Abstract
This study examined the planting density tolerance, grain yield improvement potential, and mechanisms of high-yielding spring maize varieties under increasing planting density and subsoiling. We planted two high-yielding spring maize varieties with a high or low tolerance to high planting densities (LM33 and XD20, respectively) at five different densities (D1: 60,000 plants ha−1, D2: 75,000 plants ha−1, D3: 90,000 plants ha−1, D4: 105,000 plants ha−1, and D5: 120,000 plants ha−1) using two tillage methods (35-cm subsoiling and 15-cm traditional rotary tillage). The response characteristics used to compare the performance of the two maize varieties under different planting densities and tillage methods included root characteristics, canopy physiology, yield, and yield components. The results show that: (1) Under rotary tillage, with the increase of planting density from 75,000 plants ha−1 to 90,000 plants ha−1, yields of high-yielding spring maize varieties improved. However, when the planting densities were beyond 90,000 plants ha−1, the yields stopped increase, or even decrease. Subsoiling increased the planting density by 15,000 plants ha−1, enhanced the highest yield by 1080 kg ha−1–1940 kg ha−1, and raised the yield gain by 11.17–30.72%. (2) Under rotary tillage, the functional indexes of the roots and canopy of high-yielding spring maize decreased as planting density increased, and the largest reductions of root dry weight, leaf area index (LAI) of post-anthesis, light transmission percentage (LTP) of ear leaves, bottom leaves LTP, and dry matter accumulation all occurred between D2 and D4. The largest decline of high tolerance variety emerged between D3 and D5, and the extent was smaller than the low tolerance variety. (3) Compared with rotary tillage, subsoiling reduced the extent declines in root dry weight, root length, and root surface area; delayed the attenuation of LAI and the relative chlorophyll content (SPAD) determined in leaves; and improved the LTP of ear layers and bottom layer during the late growth stage. The post-anthesis populations dry matter accumulation of XD20 and LM33 increased by 7.07% and 13.18%, respectively. In addition, subsoiling significantly increased the number of kernels/spike and 1000-grain weight as the planting density increased. Meanwhile, the planting densities at which dry root weight, population LAI, ear leaf LTP, bottom leaf LTP, and dry matter accumulation arose the largest reductions was raised to 15,000 plants ha−1. The effects of subsoiling in the high density-tolerant variety were more pronounced than the low density-tolerant variety.
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Claims 16
Claim · model-written summary
Under rotary tillage, raising planting density from 75,000 to 90,000 plants per hectare improved yields of high-yielding spring maize varieties.
- Treatment
- increase of planting density from 75,000 plants ha−1 to 90,000 plants ha−1e0
- Outcome
- yieldse0
- Direction
- improvede0
- Qualifier
- Under rotary tillagee0
Zea maysNot reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Under rotary tillage, with the increase of planting density from 75,000 plants ha−1 to 90,000 plants ha−1, yields of high-yielding spring maize varieties improved”
Claim · model-written summary
Beyond 90,000 plants per hectare the yields of high-yielding maize stopped increasing or even decreased.
- Treatment
- planting densities were beyond 90,000 plants ha−1e0
- Outcome
- yieldse0
- Direction
- stopped increasee0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“when the planting densities were beyond 90,000 plants ha−1, the yields stopped increase, or even decrease”
t0“High-Yielding Maize”
Claim · model-written summary
Subsoiling increased the planting density (tolerated) by 15,000 plants per hectare.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Subsoiling increased the planting density by 15,000 plants ha−1”
t0“High-Yielding Maize”
Claim · model-written summary
Subsoiling enhanced the highest maize yield by 1080 to 1940 kg per hectare.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“enhanced the highest yield by 1080 kg ha−1–1940 kg ha−1”
e1“Subsoiling increased”
t0“High-Yielding Maize”
Claim · model-written summary
Subsoiling raised the maize yield gain by 11.17-30.72%.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“raised the yield gain by 11.17–30.72%”
e1“Subsoiling increased”
t0“High-Yielding Maize”
Claim · model-written summary
Under rotary tillage, functional indexes of roots and canopy of high-yielding spring maize decreased as planting density increased.
