Optimization of Manure Levels and Application Depth via Subsoil Technology Machine for Enhancing Soil Physicochemical Properties Under Saline Conditions

In a 2025 field experiment at Bajiazi Village, Dongsanjiazi Township, Qian Gorlos Mongol Autonomous County, Songyuan City Jilin Province China the effects of animal manure on soil salinity (EC) and pH and bulk density were studied using silty loam soil. The experiment tested manure quantities (0, 20, 40 tons/ha), application depths (10, 20, 30 cm), and techniques (mixing vs. subsurface laying). A split-split plot design in a randomized complete block design (RCBD) was used, with corn (Zea mays L.) planted immediately after manure application. Soil samples were collected post-harvest to measure EC, pH and bulk density. Results showed that higher manure levels (40 tons/ha) significantly reduced EC (4.63 dS m⁻¹) and pH (7.97) compared to the control (6.81 dS m⁻¹ and 8.12, respectively). Increasing application depth from 10 to 30 cm reduced EC (6.13 to 5.48 dS m⁻¹) but had no significant effect on pH. Mixing manure with soil yielded lower EC (5.42 dS m⁻¹) than subsurface laying (6.13 dS m⁻¹), though pH remained unaffected by application method. The lowest EC (3.99 dS m⁻¹) was observed with 40 tons/ha mixed at 30 cm depth, while the lowest pH (7.95) occurred at 30 cm depth. Soil bulk density decreased from 1.23 to 1.20 Mg m⁻³ as application depth increased from 10 to 30 cm. Mixing manure with soil further reduced bulk density, with the best results at 40 tons/ha mixed to 30 cm depth. The study highlights that manure application depth and method significantly influence soil salinity and bulk density, offering strategies to mitigate salinity stress and improve soil health.