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Comparison of Crop‐Based Indicators with Soil Nitrate Test for Corn Nitrogen Requirement
Author(s) -
Ma B. L.,
Subedi K. D.,
Costa C.
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/agronj2005.0462
Subject(s) - agronomy , sowing , canopy , fertilizer , amendment , growing season , nitrogen , environmental science , crop , field experiment , soil test , human fertilization , nitrate , soil water , chemistry , biology , botany , soil science , ecology , organic chemistry , political science , law
Nitrogen amendment based on soil mineral N content before planting is unreliable in humid regions. A field experiment was conducted for 3 yr to (i) determine the appropriate rates and timing of N applications in the humid environment of eastern Ontario, Canada (45°23′ N, 75°43′ W); (ii) evaluate the ability of nondestructive plant‐based methods compared with presidedress soil nitrate concentration test in discriminating fertilization N rates near sidedress time; and (iii) document how yearly variations in environmental conditions affect the ability of different approaches to assess corn ( Zea mays L.) N status. Two hybrids were grown under eight combinations of rates and timing of N application in a factorial experiment. Leaf greenness and canopy reflectance were simultaneously measured from the V5 to V8 stages and at three occasions thereafter. Plant total N and soil available N NO 3 − and NH 4 + at V6 were analyzed. Relationships of parameters collected early in the growing season vs. grain yield, harvest index, and total plant N uptake at maturity were determined. In 2 yr (2000 and 2002), grain yields increased significantly with fertilizer rates up to 120 kg N ha −1 . While soil mineral N and plant N concentrations differentiated 0 N from preplant N at 40 kg N ha −1 , both leaf chlorophyll and canopy reflectance measured at V6 stage responded linearly to fertilizer N up to 120 kg N ha −1 . We concluded that these leaf and canopy optical measurements could be used as crop‐based indicators for early‐season N amendment.