Based on the long-term fertilization station in fluvo-aquic soil region, this study investigated how bacterial community structure, ecological network, and key species in response to fertilization.

Based on the long-term experiment started from 1990, soil was sampled after wheat maturity in 2023, and high-throughput sequencing and ecological network analysis were used to examine dynamics in soil organic carbon (SOC) and other nutrients, enzyme activity, bacterial community composition, ecological network and stochastic process under four treatments: no fertilization (CK), mineral nitrogen (N), phosphorus (P), and potassium (K) (NPK), NPK+straw (NPKS), and NPK+manure (NPKM).

The combined application of organic and inorganic fertilizers significantly increased SOC and other soil nutrients, as well as soil enzyme activity. Compared with CK, SOC content under NPKS and NPKM increased by 52.1% and 81.9%, respectively, and particulate carbon increased by 60.6% and 137.4%, respectively, and easily oxidized organic carbon increased by 45.3% and 63.4%, respectively; additionally, β-N-acetylglucosaminidase activity increased by 7.2% and 12.6%, respectively, while alkaline phosphatase activity increased by 166.4% and 216.2% (P<0.05), respectively. Notably, β-1,4-glucosidase activity was the highest under NPKS (63.82 μmol·g^-1·d^-1). In terms of bacterial diversity, α-diversity significantly decreased under NPKS compared with CK, with reductions of 5.4%, 5.2%, and 2.6% in the Ace, Chao1, and Shannon indices, respectively (P<0.05). Fertilization treatment alerted bacterial community structure, while NPKS and NPKM exhibited similar compositions. Compared with CK, NPKS significantly reduced the relative abundance of Chloroflexi, Gemmatimonadota, and Methylomirabilota, while NPKM significantly increased the relative abundance of Bacteroidota (P<0.05). Redundancy analysis identified ammonium nitrogen (NH₄⁺-N), nitrate nitrogen (NO₃^--N), and organic carbon (SOC) as the primary environmental factors shaping microbial community structure. Network analysis showed, compared with CK, NPKM increased the complexity, stability of the bacterial community network and the proportion of positive correlations between species. Furthermore, both NPKS and NPKM significantly enhanced the relative abundances of eight keystone taxa, including members of Actinobacteriota (order Microtrichales), Chloroflexi (order Thermomicrobiales), Bacteroidota (orders Chitinophagales and Cytophagales), Myxococcota (uncultured order bacteriap25), and Proteobacteria (order Burkholderiales) (P<0.05). These keystone taxa were closely associated with soil carbon, nitrogen, phosphorus, and other material cycling, as well as plant growth promotion. Partial least squares path modeling suggested that fertilization did not directly impact key species but exerted an indirect influence by significantly affecting soil pH, regulating community composition, and increasing soil nutrient availability.

Long-term combined application of organic and inorganic fertilizers enhanced soil nutrient content and extracellular enzyme activity, regulated microbial community composition and structure, affected bacterial network complexity and stability, and increased the relative abundance of key species involved in soil nutrient cycling and material transformation. These findings provided valuable insights into the interactions between soil properties and microbial communities under long-term fertilization, contributing to a deeper understanding of bacterial community dynamics and key species in agricultural ecosystems.

Based on the long-term rotation experiment, this study explored the characteristics of ammonia volatilization and crop yield change in Fluvo-aquic soil.

The long-term experiment started in 2016, and this study carried out 2023-2024. A randomized block design with five crop rotation treatments were set as: (1) continuous wheat-maize (WMWM); (2) continuous wheat-peanut (WPWP); (3) continuous wheat-soybean (WSWS); (4) 1-year wheat-maize + 1-year wheat-soybean (WMWS); (5) 1-year wheat-maize + 1-year wheat-summer peanut (WMWP). The ammonia volatilization rate (AVR) and cumulative volatilization (ACV), the content of different nitrogen forms in soil, nitrogen content in crop, and crop yield were measured and analyzed.

