Plant Science Today · 2026
Deep sub-soiling improves soil-water conductance, root architecture and cotton yield in semi-arid systems
Brar, H. S., Singh, M.
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Deep sub-soiling improves soil-water conductance, root archi…
Abstract
Cotton productivity in the Indo-Gangetic loamy sands has remained stagnant, largely due to subsoil compaction, which restricts water infiltration and root elongation. This study quantified the effects of one-time sub-soiling, applied as single or cross passes at different spacings, on soil hydraulics, root and fruit development and seed cotton yield (SCY) using analytical approaches beyond conventional mean comparisons. Five tillage treatments, including conventional tillage (CT) and 4 subsoiling configurations, were evaluated across 3 site-years on fixed plots in Punjab, India. Treatment responses were assessed using effect size estimates (Hedges g) for key traits, while a piecewise structural equation model traced the causal pathways linking tillage intensity (TI) to infiltration rate (IR), root length (RL), fruiting capacity and yield. A quadratic response surface regression was used to identify the joint optimum of the IR and RL. Cross sub-soiling at 1 × 1 m spacing increased infiltration by 10–13 mm h-1, enhanced rooting depth by 31–33 % and improved SCY by approximately 33 % relative to CT. Structural equation modelling indicated that 57 % of the total tillage effect on yield was mediated through improved soil hydraulics, with an additional 34 % being mediated through enhanced fruiting capacity. The response surface explained 80 % of the yield variability and identified an optimum near a 40 mm h-1 IR and 110 cm RL, with small deviations causing substantial yield losses. Overall, deep, closely spaced cross sub-soiling improved soil-root functioning and translated these gains into higher fruit retention and yield, providing a robust framework for optimising sub-soiling strategies in semi-arid cotton systems.
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Cotton productivity in the Indo-Gangetic loamy sands has remained stagnant, largely due to subsoil compaction, which restricts water infiltration and root elongation. This study quantified the effects of one-time sub-soiling, applied as single or cross passes at different spacings, on soil hydraulics, root and fruit development and seed cotton yield (SCY) using analytical approaches beyond conventional mean comparisons. Five tillage treatments, including conventional tillage (CT) and 4 subsoiling configurations, were evaluated across 3 site-years on fixed plots in Punjab, India. Treatment responses were assessed using effect size estimates (Hedges g) for key traits, while a piecewise structural equation model traced the causal pathways linking tillage intensity (TI) to infiltration rate (IR), root length (RL), fruiting capacity and yield. A quadratic response surface regression was used to identify the joint optimum of the IR and RL. Cross sub-soiling at 1 × 1 m spacing increased infiltration by 10–13 mm h-1, enhanced rooting depth by 31–33 % and improved SCY by approximately 33 % relative to CT. Structural equation modelling indicated that 57 % of the total tillage effect on yield was mediated through improved soil hydraulics, with an additional 34 % being mediated through enhanced fruiting capacity. The response surface explained 80 % of the yield variability and identified an optimum near a 40 mm h-1 IR and 110 cm RL, with small deviations causing substantial yield losses. Overall, deep, closely spaced cross sub-soiling improved soil-root functioning and translated these gains into higher fruit retention and yield, providing a robust framework for optimising sub-soiling strategies in semi-arid cotton systems.
Cotton productivity in the Indo-Gangetic loamy sands has remained stagnant, largely due to subsoil compaction, which restricts water infiltration and root elongation. This study quantified the effects of one-time sub-soiling, applied as single or cross passes at different spacings, on soil hydraulics, root and fruit development and seed cotton yield (SCY) using analytical approaches beyond conventional mean comparisons. Five tillage treatments, including conventional tillage (CT) and 4 subsoiling configurations, were evaluated across 3 site-years on fixed plots in Punjab, India. Treatment responses were assessed using effect size estimates (Hedges g) for key traits, while a piecewise structural equation model traced the causal pathways linking tillage intensity (TI) to infiltration rate (IR), root length (RL), fruiting capacity and yield. A quadratic response surface regression was used to identify the joint optimum of the IR and RL. Cross sub-soiling at 1 × 1 m spacing increased infiltration by 10–13 mm h-1, enhanced rooting depth by 31–33 % and improved SCY by approximately 33 % relative to CT. Structural equation modelling indicated that 57 % of the total tillage effect on yield was mediated through improved soil hydraulics, with an additional 34 % being mediated through enhanced fruiting capacity. The response surface explained 80 % of the yield variability and identified an optimum near a 40 mm h-1 IR and 110 cm RL, with small deviations causing substantial yield losses. Overall, deep, closely spaced cross sub-soiling improved soil-root functioning and translated these gains into higher fruit retention and yield, providing a robust framework for optimising sub-soiling strategies in semi-arid cotton systems.
