Straw returning inhibits tillering at the early stage of rice growth and thus affects grain yield. Sulfur-coated urea (SCU) has been expected to increase nitrogen use efficiency (NUE) and yield, save labor input, and reduce environmental pollution in crop production. Nevertheless, the sulfur coatings of SCU are easy to break and then shorten the nutrient release cycle. Whether there was a complementary effect between straw returning and SCU in NUE and grain yield had remained elusive. To investigate the effects of straw returning combined with the application of SCU on NUE and rice yield, a two-year field experiment was conducted from 2022 to 2023 with three treatments (straw returning combined with conventional urea (SRU), no straw returning combined with SCU (NRS), straw returning combined with SCU (SRS)). We found that straw returning combined with the application of SCU increased rice yield and NUE significantly. Compared with SRU and NRS, SRS treatments significantly increased grain yield by 14.61–16.22%, and 4.14–7.35%, respectively. Higher effective panicle numbers per m² and grain numbers per panicle were recorded in NRS and SRS treatments than SRU. SRS treatment increased nitrogen recovery efficiency by 79.53% and 22.97%, nitrogen agronomic efficiency by 18.68% and 17.37%, and nitrogen partial factor productivity by 10.51% and 9.81% compared with SRU and NRS treatment, respectively. The enhanced NUE in SRS was driven by higher leaf area index, SPAD value, net photosynthetic rate, carbon metabolic enzyme (RuBP and SPS) activity, nitrogen metabolic enzyme (NR, GS, and GOGAT) activity, sucrose and nitrogen content in leaves, and nitrogen accumulation in plant during grain filling. Moreover, the improved yield in SRS was closely related to superior NUE. In conclusion, straw returning combined with application of SCU boosted grain yield and NUE via enhanced carbon–nitrogen metabolism during the late growth period in rice.

Under the one-season-a-year cropping pattern in Northeast China, continuous cropping is one of the main factors contributing to the degradation of black soil. Previous studies (on maize–soybean, maize–peanut, and maize–wheat intercropping) have shown that intercropping can alleviate this problem. However, it is not known whether intercropping is feasible for maize and rice under dry cultivation, and its effects on yield and soil fertility are unknown. A three-year field-orientation experiment was conducted at Jilin Agricultural University in Changchun city, Jilin Province, China, consisting of three cropping regimes, namely rice under dry cultivation–maize intercropping (IRM), sole rice under dry cultivation (SR), and sole maize (SM). All straw was fully returned to the field after mechanical harvesting. Rice under dry cultivation–maize intercropping with a land-equivalent ratio of 1.05 (the average of three years values) increased the total yield by 8.63% compared to the monoculture system. The aggressivity (A), relative crowding coefficient (K), time–area-equivalent ratio (ATER), and competition ratio (CR) value were positive or ≥1, also indicating that the rice under dry cultivation–maize intercropping had a yield advantage of the overall intercropping system. This is because the intercropped maize root length density (RLD) increased by 33.94–102.84% in the 0–40 cm soil layer, which contributed to an increase in the soil porosity (SP) of 5.58–10.10% in the 0–30 cm soil layer, an increase in the mean weight diameter of soil aggregates (MWD) of 3.00–15.69%, an increase in the geometric mean diameter of soil aggregates (GMD) of 8.16–26.42%, a decrease in the soil bulk density (SBD) of 4.02–7.35%, and an increase in the soil organic matter content (SOM) of 0.60–4.35%. This increased the water permeability and aeration of the soil and facilitated the absorption of nutrients and water by the root system and their transportation above ground, and the plant nitrogen, phosphorus, and potassium accumulation in the intercropping system were significantly higher than that in monoculture treatment, further promoting the total yield of intercropping. This suggests that rice under a dry cultivation–maize intercropping system is feasible in Northeast China, mainly because it promotes belowground root growth, improves the soil environment, and increases the total yield of intercropping.

Combining straw return with nitrogen fertilizer application is an effective strategy to enhance farmland productivity, improve soil structure, and mitigate climate change. Although straw return practices are widely recommended in agricultural ecosystems targeting sustainable agriculture, few studies have investigated the combined effects of consecutive years of straw return and nitrogen-fertilizer interactions on rice yield, nitrogen use, and lodging resistance, as well as the potential interactions among these variables. To investigate the effects of consecutive years of rice straw return and nitrogen fertilizer inputs on rice growth, a straw return experiment was conducted in 2021–2022 in Northeast China. The test crop was rice (cv. Jinongda No. 667), with four nitrogen fertilizer levels: 0 kg/ha (N0), 125 kg/ha (N1), 150 kg/ha (N2), and 175 kg/ha (N3). Five straw-return treatments were applied: no straw (S0), straw return to the field for one year (S1), continuous straw return to the field for two years (S2), continuous straw return to the field for three years (S3), and continuous straw return to the field for four years (S4). Results indicated that under the same straw return year, the N3 yield, nitrogen accumulation, nitrogen use efficiency, and apparent utilization were the highest. Under the same nitrogen treatment condition, S1 significantly reduced yield, nitrogen accumulation, nitrogen use efficiency, apparent nitrogen utilization, and lodging index compared to S0. However, under N3 conditions, S3 did not significantly differ from S0. Both S3 and N3 enhanced nitrogen uptake, translocation, and accumulation in rice. Their significant interactive effect increased yield while simultaneously enhancing the lodging resistance and stem strength. The study findings highlighted the effects of years of straw return and nitrogen fertilizer application on crop yield and resistance traits. They further demonstrated that the combination of straw return and optimized nitrogen fertilizer inputs could improve resource utilization and result in a high-yielding and efficient crop population.

This study used DIA-based proteomics to elucidate how foliar application of glycine betaine (GB) and zinc (Zn) synergistically regulates quality formation in dry-cultivated rice. GB and Zn effectively improved both the appearance and eating quality of rice through multi-level coordinated actions. GB primarily enhanced drought tolerance and quality by regulating key protein expression: upregulated RRM domain proteins potentially directly regulated starch and protein synthesis; increased disease resistance proteins activated immune priming, establishing a dual "drought tolerance-immunity" protective system; SNF2 chromatin remodeling proteins participated in epigenetic reprogramming; and amino acid transporters optimized nitrogen allocation. Zn induced functional proteins that enhancedmetabolic homeostasis: Pyridoxal 5-phosphate synthase promoted antioxidant synthesis; dCTP pyrophosphatase and tRNA pseudouridine synthase ensured genomic stability and accurate protein synthesis; and 3-isopropylmalate dehydratase promoted the accumulation of flavor precursors. The combined application of GB and Zn produced significant synergistic effects: upregulated Hexosyltransferase served as a key node, likelystabilizing osmolytes and antioxidants via glycosylation modifications and participating in zinc ligand synthesis to facilitate zinc transport and grain enrichment. Persistent upregulation of Receptor-like serine/threonine-protein kinase (RLK) enhanced signal perception and transduction, thereby initiating drought-resistance defense pathways. Physiologically, combined foliar application significantly enhanced photosynthetic, promoted osmolyte accumulation, and increased antioxidant enzyme activities. Overall, GB stabilizes functional proteins, while Zn servesas a cofactor to activate enzymatic activity. Together, they create a"signal perception-defense activation-nutrition optimization" pathway that mitigates oxidative damage while enhancing stress resistance and quality in dry-cultivated rice, providing a theoretical foundationfor cultivating stress-resistant and high-quality crops.