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Chlorophyll Meter– and Leaf Color Chart–Based Nitrogen Management for Rice and Wheat in Northwestern India
Author(s) -
Singh Bijay,
Singh Yadvinder,
Ladha Jagdish K.,
Bronson Kevin F.,
Balasubramanian Vethaiya,
Singh Jagdeep,
Khind Charan S.
Publication year - 2002
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/agronj2002.8210
Subject(s) - transplanting , oryza sativa , loam , agronomy , mathematics , cultivar , crop , yield (engineering) , chlorophyll , environmental science , horticulture , biology , soil water , sowing , soil science , biochemistry , materials science , gene , metallurgy
Overapplication of N in cereal crops leads to low N recovery efficiency and risk of NO 3 pollution of ground water. The chlorophyll meter, also known as SPAD meter, is a simple, portable diagnostic tool for identifying crop N status. We used it to test need‐based N management approaches for rice ( Oryza sativa L.) and wheat ( Triticum aestivum L.) on a loamy sand in northwestern India. Applying 30 kg N ha −1 each time the SPAD value fell below the critical value of 37.5 resulted in application of 90 kg N ha −1 , which produced rice yields equivalent to those with 120 kg N ha −1 applied in three splits. Using a SPAD value of 35 was inadequate for the two rice cultivars because it resulted in application of only 60 kg N ha −1 and, thus, low yields. With high inherent soil fertility resulting in rice yield of >3 Mg ha −1 in zero‐N plots, applying N basally or a week after rice transplanting did not further increase yield. Limited experimentation with leaf color chart (LCC) indicated that N management based on LCC shade 4 helped avoid overapplication of N to rice. Wheat responded to N application at maximum tillering (MT) when SPAD value fell below 44. Wheat yield increased by 20% when 30 kg N ha −1 was applied at SPAD value of 42 at MT. Results show that plant need–based N management through chlorophyll meter reduces N requirement of rice from 12.5 to 25%, with no loss in yield.