Findings
What changed what, as the paper reports it. Grouped by the measured property. The largest groups are open; open the others as you need them.
seed-cotton yield
↑ 1= 12
- increase
cross subsoiling CSS1 and CSS1.5, agreeing variants vs. CT, conventional shallow tillage without subsoilingsignificant · PAU Regional Research Station, Bathinda · PAU Regional Research Station, Abohar · Pooled site-years;CSS1 andCSS1.5 independently significant Welch .05;not an invented pooled-treatment contrast.
Numbers
- SMD 1.05 · CSS1;Hedges g
- SMD 0.88 · CSS1.5;Hedges g
Source · p. 5 “Large positive effects of CSS1 + CT and CSS1.5 + CT on hydraulic traits cascaded to moderate gains in canopy traits and yield”
Source · p. 5 “(1.05 SD), followed by +CSS1.5 (0.88 SD)”
- no effect
single-pass subsoiling SS1 and SS1.5, agreeing variants vs. CT, conventional shallow tillage without subsoilingnot significant · PAU Regional Research Station, Bathinda · PAU Regional Research Station, Abohar · Pooled site-years;both independently tested single-pass variants unstarred Fig2 Welch .05. Individual site-year LSD comparisons sometimes significant.
Source · p. 5 “treatments showed smaller and statistically non-significant effect sizes.”
field-saturated infiltration rate
↑ 11
- increase
subsoiling, SS1/SS1.5/CSS1/CSS1.5 agreeing variants vs. CT, conventional shallow tillage without subsoilingsignificant · 2015–2016 Bathinda;2015 Abohar · PAU Regional Research Station, Bathinda · PAU Regional Research Station, Abohar · Pooled site-year Welch comparisons separately for each variant; all significant at .01 or smaller (SS1.5 .01,others .001);60DAS. Site-year SS1.5 Bathinda2015 LSD pair is null.
Source · p. 5 “Single-pass sub-soiling showed a clear intensity gradient: +SS1 raised infiltration by 2.18 SD, whereas the less intense +SS1.5 achieved only 1.19 SD.”
Source · p. 5 “The two cross sub-soiling options (+CSS1 and +CSS1.5) showed the largest hydraulic effect sizes in the pooled analysis”
maximum rooting depth (RL)
↑ 11
- increase
subsoiling, SS1/SS1.5/CSS1/CSS1.5 agreeing variants vs. CT, conventional shallow tillage without subsoilingsignificant · PAU Regional Research Station, Bathinda · PAU Regional Research Station, Abohar · Pooled site-years; all four separately tested variants p<.001,Fig2;90–100DAS; no assumed fixed sampling depth.
Source · p. 3 “Subsoiling treatments produced markedly longer and heavier roots (Table 1).”
Source · p. 5 “root depth by 5.26 and 3.88 SD (p \<0.001)”
sympodial branches per plant
↑ 11
- increase
CSS1, cross-subsoiling1x1m vs. CT, conventional shallow tillage without subsoilingsignificant · PAU Regional Research Station, Bathinda · PAU Regional Research Station, Abohar · Pooled site-years,Fig2 Welch p<.05; CSS1 only, other pooled variants unstarred.
Source · p. 5 “At Bathinda-2015, +CSS1 raised sympodial branches per plant by 30 % over CT”
bolls per square metre
↑ 11
- increase
subsoiling, SS1/SS1.5/CSS1/CSS1.5 agreeing variants vs. CT, conventional shallow tillage without subsoilingsignificant · PAU Regional Research Station, Bathinda · PAU Regional Research Station, Abohar · Pooled site-years, four separately tested variants,Fig2 Welch;SS1.5 .05,SS1 .01,CSS variants .001.
Source · p. 5 “These hydraulic improvements were associated with moderate increases in reproductive traits such as boll number and boll weight.”
mean boll weight
↑ 11
- increase
subsoiling, SS1/SS1.5/CSS1/CSS1.5 agreeing variants vs. CT, conventional shallow tillage without subsoilingsignificant · PAU Regional Research Station, Bathinda · PAU Regional Research Station, Abohar · Pooled site-years, four separately tested variants,Fig2 Welch;single passes .05,CSS1 .001,CSS1.5 .01;individual Abohar year LSD pairs null.
