The Carbon Mineralization in Different Soil Textures Affected by Wheat Straw and Soil Salinity

To study the effect of different salinities (0, 10, 30 and 60 dS/m) and wheat straw levels (0 and 2% by weight with C/N = 89.5) on carbon mineralization during 180 days (1, 2, 3, 5, 8, 11, 15, 19, 24, 29, 36, 46, 60, 75, 90, 120, and 180), this study was conducted at the Soil and Water Research Institute, Karaj, Iran in 2022. For this purpose, three soils with low salinity (0.84-1.1 dS/m) and low organic carbon (0.22-0.98%) with different textural classes (Loamy, Clay Loam, and Silty Loam) were selected from Iranian agricultural soils. The results showed that the amount of cumulative mineralized carbon in loamy soil ranged from 93 to 2379 mg/kg, in clay loam soil ranged from 172 to 2277 mg/kg, and in the silty loam ranged from 122 to 3158 mg/kg. Furthermore, in the studied soils, the highest amount of cumulative mineralized carbon was measured at natural soil salinity levels (i.e., low salinity 0.84-1.1 dS/m) and the lowest amount of cumulative mineralized carbon was measured in high salinity treatments. In all three soils, the amount of mineralized carbon increased rapidly in the first week and then gradually decreased, which is due to the availability of easily degradable parts of organic matter against a wide range of microorganisms in the early stages of decomposition. In general, it is concluded that the presence of wheat straw in the soil may decrease the negative effects of high salt concentrations on carbon mineralization and reduce losses.