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Temporal Origin of Nitrogen in the Grain of Tropical Wet‐Season Rice
Author(s) -
Sheehy J. E.,
Mnzava M.,
Cassman K. G.,
Mitchell P. L.,
Ferrer A. B.,
Robles R. P.,
Pablico P.
Publication year - 2005
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/agronj2004.0081
Subject(s) - panicle , oryza sativa , transplanting , nitrate , agronomy , urea , nitrogen , chemistry , crop , growing season , horticulture , biology , sowing , biochemistry , organic chemistry , gene
The total N in the grain is the integral of the product of the total N absorbed at any instant and the fraction of that N eventually allocated to the grain. We investigated the temporal origin of N in the grain of a wet season rice crop and tested the suitability of 15 N nitrate (NH 4 15 NO 3 ) as a label for that purpose. The total N content of rice ( Oryza sativa L.) plants was measured by growth analysis throughout the duration of the crop and the measurements were used to calculate the rate of total N uptake. A point‐placement technique was used to deliver small amounts of 15 N nitrate to roots of the rice plant and this enabled the eventual fate of the total N absorbed at any time to be determined. The rate at which N was acquired by the panicle exceeded that by the whole plant at 64 d after transplanting (DAT); thereafter, N was transferred from the leaves to the panicle. About 60% of N in the grain was acquired before panicle initiation and was transferred from leaves during grain filling. A comparison between the uptake and retention of labeled nitrate and urea applied separately at 35 DAT showed that 21 and 58% of the 15 N nitrate and 15 N urea, respectively, were recovered. There were no advantages of using 15 N nitrate as opposed to 15 N urea as a label in such research of irrigated rice.