Effect of Intensive Greenhouse Vegetable Cultivation on Selenium Availability in Soil

Soil properties dramatically change after long-term greenhouse vegetable cultivation, which further affects soil selenium (Se) nutritional status and plant Se uptake. An evaluation of Se availability after long-term greenhouse vegetable cultivation (GVC) can help in better understanding its influential factors under GVC conditions and will also facilitate further regulation of soil Se nutrition in GVC systems. Two typical GVC bases were chosen: one with clayey and acidic soil in Nanjing, southern China, and the other with sandy alkaline soil in Shouguang, northern China. Twenty-seven surface soil samples at the Nanjing base and 61 surface soil samples at the Shouguang base were collected according to cultivation duration and cultivation intensity. Soil properties including soil available Se (PO^3-₄-Se) and total Se (T-Se) were analyzed. The results showed that soil PO^3-₄-Se was significantly and negatively correlated with soil Olsen-P, available K (A-K), and electrical conductivity (EC) at the Nanjing base. At the Shouguang base, however, no significant correlation was found between soil PO^3-₄-Se and Olsen-P and EC, and soil PO^3-₄-Se increased with increasing soil organic matter (OM). Intensively utilized greenhouse vegetable cultivation caused significant changes in soil properties and further affected soil Se availability. Due to different management practices, the dominant factors affecting Se availability varied between the two GVC bases. At the Nanjing base, the dominant influential factor on soil Se availability was soil nutritional status, especially Olsen-P and A-K status. At the Shouguang base, where organic fertilizers were applied at high rates, soil OM was the dominant influential factor.