Abstract
Long-term intensive cultivation has caused soil fertility decline and structural degradation in the Songnen Plain, thereby constraining maize root development and yield formation. As a fundamental conservation tillage practice, straw return enhances soil function by incorporating exogenous organic matter and regulating root-shoot physiological processes. However, the mechanism underlying yield improvement through root–photosynthesis–nitrogen synergy remains insufficiently understood. A field experiment was conducted to assess the effects of conventional tillage (CT), straw incorporation (SI), straw mulching (SM), and deep straw incorporation (DF) on maize physiological traits and yield. Compared with CT, DF markedly enhanced root morphology and physiology, increasing the root length, surface area, volume, and root-shoot ratio by 16.46%, 23.87%, 26.64%, and 51.34%, respectively. The root bleeding intensity increased by 23.63%, whereas amino acid and nitrate contents in the bleeding sap increased by 29.20% and 65.93%, respectively, indicating improved root nutrient transport capacity. The enhanced root system positively influenced shoot photosynthesis by increasing the chlorophyll SPAD value by 16.05%, net photosynthetic rate (Pn) by 11.28%, and the activities of RuBP, PEP, nitrate reductase (NR), and glutamine synthetase (GS) by 10.59%, 24.36%, 29.94%, and 12.47%, respectively. These synergistic improvements significantly promoted post-anthesis biomass accumulation and yield formation. DF increased nitrogen and dry matter accumulation at the R3 stage by 26.61% and 15.67%, respectively, and resulted in an average yield increase of 8.34%, which was primarily due to an 11.96% increase in 100-grain weight. Although SI and SM also improved certain physiological indices, their effects were weaker than those of DF. RF analysis identified sap nitrate content (RNO), bleeding intensity (RBI), root length (RL), and root volume (RV) as key yield determinants. PLS-SEM further revealed that straw return enhanced root morphology and bleeding traits (path coefficients: 0.96 and 0.82), which subsequently improved leaf photosynthetic traits (path coefficients: 0.52 and 0.39) and biomass accumulation (path coefficient: 0.71). Collectively, these improvements promoted post-anthesis nitrogen accumulation and dry matter partitioning into grains. These findings elucidated the physiological mechanism by which deep straw incorporation increased maize yield through root system optimization, providing a theoretical basis for conservation tillage optimization in the thin-layer Mollisol region of the Songnen Plain.
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Claims 20
Claim · model-written summary
Compared with conventional tillage, deep straw incorporation increased maize root length by 16.46%.
- Treatment
- deep straw incorporation (DF)e2
- Outcome
- root lengthe0
- Direction
- increasinge0
- Value
- 16.46%e0
- Comparator
- CTe1
Zea maysOrganisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Maize”
e0“increasing the root length, surface area, volume, and root-shoot ratio by 16.46%, 23.87%, 26.64%, and 51.34%, respectively”
e1“Compared with CT, DF”
e2“deep straw incorporation (DF)”
Claim · model-written summary
Compared with conventional tillage, deep straw incorporation increased maize root surface area by 23.87%.
- Treatment
- deep straw incorporation (DF)e2
- Outcome
- surface areae0
- Direction
- increasinge0
- Value
- 23.87%e0
- Comparator
- CTe1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Maize”
e0“increasing the root length, surface area, volume, and root-shoot ratio by 16.46%, 23.87%, 26.64%, and 51.34%, respectively”
e1“Compared with CT, DF”
e2“deep straw incorporation (DF)”
Claim · model-written summary
Compared with conventional tillage, deep straw incorporation increased maize root volume by 26.64%.
- Treatment
- deep straw incorporation (DF)e2
- Outcome
- volumee0
- Direction
- increasinge0
- Value
- 26.64%e0
- Comparator
- CTe1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Maize”
e0“increasing the root length, surface area, volume, and root-shoot ratio by 16.46%, 23.87%, 26.64%, and 51.34%, respectively”
e1“Compared with CT, DF”
e2“deep straw incorporation (DF)”
Claim · model-written summary
Compared with conventional tillage, deep straw incorporation increased the maize root-shoot ratio by 51.34%.
- Treatment
- deep straw incorporation (DF)e2
- Outcome
- root-shoot ratioe0
- Direction
- increasinge0
- Value
- 51.34%e0
- Comparator
- CTe1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Maize”
e0“increasing the root length, surface area, volume, and root-shoot ratio by 16.46%, 23.87%, 26.64%, and 51.34%, respectively”
e1“Compared with CT, DF”
e2“deep straw incorporation (DF)”
Claim · model-written summary
Compared with conventional tillage, deep straw incorporation increased maize root bleeding intensity by 23.63%.
