Abstract
Soil salinity and alkalinity can inhibit crop growth and reduce yield, and this has become a global environmental concern. Combined changes in nitrogen (N) application and hill density can improve rice yields in sodic saline–alkaline paddy fields and protect the environment. We investigated the interactive effects of N application rate and hill density on rice yield and N accumulation, translocation and utilization in two field experiments during 2018 and 2019 in sodic saline–alkaline paddy fields. Five N application rates (0 (control), 90, 120, 150, and 180 kg N ha–1 (N0–N4), respectively) and three hill densities (achieved by altering the distance between hills, in rows spaced 30 cm apart: 16.5 cm (D1), 13.3 cm (D2) and 10 cm (D3)) were utilized in a split-plot design with three replicates. Nitrogen application rate and hill density significantly affected grain yield. The mathematical model of quadratic saturated D-optimal design showed that with an N application rate in the range of 0–180 kg N ha–1, the highest yield was obtained at 142.61 kg N ha–1 which matched with a planting density of 33.3×104 ha–1. Higher grain yield was mainly attributed to the increase in panicles m–2. Nitrogen application rate and hill density significantly affected N accumulation in the aboveground parts of rice plants and showed a highly significant positive correlation with grain yield at maturity. From full heading to maturity, the average N loss rate of the aboveground parts of rice plants in N4 was 70.21% higher than that of N3. This is one of the reasons why the yield of N4 treatment is lower than that of the N3 treatment. Nitrogen accumulation rates in the aboveground parts under treatment N3 (150 kg N ha–1) were 81.68 and 106.07% higher in 2018 and 2019, respectively, than those in the control. The N translocation and N translocation contribution rates increased with the increase in the N application rate and hill density, whereas N productivity of dry matter and grain first increased and then decreased with the increase in N application rate and hill density. Agronomic N-use efficiency decreased with an increase in N application rate, whereas hill density did not significantly affect it. Nitrogen productivity of dry matter and grain, and agronomic N-use efficiency, were negatively correlated with grain yield. Thus, rice yield in sodic saline–alkaline paddy fields can be improved by combined changes in the N application rate and hill density to promote aboveground N accumulation. Our study provides novel evidence regarding optimal N application rates and hill densities for sodic saline–alkaline rice paddies.
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Claims 15
Claim · model-written summary
Nitrogen application rate and hill density significantly affected grain yield.
- Taxon
- rice
Oryza sativat0 - Treatment
- Nitrogen application rate and hill densitye0
- Outcome
- grain yielde0
Not reportedComparatorDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Nitrogen application rate and hill density significantly affected grain yield”
t0“rice”
Claim · model-written summary
The model predicted highest yield at 142.61 kg N ha–1 with planting density 33.3×104 ha–1.
- Taxon
- riceOryza sativat0
- Treatment
- planting density of 33.3×104 ha–1e0
- Outcome
- highest yielde0
- Value
- 142.61 kg N ha–1e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the highest yield was obtained at 142.61 kg N ha–1 which matched with a planting density of 33.3×104 ha–1”
t0“rice”
Claim · model-written summary
Higher grain yield was mainly attributed to more panicles per square metre.
- Taxon
- riceOryza sativat0
- Outcome
- grain yielde0
- Qualifier
- increase in panicles m–2e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Higher grain yield was mainly attributed to the increase in panicles m–2”
t0“rice”
Claim · model-written summary
Nitrogen rate and hill density significantly affected aboveground rice nitrogen accumulation.
- Taxon
- riceOryza sativae0
- Treatment
- Nitrogen application rate and hill densitye0
- Outcome
- N accumulation in the aboveground parts of rice plantse0
Not reportedComparatorDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Nitrogen application rate and hill density significantly affected N accumulation in the aboveground parts of rice plants”
Claim · model-written summary
Aboveground nitrogen accumulation was highly significantly positively correlated with grain yield at maturity.
- Taxon
- riceOryza sativat0
- Organ / stage
- maturitye0
- Outcome
- grain yield at maturitye0
- Direction
- positivee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“showed a highly significant positive correlation with grain yield at maturity”
t0“rice”
Claim · model-written summary
From full heading to maturity, N4 had an aboveground nitrogen loss rate 70.21% higher than N3.
