Introduction: The partial substitution of chemical fertilizer with organic manure takes on a critical significance to enhancing soil quality and boosting sustainable agricultural development. However, rare research has studied the effects of partial substitution of chemical fertilizer with organic manure on soil bacterial community diversity and enzyme activity in maize field in the mountain red soil region of Yunnan.Methods: In this study, four treatments were set up in which chemical fertilizer (the application rates of N, P₂O₅ and K₂O were 240, 75 and 75 kg·ha⁻¹, respectively) was substituted by 10% (M10), 20% (M20), 30% (M30) and 40% (M40) of organic manure with equal nitrogen, as well as two control treatments of single application of chemical fertilizer (M0) and no fertilization (CK). The maize (Zea mays L.) crop was sown as a test crop in May 2018. The effects of partial substitution of chemical fertilizer with organic manure on soil physicochemical properties, soil bacterial community diversity and enzyme activity were studied.Results: The activities of Cellulase (CBH), Invertase (INV) and β-glucosidase (BG) increased with the increase of organic manure substitution ratio. The activities of β-1,4-N-acetylglucosaminidase (NAG), Urease (URE), and leucine aminopeptidase (LAP) also had the same trend, but the highest activities were 159.92 mg·g⁻¹·h⁻¹, 66.82 mg·g⁻¹·h⁻¹ and 143.90 mg·g⁻¹·h⁻¹ at 30% substitution ratio. Compared with CK and M0 treatments, Shannon index increased notably by 82.91%–116.74% and 92.42%–128.01%, respectively, at the organic manure substitution ratio ranging from 10% to 40%. Chao1 and ACE index increased significantly at the organic manure substitution ratio ranging from 10% to 30%. Proteobacteria was the dominant phylum in all treatments, the relative abundance of Proteobacteria decreased as the organic manure substitution ratio increased. Redundancy analysis showed that microbial biomass C was the main factor affecting the bacterial community composition under partial replacement of chemical fertilizer treatment, while Actinobacteria was the main factor affecting the enzyme activity. In addition, the maize yield of M30 and M40 treatments was significantly higher than that of CK and M0-M20 treatments, and the yield of M30 treatment was the highest, reaching 7652.89 kg·ha⁻¹.Conclusion: Therefore, the partial substitution of chemical fertilizer with organic manure can improve soil biological characteristics, while increasing bacterial community diversity and soil enzyme activity. Therefore, a thirty percent organic manure substitution was determined as the optimal substitution ratio for maize farmland in the mountain red soil area of Yunnan, China.

In spite of the fact that rock weathering performs an essential task in the evolution of the Earth’s surface, the quantitative assessment between pH and rates of chemical weathering remain unclear. This study aims to characterize the chemical weathering rate of purple rocks and then develops a model to calculate the release rates of cations (K⁺, Na⁺, Ca²⁺and Mg²⁺) under various pH conditions. Two types of purple rock were sampled from the Shaximiao Group (J₂s) and Penglaizhen Group (J₃p), and a series of laboratory experiments were performed by soaking the purple rocks in solutions with pHs from 2.5 to 7.0, over 24 treatment cycles. The results showed that the release rates of cations apparently increased as the pH decreased. The release of Ca²⁺was the dominant process of chemical weathering in J₃p under various pH treatments, while K⁺and Na⁺were remarkably high in J₂s (with the exception of the pH 2.5 treatment). Quantitative analysis revealed that the rate of cation release was significantly related to the H⁺concentration (p < 0.001) and the air temperature (p < 0.001). The relationship between cation release and acidity was found to be an exponential function. Our results suggested that solution acidity serves as an important driving force for cation release rates from purple rocks and that environmental acidification would enhance rock weathering.

Rational fertilization boosts crop yields and enhances nutritional value, but over-fertilization is counterproductive. Furthermore, water eutrophication caused by excessive use of nitrogen fertilizers has become a major agricultural non-point source pollution problem in the Erhai Lake Basin of China. This study took high-fertility soil as the research object and set up six treatments: no fertilization (CK), local recommended fertilization (T1), optimized chemical fertilizer (T2), organic fertilizer replacing 20% (T3), 40% (T4), 60% (T5) of chemical fertilizer with equal nitrogen. The results show that replacement of chemical nitrogen fertilizers with organic nitrogen fertilizers at an appropriate ratio can optimize soil nitrogen supply, enhance the activity of soil nitrogen cycle enzymes, thereby promoting the activity of nitrogen metabolism enzymes and nitrogen assimilation capacity in potato plants, and ultimately achieve a synergistic effect of increased yield, improved quality and higher fertilizer use efficiency. Among the treatments, the nitrate reductase (S-NR) activity in potato leaves was 36.74% and 41.66% higher under T3 than T1 and T4, respectively. For potato quality, Vitamin C (VC) content was 17.41% higher under T3 than T2; soluble protein content was 11.44%, 10.63%, and 9.44% higher under T3 than T1, T2, and T4, respectively. The replacement of chemical fertilizers with organic fertilizers mainly enhances the protein content in potato tubers by increasing soil urease (S-URE) activity and leaf relative chlorophyll content (SPAD) value. Based on the comprehensive differential combination evaluation model, considering potato metabolic absorption, yield, quality, and soil nitrogen content, the T3 treatment is the optimal fertilization method in the Erhai Lake Basin of China.

