Nitrogen (N) is a key nutrient influencing wheat growth, grain yield, and quality. A long-term field experiment was conducted using cultivar Zhengmai 1860 to clarify the effects of N topdressing on grain protein composition, starch accumulation, and yield. Treatments included a basal N application of 150 kg ha⁻¹ (N1) combined with four topdressing rates at jointing: 37.5, 75, 112.5, and 150 kg ha⁻¹ (N1 + 37.5, N1 + 75, N1 + 112.5, N1 + 150). Nitrogen topdressing significantly affected the physiological and biochemical characteristics of grains at different spike positions. Amylopectin, globulin, soluble starch (SS), and soluble starch synthase (SSS) accumulated most under 75–112.5 kg ha⁻¹, with N1 + 75 showing the strongest response in basal and middle spike grains. Amylose and granule-bound starch synthase (GBSS) peaked at the middle spike under N1 + 112.5. Protein component (gliadin, glutelin, albumin), amino acids, glutamate synthase (GOGAT), and glutamine synthetase (GS) increased progressively with higher N rates, with maximum accumulation at N1 + 150. Nitrogen topdressing also enhanced spike number (5.05–37.13%), grains per spike (3.86–16.22%), and 1000-grain weight (2.72–5.79%), with the highest yield (9451.7 kg ha⁻¹) at N1 + 112.5. These results highlight the critical role of optimized N management in improving grain composition and yield in wheat.

Increasing species richness through rotation is considered a promising measure to enhance agroecosystem functions and services. However, the legacy effects of introducing legumes into a wheat–maize rotation in the North China Plain on soil microecology, especially the soil metabolome, in the succeeding wheat season have not been elucidated. This study established three cropping systems: (1) a continuous winter wheat–summer maize rotation (M), (2) a winter wheat–summer peanut (summer maize) rotation (PM), and (3) a winter wheat–summer soybean (summer maize) rotation (SM). The soil physicochemical properties, microbial communities, and metabolomes were analyzed at the stage of the succeeding wheat crop. Introducing peanuts or soybeans into a wheat–maize rotation significantly reduced the soil bacterial abundance and increased the soil fungal Shannon index. This rotation adjustment had a substantial impact on the structure and taxa composition of the soil microbial community. Crop diversification increased the number of total edges, the average degree, and the average number of neighbors in the soil microbial co-occurrence network. Different crop rotations significantly affected the soil metabolic profiles in the positive and negative ion modes. Crop diversification significantly reduced the abundance of coumarin and coumaric acid in the soils. In conclusion, introducing peanuts or soybeans into a wheat–maize rotation could increase the soil fungal community diversity, change the soil microbial community structure and taxa composition, increase the complexity of the soil microbial ecological network, and reduce the abundance of soil allelochemicals. Our study demonstrated the continuity of the impact of crop rotation on soil ecology, and revealed the ecological advantages of crop diversification from the perspective of soil microbiology and metabolomics.

Introduction: In the Huang-Huai region of China, low spring temperatures during the jointing stage frequently cause substantial yield losses in winter wheat, posing a serious threat to wheat production. Methods: To develop a safe and effective exogenous regulation strategy, we investigated the effects of foliar application of a compound formulation containing diethyl aminoethyl hexanoate (DA-6) and 28-homobrassinolide (28-HBL) at different concentrations on two winter wheat cultivars, Bainong207 (BN207) and Zhengmai136 (ZM136), under simulated low-temperature (LT) stress (−3°C for12h) during the jointing stage. Physiological and yield-related parameters, including leaf antioxidant enzyme activities, osmoregulatory substance contents, cell ultrastructure, chlorophyll fluorescence parameters, seed-setting rates at different spikelet positions, and yield components, were evaluated to identify the optimal application rate and elucidate the physiological mechanisms underlying enhanced cold tolerance. Results: The results showed that foliar application of the DA-6/28-HBL compound formulation, particularly at 10mL/667m ² (N2), significantly increased the activities of leaf antioxidant enzymes, including super oxide dismutase (SOD)and catalase (CAT). It also promoted the accumulation of soluble sugars, soluble proteins, and proline while reducing malondialdehyde (MDA) content. These physiological responses effectively maintained the integrity of leaf cell ultrastructure and improved photosystemII (PSII) activity. Collectively, these improvements enhanced the cold tolerance of the plants. Compared with the water-spray treatment, the N2 treatment significantly increased the grain number per spike by 13.7% in BN207 and 14.2% in ZM136 ( p <0.05), thereby substantially reducing yield loss under LT stress. The greatest increases in seed setting rate and grain dry weight were observed at the upper spikelet positions (G1 and G2). Among the two cultivars, BN207exhibited greater tolerance to LT stress than ZM136. Discussion: Overall, foliar application of the DA-6/28-HBL compound formulation effectively alleviated LT-induced damage during the jointing stage, providing a safe and effective exogenous strategy for enhancing cold tolerance in wheat cultivation.

Elucidating the spatial distribution of mineral nutrients within maize ears is important for improving both grain yield and nutritional quality. A five-year field study was conducted in the North China Plain to investigate how soil N and foliar Zn applications influenced grain yield and nutrient distribution among kernel positions within the maize ear. Ten maize cultivars were initially screened for responsiveness to foliar zinc, and two contrasting cultivars, Zhengdan 958 (zinc-responsive) and Longping 638 (zinc-low-responsive), were selected for detailed evaluation under three N application rates, with or without foliar Zn application. Nutrient concentrations of N, P, K, Cu, Mn, Fe and Zn were highest in basal kernels and declined toward the upper ear, with their accumulation represented as basal > middle > upper. Increasing N rates enhanced grain yield and total mineral accumulation and altered nutrient partitioning within the ear. A total of 225 kg N ha⁻¹ increased Zn concentration in the upper kernel but decreased in the basal kernel, while increased proportions of N, Mn and Zn accumulated in the basal kernel but decreased in the middle kernel, relative to 180 kg N ha⁻¹. Foliar Zn significantly reduced barren tip length, increased Zn concentration and accumulation, and decreased P concentration but had little effect on nutrient distribution among ear positions. Strong positive relationships were observed between mineral concentrations in whole-ear grain and those in individual ear positions. Thus, N and Zn management could influence maize yield and grain mineral nutrition allocation among ear positions, providing new insights into enhancing the mineral nutritional quality of maize grain.