The summer maize-winter barley (or wheat) rotation system is a conventional farming method in coastal areas of east China. However, researchers have paid little attention to the increasing soil degradation after successive crop rotation in coastal saline agriculture. In the current study, a two-year field experiment was conducted to investigate the changes in soil physio-chemical properties and crop grain yields under the maize-barley rotation system. Wheat straw derived biochar (BC) was applied to topsoil (0~20 cm) at four different rates (0, 7.5, 15 and 30 Mg ha⁻¹) before summer maize cultivation, and no biochar was added in the cultivation of the winter barley. Bulk density (BD), water holding capacity (WHC), water stable aggregate (WSA), soil electrical conductivity (EC), pH (1:5 water w/v) and soil organic carbon (SOC), at the harvesting time of maize and barley, were analyzed. The application of biochar increased WHC and macro-aggregate (>2 mm) content after barley harvest. Soil EC was mainly affected by the rain during maize cultivation and increased only slightly under BC treatments. However, no difference in EC was found among all treatments after barley harvest. The application of BC at 30 Mg ha⁻¹ increased the maize yield by 66% but produced no difference in the barley yield. We concluded that biochar could be an effective option to mitigate soil degradation and improve crop productivity in coastal saline agriculture.

A field experiment was conducted to investigate the effects of biochar (BC), fulvic acid (FA) and Bacillus subtilis (BS) on soil properties and crop growth in the coastal salt-affected soil. Four levels of BC (0, 7.5, 15, 30 t ha⁻¹), two levels of FA (0, 1.5 t ha⁻¹) and BS suspension (0, 108 CFU mL⁻¹) were designed during the maize cultivation. The results showed that 30 t ha⁻¹ BC treatment was the most beneficial for improving the soil qualities. The grain yields in treatments containing FA and BS were lower than that in the BC treatments, and they were lower than that in the CK treatment. The treatment of 15 t ha⁻¹ BC + BS obtained the highest grain yield, which was 1.75 times more than CK. An antagonism effect of the combination of FA and BS induced a grain yield decrease, and a higher content application of BC alleviated the negative effects.

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.

Irrigation is the primary agricultural utilization of water resources worldwide, and it produces 36% of the food. The quality of irrigation water influences crop growth and food safety. The coastal river delta region supplies huge area lands for developing agriculture, and the irrigation in this area is composed of many resources for its special location. This study investigated the agricultural water with different resources and evaluated its quality in the Yellow River Delta. The water samples included irrigation water, underground water, and drainage water. The sampling points were designed in the typical areas of Kenli county and Guangrao county in Dongying city, which is the core area of the Yellow River Delta. Through testing the ions composition and the parameters of electrical conductivity (EC), pH, and so on, six evaluation methods were conducted to assess the water quality. The results suggested that the Yellow River water has good quality for irrigation or unconventional water utilization. The high concentration of Na⁺ and Cl⁻ was the primary problem of the water resource. The rainfall was also another water resource supplement in this region. Therefore, developing saline water irrigation incorporated with salt-tolerant crop cultivation is a rational measure for improving coastal agriculture in the Yellow River Delta.

The Hetao irrigation region is located in Inner Mongolia, China, within a dry and semi-dry region. This region suffers from poor agricultural productivity and environmental damage due to the presence of saline soil. To explore the growth of salty lands using a more environmentally friendly method, this research employed three eco-conscious amendments to improve the soil. These include flue gas desulfurization gypsum (S), humic acid (H), and biochar (C). During a two-year study, the amendments were utilized to enhance the soil quality for planting sunflowers. Humic acid was used prior to every seedling season, whereas the remaining two substances were only used once. These additions increased the soil’s water-holding capacity, reduced soil salinity during sunflower growth, and improved the macroaggregate proportion. The most effective treatment for decreasing the soil’s salt content after the seedling stage was the application of humic acid (0.6 t ha⁻¹). Biochar (15 t ha⁻¹) decreased the soil’s bulk density (from 1.49 to 1.34 g cm⁻³) and mostly increased the sunflower seed yield up to 3133−3964 kg ha⁻¹. Humic acid addition significantly increased the aggregate (>0.25 mm) content up to 27.88% after the experiment, but it led to a lower seed yield (2607−3686 kg ha⁻¹). In 2019, the temperature was lower compared to 2018, which may have led to a reduction in the yield. However, these three amendments could potentially increase yields by more than conventional methods. These three environmentally friendly amendments are useful for improving saline soil and increasing yields. More studies are required to understand their impacts on larger areas and over extended periods.