Combined effects of soil waterlogging and compaction on rice (Oryza sativa L.) growth, soil aeration, soil N transformations and 15N discrimination |
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Authors: | W M H G Engelaar Taigo Matsumaru Tadakatsu Yoneyama |
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Institution: | (1) Plant Nutrition Diagnosis Laboratory, National Agriculture Research Center, Kannondai 3-1-1 Tsukuba, Ibaraki 305-8666, Japan e-mail: willeme@narc.affrc.go.jp Fax: +81-298-388951, JP;(2) School of Environmental Sciences, University of Tsukuba, Tsukuba, Ibaraki 305-8572, Japan, JP |
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Abstract: | The combined effects of soil compaction and soil waterlogging on the growth of two rice cultivars (Oryza sativa L., cultivars Kanto 168 and Koshihikari) and soil N transformations were studied in pots. Although waterlogging eliminated
initial differences in mechanical resistance between compacted and loose soils, Kanto 168 and Koshihikari roots had, respectively,
less biomass and a lower porosity if soil was compacted prior to waterlogging. The cause for this was probably established
before waterlogging. Redox values showed that upland soils were well aerated. Loose waterlogged soils contained oxic sites,
but compacted waterlogged soils did not. Potential denitrification was stimulated by waterlogging and, to a larger extent,
by plant presence. Waterlogging lowered potential nitrifying capacities, by competition between plants and micro-organisms
for NH4
+ rather than by oxygen shortage. Compaction prior to waterlogging benefited the potential nitrifying capacity of soils with
either cultivar and the potential denitrifying capacity for soils with Koshihikari. Compaction had no effect on nitrification
or denitrification in upland soils. N recoveries were low, especially in pots without plants, as a result from sampling strategy
and N loss. On day 42/43 after potting, total δ15N values of waterlogged pots were positive, whereas after 22 days all pots had negative total δ15N values. Final δ15N values of plant parts from waterlogged and upland soils were positive and negative, respectively. Although the δ15N values generally accorded well with the other results, they did not support higher N losses from compacted waterlogged soils
than from loose waterlogged soils with plants, as suggested by potential denitrifying activities.
Received: 4 February 2000 |
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Keywords: | δ 15N N transformations Rice (Oryza sativa L ) Soil aeration Soil mechanical resistance |
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