Zhe Xu

The shortage of water resources, the serious harm of soil salinization and the large loss of nitrogen caused by excessive application of nitrogen fertilizer are the main factors restricting the sustainable development of agriculture in irrigation areas. Based on this factor, saline irrigation area needs to find a soil improvement method that can keep water and restrain salt, increase fertilizer and increase production under the condition of reducing the amount of nitrogen fertilizer application, which is of great practical significance for promoting the development of saline soil improvement technology and high and stable grain yield. In this paper, the physical and chemical properties, temporal and spatial dynamic distribution of water, fertilizer and salt content, sunflower yield and water and nitrogen use efficiency of saline soil in Hetao irrigation area were studied by means of field experiment and numerical analysis, and the improvement mechanism and water, fertilizer and salt regulation effects of different soil amendments on saline soil in irrigation area were revealed. The results showed that the biochar treatment group significantly reduced soil pH and conductivity, effectively inhibited salt accumulation in the soil, and increased soil organic matter content and nutrient content such as total nitrogen, available phosphorus and available potassium. The porous structure of biochar enhances the soil’s water retention capacity and reduces soil water evaporation. The combination of carbon and nitrogen application treatment not only reduced nitrogen loss but also prevented salt from moving to the soil surface, further optimizing the soil environment. In terms of crop growth and yield, the group treated with carbon nitrogen combined application showed the best growth performance of sunflowers, with rapid plant height growth, lush leaves, and the highest leaf area index. The overall growth momentum was stronger than other treatment groups.

Biochar is a widely recognized soil amendment used to improve soil physicochemical properties and crop productivity. However, its compositive effects on soil water, fertilizer, and carbon in cropping systems are not extensively understood. A two-year field study was conducted to investigate the influence of integrating maize-residue-derived biochar on evapotranspiration, water and fertilizer utilization efficiency, soil organic carbon (SOC) content, and soil carbon emissions in maize farming, employing drip irrigation in conjunction with film mulching. The treatments included the following three biochar amendments: 15 (B15); 30 (B30); and 45 (B45) t ha⁻¹. Biochar was exclusively incorporated prior to sowing during the initial year of the experiment, and no biochar was used as a control (CK). After two years, the biochar amendments, especially B30, improved crop water productivity and the partial factor productivities of nitrogen, phosphorus, and potassium fertilizer. Relative to CK, the biochar amendments significantly reduced soil CO₂ and CH₄ emissions during crop growth by 17.6–40.6% and −1.21–268.4%, respectively, averaged across two years. The best treatment effect was achieved by adding 15 t ha⁻¹ of biochar. The biochar needed replenishing in the third year for B30 and in the fourth year for B45 to increase the SOC content by 20 g kg⁻¹. An application rate of 22 metric tons per hectare of biochar is proposed to optimize water and fertilizer utilization efficiency, alongside augmenting the soil organic matter content, within maize farming under drip irrigation and mulching practices on sandy loam soil. However, the biochar must be added at 20 t ha⁻¹ in the third year to counterbalance soil carbon losses and improve SOC.