Effects of Organic Base Fertilizer and Inorganic Topdressing on Alfalfa Productivity and the Soil Bacterial Community in Saline Soil of the Huanghe River Delta in China

Alfalfa (Medicago sativa L.) is an important perennial legume forage that is cultivated in saline soil worldwide. This study aimed to clarify the effects of organic base fertilizer and inorganic topdressing on the productivity of alfalfa growing in saline soil. A three-year field study was conducted in which alfalfa was grown in the saline soil of the Huanghe River Delta with a control (no fertilizer) and three treatments: organic base fertilizer (Base), topdressing with urea fertilizer (Top), and combined base and topdressing fertilizers (BT). The productivity in the BT and Base treatments was 13.21 and 13.82 t center dot hm(-2) in 3 years, significantly higher than that in the Top treatment and the control. The increased productivity in the BT and Base treatments were because organic matter promoted root growth of alfalfa seedlings in saline soil. The diversity of the soil bacterial community was not affected by the BT treatment, but the Base treatment increased the abundance of Acidobacteria, and the Top treatment increased the abundance of Gemmatimonadetes. Soil bacteria play an important role in improving the productivity of alfalfa growing in saline soil, and the mechanism by which soil microbes increase yield needs to be further studied.