The potential use of lignite-based wastes (LBW) derived from humic acid extraction as an organic amendment to improve soil properties and barley growth

The extraction of humic acids from lignite has become a promising research field, owing to their fertilization potential. However, the extraction process is accompanied by the formation of lignite-based wastes (LBW). In this study, we investigated the potential of LBW, as an organic amendment, to improve the quality and productivity of degraded soils. Accordingly, a study was assessed in a pot experiment using saline sandy soil collected from an arid region. LBW were applied at 0 (control soil—CS), 4 (LBW4), 6 (LBW6), and 8 g kg −1 of soil (LBW8). Soil quality indicators (salinity, nutrient status, and microbial biomass) and barley growth parameters (yield, chlorophyll, stomatal conductance, proline, and sugar content) were evaluated. After 1 year of LBW addition, soil organic matter and nutrient status have increased in a dose-dependent manner, showing higher contents in the soils amended with the highest rate (8 g kg −1 ). Subsequently, soil carbon and nitrogen microbial biomass were enhanced regardless of the increase in soil salinity (EC >4 dS m −1 ). This fact was attributed to the unavailability of sodium for plant uptake. Barley growth has also shown higher straw and grain yield in LBW8 (2.84 and 2.37 t ha −1 ) compared to control soils (0.41 and 0.47 t ha −1 ). The high proline and stomatal conductance in LBW8 are proof of barley resistance to salinity stress. Therefore, we recommend the application of LBW at 8 g kg −1 to improve the quality and barley yield in saline soils.