In this study, the preparation of apricot kernel shell biochar by a hydrothermal method and its adsorption mechanism for atrazine was studied by scanning electron microscopy (SEM) and infrared spectrum (FTIR) analytical techniques. The results show that the biochar prepared from the apricot kernel shell has an evenly distributed, nonaggregated carbon microsphere structure and contains a large number of oxygen-containing groups. The higher the preparation temperature is, the more functional groups exist and the better the potential adsorption performance is. The adsorption kinetics of atrazine on apricot kernel shell biochar were fitted with a quasi-second-order kinetic equation (R² ≥ 0.995, p < 0.05). The isothermal adsorption data were in accordance with the Freundlich model (R² ≥ 0.911, p < 0.05). The adsorption of atrazine on apricot kernel shell biochar includes two processes: surface adsorption and diffusion. The adsorption capacity of apricot kernel shell biochar for atrazine increases with increasing preparation temperature and decreases with increasing pH and Ca²⁺ concentration. The adsorption mechanism includes hydrogen bonding and hydrophobic interactions. Therefore, biochar prepared from apricot shells, an agricultural waste, exhibits good adsorption performance for atrazine and has a good application prospect in addressing agricultural non-point source pollution, especially in pesticide residue pollution control.

Straw return is a common cultivation to improve soil fertility and realize sustainable agricultural development. However, the effect of returning interval on the corn straw humification process in northeast China is little known. In this study, a four-year field trial was conducted to investigate the characteristics of soil carbon sequestration under the annual deep straw return (T1), the biennial deep straw return (T2), and the non-straw return (T3) in Jilin Province, China. In order to precisely evaluate the soil organic carbon density (SOCD), each soil horizon was divided differently according to the actual situation, rather than a fixed thickness. The results show that both the annual and the biennial deep straw return had a significantly positive influence on the content of soil organic carbon (SOC), humic acid, fulvic acid, and humin in the plough pan (straw-applied horizon), compared to the no-straw return. SOC of the cambic horizon and the C horizon in annual straw return was 28.78%, 47.44% higher than the biennial straw return, but it was 27.58% lower in the plough pan. The SOCD in the plough pan in the biennial straw return was higher than the annual straw return, but their difference in the entire soil profile was not significant. However, the conversion rate of straw carbon to SOC was 18.42% in the annual straw return and 21.05% in the biennial straw return. The straw return amount was not a key factor affecting the SOC sequestration in the cold area; it was restricted by the comprehensive effects of the cold weather, the intensity of soil disturbance, C/V and the initial SOC content. In conclusion, the biennial deep straw return was a better management tool, as it generally had an identical quality and quantity of soil organic carbon and a higher straw conversion rate relative to the annual deep straw return.

Simultaneous achievement of high yield and excellent quality in rice is essential for food security and human health. The coordinated application of nitrogen (N) and sulfur (S) can effectively increase the grain yield (GY) and grain protein concentration (GPC) of rice. A two-season field experiment was conducted to investigate the synergistic effects of combined N and S application on the GY and GPC of rice. This study employed four N rates (0, 120, 180, and 240 kg ha⁻¹, designated as N0, N1, N2, and N3, respectively) and four S rates (0, 30, 45, and 60 kg ha⁻¹, designated as S0, S1, S2, and S3, respectively) using two rice cultivars: Jiujiuxiang (JJX) and Jiuxiangyou (JXY). The experimental results demonstrate that N and S exert significant effects on the GY and GPC of rice, with notable interactive effects between these two nutrient elements. The synergistic fertilization of N and S enhanced the GY by improving rice plant photosynthesis and dry matter accumulation while increasing GPC through elevated cysteine concentration in grains. Compared to the unfertilized treatment, the GY of the JJX cultivar showed increases of 68.3–143.2% (Season I) and 59.4–133.4% (Season II) under combined N and S applications, while the GY of the JXY cultivar increased by 53.2–144.1% (Season I) and 66.0–192.9% (Season II). Similarly, the GPC of the JJX cultivar showed increases of 7.5–43.4% (Season I) and 5.7–43.9% (Season II) under combined N and S applications, while the GPC of the JXY cultivar increased by 13.1–66.7% (Season I) and 13.3–61.0% (Season II). Overall, whether on the JJX or JXY cultivars, the application of 180 kg ha⁻¹ of N combined with 45 kg ha⁻¹ of S (i.e., the N2S2 treatment) synergistically enhances GY and GPC in rice. The synergistic fertilization of N and S synergistically enhances both rice yield and nutritional quality by regulating plant growth dynamics, which meet the requirements for healthy and sustainable development in rice production systems.