- Treatment
- deep straw incorporation (DF)e2
- Outcome
- root bleeding intensitye0
- Direction
- increasede0
- Value
- 23.63%e0
- Comparator
- CTe1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Maize”
e0“The root bleeding intensity increased by 23.63%, whereas amino acid and nitrate contents in the bleeding sap increased by 29.20% and 65.93%, respectively”
e1“Compared with CT, DF”
e2“deep straw incorporation (DF)”
Claim · model-written summary
Compared with conventional tillage, deep straw incorporation increased the amino acid content of maize bleeding sap by 29.20%.
- Organ / stage
- bleeding sape0
- Treatment
- deep straw incorporation (DF)e2
- Outcome
- amino acide0
- Direction
- increasede0
- Value
- 29.20%e0
- Comparator
- CTe1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Maize”
e0“The root bleeding intensity increased by 23.63%, whereas amino acid and nitrate contents in the bleeding sap increased by 29.20% and 65.93%, respectively”
e1“Compared with CT, DF”
e2“deep straw incorporation (DF)”
Claim · model-written summary
Compared with conventional tillage, deep straw incorporation increased the nitrate content of maize bleeding sap by 65.93%.
- Organ / stage
- bleeding sape0
- Treatment
- deep straw incorporation (DF)e2
- Outcome
- nitratee0
- Direction
- increasede0
- Value
- 65.93%e0
- Comparator
- CTe1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Maize”
e0“The root bleeding intensity increased by 23.63%, whereas amino acid and nitrate contents in the bleeding sap increased by 29.20% and 65.93%, respectively”
e1“Compared with CT, DF”
e2“deep straw incorporation (DF)”
Claim · model-written summary
Compared with conventional tillage, deep straw incorporation increased maize chlorophyll SPAD value by 16.05%.
- Treatment
- deep straw incorporation (DF)e2
- Outcome
- chlorophyll SPAD valuee0
- Direction
- increasinge0
- Value
- 16.05%e0
- Comparator
- CTe1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Maize”
e0“increasing the chlorophyll SPAD value by 16.05%, net photosynthetic rate (Pn) by 11.28%, and the activities of RuBP, PEP, nitrate reductase (NR), and glutamine synthetase (GS) by 10.59%, 24.36%, 29.94%, and 12.47%, respectively”
e1“Compared with CT, DF”
e2“deep straw incorporation (DF)”
Claim · model-written summary
Compared with conventional tillage, deep straw incorporation increased maize net photosynthetic rate (Pn) by 11.28%.
- Treatment
- deep straw incorporation (DF)e2
- Outcome
- net photosynthetic rate (Pn)e0
- Direction
- increasinge0
- Value
- 11.28%e0
- Comparator
- CTe1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Maize”
e0“increasing the chlorophyll SPAD value by 16.05%, net photosynthetic rate (Pn) by 11.28%, and the activities of RuBP, PEP, nitrate reductase (NR), and glutamine synthetase (GS) by 10.59%, 24.36%, 29.94%, and 12.47%, respectively”
e1“Compared with CT, DF”
e2“deep straw incorporation (DF)”
Claim · model-written summary
Compared with conventional tillage, deep straw incorporation increased maize RuBP activity by 10.59%.
- Treatment
- deep straw incorporation (DF)e2
- Outcome
- RuBPe0
- Direction
- increasinge0
- Value
- 10.59%e0
- Qualifier
- activitiese0
- Comparator
- CTe1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Maize”
e0“increasing the chlorophyll SPAD value by 16.05%, net photosynthetic rate (Pn) by 11.28%, and the activities of RuBP, PEP, nitrate reductase (NR), and glutamine synthetase (GS) by 10.59%, 24.36%, 29.94%, and 12.47%, respectively”
e1“Compared with CT, DF”
e2“deep straw incorporation (DF)”
Claim · model-written summary
Compared with conventional tillage, deep straw incorporation increased maize PEP activity by 24.36%.
- Treatment
- deep straw incorporation (DF)e2
- Outcome
- PEPe0
- Direction
- increasinge0
- Value
- 24.36%e0
- Qualifier
- activitiese0
- Comparator
- CTe1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Maize”
e0“increasing the chlorophyll SPAD value by 16.05%, net photosynthetic rate (Pn) by 11.28%, and the activities of RuBP, PEP, nitrate reductase (NR), and glutamine synthetase (GS) by 10.59%, 24.36%, 29.94%, and 12.47%, respectively”
e1“Compared with CT, DF”
e2“deep straw incorporation (DF)”
Claim · model-written summary
Compared with conventional tillage, deep straw incorporation increased maize nitrate reductase (NR) activity by 29.94%.
