Nitrogen immobilization in paddy soils as affected by redox conditions and rice straw incorporation
Articolo
Data di Pubblicazione:
2014
Abstract:
Biotic and abiotic processes controlling nitrogen (N) immobilization in paddy soils may significantly affect
nutrient availability for plant uptake during the rice cropping season, as well as the efficiency of applied N
fertilizers. Understanding the influence of water and crop residue management practices on N availability,
however, requires detailed insight into the mechanisms and factors controlling N immobilization in these soils.
We evaluated changes in fertilizer-15N immobilization in a paddy topsoil incubated for 160 d under flooded or
non-flooded conditions, with or without rice straw incorporation. The distribution of immobilized N between
different soil fractions and interlayer N fixation was assessed by combining aggregate-size, density and chemical
fractionation with stable isotope analysis, while compound-specific δ15N analysis of individual amino sugars was
used to evaluate microbial utilization of applied N. Fast immobilization of applied N (≈ 48% applied N) was
observed in both flooded (Eh = +0.4 to –0.2 V) and non-flooded (Eh = +0.4 to +0.6 V) soils, however in the latter
most of this N was released during incubation. The finer soil fractions served as the greatest sink of immobilized
N, retaining 5–36% of the added N. Although biotic processes were mainly responsible for N retention, about 4–
11% of N applied to flooded soils was weakly fixed within the interlayer of clay minerals, primarily associated
with microaggregates. Straw addition further enhanced N immobilization under both oxic and anoxic conditions,
with ≈ 12% of total immobilized N (2–4% of applied N) associated with the light organic matter fraction. The
increasing incorporation of applied N into microbial residues suggested that addition of rice straw to paddy soils
may lead to effective microbial-mediated immobilization and stabilization of significant portions of N inputs.
Tipologia CRIS:
03A-Articolo su Rivista
Keywords:
Fertilizer-derived nitrogen, aggregate-size fractionation, interlayer fixation, amino sugars, compound specific
δ15N stable isotope mass spectrometry
Elenco autori:
Said-Pullicino D; Cucu MA; Sodano M; Birk JJ; Glaser B; Celi L
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