The ACV in summer-autumn season was higher than that in wheat season, and the AVR in both seasons concentrated in 1st-9th day after fertilization. Under the same fertilization condition, at the summer-autumn season, the AVR peak in WMWM treatment was the highest one with 4.15 kg·hm^-2·d^-1. At the wheat season, the lowest AVR of wheat base fertilizer was observed under WMWS (0.77 kg·hm^-2·d^-1), and the lowest AVR after topdressing fertilizer was under WSWS (0.40 kg·hm^-2·d^-1). The lowest ACV was under WMWP and WMWS during both summer-autumn and wheat seasons, which decreased by 18.7% and 14.8%, 12.5% and 28.6%, respectively, compared with WMWM. In the 0-20 cm soil layer, the content of ammonium, nitrate, and total nitrogen under WPWP and WSWS were significantly higher than those under WMWM during the two seasons. Compared with WMWM, the content of nitrogen in wheat grains under WPWP and WSWS were increased by 12.9% and 17.2%, respectively, and the similar trend was observed in grain nitrogen accumulation, with 135 kg·hm^-2 and 137 kg·hm^-2, respectively. The maize equivalent yield (MEY equal to price yield) under WPWP treatment was significantly higher than other treatments, which was 41.7% higher than that under WMWM treatment. Compare with WMWM, the panicle number (7.0% and 3.5%), kernel number per spike (20.7% and 15.9%), thousand grain weight (5.4% and 4.1%) and yield (10.8% and 10.9%) were enhanced under WPWP and WSWS treatment. During the whole rotation cycle, crops absorbed nitrogen accounted for 43.8%-56.3%, and ammonia volatilization accounted for 1.9%-4.5%. The highest crop absorbed proportion was under WMWP, while the lowest proportion ammonia volatilization was under WSWS.

In the Fluvo-aquic soil area of northern Henan Province, the rotation of wheat and legume crops improved the soil nutrient, reduced the soil ammonia volatilization, increased the nitrogen content and wheat yield, which was recommended as a suitable rotation mode in this area.

This study was aimed to select the optimum tillage pattern by investigating the dynamic changes of different tillage patterns on soil nutrients, microbial biomass, and enzyme activities during different wheat growth stages in fluvo-aquic soil in Huang-Huai Plain.

The field experiment was carried out from 2016 to 2019. Five rotation tillage modes were set as: (1) Continuous Rotary Tillage (RT-RT-RT); (2) Deep tillage-Rotary tillage-Rotary tillage (DT-RT-RT); (3) Deep tillage-Rotary tillage-Shallow rotary tillage (DT-RT-SRT); (4) Deep tillage-Shallow rotary tillage-Shallow rotary tillage (DT-SRT-SRT); (5) Deep tillage-Shallow rotary tillage-Rotating tillage (DT-SRT-RT). Three years is a cycle. In the third year of the 3-year cycle, i.e. 2019, 0-40 cm soil layer samples were taken at the wheat greening stage (GS), jointing stage (JS), filling stage (FS), and maturity stage (MS). The contents of alkali hydrolyzed nitrogen (AN), available phosphorus (AP), available potassium (AK), soil microbial biomass carbon (SMBC), soil microbial biomass nitrogen (SMBN), and the activities of urease, invertase, and neutral phosphatase in different soil layers were measured and analyzed.

All soil indicators were decreased with the soil depths during the whole wheat growth stage. Compared with RT-RT-RT, the increment of available nutrients contents at 20-40 cm soil layer were significantly higher than those at 0-20 cm soil layer under the treatments with deep tillage combined with rotary tillage or shallow rotary tillage, but which presented few effects on soil microbial biomass and enzyme activities under soil layers compared with the effects on soil available nutrients. The dynamic changes of each soil indicators under different treatments during the wheat main growth stages were consistent with the growth and fertilizer requirements of crops. The AP, AK, SMBC, SMBN, urease, neutral phosphatase activities were showed an “N” type trend and reached to peak at the jointing stage. The sucrase activity was gradually increased with the growth stage. In 0-20 cm soil layer, the contents of AN, AP and AK under DT-SRT-RT treatment at the jointing stage were significantly higher than that under other treatments, and the highest value were 91.74 mg·kg^-1, 27.17 mg·kg^-1 and 139.81 mg·kg^-1, respectively. The AN and AP were significantly affected by rotation tillage patterns and soil depths. While the AK was affected by wheat growth stages, soil layers, and rotation tillage patterns, but the interaction among them was not obvious. During the whole growth period, compared with RT-RT-RT, in 0-40 cm soil layer, the SMBC and SMBN content under DT-RT-RT and DT-SRT-RT treatments were higher. The DT-SRT-RT treatment could significantly increase the activities of soil urease, invertase and neutral phosphatase, and their growth rates were between 3.79%-27.69%, 12.29%-36.10% and 8.61%-35.91%, respectively. In the whole wheat growth period, the soil microbial biomass and enzyme activities were significantly affected by different soil depth and rotation tillage mode, but the interaction between them on SMBN content, invertase, and neutral phosphatase activity was not significant. The wheat yield under the other treatments in 2019 was higher than that under RT-RT-RT, and the highest one was 6 557 kg·hm^-2 under DT-SRT-RT.

