Soil conditioners strategies for enhancing selenium bioavailability, and maize biomass in selenium-rich dryland soils

Low selenium bioavailability in selenium-rich soils represents a key constraint limiting selenium biofortification in agriculture. This study evaluated soil conditioning strategies to enhance selenium bioavailability, providing a theoretical foundation for efficient utilization of selenium-enriched soil resources. A pot experiment tested four soil conditioners: organic fertilizer, potassium humate, lime, and biochar, across three consecutive maize plantings. Soil conditioners effectively modified soil physicochemical properties: lime significantly increased pH and available phosphorus, while organic fertilizer increased available sulfur. These amendments markedly affected soluble and exchangeable selenium fractions. All treatments progressively increased the proportion of soluble selenium, with lime and biochar showing the most substantial gains in batches two and three (0.59%, 0.23%, 0.67%, and 0.30%, respectively). Organic fertilizer, lime, and biochar consistently elevated root selenium concentrations across all three batches by 7.79-11.01%, 33.31-135.41%, and 28.84-40.81%, respectively. Potassium humate increased root selenium by 9.04-26.42% in batches two and three. Notably, only lime consistently enhanced shoot selenium by 40.13-87.38% across all batches, while biochar increased shoot selenium by 5.60% in batch three. Plant selenium translocation analysis revealed that only lime treatment in batch three significantly increased the selenium transfer coefficient. Correlation analysis demonstrated a highly significant positive relationship between shoot selenium content and soil pH, whereas root selenium showed no significant correlation with soluble or exchangeable selenium fractions. In selenium-rich dryland soils, conditioner application increases soil pH, thereby enhancing selenium availability and root absorption. Lime proved most effective for increasing crop selenium content, while biochar also substantially improved soil selenium availability.