Effects of Compaction Stress, Biochar Application Rate, Irrigation Water Quality, and Their Interactions on Selected Physical Properties of Gypsiferous Soil

• Ahmed Abdullah Fattah 1, Rowaida Khalid Sabber 2

  Author

This study was conducted in the laboratories of the Department of Soil Sciences and Water Resources, College of Agriculture, Tikrit University during the growing season 2024 to investigate the effect of compaction stress represented by bulk densities (1.2, 1.3, 1.4, 1.5, 1.6, and 1.7 Mg m-3), biochar application rates (0, 0.5, and 1% w/w), irrigation water quality (River water (EC = 0.680 dS m-1), well water (EC = 2.740 dS m-1), and drainage water (EC = 6.320 dS m-1) and their interaction on selected physical properties of a gypsiferous soil. The results showed that increasing bulk density significantly affected all measured soil physical properties. Total porosity decreased to 0.343, and saturated hydraulic conductivity declined to 0.04 cm min⁻¹, whereas shear strength increased to 2.28 kg cm⁻² and soil penetration resistance increased to 52.55 kPa cm⁻². Soil water content at field capacity, permanent wilting point and available water also decreased with increasing compaction. When the application rate of biochar was increased to 1%, the physical properties of the soil were significantly improved. The mean total porosity was increased to 0.458, the saturated hydraulic conductivity was 0.33cm min-1 and the soil penetration resistance was decreased to 31.28kPa cm-2. Moreover, biochar improved the water holding capacity of the soil and increased the moisture content of the soil. Also, the quality of irrigation water had a significant effect on all studied properties.

Significant two-way and three-way interactions were observed among compaction stress, biochar application, and irrigation water quality. The best overall soil physical properties were obtained with 1% biochar application, River water irrigation, and the lowest bulk density, whereas the poorest results were recorded under no biochar application, drainage water irrigation, and the highest bulk density.

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