Search Results (9)

Replacing partial chemical fertilizers with organic fertilizer can increase organic carbon input, change soil nutrient stoichiometry and microbial metabolism, and then affect soil organic carbon (SOC) storage. A 6-year field experiment was used to explore the mechanism of SOC storage under different ratios of manure substitution in northeast China, with treatments including chemical fertilizer application alone (nitrogen, phosphorus, and potassium, NPK) and replacing 1/4 (1/4M), 2/4 (2/4M), 3/4 (3/4M), and 4/4 (4/4M) of chemical fertilizer N with manure N. Soil nutrients, enzymatic activity, and SOC fractions were analyzed to evaluate the effect of different manure substitution ratios on SOC storage. A high ratio of manure substitution (>1/4) significantly increased soil total N, total P, total K, and available nutrients (NO₃⁻-N, available P, and available K), and the 4/4M greatly decreased the C/N ratio compared to the NPK. Manure incorporation increased microbial biomass carbon (MBC) by 18.3–53.0%. Treatments with 50%, 75%, and 100% manure substitution (2/4M, 3/4M, and 4/4M) enhanced bacterial necromass carbon (BNC), fungal necromass carbon (FNC), and total microbial necromass carbon (MNC) by 31.9–63.5%, 25.5–107.1%, and 27.4–94.2%, respectively, compared to the NPK treatment. Notably, the increase in FNC was greater than that of BNC as the manure substitution ratio increased. The increasing manure substitution significantly enhanced particulate organic C (POC) and total SOC but did not affect mineral-associated organic C (MAOC). High soil N and P supplies decreased leucine aminopeptidases (LAPs) and alkaline phosphatase activities but increased the activity ratio of β-glucosidase (BG)/(N-acetyl-glucosaminidase (NAG) + LAP). Treatments with 25% manure substitution (1/4M) maintained maize and soybean yield, but with increasing manure rate, the maize yield decreased gradually. Overall, the high ratio of manure substitution enhanced SOC storage via increasing POC and MNC, and decreasing the decomposition potential of manure C and soil C resulting from low N- and P-requiring enzyme activities under high nutrient supplies. This study provides empirical evidence that the rational substitution of chemical fertilizers with manure is an effective measure to improve the availability of nutrients, and its effect on increasing crop yields still needs to be continuously observed, which is still a beneficial choice for enhancing black soil fertility. Full article

Ecological restoration has increasingly been employed to reverse land degradation and increase carbon (C) sink, especially in ecologically fragile karst areas. Microbial necromass carbon (MNC) constitutes a critical pool within soil organic carbon (SOC), contributing substantially to long-term C sequestration through mineral stabilization. However, its distribution patterns across soil profiles and grassland restoration stages in karst areas remain unclear. To address this knowledge gap, the contents of bacterial necromass C (BNC), fungal necromass C (FNC), and their contributions to SOC were estimated based on glucosamine and muramic acid contents across the soil profile (0–20 cm, 20–40 cm, 40–60 cm, 60–80 cm, and 80–100 cm) for four subalpine restoration stages (grazing enclosure for 5, 11, 17, and 25 years) in the karst region. Our findings demonstrated that both soil depth and grassland restoration stages effectively influenced the BNC and FNC contents. On average, the soil BNC, FNC, and total MNC at the depth of 80–100 cm reduced by 70.50%, 59.70%, and 62.18% compared with in topsoil (0–20 cm), respectively. However, the FNC/BNC ratio gradually increased with the increase in soil depth, which was 43.15% higher at 80–100 cm soil depth than in topsoil, suggesting that the accumulation efficiency of FNC was higher compared to BNC in the deep soil. The BNC, FNC, and MNC were positively correlated with the grassland restoration stage, while FNC/BNC ratio had a negative relationship with the restoration stage (R² = 0.45, p < 0.001). FNC contributed significantly more to SOC (28.6–36.4%) compared to BNC (7.7–9.9%) at all soil depths, indicating that soil fungal necromass has an essential effect on SOC sequestration. The results of the random forest model and distance-based redundancy analysis identified that pH, soil water content, and dissolved organic carbon were the three most essential predictors for the contribution of MNC to SOC. Our study highlights the importance of microbial necromass to SOC accumulation, providing significant scientific implications for the C pool management during the restoration of degraded grasslands in karst regions. Full article

