Abstract
Site-specific fertilizer nitrogen (N) management using chlorophyll meter (SPAD meter) can help drawing in-season need-based N topdressing decisions. However, SPAD meter based threshold chlorophyll value to trigger supplement N in spring maize is indistinct. Field studies were conducted for two years in sub-tropical and sub-humid climate to study variations in spectral properties and to establish threshold SPAD value for need-based N management in spring maize cultivars. Results specified that N concentration of topmost fully expanded leaf was closely correlated with SPAD meter readings from six-leaf stage (V6) to tasseling stages (VT). The Cate-Nelson plot expressed SPAD 50 as the threshold value to determine plant N need at different growth stages. Need-based topdressings of 30 kg N ha−1, whenever SPAD reading fell below the threshold 50 improved grain yield production by 7.6 to 10.2 per cent over soil test-based N application. SPAD threshold 45 guided N management was inadequate to meet plant N demand, whereas SPAD threshold 55 guided N application lead to N doses in excess of crop requirement without yield benefits. SPAD threshold 50 guided N management ensured better demand-supply synchrony throughout the growth stages and thus reported better N recovery and agronomic efficiencies over soil test-based N management.
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Claims 7
Claim · model-written summary
Leaf nitrogen concentration was closely correlated with SPAD readings from V6 to VT.
- Organ / stage
- six-leaf stage (V6) to tasseling stages (VT)e0
- Treatment
- SPAD meter readingse0
- Outcome
- N concentration of topmost fully expanded leafe0
Zea maysNot reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“N concentration of topmost fully expanded leaf was closely correlated with SPAD meter readings from six-leaf stage (V6) to tasseling stages (VT)”
t0“spring maize”
Claim · model-written summary
SPAD 50 was identified as the threshold for plant N need at different stages.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The Cate-Nelson plot expressed SPAD 50 as the threshold value to determine plant N need at different growth stages”
t0“spring maize”
Claim · model-written summary
SPAD 50 guided 30 kg N ha−1 topdressing improved grain yield by 7.6 to 10.2 per cent against soil test application.
- Treatment
- Need-based topdressings of 30 kg N ha−1e0
- Outcome
- grain yield productione0
- Direction
- improvede0
- Value
- 7.6 to 10.2 per cente0
- Comparator
- soil test-based N applicatione0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Need-based topdressings of 30 kg N ha−1, whenever SPAD reading fell below the threshold 50 improved grain yield production by 7.6 to 10.2 per cent over soil test-based N application”
t0“spring maize”
Claim · model-written summary
SPAD 45 guided management was inadequate for N demand.
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“SPAD threshold 45 guided N management was inadequate to meet plant N demand”
t0“spring maize”
Claim · model-written summary
SPAD 55 guided N application exceeded crop requirements without yield benefit.
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“SPAD threshold 55 guided N application lead to N doses in excess of crop requirement without yield benefits”
t0“spring maize”
Claim · model-written summary
SPAD 50 guided management improved nitrogen demand supply synchrony.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“SPAD threshold 50 guided N management ensured better demand-supply synchrony throughout the growth stages”
t0“spring maize”
Claim · model-written summary
SPAD 50 guided management improved N recovery and agronomic efficiencies against soil test management.
- Treatment
- SPAD threshold 50 guided N managemente0
- Outcome
- N recovery and agronomic efficienciese0
- Direction
- bettere0
- Comparator
- soil test-based N managemente0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“SPAD threshold 50 guided N management ensured better demand-supply synchrony throughout the growth stages and thus reported better N recovery and agronomic efficiencies over soil test-based N management”
t0“spring maize”
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