Abstract
The contributions of the different leaf layers to maize yields identified as middle leaf > lower leaf > upper leaf, where the vertical photosynthetically active radiation (PAR) in the canopy gradually decreases. We hypothesized that the allocation of more PAR and nitrogen (N) to the highest contributing leaves will would be beneficial for higher yields and N use efficiencies. The N application rate and plant density effectively regulated the canopy light and N distribution. We evaluated the interactive effects of N rate and plant density on the agronomic and ecophysiological characteristics of leaves at different orientations in a 2019/2020 field experiment. In this study, an N application rate of 180 kg ha –1 coupled with a plant density of 82,500 plants ha –1 achieved the highest yield and N recovery efficiency (NRE). In contrast to the traditional farming practices in northern China, the density was increased and N rate was reduced. Densification from 52,500 to 82,500 plants ha –1 increased the population leaf area index (LAI) by 37.1% and total photosynthetically active radiation (TPAR) by 29.2%; however, excessive density (from 82,500 to 97,500 plants ha –1 ) drastically reduced the proportion of TPAR by 28.0% in the lower leaves. With increased density, the leaf areas and angles of the upper leaves decreased much more than those of the other leaves, which allowed the middle and lower leaves to access more light, which manifested a smaller extinction coefficient for light ( K L ). A high yield (>1,000 kg ha –1 ) of maize could be achieved simultaneously with higher NRE; however, it was negatively correlated with internal N use efficiency (IE N ). Higher N concentrations and lower total performance index (PI total ) in the lower leaves may be an important rationale for the reduction of IE N in high-yielding maize. Additionally, decreased N rate without yield reduction under higher densities was primarily attributed to the more uniform vertical N distribution [a smaller extinction coefficient for N ( K N )]. These results suggest that the N fertilizer rate can be moderately reduced without a reduction in maize yield under high plant densities in northern China.
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Claims 13
Claim · model-written summary
Middle leaves contributed more to maize yield than lower leaves, which contributed more than upper leaves.
Zea maysOrganisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“maize”
e0“middle leaf > lower leaf > upper leaf”
Claim · model-written summary
Nitrogen rate and density regulated canopy light and nitrogen distribution.
Not reportedComparatorDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“maize”
e0“The N application rate and plant density effectively regulated the canopy light and N distribution”
Claim · model-written summary
180 kg ha –1 nitrogen with 82,500 plants ha –1 achieved the highest yield and nitrogen recovery efficiency.
- Treatment
- N application rate of 180 kg ha –1 coupled with a plant density of 82,500 plants ha –1e0
- Outcome
- yield and N recovery efficiency (NRE)e0
- Direction
- higheste0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“maize”
e0“an N application rate of 180 kg ha –1 coupled with a plant density of 82,500 plants ha –1 achieved the highest yield and N recovery efficiency (NRE)”
Claim · model-written summary
Increasing density from 52,500 to 82,500 plants ha –1 raised leaf area index by 37.1%.
- Treatment
- 82,500 plants ha –1e0
- Outcome
- population leaf area index (LAI)e0
- Direction
- increasede0
- Value
- 37.1%e0
- Comparator
- 52,500e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“maize”
e0“Densification from 52,500 to 82,500 plants ha –1 increased the population leaf area index (LAI) by 37.1%”
Claim · model-written summary
Increasing density from 52,500 to 82,500 plants ha –1 raised total photosynthetically active radiation by 29.2%.
- Treatment
- 82,500 plants ha –1e0
- Outcome
- total photosynthetically active radiation (TPAR)e0
- Direction
- increasede0
- Value
- 29.2%e0
- Comparator
- 52,500e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“maize”
e0“Densification from 52,500 to 82,500 plants ha –1 increased the population leaf area index (LAI) by 37.1% and total photosynthetically active radiation (TPAR) by 29.2%”
Claim · model-written summary
Increasing density from 82,500 to 97,500 plants ha –1 reduced the lower-leaf TPAR proportion by 28.0%.
- Organ / stage
- lower leavese0
- Treatment
- 97,500 plants ha –1e0
- Outcome
- proportion of TPARe0
- Direction
- reducede0
- Value
- 28.0%e0
- Comparator
- 82,500e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“maize”
e0“excessive density (from 82,500 to 97,500 plants ha –1 ) drastically reduced the proportion of TPAR by 28.0% in the lower leaves”
Claim · model-written summary
With greater density, upper-leaf area and angle declined more than in other leaves.
- Organ / stage
- upper leavese0
- Outcome
- leaf areas and anglese0
- Direction
- decreasede0
- Comparator
- other leavese0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“maize”
e0“With increased density, the leaf areas and angles of the upper leaves decreased much more than those of the other leaves”
Claim · model-written summary
Greater density gave middle and lower leaves more light and a smaller extinction coefficient.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“maize”
e0“which allowed the middle and lower leaves to access more light, which manifested a smaller extinction coefficient for light ( K L )”
Claim · model-written summary
High yield above 1,000 kg ha –1 coincided with higher nitrogen recovery efficiency.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“maize”
e0“A high yield (>1,000 kg ha –1 ) of maize could be achieved simultaneously with higher NRE”
Claim · model-written summary
High yield was negatively correlated with internal nitrogen use efficiency.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“maize”
e0“A high yield (>1,000 kg ha –1 ) of maize could be achieved simultaneously with higher NRE; however, it was negatively correlated with internal N use efficiency (IE N )”
Claim · model-written summary
Lower leaves had higher nitrogen concentrations and lower total performance index in high-yielding maize.
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“maize”
e0“Higher N concentrations and lower total performance index (PI total ) in the lower leaves may be an important rationale for the reduction of IE N in high-yielding maize”
Claim · model-written summary
More uniform vertical nitrogen distribution was proposed to explain maintained yield with reduced nitrogen rate at higher density.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“maize”
e0“decreased N rate without yield reduction under higher densities was primarily attributed to the more uniform vertical N distribution [a smaller extinction coefficient for N ( K N )]”
Claim · model-written summary
The authors suggest moderately reducing nitrogen fertilizer at high density without reducing maize yield in northern China.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“maize”
e0“the N fertilizer rate can be moderately reduced without a reduction in maize yield under high plant densities in northern China”
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