Soil microbial inoculants for sustainable agriculture: Limitations and opportunities

The burgeoning global market for soil microbial inoculants for use in agriculture is being driven by pressure to increase sustainable crop production by managing pests and diseases without environmental impacts. Microbial inoculants, based predominantly on bacteria and fungi, are applied to soil as alternatives to conventional inorganic fertilizers (biofertilizers) or to carry out specific functions including biocontrol of pests and diseases (biopesticides), or for bioremediation and enhancement of soil characteristics. While some soil inoculants such as rhizobia have a long and successful history of use, others have performed inconsistently in the field and failed to live up to their promise suggested by laboratory testing. A more precise understanding of the ecology and modes of action of inoculant strains is key to optimizing their efficacy and guiding their targeted use to situations where they address key limitations to crop production. This will require greater collaboration between science disciplines, including microbiology, plant and soil science, molecular biology and agronomy. Inoculants must be produced and formulated to ensure their effective establishment in the soil and practicality of implementation alongside existing cropping practices. New approaches to strain selection and construction of beneficial microbial consortia should lead to more efficacious inoculant products. Extensive and rigorous field evaluation of inoculants under a range of soil and environmental conditions has rarely been undertaken and is urgently needed to validate emerging inoculant products and underpin successful implementation by growers, especially in a market that is largely unregulated at present.     

牧场土壤碳、氮和微生物动力学研究:放牧强度和种植方式的影响

Management intensity critically influences the productivity and sustainability of pasture systems through modifying soil microbes, and soil carbon(C) and nutrient dynamics; however, such effects are not well understood yet in the southeastern USA. We examined the effects of grazing intensity and grass planting system on soil C and nitrogen(N) dynamics, and microbial biomass and respiration in a long-term field experiment in Goldsboro, North Carolina, USA. A split-plot experiment was initiated in 2003 on a highly sandy soil under treatments of two grass planting systems(ryegrass rotation with sorghum-sudangrass hybrid and ryegrass seeding into a perennial bermudagrass stand) at low and high grazing densities. After 4 years of continuous treatments, soil total C and N contents across the 0–30 cm soil profile were 24.7% and 17.5% higher at the high than at the low grazing intensity, likely through promoting plant productivity and C allocation belowground as well as fecal and urinary inputs. Grass planting system effects were significant only at the low grazing intensity, with soil C, N, and microbial biomass and respiration in the top 10 cm being higher under the ryegrass/bermudagrass than under the ryegrass/sorghum-sudangrass hybrid planting systems. These results suggest that effective management could mitigate potential adverse effects of high grazing intensities on soil properties and facilitate sustainability of pastureland.     

Soil microbial biomass and activity: the effect of site characteristics in humid temperate forest ecosystems

Microbial biomass, respiratory activity, and in‐situ substrate decomposition were studied in soils from humid temperate forest ecosystems in SW Germany. The sites cover a wide range of abiotic soil and climatic properties. Microbial biomass and respiration were related to both soil dry mass in individual horizons and to the soil volume in the top 25 cm. Soil microbial properties covered the following ranges: soil microbial biomass: 20 µg C g^–1–8.3 mg C g^–1 and 14–249 g C m^–2, respectively; microbial C–to–total organic C ratio: 0.1%–3.6%; soil respiration: 109–963 mg CO₂‐C m^–2 h^–1; metabolic quotient (qCO₂): 1.4–14.7 mg C (g C_mic)^–1 h^–1; daily in‐situ substrate decomposition rate: 0.17%–2.3%. The main abiotic properties affecting concentrations of microbial biomass differed between forest‐floor/organic horizons and mineral horizons. Whereas microbial biomass decreased with increasing soil moisture and altitude in the forest‐floor/organic horizons, it increased with increasing N_tot content and pH value in the mineral horizons. Quantities of microbial biomass in forest soils appear to be mainly controlled by the quality of the soil organic matter (SOM), i.e., by its C : N ratio, the quantity of N_tot, the soil pH, and also showed an optimum relationship with increasing soil moisture conditions. The ratio of C_mic to C_org was a good indicator of SOM quality. The quality of the SOM (C : N ratio) and soil pH appear to be crucial for the incorporation of C into microbial tissue. The data and functional relations between microbial and abiotic variables from this study provide the basis for a valuation scheme for the function of soils to serve as a habitat for microorganisms.     