During this experimental period, in Fluvo-aquic soil in Huang-Huai Plain, the DT-SRT-RT treatment had the best effect on improving available nutrients contents, SMBC, SMBN, and soil enzyme activity, thereby further ensuring the high yield of wheat.

This study aimed to explore the optimum tillage mode in northern Henan province based on the long-term experiment.

This study was based on the long-term tillage experiment started from 2016, which included different combination of three tillage practices, rotary tillage, shallow rotary tillage, and deep tillage before winter wheat sowed. The different combinations were 3-year cycle. Five typical treatments were selected: (1) continuous rotary tillage (RT-RT-RT); (2) Deep tillage-rotary tillage-rotary tillage (DT-RT-RT); (3) Deep tillage-rotary tillage-shallow rotary tillage (DT-RT-SRT); (4) Deep tillage- shallow rotary tillage- shallow rotary tillage (DT-SRT-SRT); (5) Deep tillage- shallow rotary tillage-rotary tillage (DT-SRT-RT). During the wheat season in 2021, root growth indexes, wheat photosynthetic characteristics, total nutrients of all organs at maturity, soil porosity, soil bulk density, aggregate distribution and wheat yield were measured and analyzed.

Compared with RT-RT-RT, the wheat root indexes were improved under the treatments with rotation tillage, therein, DT-SRT-RT displayed the outstanding one. The highest increment of root indexes was at jointing stage. The total root length (RL), surface area (SA), volume (RV), and diameter (RD) were increased by 80.8%, 54.1%, 51.5%, and 21.9%, respectively. The increment was decreased with wheat growth, with the relevant value as 39.0%-28.8% (RL), 21.7%-10.8% (SA), 12.4%-17.8% (RV), and 17.5%-24.5% (RD), respectively. Rotational tillage treatments promoted the wheat photosynthetic characteristics, similar as root indexes, while DT-SRT-RT was demonstrated the better effect among all the treatments. Compared with RT-RT-RT, under DT-SRT-RT, the net photosynthetic rate (Pn), stomatal conductance (Gs), and transpiration rate (Tr) was increased by 25.7%, 41.5%, and 20.5% respectively, at the jointing stage, which was increased by 55.4%, 21.7%, and 17.4%, respectively, at the flowering stage. At the filling stage, the Pn and Gs were increased by 9.7% and 13.6%, respectively, while the Tr was decreased by 6.7%. The nutrient in wheat organ was promoted under the treatments with rotation tillage compared to RT-RT-RT. Therein, under DT-SRT-RT, the TN in leaves, stems, and roots was increased by 66.2%, 80.1% and 61.1%, respectively; the TP in leaves and stems increased by 31.2% and 38.4%; the TK in roots was increased by 50.0%. Compared with RT-RT-RT, the soil porosity was improved in the 20-30 cm soil layer with the increment of 27.1%. The treatments with rotation tillage decreased the soil bulk density in the 0-30 cm soil layer. Meanwhile, the aggregate size with >0.25 mm was increased under the treatments with rotation tillage, especially, it was significant increases under DT-SRT-SRT in the 0-20 cm soil layer. However, the silt and clay proportion were decreased under the treatments with rotation tillage. Additionally, the root-shoot (R/S) ratio, numbers of ears, grain number per spike, 1000-grain weight and yield under the treatments with rotation tillage were higher than those under RT-RT-RT. The R/S ratio increased by 55.6%, numbers of ears increased by 45.3%, and yield increased by 20.7% under DT-SRT-RT. The correlation analysis showed that the yield positively correlated with root length and Stomatal conductance and net photosynthetic rate.

In conclusion, the rotation tillage mode improved the soil porosity and root architecture, raised the photosynthetic rate, enriched the TN, TP, and TK in wheat organs, and increased wheat yield. Therein, the DT-SRT-RT demonstrated the better effect.