This study used polystyrene latex colloids as model microplastic particles (MPs) and systematically investigated their retention and transport in glass bead-packed columns. Different pore volumes (PVs) of MP influent suspension were first injected into the columns at different ionic strengths (ISs). The breakthrough curves (BTCs) were obtained by measuring the MP concentrations of the effluents. Column dissection was then implemented to obtain retention profiles (RPs) of the MPs by measuring the concentration of attached MPs at different column depths. The results showed that the variation in the concentrations of retained MPs with depth changed from monotonic to non-monotonic with the increase in the PV of the injected influent suspension and solution IS. The non-monotonic retention was attributed to blocking of MPs and transfer of these colloids among collectors in the down-gradient direction. The BTCs were well simulated by the convection-diffusion equation including two types of first-order kinetic deposition (i.e., reversible and irreversible attachment). However, this model could not well simulate the non-monotonic retention profiles due to the fact that the transfer of colloids among collectors was not considered. The results in this study are critical to developing models to simulate the fate and transport of MPs in porous media such as soil.

Mixed legume/grass grasslands are the most significant type of artificial grassland in rain-fed semi-arid regions. Understanding the contributions of legumes and grasses to grassland productivity, as well as the nitrogen-sharing mechanisms between them, is crucial to maintaining the sustainability, stability, and high yield of mixed grasslands. In this study, four commonly used cultivated species were selected: smooth bromegrass (Bromus inermis Leyss.), orchardgrass (Dactylis glomerata L.), sainfoin (Onobrychis viciifolia Scop.), and red clover (Trifolium pratense L.). Combinations of two and three species of legumes and grasses were established, with monoculture serving as the control. The results revealed that in all the monocultures and mixed grasslands comprising two or three species, the average dry matter yield (DMY) of mowed grasslands in 2017 was significantly higher than in 2018, while the average DMY of grazed summer regrowth in 2018 surpassed that of 2016 and 2017. Over the period from 2016 to 2018, smooth bromegrass and sainfoin gradually dominated the mixed grasslands, while orchardgrass and red clover exhibited a declining abundance. Over time, the ratio and amount of nitrogen (N) fixation in legumes significantly increased in both the monoculture and mixed grasslands. Similarly, the amount of nitrogen (N) received by grasses also increased significantly in mixed grasslands. However, the proportion of nitrogen fixed by legumes remained below 10% in 2016, 20% in 2017, and 30% in 2018. In contrast, nitrogen transfer from legumes to smooth bromegrass was less than 10%, while in orchardgrass, it was even lower, at less than 2%. The interannual variability in dry matter yield (DMY) and nitrogen contribution in the mixed grasslands of rain-fed semi-arid areas is primarily influenced by forage adaptability and average annual precipitation. Increasing the proportion of grazed forage relative to hay in annual forage consumption should be considered, as more extensive grazing can reduce damage from field rodents and provide higher forage quality at lower costs and energy consumption. To maintain grassland productivity, targeted grazing should be carefully planned and implemented.

Distribution and storage of soil organic and inorganic carbon under different ecological zones in Xinjiang, China

Drought and soil nutrient deficiency are critical constraints on plant growth and ecological restoration in desert steppes; however, the interactive mechanisms between arbuscular mycorrhizal fungi (AMF) and phosphorus fertilization remain poorly elucidated. To investigate the regulatory mechanisms governing root system architecture (RSA) remodeling and regrowth capability in Agropyron under drought stress, a controlled experiment was conducted using two genotypes: Inner Mongolia (NM) and Xinjiang (XJ). The experimental design comprised three water regimes (70%, 50%, and 30% field capacity [FC]), two P levels (P0, P1), and two inoculation treatments (A0, A1). The results indicated the following: (1) Although drought significantly inhibited Agropyron growth, the combined application of AMF and P (A1P1) induced a highly significant synergistic effect, augmenting total aboveground biomass by 66.08–160.58% compared to the control. This synergy exhibited distinct “environmental dependency,” being most pronounced under moderate drought conditions (50% FC). (2) Mechanistic analysis revealed that A1P1 optimized RSA by significantly increasing total root length, root surface area, and root volume (e.g., total root length increased by 281.4–375.1% under severe stress), thereby enhancing water and nutrient acquisition. (3) The A1P1 treatment significantly mitigated the decline in regrowth potential induced by successive clipping, sustaining a higher tiller number (increasing by up to 1.8-fold in the 3rd clipping). (4) The XJ genotype was characterized by higher basal biomass and root investment “high-yield phenotype”, whereas the NM genotype demonstrated greater sensitivity to AMF-P regulation “highly responsive phenotype”. In conclusion, the synergistic interaction between AMF and P mitigates drought stress by reshaping RSA and enhancing regrowth capability, providing a theoretical basis for the efficient management of arid grasslands.

