Abbasi M. Kaleem,
Shah Zahir,
Adams W. A.
Publication year - 2001
Publication title -
journal of plant nutrition and soil science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.644
H-Index - 87
eISSN - 1522-2624
pISSN - 1436-8730
DOI - 10.1002/1522-2624(200110)164:5<497::aid-jpln497>3.0.co;2-e
Subject(s) - nitrification , mineralization (soil science) , nitrogen cycle , chemistry , soil water , incubation , environmental chemistry , grassland , fertilizer , nitrogen , zoology , agronomy , soil science , environmental science , biology , biochemistry , organic chemistry
In grassland ecosystems when ample organic N is present, both, mineralization and nitrification can play an important role in determining fertilizer use efficiency as well as N losses to the environment. Laboratory incubation studies were undertaken in a controlled environment at 20 °C to establish relative potential rates of nitrification and mineral N variation in soil collected from grassland fields. Soil samples of 0—2.5, 2.5—5.0, and 5.0—7.5 cm were collected to examine the depth distribution of mineral N. Mineralization potential was determined from soil without added N while nitrification activity was measured following the addition of NH 4 + ‐N during 42 days period. Net mineralization of N ranged from 13 to 64 mg (kg soil) —1 . Of the total inorganic N found, more than 50 % was released from the surface 0—2.5‐cm and the concentration decreased with depth. In a separate experiment when 15 N was used, net mineralization was dominant over immobilization and of the gross mineralization, more than 70 % was released as inorganic N. Nitrification showed an initial lag phase, a maximum rate phase and a reduced rate phase. The maximum rate of nitrification ranged from 3.3 to 7.5 mg (kg soil) —1 day —1 being greatest in the 0—2.5 cm depth. The nitrification rate decreased and the delay phase increased with soil depth. During the study, 50 to 60 % of added NH 4 + ‐N was converted into NO 3 — ‐N indicating the presence of active nitrifiers and a large potential for nitrification in the soil. A significant variation in nitrification and mineralization rates within 0—7.5 cm was observed which is extremely important in transformations and dynamics of N in grassland ecosystems.