- Taxon
- high-yielding spring maizee0
- Treatment
- planting densitye0
- Outcome
- functional indexes of the roots and canopye0
- Direction
- decreasede0
- Qualifier
- Under rotary tillagee0
Not reportedComparator
Verbatim
e0“Under rotary tillage, the functional indexes of the roots and canopy of high-yielding spring maize decreased as planting density increased”
Claim · model-written summary
The largest reductions of root dry weight, post-anthesis LAI and ear-leaf light transmission percentage occurred between densities D2 and D4.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the largest reductions of root dry weight, leaf area index (LAI) of post-anthesis, light transmission percentage (LTP) of ear leaves, bottom leaves LTP, and dry matter accumulation all occurred between D2 and D4”
t0“High-Yielding Maize”
Claim · model-written summary
The largest reductions of bottom-leaf light transmission percentage and dry matter accumulation also occurred between densities D2 and D4.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the largest reductions of root dry weight, leaf area index (LAI) of post-anthesis, light transmission percentage (LTP) of ear leaves, bottom leaves LTP, and dry matter accumulation all occurred between D2 and D4”
t0“High-Yielding Maize”
Claim · model-written summary
The largest decline of the high-tolerance variety emerged between D3 and D5 and was smaller than that of the low-tolerance variety.
- Material
- high tolerance varietye0
- Outcome
- largest declinee0
- Qualifier
- between D3 and D5e0
- Comparator
- low tolerance varietye0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The largest decline of high tolerance variety emerged between D3 and D5, and the extent was smaller than the low tolerance variety”
t0“High-Yielding Maize”
Claim · model-written summary
Compared with rotary tillage, subsoiling reduced the declines in root dry weight, root length and root surface area.
- Treatment
- subsoilinge1
- Outcome
- declines in root dry weight, root length, and root surface areae0
- Direction
- reducede0
- Comparator
- rotary tillagee1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“subsoiling reduced the extent declines in root dry weight, root length, and root surface area”
e1“Compared with rotary tillage, subsoiling”
t0“High-Yielding Maize”
Claim · model-written summary
Compared with rotary tillage, subsoiling delayed the attenuation of LAI and leaf relative chlorophyll content (SPAD).
- Treatment
- subsoilinge1
- Outcome
- attenuation of LAI and the relative chlorophyll content (SPAD)e0
- Direction
- delayede0
- Comparator
- rotary tillagee1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“delayed the attenuation of LAI and the relative chlorophyll content (SPAD)”
e1“Compared with rotary tillage, subsoiling”
t0“High-Yielding Maize”
Claim · model-written summary
Compared with rotary tillage, subsoiling improved the light transmission percentage of the ear and bottom layers during the late growth stage.
- Treatment
- subsoilinge1
- Outcome
- LTP of ear layers and bottom layere0
- Direction
- improvede0
- Qualifier
- during the late growth stagee0
- Comparator
- rotary tillagee1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“improved the LTP of ear layers and bottom layer during the late growth stage”
e1“Compared with rotary tillage, subsoiling”
t0“High-Yielding Maize”
Claim · model-written summary
Subsoiling increased post-anthesis population dry matter accumulation of XD20 by 7.07%.
- Material
- XD20e0
- Treatment
- subsoilinge1
- Outcome
- post-anthesis populations dry matter accumulatione0
- Direction
- increasede0
- Value
- 7.07%e0
- Comparator
- rotary tillagee1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The post-anthesis populations dry matter accumulation of XD20 and LM33 increased by 7.07% and 13.18%, respectively”
e1“Compared with rotary tillage, subsoiling”
t0“High-Yielding Maize”
Claim · model-written summary
Subsoiling increased post-anthesis population dry matter accumulation of LM33 by 13.18%.
- Material
- LM33e0
- Treatment
- subsoilinge1
- Outcome
- post-anthesis populations dry matter accumulatione0
- Direction
- increasede0
- Value
- 13.18%e0
- Comparator
- rotary tillagee1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The post-anthesis populations dry matter accumulation of XD20 and LM33 increased by 7.07% and 13.18%, respectively”
e1“Compared with rotary tillage, subsoiling”
t0“High-Yielding Maize”
Claim · model-written summary
Subsoiling significantly increased kernels per spike and 1000-grain weight as planting density increased.
- Treatment
- subsoilinge0
- Outcome
- number of kernels/spike and 1000-grain weighte0
- Direction
- increasede0
- Qualifier
- as the planting density increasede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“subsoiling significantly increased the number of kernels/spike and 1000-grain weight as the planting density increased”
t0“High-Yielding Maize”
Claim · model-written summary
Subsoiling effects were more pronounced in the high density-tolerant variety than in the low density-tolerant variety.
- Material
- high density-tolerant varietye0
- Treatment
- subsoilinge0
- Outcome
- effects of subsoilinge0
- Direction
- more pronouncede0
- Comparator
- low density-tolerant varietye0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The effects of subsoiling in the high density-tolerant variety were more pronounced than the low density-tolerant variety”
t0“High-Yielding Maize”
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