Salt-affected soils is an important soil resource. Understanding fertilizer and salinity interaction are of great economic importance for improving crop yield and fertilizer use efficiency. A pot experiment was carried out to study the application of nitrogen (N) for ameliorating salt stress in wheat grown in the coastal saline soil of the Yellow River delta. Several controlling levels of salinity and nitrogen (0.7, 1.7, 2.7 g/kg, and 135, 270, and 405 kg/ha) were designed in a pot experiment in a stable water content state to investigate the N and salt interaction on soil properties and winter wheat growth characteristics. The results showed that the dry weight of winter wheat was promoted by salinity in the early growth stage (20 days), then it was gradually inhibited by nitrogen fertilizer. When winter wheat was grown by 54 days, the N and salinity had significant effects on the biomass of winter wheat. The nitrogen content of wheat shoot and root was mainly affected by N addition usage, and the largest value was obtained in 270 kg/ha N dosage treatments. The higher the salt content existed in the soil, the lower the growth rate shown in wheat cultivation. Under saline conditions, the N fertilizer application amount should be controlled to no more than 270 kg/ha, so that it could greatly promote wheat growth. Reasonable fertilizer usage could significantly contribute to crop yield and food quality of the saline agriculture in the Yellow River delta.

Coastal salt-affected soils account for a large area all around the world. Soil salinity and pH are two important parameters affecting soil quality. Investigating the correlation of electrical conductivity (EC) and pH at different soil depths in saline soil was useful for quickly assessing the saline–alkaline characteristics. During the natural desalination process in the field area of reclaimed lands, the phenomena of pH increase and nitrogen accumulation may occur. A field sampling experiment was conducted in slightly saline soil affected by natural desalination and newly reclaimed heavily saline soil. A series of soil–water ratio extracts consisting of 1:2.5, 1:5, 1:10, 1:20, and 1:40 was designed to measure the EC and pH for simulating the saline–alkaline characteristics during the soil desalination process. Meanwhile, for reasonable utilization of the naturally ameliorated slightly saline soil which consists of a high content of nitrogen, a plastic mulching (PM) accompanied with nitrogen (N) fertilizer addition experiment in maize cultivation plots was designed. Results showed that a significant correlation of EC and/or pH existed in all ratios of soil extracts, and the slightly saline soil had a higher nitrogen content (1.06 g kg−1). The EC was negatively correlated with pH at a depth of 0~100 cm in the coastal saline soil, which indicated the increase of pH value and alkalization during its natural desalination. Furthermore, PM treatments showed no significant difference with N treatments in soil bulk density and soil water content in the slightly saline soil. The PM and N treatments obtained similar grain yield, which was between 6.2 and 6.5 t ha−1. The soil salinity decreased in all treatments and the harvest index was largest in PM treated plots. Our study was beneficial for rapidly monitoring saline–alkaline characteristics and sustainable utilization of coastal saline soil resources. In addition, we should focus far more on pH improvement during the desalination process and rational utilization of chemical fertilizer for obtaining sustainable benefits in the coastal saline soil.