Huang-Huai-Hai Plain is the most important region for grain production in China. In this area, long-term rotary tillage in winter wheat and no tillage in summer maize have significantly increased soil bulk density, which impede maize root growth and reduce the grain yield. Subsoiling tillage is an effective practice to improve soil properties and crop growth. The objective of this study was to investigate the integrated effects of subsoiling tillage in both winter wheat and summer maize seasons on soil bulk density, maize root growth and spatial distribution. A two-year field experiment was conducted in winter wheat–summer maize rotation system. Tillage treatments included rotary tillage (RT) and subsoiling tillage (ST) in wheat season, and no tillage (NT), inter–row subsoiling tillage (STIR), and on–row subsoiling tillage (STOR) in maize season. It was found that in the second year, i.e., in 2018, ST decreased soil bulk density by 3.87% and increased porosity by 5.86% at 30–40 cm soil depth at maize maturity. Meanwhile, maize root length density at 40–50 cm depth increased by 30.00% and grain yield increased by 4.70% under ST. In maize season tillage treatments, STOR decreased soil bulk density by 4.52% and increased soil porosity by 6.96% at 20–30 cm soil depth. Compared with NT, the STOR significantly increased maize root length density at 20–30 cm soil depth by 78.45%, and increased root length density in a horizontal area 0–10 cm for both years, with a significant increase of 58.89% in 2018. Therefore, this study demonstrated that in the Huang-Huai-Hai Plain, which has a tidal soil type, subsoiling tillage in winter wheat season and on–row subsoiling tillage in maize season can loosen the soil and improve vertical extension of maize root system in the soil.

The scarcity of phosphorus (P) makes improving phosphorus use efficiency a critical issue in crop production. Plant rhizosphere microorganisms play a vital role in increasing phosphorus bioavailability and promoting the level of plant-absorbable P in agroecosystems. In this study, Talaromyces purpurogenus SW-10 strain with efficient organic phosphate-mineralizing ability was isolated from maize rhizosphere soil. SW-10 showed efficient phytate utilization with corresponding soluble P levels of 525.43 mg/L and produced phytase in the liquid medium. The response surface methodology (RSM) analysis showed that glucose as the carbon source and (NH₄)₂SO₄ as the nitrogen source at 28 °C and pH 7.0 promoted higher mineralization of insoluble organic phosphate. When cocultivated with different genotypes of maize seedlings, SW-10 significantly increased the shoot’s dry weight by 37.93%, root’s dry weight by 31.25%, and the plant height by 13.03% for low-P sensitive inbred line 31778, while no significant change was observed in the low-P tolerance inbred line CCM454. In addition, SW-10 strain significantly increased total P-concentration in the shoots (22.4%~32.9%) and roots (3.10%~9.77%) for both inbred lines. In conclusion, the isolated T. purpurogenus SW-10 strain possesses an efficient organic phosphate-mineralizing ability and maize plant growth-promoting effect, especially for the low-P sensitive genotype that could be exploited for enhancing P availability in agriculture.

Wheat/soybean rotation is an important double-cropping system in the Huang-Huai-Hai plain of China. Continuous soybean cropping could cause soil quality deterioration and plant growth inhibition. However, the effects of continuous wheat/soybean cropping on soybean rhizosphere microbes remain largely unknown. In this study, we compared the soybean yield and rhizosphere soil microbial community between continuous winter wheat/summer soybean (W/S) with two harvests in one year and winter wheat/summer soybean-winter wheat/summer maize (W/S-W/M) with four harvests in two years. The results showed that the soybean yield in the W/S group significantly (p < 0.05) declined within the first two years. The W/S-W/M showed higher soybean yield and soil fertility index than the W/S group. The sequencing results revealed that cropping rotation had a higher impact on the fungal community than the bacterial community. The W/S group showed 22.08–23.01% higher alpha diversity of the fungal community, but the alpha diversity of the bacterial group did not vary significantly in this group. The fungal community composition in the W/S and W/S-W/M groups differed significantly. In the W/S-W/M group, a higher relative abundance of plant growth-promoting fungi (e.g., Mortierella), nematophagous fungi (e.g., Plectosphaerella), and biological control fungi (e.g., Coniothyrium) was observed. In the W/S group, a higher relative abundance of lignocellulose-degrading fungi (e.g., Trechispora, Myceliophthora, Botryotrichum, and Coniochaeta) and pathogenic fungi (e.g., Pyrenochaetopsis and Cyphellophora) was observed. LEfSe analysis demonstrated that Mortierella, Myceliophthora, and Trechispora could serve as crucial biomarkers. Mortierella was positively associated with available P levels and negatively associated with NO₃⁻-N levels and pH while Trechispora showed the opposite trend. The findings of this study could enhance the current understanding of the mechanisms associated with the continuous wheat/soybean cropping obstacles and ensure the sustainability of agricultural production.

