Ping Cong

Salt stress and low nutrient availability in saline-alkali soils constrain crop productivity. However, the effects of different forms of exogenous carbon input on rhizosphere bacterial communities and their predicted functional potential remain unclear. A field experiment was conducted in a coastal saline-alkali maize field with four treatments: no organic amendment (CK), crushed straw return (CS), straw biochar return (CB), and granulated straw return (GS). The effects of different straw forms on soil physicochemical properties, bacterial community structure, predicted functional profiles, and maize yield were compared between rhizosphere and bulk soils. Compared with CK, GS significantly reduced rhizosphere electrical conductivity (EC) and salt content by 57.97% and 59.56%, respectively. Among the different straw forms, GS resulted in significantly lower rhizosphere salt content than CS and CB, while its EC was comparable to CS. Both CS and GS significantly increased rhizosphere available phosphorus content and increased maize yield by 24.87% and 23.35%, respectively. Straw-return treatments significantly altered bacterial community structure in both rhizosphere and bulk soils, with GS enriching a greater number of treatment-specific bacterial taxa in both habitats. Functional prediction based on bacterial community composition showed that, compared with CK, GS was associated with significantly lower predicted relative abundances of multiple MetaCyc pathways related to aerobic respiration, the tricarboxylic acid cycle, and branched-chain amino acid biosynthesis in both rhizosphere and bulk soils. Overall, different straw-return forms exerted distinct short-term effects on the soil microenvironment and bacterial communities. Notably, GS showed a relative advantage in reducing rhizosphere salinity, particularly salt content, while both CS and GS improved rhizosphere nutrient conditions and maize yield.

Introduction: Tillage depth plays a critical role in regulating soil structure, nutrient dynamics, and microbial processes that determine crop productivity and quality. Methods: A 3-year field experiment was conducted in a subtropical red soil region to evaluate the effects of rotary tillage (RT), deep tillage with middle depth (DTM), and deep plowing (DP) on soil physicochemical properties, enzyme activities, microbial biomass, and nitrogen-cycling microbial communities. Results and discussion: Results showed that RT significantly enhanced soil organic carbon, total nitrogen, available phosphorus, and microbial biomass across both 0–20 cm and 20–40 cm layers. In contrast, DP promoted higher nitrate levels, particularly in subsoils, and significantly enhanced ammonia-oxidizing bacteria (AOB) diversity in the tillage layer. Soil enzyme activities showed depth-dependent responses, with RT maintaining greater cellulase and urease activity compared to other treatments. Ammonia-oxidizing archaea (AOA) and AOB communities exhibited distinct compositional and diversity shifts under different tillage regimes, driven by soil nutrient availability, bulk density, and enzymatic activity. Co-occurrence network analysis further revealed that DTM and DP increased the complexity of AOA networks, while RT promoted higher connectivity and modularity in AOB networks. Additionally, DP significantly increased the proportion of superior-grade leaves compared to RT. Path analysis further clarified soil microbial biomass as the strongest positive direct driver of production benefits, mediating the effects of soil physicochemical and nutrient properties on crop value. These findings indicate that deep plowing boosts agricultural economic returns by optimizing the soil environment to enhance crop quality; however, to offset accelerated organic matter decomposition, integrating deep plowing with organic amendments is recommended for sustainable production.

Heat shock transcription factors (Hsfs) play important roles in plant developmental regulations and various stress responses. In present study, 46 Hsf genes in peanut (AhHsf) were identified and analyzed. The 46 AhHsf genes were classed into three groups (A, B, and C) and 14 subgroups (A1-A9, B1-B4, and C1) together with their Arabidopsis homologs according to phylogenetic analyses, and 46 AhHsf genes unequally located on 17 chromosomes. Gene structure and protein motif analysis revealed that members from the same subgroup possessed similar exon/intron and motif organization, further supporting the results of phylogenetic analyses. Gene duplication events were found in peanut Hsf gene family via syntenic analysis, which were important in Hsf gene family expansion in peanut. The expression of AhHsf genes were detected in different tissues using published data, implying that AhHsf genes may differ in function. In addition, several AhHsf genes (AhHsf5, AhHsf11, AhHsf20, AhHsf24, AhHsf30, AhHsf35) were induced by drought and salt stresses. Furthermore, the stress-induced member AhHsf20 was found to be located in nucleus. Notably, overexpression of AhHsf20 was able to enhance salt tolerance. These results from this study may provide valuable information for further functional analysis of peanut Hsf genes.

