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Estimating Grain and Straw Nitrogen Concentration in Grain Crops Based on Aboveground Nitrogen Concentration and Harvest Index
Author(s) -
Kemanian Armen R.,
Stöckle Claudio O.,
Huggins David R.
Publication year - 2007
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/agronj2006.0090
Subject(s) - sorghum , straw , agronomy , hordeum vulgare , nitrogen , poaceae , biomass (ecology) , cropping system , mathematics , biology , crop , chemistry , organic chemistry
Simulating grain ( N g ) and straw ( N s ) nitrogen (N) concentration is of paramount importance in cropping systems simulation models. In this paper we present a simple model to partition N between grain and straw at harvest for barley ( Hordeum vulgare L.), wheat ( Triticum aestivum L.), maize ( Zea mays L.), and sorghum ( Sorghum bicolor Moench). The principle of the model is to partition the aboveground N at physiologic maturity based on the relative availability of biomass and N to the grain. The inputs for the model are the harvest index (HI), representing the relative availability of biomass to the grain, and the aboveground N concentration ( N t ) at harvest, representing the availability of N. The model has five parameters, of which four (the maximum and minimum achievable grain and straw N concentrations) are readily available; the parameter C requires calibration. The model was calibrated and tested for these four species without differentiating genotypes within species. The testing included diverse experiments in wheat; comparing observed and estimated N g the relative RMSE ranged from 3 to 10% (five experiments) and was 31% in one experiment in which the estimated N g exceeded consistently the observed values. For barley, maize, and sorghum, the data availability for testing was limited, but the model performed well (relative RMSE values of 7, 7, and 18%, respectively). Therefore, the model proposed seems to be robust. It remains to be determined if the parameters and the method are useful to discriminate genotypic differences in N g within a species and if the method can be applied to legume crops.