Plant cysteine oxidase (PCO) catalyzes the oxidation of cysteine residues in the N-degron pathway, thereby regulating the stability and activity of the seventh group of ethylene response factors (ERF-VII), which play a crucial role in reactive oxygen species (ROS)-mediated signal transduction. By regulating the degradation of ERF-VII, the PCO family genes control hormone signaling, which is highly valuable for plant growth and abiotic stress responses. However, systematic studies on PCO genes in Medicago sativa, a key forage legume, remain lacking. Herein, 35 MsPCO genes were identified from the alfalfa (Medicago sativa) genome, and their biological characteristics were comprehensively analyzed via bioinformatics approaches. The results showed that MsPCO genes are asymmetrically distributed across 18 chromosomes and clustered into 5 subgroups phylogenetically. Most MsPCO proteins are hydrophilic and localized in the cytoplasm. A total of 56 duplication events were detected, with most duplicated pairs undergoing purifying selection (Ka/Ks analysis). Collinearity analysis revealed close evolutionary relationships between Medicago sativa and Medicago truncatula, Arabidopsis thaliana or Glycine max. Promoter cis-acting elements in MsPCO genes are involved in light response, stress adaptation, hormone signaling, and growth regulation. Transcriptomic data indicated differential expression of MsPCO genes under abiotic stresses. MsPCO20 is dispersed throughout the cell membrane and nucleus, whereas MsPCO19 is localized to the nucleus, according to subcellular localization experiments. These findings provide candidate genes and a theoretical basis for further functional characterization of PCO genes in alfalfa.

This study focused on alfalfa (Medicago sativa cv. Xinmu No. 4) as the experimental material, and a two-year field plot controlled experiment was conducted to compare the effects of different co-application ratios of organic and chemical fertilizers on alfalfa yield, soil nutrient status, and soil biological characteristics. The six fertilization treatments were as follows: CM0 (100% cattle manure), CM1 (75% cattle manure + 25% chemical fertilizer), CM2 (50% cattle manure + 50% chemical fertilizer), CM3 (25% cattle manure + 75% chemical fertilizer), CM4 (100% chemical fertilizer), and CK (no fertilizer application). The results showed that alfalfa hay yield was highest under the CM3 treatment in both 2024 and 2025, representing increases of 38.03% and 40.85%, respectively, compared with the control (CK). Relative to the other treatments, CM3 significantly increased soil total nitrogen, alkali-hydrolyzable nitrogen, available phosphorus, readily available potassium, and organic matter contents. In addition, CM3 markedly enhanced the activities of soil nitrate reductase (NR), nitrite reductase (NiR), and the root enzymes glutamate synthase (GOGAT) and glutamine synthase (GS). The combined application of organic and chemical fertilizers significantly reshaped the soil bacterial community structure associated with alfalfa. Under the CM3 treatment, Chao1, Shannon, and ACE indices of soil bacterial diversity increased, whereas the Simpson index decreased. Moreover, the CM3 treatment was associated with higher relative abundances of several key bacterial phyla and genera. The 25% cattle manure plus 75% chemical fertilizer (CM3) treatment exhibited the strongest overall effects, significantly increasing total alfalfa hay yield, enhancing soil macronutrient availability and key enzyme activities, improving soil microbial α-diversity, and optimizing soil bacterial community structure. This treatment consistently outperformed the no-fertilizer control (CK) and all other organic–inorganic fertilizer combinations. Collectively, these findings provide robust scientific evidence supporting strategies to increase forage productivity, mitigate environmental impacts, and promote the sustainable development of the grassland industry.