Impact of Pistachio Residues on Compactibility, and Permeability for Water and Air of Two Aridic Soils from Southeast of Iran

摘要

So far no information is available on impacts of pistachio residues on physical and mechanical properties of aridic soils. The objective of this study was to assess the influence of pistachio residue amendments on soil compactibility, saturated hydraulic conductivity (K_s), and air permeability (k_a) of two soils in Rafsanjan, Iran. Tests were set up as factorial experiments with two factors including: pistachio residue at four levels (0, 3, 6, and 9% dry basis) and two soil textures (silty clay loam and sand). The residue-treated soils were compacted using a modified Proctor test (5 blows per layer) to determine maximum dry bulk density (BD_max) and critical water content (θ_critical). Soil samples with similar BD from the dry and wet limbs of the compaction curve were used to investigate the effect of dry and wet compactions on soil pore connectivity and continuity as quantified by K_s and k_a. Residue applications decreased BD_max, but increased θ_critical compared to the control; the effects were greater for larger residue rates. The impacts were more obvious for silty clay loam soil. Both K_s and k_a of sandy soil were significantly different between the two samples with similar BD. However, such differences were not significant for the silty clay loam soil, indicating that effectiveness of pistachio residue amendments for improving soil structure depends on the soil texture. Moreover, deleterious effects of compaction on soil pore functions might not be described by bulk properties (e.g., BD) but could adequately be accounted for by intensity properties like K_s and k_a.