- Treatment
- deep straw incorporation (DF)e2
- Outcome
- nitrate reductase (NR)e0
- Direction
- increasinge0
- Value
- 29.94%e0
- Qualifier
- activitiese0
- Comparator
- CTe1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Maize”
e0“increasing the chlorophyll SPAD value by 16.05%, net photosynthetic rate (Pn) by 11.28%, and the activities of RuBP, PEP, nitrate reductase (NR), and glutamine synthetase (GS) by 10.59%, 24.36%, 29.94%, and 12.47%, respectively”
e1“Compared with CT, DF”
e2“deep straw incorporation (DF)”
Claim · model-written summary
Compared with conventional tillage, deep straw incorporation increased maize glutamine synthetase (GS) activity by 12.47%.
- Treatment
- deep straw incorporation (DF)e2
- Outcome
- glutamine synthetase (GS)e0
- Direction
- increasinge0
- Value
- 12.47%e0
- Qualifier
- activitiese0
- Comparator
- CTe1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Maize”
e0“increasing the chlorophyll SPAD value by 16.05%, net photosynthetic rate (Pn) by 11.28%, and the activities of RuBP, PEP, nitrate reductase (NR), and glutamine synthetase (GS) by 10.59%, 24.36%, 29.94%, and 12.47%, respectively”
e1“Compared with CT, DF”
e2“deep straw incorporation (DF)”
Claim · model-written summary
Compared with conventional tillage, deep straw incorporation increased maize nitrogen accumulation at the R3 stage by 26.61%.
- Organ / stage
- R3 stagee0
- Treatment
- deep straw incorporation (DF)e2
- Outcome
- nitrogene0
- Direction
- increasede0
- Value
- 26.61%e0
- Qualifier
- accumulatione0
- Comparator
- CTe1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Maize”
e0“DF increased nitrogen and dry matter accumulation at the R3 stage by 26.61% and 15.67%, respectively, and resulted in an average yield increase of 8.34%”
e1“Compared with CT, DF”
e2“deep straw incorporation (DF)”
Claim · model-written summary
Compared with conventional tillage, deep straw incorporation increased maize dry matter accumulation at the R3 stage by 15.67%.
- Organ / stage
- R3 stagee0
- Treatment
- deep straw incorporation (DF)e2
- Outcome
- dry mattere0
- Direction
- increasede0
- Value
- 15.67%e0
- Qualifier
- accumulatione0
- Comparator
- CTe1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Maize”
e0“DF increased nitrogen and dry matter accumulation at the R3 stage by 26.61% and 15.67%, respectively, and resulted in an average yield increase of 8.34%”
e1“Compared with CT, DF”
e2“deep straw incorporation (DF)”
Claim · model-written summary
Compared with conventional tillage, deep straw incorporation raised average maize yield by 8.34%.
- Treatment
- deep straw incorporation (DF)e2
- Outcome
- average yielde0
- Direction
- increasee0
- Value
- 8.34%e0
- Comparator
- CTe1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Maize”
e0“DF increased nitrogen and dry matter accumulation at the R3 stage by 26.61% and 15.67%, respectively, and resulted in an average yield increase of 8.34%”
e1“Compared with CT, DF”
e2“deep straw incorporation (DF)”
Claim · model-written summary
Compared with conventional tillage, deep straw incorporation increased maize 100-grain weight by 11.96%.
- Treatment
- deep straw incorporation (DF)e2
- Outcome
- 100-grain weighte0
- Direction
- increasee0
- Value
- 11.96%e0
- Comparator
- CTe1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Maize”
e0“an 11.96% increase in 100-grain weight”
e1“Compared with CT, DF”
e2“deep straw incorporation (DF)”
Claim · model-written summary
Straw incorporation (SI) and straw mulching (SM) also improved certain physiological indices of maize, but their effects were weaker than those of deep straw incorporation (DF).
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Maize”
e0“Although SI and SM also improved certain physiological indices, their effects were weaker than those of DF”
Claim · model-written summary
Random forest analysis identified sap nitrate content, bleeding intensity, root length and root volume as key determinants of maize yield.
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Maize”
e0“RF analysis identified sap nitrate content (RNO), bleeding intensity (RBI), root length (RL), and root volume (RV) as key yield determinants”
Claim · model-written summary
PLS-SEM showed that straw return enhanced maize root morphology and bleeding traits (path coefficients 0.96 and 0.82), which improved leaf photosynthetic traits (0.52 and 0.39) and biomass accumulation (0.71).
- Treatment
- straw returne0
- Outcome
- root morphology and bleeding traitse0
- Qualifier
- path coefficients: 0.96 and 0.82e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Maize”
e0“PLS-SEM further revealed that straw return enhanced root morphology and bleeding traits (path coefficients: 0.96 and 0.82), which subsequently improved leaf photosynthetic traits (path coefficients: 0.52 and 0.39) and biomass accumulation (path coefficient: 0.71)”
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