Foxtail millet is an important cereal crop in the North China Plain. However, excessive nitrogen fertilizer application over the years has led to declining yield and soil quality. This study investigated nutrient management strategies for foxtail millet based on crop yield levels and soil nutrient availability. In a field where targeted fertilization was conducted over six seasons, nitrogen fertilization effects and the dynamics of soil-available nitrogen were monitored continuously for two consecutive years (2022–2023) across five different foxtail millet varieties with varying yield levels. The study aimed to determine the optimal nitrogen application rate for achieving a high yield of foxtail millet, the minimum soil nitrate threshold required to maintain soil fertility, and the effective nitrogen application rate range for sustaining soil-available nitrate levels. Results showed that fertilization significantly affected dry matter weight during flowering, while variety affected dry matter weight at maturity. The average nitrogen application rate for achieving high yield across all five millet varieties was 141.3 kg·ha⁻¹. Specifically, the average nitrogen application rate of nitrogen-efficient varieties achieving high yield (5607.32–5637.19 kg·ha⁻¹) was 151.5 kg·ha⁻¹, while the average nitrogen application rate of nitrogen-inefficient varieties achieving high yield (4749.77–4847.74 kg·ha⁻¹) was 134.5 kg·ha⁻¹. Soil NH₄⁺-N and NO₃⁻-N content increased when nitrogen application rate exceeded 360 kg·ha⁻¹, posing environmental risks. To achieve high yield, soil nitrate levels would be maintained at an average of 17.23 mg·kg⁻¹ (before sowing) and 9.75 mg·kg⁻¹ (at maturity). A relationship between soil nitrate and nitrogen application rate was established: y = 867.5 − 50z (where y represents the optimal nitrogen application rate for high yield (kg·ha⁻¹), and z represents soil NO₃⁻-N content in the 0–20 cm layer before sowing, ranging from 10.0 to 17.35 mg·kg⁻¹), which provided a practical method for nitrogen fertilization to achieve high yield of foxtail millet. In this study, the fertilization strategy was optimized according to soil nutrient level and yield targets, and the nitrogen application rate was controlled within 360 kg·ha⁻¹ based on the soil nitrate nitrogen content, which will be instructive for reducing fertilizer use, maximizing fertilizer efficiency, and increasing yield.

Foxtail millet (Setaria italica (L.) P. Beauv.) is an important traditional cereal crop in dryland ecological agriculture in China and is widely grown in India, the United States, and Nigeria. It is of significance to understand the variety–location–fertilizer (V–L–F) interaction for highly efficient production. Therefore, a two-year field experiment was conducted with six varieties in five locations, and data were analyzed by combined ANOVA analysis, redundancy analysis (RDA), and additive main multiplicative interaction (AMMI). The results showed that the mean sum of squares was significantly different among years, locations, varieties, fertilizations, and their interactions, except for Y–V and V–F interactions. The contributions of various factors to yield variation varied, location was the largest contributor (38.7%), followed by year (33.6%), and variety and fertilizer contributed 7.1% and 3.2%, respectively. JI25 was widely adapted, and its yield was stable and higher than that of others over diverse environments in two years. The RDA results showed that two principal components explained more than 66.1% of the yield variance, while more than 63.0% of the variances were clustered in the first factor. Excessive single rainfall or total rainfall and air temperature (especially minimum temperature) were significantly associated with the millet yield. The results offered an important reference for variety layout, natural resource potential mining, and formulation of efficient green cultural practices.

Fasciclin-like arabinogalactan proteins (FLAs) are ubiquitous in the plant kingdom and play crucial roles throughout the entire life cycle of plant growth and development. To gain valuable genetic insights and to systematically dissect the biological functions of FLAs, we performed a comprehensive genome-wide analysis of the FLA gene family in four Poaceae species, including foxtail millet, green foxtail, switchgrass, and sorghum, along with functional characterization of key candidate genes. A total of 121 FLA family members were identified across the four species. Phylogenetic tree analysis classified these FLAs into four distinct subfamilies, within which the genes exhibited highly conserved gene structures and conserved motifs. The promoters of most FLA genes contained abundant cis-acting elements associated with stress and hormone responses. Furthermore, the saline–alkali tolerance-associated candidate gene SiFLA6 was cloned, and T₃-generation homozygous overexpression lines (OE-1 and OE-2) were generated via genetic transformation. Subcellular localization testing using the OE-1 line confirmed that SiFLA6 is located in the endoplasmic reticulum. Phenotypic assays showed that root growth of the OE-1 and OE-2 lines was less inhibited under saline–alkali stress than that of wild-type Arabidopsis thaliana (WT). Consistent with the phenotypic changes, the OE-1 line exhibited significantly higher shoot fresh and dry biomass, chlorophyll content, and activities of SOD, CAT, and POD, as well as higher K⁺/Na⁺ and Ca²⁺/Na⁺ ratios compared with WT plants. In contrast, the accumulation of H₂O₂ and MDA in the overexpression line was markedly reduced. Collectively, these results indicate that SiFLA6 overexpression improves plant saline–alkali tolerance.