The integration of manure and straw substantially affects soil organic carbon (SOC) dynamics, transformation, and long-term stabilization in agricultural systems. Dissolved organic carbon (DOC), particulate organic carbon (POC), and mineral-associated organic carbon (MOC) are the three main components of the SOC pool, each influencing soil carbon dynamics and nutrient cycling. Current research gaps remain regarding how combined fertilization practices affect the inputs of plant-originated and microbe-derived carbon into SOC pools and stability mechanisms. Our investigation measured SOC fractions (DOC, POC, MOC), SOC mineralization rate (SCMR), microbial necromass carbon, lignin phenols, enzyme activities, and microbial phospholipid fatty acids (PLFAs) over a long-term (17 years) field experiment with four treatments: mineral fertilization alone (CF), manure-mineral combination (CM), straw-mineral application (CS), and integrated manure-straw-mineral treatment (CMS). The CMS treatment exhibited notably elevated levels of POC (7.42 g kg⁻¹), MOC (10.7 g kg⁻¹), and DOC (0.108 g kg⁻¹), as well as a lower SCMR value (1.85%), compared with other fertilization treatments. Additionally, the CMS treatment stimulated the buildup of both bacterial and fungal necromass while enhancing the concentrations of ligneous biomarkers (vanillin, syringyl, and cinnamic derivatives), which correlated strongly with the elevated contents of fungal and bacterial PLFAs and heightened activity of carbon-processing enzymes (α-glucosidase, polyphenol oxidase, cellobiohydrolase, peroxidase, N-acetyl-β-D-glucosidase). Furthermore, fungal and bacterial microbial necromass carbon, together with lignin phenols, significantly contributed to shaping the composition of SOC. Through random forest analysis, we identified that the contents of bacterial and fungal necromass carbon were the key factors influencing DOC and MOC. The concentrations of syringyl phenol and cinnamyl phenols, and the syringyl-to-cinnamyl phenols ratio were the primary determinants for POC, while the fungal-to-bacterial necromass carbon ratio, as well as the concentrations of vanillyl, syringyl, and cinnamyl phenols, played a critical role in SCMR. In conclusion, the manure combined with straw incorporation not only promoted microbial growth and enzyme activity but also enhanced plant- and microbial-derived carbon inputs. Consequently, this led to an increase in the contents and stability of SOC fractions (DOC, POC, and MOC). These results suggest that manure combined with straw is a viable strategy for soil fertility due to its improvement in SOC sequestration and stability. Full article

Microbial necromass carbon (MNC) is the dominant contributor to soil organic carbon (SOC). However, the contribution of MNC in different soil compartments to SOC sequestration has not been comprehensively studied, especially under the organic fertilizers input. To address this gap, we conducted a rice root box experiment by adding organic fertilizer (straw and straw biochar) and chemical fertilizer alone to red loamy paddy soil, respectively. We found that although SOC accumulation was stimulated by both biochar and straw in the rhizosphere, more substantial SOC was sequestered in the rhizosphere due to biochar addition (increased by 25.82% compared to straw addition). Additionally, the input of organic fertilizers resulted in varying degrees of MNC retention in the different soil compartments. Compared with that in bulk soil, fungal necromass carbon (FNC) content was reduced by 1.37% and 7.06%, and bacterial necromass carbon (BNC) content was reduced by 5.53% and 9.49% in the rhizosphere and hyphosphere, respectively, following straw addition. Conversely, the addition of biochar leads to a significant increase of FNC (increased by 2.92%) and BNC (increased by 2.00%) in the rhizosphere compared with bulk soil. However, straw addition also significantly enhanced SOC thermal stability within the rhizosphere and hyphosphere soils. Based on partial least squares path modeling, we found that SOC thermal stability was significantly and positively influenced by FNC, which was strongly associated with carbon degradation gene abundance. These results emphasize the critical role of soil compartments in SOC sequestration under organic fertilizer application and underscore the importance of FNC in enhancing SOC stability in the rhizosphere. Full article

