Abstract

Soil compaction represents a critical threat to agricultural sustainability, reducing crop yields and degrading soil ecosystem functions. Traditional mechanical subsoiling provides temporary relief but often disrupts soil biological activity and requires repeated applications. This study evaluated biological subsoiling as a sustainable alternative, using deep-rooted cover crops and beneficial microorganisms to alleviate compaction and restore soil structure. A three-year field experiment was conducted across four sites with varying compaction levels (1.4-2.1 Mg m⁻³ bulk density) using randomized complete block design. Treatments included: control (no intervention), mechanical subsoiling, biological subsoiling with Raphanus sativus (tillage radish), biological subsoiling with Medicago sativa (alfalfa), combined biological approach (R. sativus + mycorrhizal inoculation), and integrated management (biological + reduced mechanical intervention). Soil physical properties, biological activity, and crop performance were monitored throughout the study period. Results demonstrated that biological subsoiling with tillage radish achieved significant bulk density reduction (15.3% decrease from 1.87 to 1.58 Mg m⁻³) and increased macro-porosity (42% improvement) compared to control treatments. The combined biological approach showed superior long-term effectiveness, maintaining lower penetration resistance (1.2 MPa vs 2.8 MPa in control) three years post-treatment. Mycorrhizal inoculation enhanced root penetration depth by 28% and improved soil aggregation (mean weight diameter increased from 1.2 to 2.1 mm). Cash crop yields following biological subsoiling increased by 18-24% compared to compacted controls, with corn yields reaching 11.2 t ha⁻¹ versus 8.9 t ha⁻¹ in untreated plots. Soil microbial biomass carbon increased by 35% in biologically treated soils, indicating enhanced biological activity and organic matter cycling. Economic analysis revealed biological subsoiling cost-effectiveness, with benefit-cost ratios of 2.3-3.1 compared to 1.8 for mechanical subsoiling. The study concludes that biological subsoiling offers a sustainable, cost-effective approach to soil compaction recovery, providing lasting improvements in soil structure and agricultural productivity.