Photosynthetic carbohydrate metabolism is an important biochemical process related to crop production and quality traits. Potassium (K) critically contributes to the process of photosynthetic carbon assimilation and carbohydrate metabolism. We explored the effects of potassium fertilization on physiological mechanisms including carbohydrate metabolism in foxtail millet and its yield. Field experiments were performed using two foxtail millet (Setaria italica L.) cultivars: 1) Jingu 21 (low-K sensitive); and 2) Zhangza 10 (low-K tolerant). Effect of five different potassium fertilizer (K₂O) rates (0, 60, 120, 180, and 240 kg·hm⁻²) were tested in two consecutive years, 2020 and 2021. We found that potassium application significantly increases the K content, dry matter accumulation and yield. Jingu 21 and Zhangza 10 had maximum yields at 180 kg·hm⁻² K application, which were 29.91% and 31.51% larger than without K application, respectively. Excessive K application (K₂₄₀) did not further improve their yields. The suitable K fertilizer application of Jingu 21 and Zhangza 10 are 195.25–204.27 and 173.95–175.87 kg·K2O·hm⁻², respectively. The net photosynthetic rate (P_n), ribulose-1,5-bisphosphate carboxylase-oxygenase (Rubisco), phosphoenolpyruvate carboxylase (PEPC), and fructose-1,6-bisphosphatase (FBPase) were positively correlated with the potassium content. Potassium application improved the availability of carbon sources for carbohydrate synthesis. Compared with the K₀ treatment, variations in the activities of sucrose phosphate synthase (SPS) and sucrose synthase (SuSy) in potassium-treated Jingu 21 (K₆₀, K₁₂₀, K₁₈₀, and K₂₄₀) were 17.94%–89.93% and 22.48%–182.10%, respectively, which were greater than those of Zhangza 10 (11.34%–71.12% and 16.18%–109.13%, respectively) and indicate that Jingu 21 is more sensitive to potassium application. The sucrose contents in the Jingu 21 and Zhangza 10 grains were 0.97%–1.15% and 1.04%–1.23%, respectively. The starch contents were 28.99%–37.75% and 24.81%–34.62%, respectively. The sucrose: ratio of Jingu 21 was smaller than that of Zhangza 10, indicating that Jingu 21 utilized nutrients better than Zhangza 10. Stepwise regression and path analysis showed that leaf and grain SuSy activity, by coordinating the source-sink relationship, have the greatest direct effect on Jingu 21 yield, whereas leaf SuSy activity, by promoting the generation of photosynthates at the source leaf, plays a leading role in Zhangza 10 yield increase. In conclusion, optimized K application can increase foxtail millet grain yield by improving photosynthesis and promoting carbohydrate accumulation and distribution.

Field experiments were conducted to investigate the effects of K application on the nitrogen and potassium utilization efficiency and yield of foxtail millet (Setaria italica L.). The experiment was performed with a completely randomized design with two millet cultivars (Jingu 21 and Zhangza 10) and five K₂O rates (0, 60, 120, 180, and 240 kg/hm²) in 2020 and 2021. We found that K promoted K and N absorption; significantly increased dry matter (DM), N, and K accumulation in millet organs; caused dry matter accumulation to peak earlier; and increased the DM accumulation rate. In addition, K accumulation preceded that of DM or N. Relative to the crop cycle, most K (61.07%) accumulated at booting, whereas N accumulated mostly (33.86%) during grain filling. N absorption efficiency increased by 31.87%, and the apparent and agronomic utilization rate of K fertilizer remained high, increasing millet yield, which peaked at a K rate of 180 kg/hm² for both cultivars, by 29.91% and 31.51% in Jingu 21 and Zhangza 10, respectively, relative to untreated controls. Stepwise regression and path analysis showed that the leaf and spike K accumulation, stem N accumulation, and stem DM were the main factors affecting yield, with DM having the greatest direct effect, followed by leaf K accumulation. The K concentration (0.77–3.04%) in Zhangza 10 was higher than that in Jingu 21 (0.69–2.91%) in untreated plants. Under the same K application rate, N and K accumulation and the harvest index were higher for Zhangza 10 than those for Jingu 21, and the nutrient utilization ability was greater for Zhangza 10. The results demonstrated that rational K fertilizer application can increase K concentration and accumulation in leaves, promote N metabolism and accumulation, increase N and K utilization efficiency, and improve DM accumulation and millet yield.

Introduction: Nicosulfuron is the leading acetolactate synthase inhibitor herbicide product, and widely used to control gramineous weeds. Here, we investigated the metabolic process of nicosulfuron into foxtail millet and maize, in order to clarify the mechanism of the difference in sensitivity of foxtail millet and maize to nicosulfuron from the perspective of physiological metabolism and provide a theoretical basis for the breeding of nicosulfuron-resistant foxtail millet varieties.Methods: We treated foxtail millet (Zhangzagu 10, Jingu 21) and maize (Nongda 108, Ditian 8) with various doses of nicosulfuron in both pot and field experiments. The malonaldehyde (MDA) content, target enzymes, detoxification enzymes, and antioxidant enzymes, as well as related gene expression levels in the leaf tissues of foxtail millet and maize were measured, and the yield was determined after maturity.Results: The results showed that the recommended dose of nicosulfuron caused Zhangzagu 10 and Jingu 21 to fail to harvest; the yield of the sensitive maize variety (Ditian 8) decreased by 37.09%, whereas that of the resistant maize variety (Nongda 108) did not decrease. Nicosulfuron stress increased the CYP450 enzyme activity, MDA content, and antioxidant enzyme activity of foxtail millet and maize, reduced the acetolactate synthase (ALS) activity and ALS gene expression of foxtail millet and Ditian 8, and reduced the glutathione S-transferase (GST) activity and GST gene expression of foxtail millet. In conclusion, target enzymes, detoxification enzymes, and antioxidant enzymes were involved in the detoxification metabolism of nicosulfuron in plants. ALS and GST are the main factors responsible for the metabolic differences among foxtail millet, sensitive maize varieties, and resistant maize varieties.Discussion: These findings offer valuable insights for exploring the target resistance (TSR) and non-target resistance (NTSR) mechanisms in foxtail millet under herbicide stress and provides theoretical basis for future research of develop foxtail millet germplasm with diverse herbicide resistance traits.

