SINGH et al. (2026) Subsurface fertigation modifies soil–plant–water interactions to improve productivity of cotton–wheat systems under reduced tillage

Identification

• Journal: Frontiers in Plant Science
• Year: 2026
• Date: 2026-03-26
• Authors: K H SINGH, Yamini Vaddula, Sudhir Kumar Mishra
• DOI: 10.3389/fpls.2026.1813404

Research Groups

• Punjab Agricultural University, Regional Research Station, Faridkot, India
• ICAR-National Institute of Abiotic Stress Management, Malegaon, Baramati, Pune, India (for Sudhir Kumar Mishra)

Short Summary

This study investigated how subsurface drip fertigation (SDF) influences soil physical properties, plant physiological functioning, and system productivity in a low-tilled cotton-wheat rotation over two growing seasons. It found that SDF significantly improves soil-plant interactions and resource-use efficiency, enhancing productivity while mitigating pressure on groundwater resources compared to conventional surface flood irrigation.

Objective

• To assess the impact of subsurface drip fertigation (SDF) on soil physical properties and physiological traits of cotton and wheat compared to conventional surface flood irrigation (SFM) with soil-applied nutrients.
• To examine root characteristics under varying lateral depths, emitter spacings, and fertigation levels in contrast to conventional practice.
• To evaluate the productivity potential of cotton–wheat cropping systems under SDF across different emitter depths, spacings, and nutrient management regimes.
• Principal Hypothesis: Subsurface lateral placement and emitter spacing would differentially modify soil moisture distribution and soil physical properties, thereby regulating root growth and physiological efficiency of cotton and wheat under low-tillage management.

Study Configuration

• Spatial Scale: Field experiments conducted at Punjab Agricultural University, Regional Research Station (RRS), Faridkot, India (30°40′ N, 74°44′ E; 200 m above mean sea level). Experimental plots measured 4.7 m × 7.5 m. Soil samples were collected from 0–0.15 m and 0.15–0.30 m depths, and root samples from 0.15 m, 0.30 m, 0.45 m, and 0.60 m depths.
• Temporal Scale: Two years, encompassing four growing seasons: summer 2021 and 2022 for cotton, and winter 2021–2022 and 2022–2023 for wheat. Physiological measurements were recorded at 60, 90, 120, and 150 days after sowing (DAS).

Methodology and Data

• Models used: Crop water demand was estimated using the evapotranspiration (ETc) method, which involves calculating water usage by multiplying the crop coefficient (Kc) with the reference evapotranspiration (ETo).
• Data sources:
  • Field experiments: Split-plot design with three replications and 18 treatment combinations.
  • Soil parameters: Initial and final soil fertility status (available N, P, organic carbon), soil bulk density (core method), and steady-state infiltration rate (double ring infiltrometer).
  • Physiological parameters: Net photosynthetic rate, transpiration rate, stomatal conductance (using CI-340 portable photosynthesis system), canopy temperature (infrared radiometer), chlorophyll content (SPAD-502 Plus meter), leaf area index (SunScan canopy analyzer), and root length density (Biovis root analysis software).
  • Plant analysis: Nitrogen and phosphorus uptake in above-ground biomass (Kjeldahl’s apparatus for N, Vanado-Molybdo-Phosphoric yellow color method for P).
  • Yield attributes: Bolls per plant, boll weight, ginning out turn (GOT), lint yield, seed yield for cotton; effective tillers, ear length, grains per ear, 1000-grain weight, and grain yield for wheat.
  • Irrigation data: Water meters installed on PVC supply pipes quantified irrigation water, applied at 80% ETc.

Main Results

• Subsurface drip fertigation (SDF) significantly moderated soil compaction, reducing soil bulk density in the upper (0–0.15 m) and subsurface (0.15–0.30 m) layers compared to surface flood irrigation (SFM). SFM consistently recorded 4–5% higher bulk density.
• Shallow lateral placement (0.25 m) consistently enhanced steady-state infiltration rate (SSIR) and soil organic carbon (SOC) compared to deeper placement (0.30 m). Higher fertigation levels also increased SOC and SSIR.
• SDF improved leaf-level gas exchange, including higher photosynthetic rate, transpiration, and stomatal conductance, which translated into greater crop productivity.
• For cotton, a lateral depth of 0.25 m and closer emitter spacing of 0.30 m optimized root-zone resource availability and physiological performance. This configuration improved lint yield by 32.6% compared to SFM. Fertigation with 0.014 kg N m⁻² (125% recommended N) in 14 equal splits further enhanced lint yield, surpassing SFM by 36.4% (e.g., 0.12036 kg m⁻² vs 0.08812 kg m⁻²).
• For wheat, shallow lateral placement (0.25 m) and closer emitter spacing (0.30 m) increased grain yield. Fertigation with 0.0125-0.00625 kg NP m⁻² (100% recommended NP) in 10 splits maximized productivity. SFM resulted in a 15.8% reduction in wheat grain yield compared to SDF (e.g., 0.432 kg m⁻² vs 0.500 kg m⁻²).
• SDF treatments consistently maintained higher root length density and nutrient uptake (N and P) in both cotton and wheat compared to SFM.

Contributions

• Demonstrates the comprehensive mechanisms by which subsurface drip fertigation (SDF) under reduced tillage improves soil physical properties, plant physiological functioning, and overall system productivity in intensive cotton–wheat rotations.
• Identifies optimal SDF configurations (lateral depth of 0.25 m, emitter spacing of 0.30 m, and specific split fertigation schedules for N and NP) for maximizing yield and resource-use efficiency in cotton and wheat.
• Provides a viable and sustainable pathway for enhancing agricultural productivity while mitigating groundwater depletion in water-scarce agroecosystems, particularly in north-western India.
• Fills a critical knowledge gap regarding the combined influence of subsurface emitter depth, spacing, and nutrient management on soil-plant-water interactions in integrated cotton–wheat systems.

Funding

The authors declared that financial support was not received for this work and/or its publication.

Citation

@article{SINGH2026Subsurface,
  author = {SINGH, K H and Vaddula, Yamini and Mishra, Sudhir Kumar},
  title = {Subsurface fertigation modifies soil–plant–water interactions to improve productivity of cotton–wheat systems under reduced tillage},
  journal = {Frontiers in Plant Science},
  year = {2026},
  doi = {10.3389/fpls.2026.1813404},
  url = {https://doi.org/10.3389/fpls.2026.1813404}
}