Abstract
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.
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Claims 7
Claim · model-written summary
SPAD-triggered 90 kg N ha −1 produced rice yields equivalent to the 120 kg N ha −1 split application.
- Taxon
- rice
Oryza sativae0 - Treatment
- Applying 30 kg N ha −1 each time the SPAD value fell below the critical value of 37.5e0
- Outcome
- rice yieldse0
- Direction
- equivalente0
- Value
- 90 kg N ha −1e0
- Comparator
- 120 kg N ha −1 applied in three splitse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“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
SPAD threshold 35 led to only 60 kg N ha −1 and low yields in two rice cultivars.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“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
Basal or one-week-post-transplant N did not further increase rice yield on high-fertility soil.
- Taxon
- riceOryza sativae0
- Treatment
- applying N basally or a week after rice transplantinge0
- Outcome
- yielde0
- Direction
- did not further increasee0
- Qualifier
- high inherent soil fertilitye0
- Comparator
- zero‐N plotse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“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
LCC shade 4 management helped avoid overapplication of N to rice.
- Taxon
- riceOryza sativae0
- Treatment
- N management based on LCC shade 4e0
- Outcome
- overapplication of N to ricee0
- Direction
- avoide0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“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 at maximum tillering when SPAD fell below 44.
- Taxon
- Wheat
Triticum aestivume0 - Treatment
- N application at maximum tillering (MT)e0
- Outcome
- respondede0
- Qualifier
- SPAD value fell below 44e0
Not reportedComparatorDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“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 42 at maximum tillering increased wheat yield by 20%.
- Taxon
- WheatTriticum aestivume0
- Treatment
- 30 kg N ha −1 was applied at SPAD value of 42 at MTe0
- Outcome
- Wheat yielde0
- Direction
- increasede0
- Value
- 20%e0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Wheat yield increased by 20% when 30 kg N ha −1 was applied at SPAD value of 42 at MT.”
Claim · model-written summary
Plant-need-based chlorophyll meter management reduced rice N requirement by 12.5 to 25% without yield loss.
- Taxon
- riceOryza sativae0
- Treatment
- plant need–based N management through chlorophyll metere0
- Outcome
- N requirement of ricee0
- Direction
- reducese0
- Value
- 12.5 to 25%e0
- Qualifier
- with no loss in yielde0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“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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- positive
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