Source · p. 5 “These hydraulic improvements were associated with moderate increases in reproductive traits such as boll number and boll weight.”
fresh root weight
↑ 11
- increase
CSS1, cross-subsoiling1x1m vs. CT, conventional shallow tillage without subsoilingsignificant · Bathinda2015,2016;Abohar2015 · PAU Regional Research Station, Bathinda · PAU Regional Research Station, Abohar · CSS1 vsCT distinct LSD letters .05 all three site-years;fresh weight.
Numbers
- treatment 59.8 vs. control 40.2 g plant-1 (+48.76 %) · Bathinda2015
- treatment 72.8 vs. control 41.5 g plant-1 (+75.42 %) · Bathinda2016
- treatment 52.5 vs. control 40 g plant-1 (+31.25 %) · Abohar2015
Source · p. 3 “the fresh root weight per plant rose by 49 %.”
dry root weight
↑ 11
- increase
CSS1, cross-subsoiling1x1m vs. CT, conventional shallow tillage without subsoilingsignificant · Bathinda2015,2016;Abohar2015 · PAU Regional Research Station, Bathinda · PAU Regional Research Station, Abohar · CSS1 vsCT distinct LSD letters .05 all three site-years;dry weight.
Numbers
- treatment 23.6 vs. control 14.3 g plant-1 (+65.03 %) · Bathinda2015
- treatment 27.6 vs. control 15.8 g plant-1 (+74.68 %) · Bathinda2016
- treatment 19.8 vs. control 15.2 g plant-1 (+30.26 %) · Abohar2015
Source · p. 3 “+CSS1 extended roots by 33 % and increased dry mass by 30 % relative to CT.”
plant height
= 11
- no effect
subsoiling, SS1/SS1.5/CSS1/CSS1.5 agreeing variants vs. CT, conventional shallow tillage without subsoilingnot significant · 2015–2016 · PAU Regional Research Station, Bathinda · All four variants share CT letter a in Bathinda both years;LSD.05;Abohar excluded.
Source · p. 5 “Plant stature was largely unaffected by subsoiling”
Set-up
Treatments
- tillage treatmentsTillage
- CT, conventional shallow tillage without subsoilingNo subsoilingsubsoiling, SS1/SS1.5/CSS1/CSS1.5 agreeing variantsSubsoilingCSS1, cross-subsoiling1x1mSubsoilingcross subsoiling CSS1 and CSS1.5, agreeing variantsSubsoilingsingle-pass subsoiling SS1 and SS1.5, agreeing variantsSubsoiling
Measured
- field-saturated infiltration rateWater infiltration rate
- Unit
- mm h-1
- Method
- double-ring infiltrometer,30/60cm,5cm head,60DAS
- maximum rooting depth (RL)Rooting depth
- Unit
- cm
- Method
- trench at90–100DAS; deepest live root intersection
- sympodial branches per plantBranches per plant
- Unit
- plant-1
- bolls per square metrePod number
- Unit
- m-2
- mean boll weightPlant biomass
- Unit
- g
- seed-cotton yieldYield
- Unit
- kg ha-1
- Method
- whole plot,all pickings,8%moisture
- fresh root weightRoot biomass
- Unit
- g plant-1
- dry root weightRoot biomass
- Unit
- g plant-1
- plant height
- Unit
- cm
Sites
PAU Regional Research Station, Bathinda
- Location
- Bathinda, Punjab, India30.16° N, 74.92° E
- Climate
- 440 mm annual precipitation
- Soil
- Ustipsamments (Typic) · USDA
- Land use
- irrigated cotton fieldPermanently irrigated land
- Management on the whole site
- cottonCotton plant/Gossypium sp.
| Depth | Texture | Clay | pH | Organic C | Bulk density |
|---|---|---|---|---|---|
| surface soil (depth unstated; jointly reported site ranges) | loamy sand | – | 8.15–8.31 | 0.32–0.37 % | – |
PAU Regional Research Station, Abohar
- Location
- Abohar, Punjab, India30.14° N, 74.20° E
- Climate
- 284 mm annual precipitation
- Soil
- Ustipsamments (Typic) · USDA
- Land use
- irrigated cotton fieldPermanently irrigated land
- Management on the whole site
- cottonCotton plant/Gossypium sp.
| Depth | Texture | Clay | pH | Organic C | Bulk density |
|---|---|---|---|---|---|
| surface soil (depth unstated; jointly reported site ranges) | loamy sand | – | 8.15–8.31 | 0.32–0.37 % | – |
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