Abstract
Abstract Field experiments were conducted to standardize protocols for site-specific fertilizer nitrogen (N) management in Bt cotton using Soil Plant Analysis Development (SPAD) chlorophyll meter. Performance of different SPAD-based site-specific N management scenarios was evaluated vis-à-vis blanket fertilizer N recommendation. The N treatments comprised a no-N (control), four fixed-time and fixed N doses (60, 90, 120, and 150 kg N ha -1 ) including the recommended dose (150 kg ha -1 ), and eight fixed-time and adjustable N doses based on critical SPAD readings of 45 and 41 at first flowering and boll formation stages, respectively. The results revealed that by applying 45 or 60 kg N ha -1 at thinning stage of the crop and critical SPAD value-guided dose of 45 or 30 kg N ha -1 at first flowering stage resulted in yields similar to that recorded by applying the recommended dose of 150 kg N ha -1 . However, significantly higher N use efficiency as well as 30–40% less total fertilizer N use was recorded with site-specific N management. Applying 30 kg N ha -1 at thinning and SPAD meter-guided 45 kg N ha -1 at first flowering were not enough and required additional SPAD meter-guided 45 kg N ha -1 at boll formation for sustaining yield levels equivalent to those observed by following blanket recommendation but resulted in 20% less fertilizer N application. Our data revealed that SPAD meter-based site-specific N management in Bt cotton results in optimum yield with dynamic adjustment of fertilizer N doses at first flowering and boll formation stages. The total amount of N fertilizer following site-specific management strategies was substantially less than the blanket recommendation of 150 kg N ha -1 , but the extent may vary in different fields.
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Claims 9
Claim · model-written summary
Applying 45 or 60 kg N ha -1 at thinning stage gave yields similar to the recommended 150 kg N ha -1.
Verbatim
e0“in Bt cotton using Soil Plant Analysis Development”
e1“The results revealed that by applying 45 or 60 kg N ha -1 at thinning stage of the crop and critical SPAD value-guided dose of 45 or 30 kg N ha -1 at first flowering stage resulted in yields similar to that recorded by applying the recommended dose of 150 kg N ha -1”
Claim · model-written summary
A critical SPAD value-guided dose of 45 or 30 kg N ha -1 at first flowering gave yields similar to the recommended 150 kg N ha -1.
Verbatim
e0“in Bt cotton using Soil Plant Analysis Development”
e1“The results revealed that by applying 45 or 60 kg N ha -1 at thinning stage of the crop and critical SPAD value-guided dose of 45 or 30 kg N ha -1 at first flowering stage resulted in yields similar to that recorded by applying the recommended dose of 150 kg N ha -1”
Claim · model-written summary
Site-specific N management gave significantly higher N use efficiency than the blanket recommendation.
Not reportedComparator
Verbatim
e0“in Bt cotton using Soil Plant Analysis Development”
e2“However, significantly higher N use efficiency as well as 30–40% less total fertilizer N use was recorded with site-specific N management”
Claim · model-written summary
Site-specific N management reduced total fertilizer N use by 30–40%.
- Taxon
- Bt cottone0
- Treatment
- site-specific N managemente2
- Outcome
- total fertilizer N usee2
- Direction
- lesse2
- Value
- 30–40%e2
Not reportedComparator
Verbatim
e0“in Bt cotton using Soil Plant Analysis Development”
e2“However, significantly higher N use efficiency as well as 30–40% less total fertilizer N use was recorded with site-specific N management”
Claim · model-written summary
Applying 30 kg N ha -1 at thinning and SPAD-guided 45 kg N ha -1 at first flowering was not enough to sustain yield.
Verbatim
e0“in Bt cotton using Soil Plant Analysis Development”
e3“Applying 30 kg N ha -1 at thinning and SPAD meter-guided 45 kg N ha -1 at first flowering were not enough and required additional SPAD meter-guided 45 kg N ha -1 at boll formation for sustaining yield levels equivalent to those observed by following blanket recommendation but resulted in 20% less fertilizer N application”
Claim · model-written summary
Additional SPAD-guided 45 kg N ha -1 at boll formation sustained yield equivalent to the blanket recommendation.
Verbatim
e0“in Bt cotton using Soil Plant Analysis Development”
e3“Applying 30 kg N ha -1 at thinning and SPAD meter-guided 45 kg N ha -1 at first flowering were not enough and required additional SPAD meter-guided 45 kg N ha -1 at boll formation for sustaining yield levels equivalent to those observed by following blanket recommendation but resulted in 20% less fertilizer N application”
Claim · model-written summary
The additional SPAD-guided boll-formation dose resulted in 20% less fertilizer N application.
- Taxon
- Bt cottone0
- Treatment
- additional SPAD meter-guided 45 kg N ha -1 at boll formatione3
- Outcome
- fertilizer N applicatione3
- Direction
- lesse3
- Value
- 20%e3
Not reportedComparator
Verbatim
e0“in Bt cotton using Soil Plant Analysis Development”
e3“Applying 30 kg N ha -1 at thinning and SPAD meter-guided 45 kg N ha -1 at first flowering were not enough and required additional SPAD meter-guided 45 kg N ha -1 at boll formation for sustaining yield levels equivalent to those observed by following blanket recommendation but resulted in 20% less fertilizer N application”
Claim · model-written summary
SPAD meter-based site-specific N management resulted in optimum yield.
Not reportedComparatorDirection
Verbatim
e0“in Bt cotton using Soil Plant Analysis Development”
e4“Our data revealed that SPAD meter-based site-specific N management in Bt cotton results in optimum yield with dynamic adjustment of fertilizer N doses at first flowering and boll formation stages”
Claim · model-written summary
Total fertilizer N under site-specific strategies was substantially less than the blanket recommendation of 150 kg N ha -1.
Verbatim
e0“in Bt cotton using Soil Plant Analysis Development”
e5“The total amount of N fertilizer following site-specific management strategies was substantially less than the blanket recommendation of 150 kg N ha -1, but the extent may vary in different fields”
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