Microbial necromass carbon (MNC) is crucial for soil carbon sequestration in bamboo (Phyllostachys edulis) forests. However, the response of MNC to bamboo-sourced organic fertilizers (BSOF) prepared by composting bamboo plant growth-promoting microorganisms and bamboo residues remains unclear. This study examined MNC and its contribution to soil organic carbon (SOC) in Moso bamboo plantations under four BSOF treatments: control (CK, 0 t·hm⁻²), low fertilizer application (LF, 7.5 t·hm⁻²), medium fertilizer application (MF, 15 t·hm⁻²), and high fertilizer application (HF, 30 t·hm⁻²) across 0–20 cm and 20–40 cm soil layers. In these two layers, HF and MF significantly (p < 0.05) increased the total MNC, fungal necromass carbon (FNC), and their contributions to SOC compared to CK, and HF led to higher (p < 0.05) bacterial necromass carbon (BNC) levels and SOC contributions than LF and CK. Soil depth and BSOF treatment were found to interact significantly. A random forest model showed that in the 0–20 cm layer, SOC was the best predictor of total MNC and FNC, whereas available potassium was optimal for BNC. Nitrate-nitrogen (NO₃⁻-N) was the top predictor for total MNC, BNC, and FNC in the 20–40 cm layer. Partial least squares path modeling indicated that available soil nutrients directly influenced BNC and FNC, affecting SOC accumulation. These findings suggest a new method for enhancing soil carbon sequestration in bamboo forests. Full article

Cross-kingdom rotation offers several agronomic and ecological benefits, including enhanced soil nutrient availability, reduced pest and disease prevalence, improved soil structure, and minimized chemical inputs, which contribute to a dynamic and resilient soil ecosystem, thereby fostering biodiversity and ecological balance. Additionally, crop diversity encourages plant root exudates that feed a wider range of beneficial soil microbes, ultimately leading to a balanced soil food web. Integrating rice cultivation with the edible mushroom Stropharia rugosoannulata further improves soil fertility and enhances organic carbon sequestration. This rotation introduces organic matter into the soil, affecting microbial community structure and supporting the decomposition of complex organic materials via lignocellulose-decomposing fungi. These processes contribute to soil organic carbon accumulation, nutrient cycling, and long-term soil health. The study emphasizes the importance of microbial communities (including live biomass and necromass) in maintaining ecosystem stability and highlights the potential of the rice–S. rugosoannulata rotation model as a sustainable agricultural practice. Further research is needed to clarify how fungal necromass contributes to soil carbon accumulation and to optimize agricultural practices for improving soil health and carbon sequestration in response to climate change. These findings provide valuable insights for developing sustainable agricultural strategies that balance productivity with environmental conservation. Full article

This study examines how nitrogen and phosphorus fertilization influence soil microbial necromass carbon (MNC) content of farmland on the Loess Plateau, central Gansu. Based on an extensive (6 years) experiment, a control (CK, no fertilization) and three treatment groups employing different fertilization methods, namely, nitrogen fertilization (N, 115 kg·ha⁻¹), phosphorus fertilization (P, 115 kg·ha⁻¹), and combined fertilization of nitrogen and phosphorus (NP, 115 kg·ha⁻¹ each), were set up in this research. The results show that, in the tillage soil layer (within a depth range of 0–20 cm), the application of nitrogen and/or phosphorous fertilizers can significantly reduce the ratio between glucosamine and muramic acid (GluN/MurA) (p < 0.05), with a reduction range of 12.70–35.29%. Phosphorus fertilization can also reduce the content of fungal necromass carbon (FNC) and MNC and their contributions to SOC (p < 0.05). In addition, phosphorus fertilization and combined fertilization of nitrogen and phosphorus can both increase the content of bacterial necromass carbon (BNC) and contribute to the content of SOC (p < 0.05). Primarily because of the reduced accumulation efficiency of FNC, the combined fertilization of nitrogen and phosphorus can significantly decrease the accumulation efficiency of MNC. In the non-tillage soil layer (within depth range of 20–40 cm), both nitrogen fertilization and the combined fertilization of nitrogen and phosphorus can increase the content of FNC and MNC in soils and their impacts on SOC (p < 0.05). The addition of nitrogen and/or phosphorus fertilizers does not alter the accumulation efficiency of soil MNC. Total phosphorus (TP), total nitrogen (TN), soil pH, nitrogen-to-carbon ratio of microbial biomass (MBN/MBC), leucine aminopeptidase (LAP), and β-glucosidase activities (BG) are the primary factors that affect changes in FNC, BNC, and MNC. In summary, phosphorus fertilization alone decreases soil MNC contribution to SOC and reduces carbon pool stability in the tillage layer. On the contrary, both nitrogen fertilization and the combined fertilization of nitrogen and phosphorus can increase the content of soil MNC in the non-tillage layer and its impact on SOC, thus improving the stability of SOC. Full article