- Taxon
- riceOryza sativae0
- Organ / stage
- full heading to maturitye0
- Treatment
- N4e0
- Outcome
- average N loss rate of the aboveground parts of rice plantse0
- Direction
- highere0
- Value
- 70.21%e0
- Comparator
- N3e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“From full heading to maturity, the average N loss rate of the aboveground parts of rice plants in N4 was 70.21% higher than that of N3”
Claim · model-written summary
N4 yielded less than N3.
- Taxon
- riceOryza sativat0
- Treatment
- N4 treatmente0
- Outcome
- yielde0
- Direction
- lowere0
- Comparator
- N3 treatmente0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the yield of N4 treatment is lower than that of the N3 treatment”
t0“rice”
Claim · model-written summary
N3 aboveground nitrogen accumulation rate was 81.68% above control in 2018.
- Taxon
- riceOryza sativat0
- Treatment
- N3 (150 kg N ha–1)e0
- Outcome
- Nitrogen accumulation rates in the aboveground partse0
- Direction
- highere0
- Value
- 81.68e0
- Qualifier
- 2018e0
- Comparator
- controle0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Nitrogen accumulation rates in the aboveground parts under treatment N3 (150 kg N ha–1) were 81.68 and 106.07% higher in 2018 and 2019, respectively, than those in the control”
t0“rice”
Claim · model-written summary
N3 aboveground nitrogen accumulation rate was 106.07% above control in 2019.
- Taxon
- riceOryza sativat0
- Treatment
- N3 (150 kg N ha–1)e0
- Outcome
- Nitrogen accumulation rates in the aboveground partse0
- Direction
- highere0
- Value
- 106.07%e0
- Qualifier
- 2019e0
- Comparator
- controle0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Nitrogen accumulation rates in the aboveground parts under treatment N3 (150 kg N ha–1) were 81.68 and 106.07% higher in 2018 and 2019, respectively, than those in the control”
t0“rice”
Claim · model-written summary
Nitrogen translocation and its contribution rate increased with nitrogen application rate and hill density.
- Taxon
- riceOryza sativat0
- Treatment
- N application rate and hill densitye0
- Outcome
- N translocation and N translocation contribution ratese0
- Direction
- increasede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The N translocation and N translocation contribution rates increased with the increase in the N application rate and hill density”
t0“rice”
Claim · model-written summary
Nitrogen productivity of dry matter and grain first increased and then decreased with nitrogen rate and hill density.
- Taxon
- riceOryza sativat0
- Treatment
- N application rate and hill densitye0
- Outcome
- N productivity of dry matter and graine0
- Direction
- first increased and then decreasede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“N productivity of dry matter and grain first increased and then decreased with the increase in N application rate and hill density”
t0“rice”
Claim · model-written summary
Agronomic nitrogen use efficiency decreased as nitrogen rate increased.
- Taxon
- riceOryza sativat0
- Treatment
- N application ratee0
- Outcome
- Agronomic N-use efficiencye0
- Direction
- decreasede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Agronomic N-use efficiency decreased with an increase in N application rate”
t0“rice”
Claim · model-written summary
Hill density did not significantly affect agronomic nitrogen use efficiency.
- Taxon
- riceOryza sativat0
- Treatment
- hill densitye0
- Outcome
- Agronomic N-use efficiencye0
- Direction
- did not significantly affecte0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Agronomic N-use efficiency decreased with an increase in N application rate, whereas hill density did not significantly affect it”
t0“rice”
Claim · model-written summary
Nitrogen productivity of dry matter and grain and agronomic nitrogen use efficiency were negatively correlated with grain yield.
- Taxon
- riceOryza sativat0
- Outcome
- grain yielde0
- Direction
- negatively correlatede0
- Qualifier
- Nitrogen productivity of dry matter and grain, and agronomic N-use efficiencye0
Not reportedOrgan / stage
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Nitrogen productivity of dry matter and grain, and agronomic N-use efficiency, were negatively correlated with grain yield”
t0“rice”
Claim · model-written summary
The authors recommend combining nitrogen rate and hill density to promote aboveground nitrogen accumulation and improve rice yield.
- Taxon
- riceOryza sativae0
- Treatment
- combined changes in the N application rate and hill densitye0
- Outcome
- rice yield in sodic saline–alkaline paddy fieldse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“rice yield in sodic saline–alkaline paddy fields can be improved by combined changes in the N application rate and hill density to promote aboveground N accumulation”
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