Aims: This study aimed to evaluate how the combined application of slow-release nitrogen fertilizer and urea influences nitrogen losses via runoff and the yield performance of silage maize in red soil sloping cropland, in order to support region-specific strategies for soil and water conservation and efficient nitrogen management in maize-based systems. Methods: A one-year field runoff plot experiment was conducted under natural rainfall conditions. Three fertilization treatments with equal nitrogen input were established: conventional urea application (CK), 25% controlled-release nitrogen fertilizer combined with 75% urea (P1), and 50% controlled-release nitrogen fertilizer combined with 50% urea (P2). Results: (1) Co-application of slow-release fertilizer and urea significantly improved soil and water conservation compared to CK; total runoff was reduced by 9.17% and 8.29% under P1 and P2, respectively; and soil loss was reduced by 16.45% and 12.25%. (2) The co-application of slow-release fertilizer effectively reduced nitrogen losses from sloping farmland. Compared to CK, both P1 and P2 reduced losses of total nitrogen (TN), nitrate nitrogen (NO₃⁻-N), and ammonium nitrogen (NH₄⁺-N) during the maize growth period, with the reductions under P2 being most pronounced. (3) The co-application of slow-release fertilizer and urea enhanced maize nitrogen uptake and increased maize yield. Conclusions: Based on the results of this single-year field experiment, the combined application of controlled-release nitrogen fertilizer and urea showed potential advantages in reducing runoff-related nitrogen losses while improving crop productivity in red-soil sloping cropland. Among the treatments, P2 (50% controlled-release nitrogen substitution) exhibited relatively better overall performance. However, the broader applicability of these findings requires further verification through multi-year field experiments under different climatic conditions.

Background and Aims Enhancing the stability of soil aggregates can slow down soil erosion. However, the stabilization mechanisms of soil aggregates under different planting patterns and growth stages of maize ( Zea mays L.) and potato ( Solanum tuberosum L.), specifically in relation to the role of arbuscular mycorrhizal fungi (AMF), remains limited in the southwest region of China. The major objective of this study was to determine the changes of soil nutrient content, enzyme activity, glomalin-related soil protein (GRSP) content, AMF community and characteristics of soil aggregates and their interrelationship under different planting patterns and growth stages of maize and potato. Methods A long-term positioning experiment commenced in 2018. Three treatments of maize monoculture, potato monoculture and maize-potato intercropping were established. Non-rhizosphere soil samples were collected at three distinct growth stages for each crop: for maize, these stages were jointing (T1), tasseling (T2), and maturity (T3); for potato, the stages were seedling (T1), peak flowering (T2), and maturity (T3). The analysis focused on changes in soil nutrient content, GRSP content, enzyme activity, and characteristics of soil aggregates. Additionally, the AMF community in both rhizosphere and non-rhizosphere soils was analyzed during the T2 stage of maize and potato. Results The results showed that: (1) Across crop growth periods, the mean weight diameter ( MWD ) of non-rhizosphere soil was highest under maize and potato intercropping at T2 (1.02), followed by potato intercropping at T3 (0.98). (2) Compared with monoculture, the intercropping of maize and potato significantly enhanced the activities of urease (URE), invertase (INV), and catalase (CAT) in the rhizosphere soils of both crops at the T2 stage. Meanwhile, this intercropping pattern also increased the proportion of soil aggregates > 2 mm and the MWD in the non-rhizosphere soils of the two crops, with the magnitude of these improvements ranged from 10.98% to 88.84%. Additionally, potato intercropping increased the relative abundance of unclassified_f__Gigasporaceae and Gigaspora , as well as the Shannon index of the AMF community in rhizosphere soil at T2 stage. (3) During the T2 period, the activities of INV and CAT in rhizosphere soil was significantly higher than in non-rhizosphere soil of maize monoculture and potato intercropping. Conclusion Redundancy analysis revealed the following key finding: During the T1 stage, environmental factors had no significant effect on the stability of non-rhizosphere soil aggregates. At T2, INV, Gigaspora and Diversispora were the primary drivers of non-rhizosphere soil aggregate stability, while CAT and Diversispora dominated the regulation of rhizosphere soil aggregate stability. In the T3 stage, total glomalin-related soil protein (T-GRSP) and CAT were the main factors affecting non-rhizosphere soil aggregate stability. Further structural equation modeling analysis indicated that AMF community diversity, soil organic matter, and T-GRSP directly promoted soil aggregate stability, whereas CAT exerted an indirect positive effect-these patterns were observed during T2 stage. Collectively, these results clarify the mechanism underlying soil fertility improvement under crop diversity.