Different cultivation measures, including seeding patterns, plastic film mulching, and drip irrigation, significantly affect crop growth and yield. This study conducted a two-year field experiment, involving eight treatments: hole seeding and drill seeding, mulching and bare land, as well as with and without drip irrigation. Analyzed the impact on agronomic traits, photosynthesis, chlorophyll fluorescence parameters, and yield components during the growth period of foxtail millet. The results of two years indicate that the growth trend of foxtail millet was consistent under both hole seeding and drill seeding. The best performance was achieved with drip irrigation treatment for mulching, followed by drip irrigation for bare land, no drip irrigation for mulching, and no drip irrigation for bare land. In 2024, the maximum yield of HFD in hole seeding pattern was 4627.55 kg/ha. The maximum yield of DFD in drill pattern is 4430.22 kg/ha. In summary, based on the comprehensive optimization of two years of data and the effective accumulated temperature in the local area, the best planting method is hole seeding, mulching, and drip irrigation. In cold and cool regions, mulching with film aids in increasing the accumulated temperature of the tillage layer. Hole seeding is conducive to enhancing seedling quality. Performing drip irrigation once during the late heading stage stimulates the growth and fruiting of foxtail millet, thereby increasing yield.

As a strategic crop of dry farming in northern China, the photosynthetic characteristics and stress resistance of foxtail millet (Setaria italica L.) are crucial to yield formation. This study aimed to explore the physiological characteristics of various foxtail millet varieties and screen high-efficiency varieties adapted to semi-arid climates. In the agro-pastoral ecotone of northern Shanxi Province, the physiological and ecological parameters, etc. of six cultivars were measured. The results showed that different cultivars had bimodal diurnal photosynthetic curves with distinct peak values and midday depression degrees, reflecting varied responses to high midday temperature and light stress. Dabaigu and Jingu 21 performed superiorly, with mean daily net photosynthetic rates (Pn) of 22.99 and 20.72 µmol·m⁻²·s⁻¹, significantly higher than Jinmiao K1 (12.87 µmol·m⁻²·s⁻¹). Chlorophyll fluorescence analysis showed Dabaigu had higher potential activity (F_v/F₀) of 3.98 than Jinmiao K1 (2.40). Jingu 21 synergistically optimized plant height, stem diameter, and biomass accumulation. Dabaigu and Jingu 21 are elite cultivars for the agro-pastoral ecotone of northern Shanxi Province due to high photosynthetic efficiency, strong photoprotection, and morphological plasticity.

Foxtail millet planting has a long history and profound role in agricultural civilization. However, weeds have become one of the obstacles restricting the development of the foxtail millet industry. Penoxsulam, as an early post-emergence herbicide for controlling gramineous weeds in paddy fields, is effective for some broadleaf weeds. In this study, six different doses (CK, 0.5X, 1X, 2X, 3X, 4X) of penoxsulam were sprayed at the 3–5 leaf stage of the conventional variety Jingu 21 to study its effect on the growth and development of foxtail millet, in order to screen out the appropriate spraying concentration. The main results are as follows: Within 15 days after spraying penoxsulam, the plant height and leaf area of foxtail millet decreased with the increase in spraying dose, and gradually recovered 15–25 days after spraying, but there were still significant differences compared with CK. The photosynthetic pigment content, net photosynthetic rate (Pn), transpiration rate (Tr), stomatal conductance (Gs), the maximum photochemical efficiency (Fv/Fm), photosynthetic system II actual photochemical efficiency (Y(II)), and photochemical quenching coefficient (qP) of foxtail millet decreased with an increase in the penoxsulam spraying dose, while the intercellular CO₂ concentration (Ci) and non-photochemical quenching coefficient (NPQ) showed an upward trend. There was almost no significant difference in each index between the spraying dose of 0.5X and 1X and CK, but the photosynthesis of foxtail millet leaves was still significantly inhibited under a spraying dose of 3X and 4X. Penoxsulam had certain growth-inhibiting effects on Echinochloa crus-galli (L.) Beauv. (E. crus-galli), Digitaria sanguinalis (L.) Scop. (D. sanguinalis), Chenopodium album L. (C. album), and Amaranthus retroflexus L. (A. retroflexus) which increased as the spraying dosage increased. Our study found that spraying dose groups of 0.5X and 1X penoxsulam were safe for foxtail millet growth and could be used to control gramineous weeds in fields. Other spraying doses are not recommended in the field due to their serious phytotoxicity to foxtail millet, which provides a new measure for weed control in foxtail millet fields.