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This article in AJ

  1. Vol. 94 No. 4, p. 821-829
     
    Received: Aug 7, 2001


    * Corresponding author(s): j.k.ladha@cgiar.org
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doi:10.2134/agronj2002.8210

Chlorophyll Meter– and Leaf Color Chart–Based Nitrogen Management for Rice and Wheat in Northwestern India

  1. Bijay Singha,
  2. Yadvinder Singha,
  3. Jagdish K. Ladha *b,
  4. Kevin F. Bronsonc,
  5. Vethaiya Balasubramanianb,
  6. Jagdeep Singha and
  7. Charan S. Khinda
  1. a Dep. of Soils, Punjab Agric. Univ., Ludhiana 141004, Punjab, India
    b IRRI, DAPO Box 7777, Metro Manila, Philippines
    c Soil and Water Sci. Div., IRRI, DAPO Box 7777, Metro Manila, Philippines

Abstract

Overapplication of N in cereal crops leads to low N recovery efficiency and risk of NO3 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.

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Copyright © 2002. American Society of AgronomyPublished in Agron. J.94:821–829.