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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Claims 8
Claim · model-written summary
Applying 30 kg N ha−1 at each SPAD drop below 37.5 gave rice yields equivalent to 120 kg N ha−1 applied in three splits
- Taxon
- rice
Oryza sativae1 - Treatment
- Applying 30 kg N ha−1 each time the SPAD value fell below the critical value of 37.5e1
- Outcome
- yieldse1
- Direction
- equivalente1
- Comparator
- 120 kg N ha−1 applied in three splitse1
- Setting
- loamy sand in northwestern Indiae0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“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”
e1“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”
Claim · model-written summary
A SPAD threshold of 35 gave low rice yields in two cultivars
- Taxon
- riceOryza sativae2
- Material
- two rice cultivarse2
- Treatment
- SPAD value of 35e2
- Outcome
- yieldse2
- Direction
- lowe2
- Qualifier
- only 60 kg N ha−1e2
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e2“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”
Claim · model-written summary
Applying N basally or a week after transplanting did not further increase rice yield under high inherent soil fertility
- Taxon
- riceOryza sativae3
- Treatment
- applying N basally or a week after rice transplantinge3
- Outcome
- yielde3
- Direction
- did not further increasee3
- Qualifier
- high inherent soil fertilitye3
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e3“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”
Claim · model-written summary
N management based on leaf color chart shade 4 helped avoid overapplication of N to rice
- Taxon
- riceOryza sativae4
- Treatment
- N management based on LCC shade 4e4
- Outcome
- overapplication of Ne4
- Direction
- helped avoide4
- Qualifier
- Limited experimentatione4
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e4“Limited experimentation with leaf color chart (LCC) indicated that N management based on LCC shade 4 helped avoid overapplication of N to rice”
Claim · model-written summary
Wheat responded to N application at maximum tillering when SPAD value fell below 44
- Taxon
- Wheat
Triticum aestivume5 - Treatment
- at maximum tillering (MT) when SPAD value fell below 44e5
- Outcome
- responded to N applicatione5
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e5“Wheat responded to N application at maximum tillering (MT) when SPAD value fell below 44”
Claim · model-written summary
Applying 30 kg N ha−1 at SPAD value 42 at maximum tillering increased wheat yield by 20%
- Taxon
- WheatTriticum aestivume6
- Treatment
- 30 kg N ha−1 was applied at SPAD value of 42 at MTe6
- Outcome
- yielde6
- Direction
- increasede6
- Value
- 20%e6
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e6“Wheat yield increased by 20% when 30 kg N ha−1 was applied at SPAD value of 42 at MT”
Claim · model-written summary
Chlorophyll-meter need-based N management reduces the N requirement of rice from 12.5 to 25%
- Taxon
- riceOryza sativae7
- Treatment
- plant need–based N management through chlorophyll metere7
- Outcome
- N requirement of ricee7
- Direction
- reducese7
- Value
- from 12.5 to 25%e7
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e7“plant need–based N management through chlorophyll meter reduces N requirement of rice from 12.5 to 25%, with no loss in yield”
Claim · model-written summary
Chlorophyll-meter need-based N management gave no loss in rice yield
- Taxon
- riceOryza sativae7
- Treatment
- plant need–based N management through chlorophyll metere7
- Outcome
- yielde7
- Direction
- no losse7
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e7“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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