When biochars are produced, feedstock is a crucial factor that determines their physicochemical properties. However, the characteristics of tropical crop waste-derived biochar have not been described and limit its availability. In this study, pineapple leaf (PAL), banana stem (BAS), sugarcane bagasse (SCB) and horticultural substrate (HCS), were used to prepare biochar at 300, 500 and 700 °C. Properties of biochars and their applications were analysed. The results indicated that hydrophobicity, nonpolarity and aromaticity of SCB biochar (SCBB) were higher than other biochars due to the loss of H (hydrogen), O (oxygen), and N (nitrogen). The pH of PAL biochar (PALB) and BAS biochar (BASB) ranged from 9.69 to 10.30 higher than that of SCBB and HCS biochar (HCSB) with 7.17–9.77. In PALB and BASB, sylvite was the dominant crystal structure. With temperature rising, C–H stretching, C=C stretching and H–O in alcohol groups decreased, and Si–O stretching in HCSB and SCBB strengthened. Biochars obtained at 500 °C, especially SCBB and HCSB, significantly promoted the growth of maize. The PALB and BASB greatly increased the soil pH/EC to 6.90–7.35 and 0.67–0.95 ms/cm, while those of SCBB and HCSB were 5.97–6.74 and 0.23–0.45 ms/cm. The application of the biochars to the soil increased soil pH, reducing the acidic soil stress in maize growth, especially PAL and BAS biochars prepared at 300 °C. Biochar prepared at lower temperature will greatly reduce energy consumption and increase the utilization efficiency of tropical agricultural waste resources.

Ammonia-oxidizing archaea (AOA) and bacteria (AOB) are the most important ammonia oxidation functional community, while the coastal environment just provides a different oxygen environment for the ammonia oxidation process. However, few surveys concentrated on the influence of oxygen concentration on the niche specialization of AOA and AOB in the ocean intertidal zones. Here, high-throughput sequencing by Illumina MiSeq and qPCR were applied to detect the change of abundance, diversity as well as community structure of both AOA and AOB with 0–60 cm sediments depth in the intertidal zone in Qingdao, China. Results showed that the AOA/AOB amoA gene copy numbers and AOA/AOB OTU numbers rate increased as sediment depth went more profound, which indicated that AOA was more adaptive to oxygen-limited niches compared to AOB. Oxygen indeed led to the niche specialization of AOA and AOB in intertidal sediments. The dominant AOA and AOB were the clusters of Nitrosopumilus and Nitrosospira, respectively, which indicated ecological success in the intertidal zone. A significant and positive correlation (p < 0.01) between AOB abundance/AOB OTU numbers and Oxidation-reduction potential (ORP) was observed. In addition, both total nitrogen (TN) (p < 0.01) and pH (p < 0.05) were significantly negatively correlated to AOB abundance. TN was also significantly negatively correlated to AOB OTU numbers (p < 0.05). Hence, oxygen led to niche specialization of AOA and AOB, especially under anoxic conditions, AOA played a dominant role in the process of ammonia oxidation. The Nitrosopumilus and Nitrosospira clusters were the dominant AOA and AOB, respectively, representing an ecological success in the intertidal zone.

Long term tobacco planting leads to soil acidification. A ten-year experiment with various fertilization treatments (no fertilization (CK), chemical fertilizer (CF), organic-inorganic compound fertilizer (OCF), and organic fertilizer (OF)) was carried out between 2010 and 2020 in a continuous cropping system of Nicotiana tabacum in the brown soil of eastern China, to assess the effects of organic fertilizer on the improvement of tobacco planting soil acidification. The results indicated that treatments OCF and OF reduced the soil exchangeable acid content, of which the exchangeable aluminum showed the largest reduction by 51.28% with the OF treatment. In contrast, treatment CF showed more significant increases in exchangeable aluminum (Al) and Al saturation, and also apparently increased soil NO₃⁻-N, NH₄⁺-N and nitrification potential (NP) than other treatments. Treatments of OCF and OF significantly increased the total amount of exchangeable base (EBC) by 37.19% and 42.00% compared with CF, respectively. Redundancy analysis (RDA) showed that NP, NH₄⁺-N, and NO₃⁻-N were the important factors indicating soil acidification, while EBC and exchangeable K were the significant factors restricting soil acidification. Inevitably, OCF could improve the soil organic carbon pool and labile organic carbon pool. The structural equation model (SEM) showed that OCF treatment increased the soil organic carbon pool mainly by inhibiting soil nitrification and reducing the content of exchangeable Al. In conclusion, both OF and OCF treatments were effective methods to alleviate tobacco planting soil acidification, however OCF had more advantages in improving soil organic carbon pool.