Tillage practices can directly affect soil quality, influencing soil properties, crop growth, and soil microbial community characteristics. However, the influence of long-term tillage practices on the rhizosphere bacterial community in lime concretion black soil remains largely unknown. In this study, the effects of nine-year rotary tillage (RT), no-tillage (NT), subsoiling tillage (ST), and plow tillage (PT) on soil chemical properties, microbial community structure, and correlations between bacterial communities and soil properties in the maize rhizosphere were investigated. The results revealed that the maize yield in ST and PT was higher by 10.61% and 10.26% than that in RT and by 10.25% and 9.90% than that in NT, respectively. The soil organic matter (SOM) and total nitrogen (TN) contents in NT and ST were significantly higher than those in RT and PT, whereas the available phosphorus (AP) content in ST and PT was significantly higher than that in NT and RT. The diversity and richness of the soil bacterial communities exhibited a trend of NT > RT > PT > ST. The principal component analysis revealed that the soil bacterial community differed among treatments. Linear discriminant analysis effect size (LEfSe) analysis demonstrated that Proteobacteria, Armatimonadetes, Verrucomicrobia, and Chloroflexi could serve as crucial biomarkers. Phylogenetic investigation of communities by reconstruction of unobserved states (PICRUSt) results revealed that genes involved in carbon, lipid, and xenobiotic metabolism were enriched under ST and PT, whereas those involved in nitrogen and carbon fixation were enriched under NT. Besides, Proteobacteria, Verrucomicrobia, and Armatimonadetes were positively associated with AP levels and negatively associated with pH; however, Acidobacteria, Bacteroidetes, and Planctomycetes exhibited an opposite trend. Overall, ST and PT improved the soil properties and environmental suitability by increasing the bacterial keystone taxa; thus, these practices improved crop yield. These findings could enhance our understanding of the rhizosphere functional microbial community in lime concretion black soil for winter wheat–summer maize double-cropping system.

Talaromyces purpurogenus, an endophytic fungus, exhibits beneficial effects on plants during plant–fungus interactions. However, the molecular mechanisms underlying plants’ responses to T. purpurogenus under low-phosphorous (P) stress are not fully understood. In this study, we investigated the transcriptomic changes in maize with low-P-sensitive (31778) and -tolerant (CCM454) genotypes under low-P stress and its symbiotic interaction with T. purpurogenus. Its colonization enhanced plant growth and facilitated P uptake, particularly in 31778. Transcriptome sequencing revealed that 135 DEGs from CCM454 and 389 from 31778 were identified, and that only 6 DEGs were common. This suggested that CCM454 and 31778 exhibited distinct molecular responses to T. purpurogenus inoculation. GO and KEGG analysis revealed that DEGs in 31778 were associated with nicotianamine biosynthesis, organic acid metabolic process, inorganic anion transport, biosynthesis of various secondary metabolites and nitrogen metabolism. In CCM454, DEGs were associated with anthocyanin biosynthesis, diterpenoid biosynthesis and metabolic process. After T. purpurogenus inoculation, the genes associated with phosphate transporter, phosphatase, peroxidase and high-affinity nitrate transporter were upregulated in 31778, whereas AP2-EREBP-transcription factors were detected at significantly higher levels in CCM454. This study provided insights on the molecular mechanisms underlying plant–endophytic fungus symbiosis and low-P stress in maize with low-P-sensitive and -tolerant genotypes.

Drip tape layout and flow rate are crucial variables that impact the effects of drip fertigation. To investigate the influence of drip tape layout and flow rate on the soil water and nitrogen transport in summer maize in sandy tidal soil, field experiments were conducted for two years. Two drip tape layouts were set: one tape serving for two crop rows (N) and one tape serving for each crop row (E), with two levels of drip flow rate, i.e., high (2 L/h; H) and low (1.3 L/h; L). The results show that under the same drip tape layout, the lower the drip emitter flow rate, the more upright the shape of wetted soil volume. The maximum vertical and horizontal water transport distance under NL treatment was higher than that under NH, EH, and EL treatments. After surface drip fertigation, nitrate nitrogen accumulated near and at the edge of the wetted soil volume. In 2020, under NL treatment, nitrate nitrogen transported to a 55 cm soil layer, which was 22.22%, 71.42%, and 57.14% deeper than that under NH, EH, and EL treatments, respectively. In 2021, nitrate nitrogen could transport to a 60 cm soil layer in both NL and NH treatments. The maximum concentration of ammonium nitrogen was nearby the emitter. Under NL treatment, ammonium nitrogen was transported to 48 and 60 cm soil layers below the emitter in 2020 and 2021, respectively, which was deeper than that observed under NH, EH, and EL treatments. The soil inorganic nitrogen residue of the NL was lower than that of the NH, EH, and EL treatments. Compared with NH, EH, and EL treatments, the two-year maize yield under NL treatment increased by 11.09%, 13.47%, and 8.66% on average, respectively. NL treatment exhibited the highest water use efficiency and nitrogen fertilizer productivity. Therefore, NL treatment (one drip tape serving for two rows with 1.3 L/h flow rate) could promote the absorption of water and nutrients, reduce inorganic nitrogen residue, and to obtain high maize yield in sandy tidal soil.