The use of shallow saline groundwater may alleviate the shortage of freshwater resources in the Low Plain around the Bohai Sea in China. The soil salt levels and the responses of cotton seed emergence, growth, and yield to continuous irrigation with saline water were investigated from 2012 to 2014. Four salinity levels were tested: 1.3 (S1, control), 5.4 (S2), 8.8 (S3), and $12.4\mathrm{dS}/\mathrm{m}$ (S4). Irrigation was initiated when the soil moisture content in the 0–60 cm layer was below 60% of field capacity. Soil salinity within the cotton root zone increased with an increase in irrigation water salinity, but the effect was not cumulative over the experimental period to because of the leaching effect associated with summer rainfall. The cotton emergence percentage decreased as the irrigation water salinity increased. Compared with S1, the average seedling establishment rates over the three seasons examined decreased by 2.1, 5.1, and 20.2% with S2, S3, and S4, respectively. Large variations in seedling establishment rates were observed between the seasons, and this variability increased with increase in irrigation water salinity. Maximum plant height, leaf area index, and number of fruiting shoots decreased by S3 and S4, and some of these differences were statistically significant ($p<0.05$ ). Cotton growth was not negatively affected until irrigation water salinity reached $8.8\mathrm{dS}/\mathrm{m}$ . Cotton yields were close to that produced by freshwater irrigation (S1) when the irrigation water salinity was below $8.8\mathrm{dS}/\mathrm{m}$ , but it significantly ($p<0.05$ ) decreased by 7.3% in 2012, 11.1% in 2013, and 8.6% in 2014 when the irrigation water salinity was $12.4\mathrm{dS}/\mathrm{m}$ , mainly due to the elevated soil osmotic potential. These results show that cotton can be irrigated successfully with water of $\le 8.8\mathrm{dS}/\mathrm{m}$ . Furthermore, the mitigation of salt accumulation by heavy rainfall indicates that long-term use of saline water irrigation is feasible in this region.

Saline water irrigation has been widely used for crop production where agriculture is short of freshwater. However, information about the response of soil respiration to saline water irrigation is limited. To identify the effect of saline water irrigation on soil respiration, the experiment based on long-term saline water irrigation cotton fields (since 2006) was conducted in the Heilonggang area in 2021. Five salinity levels in irrigation water were tested (3.4 [S1], 7.1 [S2], 10.6 [S3], 14.1 [S4], and 17.7 dS m⁻¹ [S5]), and deep ground water (1.3 dS m⁻¹) was used as the control (CK). After 15 years of saline water irrigation, we monitored soil physicochemical properties and soil respiration. In addition, we developed a structural equation model of the relationship between them. The results demonstrated that saline water irrigation significantly reduced soil water-stable aggregate content and porosity by 4.42–45.33% and 6.52–14.10%, respectively, and attenuated soil cellulase, α-glucosidase, and alkaline phosphatase activity. Soil respiration under saline water irrigation was significantly reduced by 5.28–33.08%. Moreover, saline water irrigation with salinity below 10.6 dS m⁻¹ had no significant effect on cotton yield. Moreover, soil salinity (62%), water-stable aggregate content (46%), and soil porosity (25%) had significant effects on soil respiration, and soil porosity had a significant positive effect on soil alkaline phosphatase activity according to the structural equation model. Overall, saline irrigation with salinity below 10.6 dS m⁻¹ can alleviate water shortages and reduce soil carbon emissions without affecting cotton yield in the study area.

Winter wheat and cotton are the main crops grown on the North China Plain (NCP). Cotton is often transplanted after the winter wheat harvest to solve the competition for cultivated land between winter wheat and cotton, and to ensure that both crops can be harvested on the NCP. However, the root system of transplanted cotton is distorted due to the restrictions of the seedling aperture disk before transplanting. Therefore, the investigation of the deformed root distribution and water uptake in transplanted cotton is essential for simulating soil water movement under different irrigation methods. Thus, a field experiment and a simulation study were conducted during 2013–2015 to explore the deformed roots of transplanted cotton and soil water movement using border irrigation (BI) and surface drip irrigation (SDI). The results showed that SDI was conducive to root growth in the shallow root zone (0–30 cm), and that BI was conducive to root growth in the deeper root zone (below 30 cm). SDI is well suited for producing the optimal soil water distribution pattern for the deformed root system of transplanted cotton, and the root system was more developed under SDI than under BI. Comparisons between experimental data and model simulations showed that the HYDRUS-2D model described the soil water content (SWC) under different irrigation methods well, with root mean square errors (RMSEs) of 0.023 and 0.029 cm³ cm⁻³ and model efficiencies (EFs) of 0.68 and 0.59 for BI and SDI, respectively. Our findings will be very useful for designing an optimal irrigation plan for BI and SDI in transplanted cotton fields, and for promoting the wider use of this planting pattern for cotton transplantation.

In order to explore the effects of subsoiling tillage measures on the construction of soil cultivated horizon and the yield and water use efficiency of winter wheat in the North China Plain, three tillage methods, including no tillage (PZ), rotary tillage (PR), and subsoiling (PS), combined with straw returning measures were implemented in the winter wheat season in Xinxiang, Henan Province from 2016 to 2018. The effects of tillage measures on the improvement of cultivated land quality and the water saving and yield increase of winter wheat were investigated. The results showed that compared with no-tillage treatment, subsoiling significantly reduced soil bulk density by 8.88% and increased soil porosity by 13.04% in 20–40 cm soil layer; significantly reduced soil compaction by 56.96% in 0–40 cm soil layer; subsoiling combined with straw returning significantly increased soil organic carbon content in plough layer of winter wheat, whereas rotary tillage decreased soil organic carbon content. Subsoiling is more conducive to soil moisture movement to the deep layer after irrigation or rainfall, and the water consumption of subsoiling is the largest in the whole growth period of winter wheat. Subsoiling could better coordinate the relationship between water consumption and yield, which increased yield by 34.48–38.10% and water use efficiency by 19.57–21.96% compared with no-tillage treatment, respectively. Therefore, subsoiling before sowing combined with straw returning was beneficial to the reasonable construction of soil cultivated horizon, and significantly improved the yield and water use efficiency of winter wheat under the climatic conditions in the North China Plain.