Effects of wheat straw biochar and irrigation water on hydraulic and chemical properties of a sandy loam soil after faba bean cultivation

Nowadays, applying soil amendments is one of the most important ways to cope with water shortages and improve soil physical properties. In this regard, a greenhouse experiment was conducted to study the effect of different levels of irrigation water and wheat straw biochar on physical and chemical properties of a sandy loam soil, after harvesting faba bean. The experiment was performed with 5 biochar levels (0, 8, 16, 24 and 32 g kg-1) and 3 irrigation levels (100%, 75% and 50% of crop water requirement) using completely randomized design in three replications. Lowering the irrigation level to 50% did not influence soil physical and chemical properties except for saturated hydraulic conductivity (Ks), as Ks was significantly declined under 50% irrigation water levels as compared with full irrigation. Soil bulk density and particle density of 32 g kg-1 biochar treatment (B32) was reduced by 47% and 27%, respectively, while soil porosity and Ks increased as compared to no biochar application (B0). Under B32 treatment, the saturated electrical conductivity increased 5.6 times, and the cation exchange capacity and sodium adsorption ratio (SAR) was increased by 40.3% and 53.6% in comparison with B0, respectively. This made the soil saline (ECe>4 dS/m) but not sodic (SAR-1)1/2). It can be concluded that although, biochar level of 24 g kg-1 did not considerably increase soil water holding capacity compared to B0, it significantly improved the other soil physical and chemical properties, therefore, it can be used as soil amendment.