Effect of Mechanical disassembly compressed subsoil on the macronutrient content (N,P,K) of soybean plants

Abstract

This study was conducted in Latakia at the Dabba Research Station on clay loam soil. The experiment was designed as a randomized complete block design with six treatments and three replicates per treatment. The soil was exposed to three levels of pressure
 (0, 187.5, and 307.4 kPa). After compaction, the soil was tilled uniformly to a depth of 20 cm, while the subsurface layers remained compacted at different levels. Mechanical disassembly of the compacted subsurface soil was performed at the shrinkage limit (SL), in addition to a control treatment without disassembly.

The study showed a significant increase in bulk density by increasing the pressure and the highest value was at 307.4 Kpa. Mechanical disassembly significantly reduced bulk density by 0.11 and 0.17 g.cm⁻³ at 187.5 and 307.4 kPa, respectively. That confirm the important role of disassembly by moving the layers of compressed subsurface soil. Disassembly also significantly increased macro porosity by 4.17% and 6.44% at 187.5 and 307.4 kPa, respectively, compared with the non-disassembled treatments. Similarly, pores larger than 10 µm increased by 3.78% and 6.70% at the respective pressure levels. Soil compaction reduced the proportion of pores associated with available water capacity by 3.69%, whereas mechanical disassembly increased these pores by 2.91% at 307.4 kPa. In addition, compaction led to a decrease in saturated hydraulic conductivity with increasing pressure, from 1.17 m.day⁻¹ at 187.5 kPa to 0.091 m.day⁻¹ at 307.4 kPa. Mechanical disassembly significantly improved hydraulic conductivity, with increases of 0.69 and
 1.43 m day⁻¹ at 187.5 and 307.4 kPa, respectively.