Carbon–nitrogen (C-N) coupling is a fundamental concept in ecosystem ecology. Long-term excessive fertilization in tea plantations has caused soil C-N imbalance, leading to ecological issues. Understanding soil C-N coupling under nitrogen loading is essential for sustainable management, yet the mechanisms remain unclear. This study examined C-N coupling in tea plantation soils under five fertilization regimes: no fertilization, chemical fertilizer, chemical + organic cake fertilizer, chemical + microbial fertilizer, and chemical + biochar. Fertilization mainly increased particulate organic carbon (POC) and inorganic nitrogen, driven by changes in bacterial community composition and function. Mixed fertilization treatments enhanced the association between bacterial communities and soil properties, increasing ecological complexity without altering overall trends. Fungal communities had a minor influence on soil C-N dynamics. Microbial necromass carbon (MNC) and microbial carbon pump (MCP) efficacy, representing long-term carbon storage potential, showed minimal responses to short-term fertilization. However, the microbial necromass accumulation coefficient (NAC) was nitrogen-sensitive, indicating short-term responses. PLS-PM analysis revealed consistent C-N coupling across the treatments, where soil nitrogen influenced carbon through enzyme activity and MCP, while bacterial communities directly affected carbon storage. These findings provide insights for precise soil C-N management and sustainable tea plantation practices under climate change. Full article

The form and distribution of organic carbon in soil affect its stability and storage, and nitrogen (N) fertilization can affect the transformation and accumulation of soil organic carbon (SOC), whereas how the N fertilizer rate affects SOC storage by regulating its fractions in a potato continuous cropping system is unknown. A 6-year field experiment was conducted to study the effect of different N fertilizer rates (NE (Nutrient Expert) –N, NE–1/2N, NE, and NE+1/2N) on the changes in SOC and its fractions in a potato continuous cropping system in North China. Soil NO₃⁻-N gradually increased with increasing N fertilizer rates, whereas the N fertilizer rate had less effect on NH₄⁺-N. Compared with the NE−N treatment, the increasing N fertilization increased the SOC and its components, whereas these C fractions did not continue to increase or began to decrease after N fertilization exceeded the rate applied in the NE treatment. While the increase in mineral-associated organic C (MAOC; 16.1–17.2% and 26.1–52.7% in the 0–20 cm and 20–40 cm layers, respectively) was greater than that of particulate organic C (POC; 3.7–7.4% and 11.5–16.4% in the 0–20 cm and 20–40 cm layers, respectively), the increase in bacterial necromass C (BNC; 9.2–21.8% and 28.9–40.4% in the 0–20 cm and 20–40 cm layers, respectively) was greater than that of fungal necromass C (FNC; 6.2–10.1% and 7.1–24.9% in the 0–20 cm and 20–40 cm layers, respectively). Furthermore, the increase in FNC was greater than that of BNC in the 20–40 cm layer of the same treatment. SOC was significantly and positively correlated with MAOC and FNC, and the correlation between SOC and both MNC and FNC was more significant in the 20–40 cm layer than in the 0–20 cm layer. Overall, in the potato continuous cropping system in North China, N fertilization improved SOC storage by increasing MNC to form MAOC, and optimizing N fertilization based on the NE system could better balance the increase and mineralization loss of SOC to achieve high SOC sequestration. Full article