Divergence in the soil and rhizosphere microbial communities of monoculture and silvopastoral traditional C. dodecandra agroforestry systems in Yucatan,Mexico

Numerous works have reported the impact on soil properties and microbial communities of intensive soil management, but very little is known about the impact caused by traditional agroforestry systems carried out by smallholders. To investigate whether the different smallholder's management between a monoculture plantation of Cordia dodecandra trees and a Silvopastoral system has led to a divergence in these ecosystems, soil properties, as well as soil and Cordia dodecandra rhizosphere microbial communities were analysed by MiSeq amplicon sequencing. The main findings were (i) Large variation in the soil properties of the Silvopastoral system suggests that it has a greater heterogeneity; (ii) Organic carbon, organic matter, carbonates, nitrogen, inorganic phosphorous and calcium, was significantly higher in the soil of the Silvopastoral system. (iii) The relative abundance of the major prokaryotic orders in soil and rhizospheres displayed small differences between the two agroforestry systems, and diversity indexes were slightly higher in the Silvopastoral system. (iv) The fungal orders Hypocreales and Pleosporales were more abundant in the Silvopastoral system than in the monoculture. Other evaluated parameters showed only minor or no difference. Thus, the main conclusion is that these soils have diverged in some properties and fungal orders, but not in their prokaryotic communities. To our knowledge, this is the first report on the divergence in soil properties and microbiota of these two extended smallholder agroforestry systems and therefore can serve as reference for future works.     

宁夏盐池县草地沙化对植被与土壤特征的影响

通过野外调查和室内分析相结合的方法,研究了盐池县不同沙化程度下草地植被特征和土壤特性的变化,以探讨植被和土壤对沙化的响应机制。结果表明,随着草地沙化程度的加剧,植被组成发生变化,多年生草本植物呈逐渐减少,一年生草本植物呈逐渐增加的趋势;生物多样性指数变化趋势为轻度沙化草地到中度沙化草地增加,自中度沙化草地至极度沙化草地先降低后又增加,中度沙化阶段是草地植物群落特征变化的重要转折时期。随着草地沙化加剧,土壤含水量、有机质、氮含量降低;重度沙化阶段土壤磷、钾含量最高,pH值和可溶性盐无明显变化规律。     

功能菌剂与生物炭配施对沙化土壤的影响

研究生物炭和功能菌剂协同调控沙化土壤养分和微生物多样性与功能，可为沙化土壤肥力培育提供理论依据。选择毛乌素沙地典型生态经济林沙化土壤为研究对象，采用田间定位试验，运用高通量扩增测序技术，解析不同添加量(2%,4%,8%)生物炭处理及其配施定量功能菌剂(枯草芽孢杆菌+巨大芽孢杆菌+胶质芽孢杆菌)处理对土壤化学性质及细菌菌群多样性与功能的影响。结果表明：(1)与单一生物炭处理相比，生物炭+功能菌剂处理组土壤有效氮、磷养分含量分别提升44.71%和187.36%;(2)生物炭单施或者配施功能菌剂均使酸杆菌门相对丰度显著降低，而生物炭+功能菌剂处理中厚壁菌门的相对丰度，分别增加163.80%,155.15%,100.21%,并且不同程度上调土壤细菌物种丰富度和多样性；(3)功能菌剂与生物炭配施改变土壤细菌介导的碳氮循环功能，如显著提高土壤细菌的有机物质分解功能，壳聚糖和木聚糖分解过程较对照组分别上升186.54%,242.46%,增强细菌的氨化和呼吸功能，而单施生物炭处理提升细菌的反硝化与固氮功能。综上，生物炭和功能菌剂的添加提高土壤有效氮磷养分含量，显著改变土壤细菌群落多样性与群落功能，生物...     

Soil microbial biomass C:N:P stoichiometry and microbial use of organic phosphorus

Microbial mineralization and immobilization of nutrients strongly influence soil fertility. We studied microbial biomass stoichiometry, microbial community composition, and microbial use of carbon (C) and phosphorus (P) derived from glucose-6-phosphate in the A and B horizons of two temperate Cambisols with contrasting P availability. In a first incubation experiment, C, nitrogen (N) and P were added to the soils in a full factorial design. Microbial biomass C, N and P concentrations were analyzed by the fumigation-extraction method and microbial community composition was analyzed by a community fingerprinting method (automated ribosomal intergenic spacer analysis, ARISA). In a second experiment, we compared microbial use of C and P from glucose-6-phosphate by adding ¹⁴C or ³³P labeled glucose-6-phosphate to soil. In the first incubation experiment, the microbial biomass increased up to 30-fold due to addition of C, indicating that microbial growth was mainly C limited. Microbial biomass C:N:P stoichiometry changed more strongly due to element addition in the P-poor soils, than in the P-rich soils. The microbial community composition analysis showed that element additions led to stronger changes in the microbial community in the P-poor than in the P-rich soils. Therefore, the changed microbial biomass stoichiometry in the P-poor soils was likely caused by a shift in the microbial community composition. The total recovery of ¹⁴C derived from glucose-6-phosphate in the soil microbial biomass and in the respired CO₂ ranged between 28.2 and 37.1% 66 h after addition of the tracer, while the recovery of ³³P in the soil microbial biomass was 1.4–6.1%. This indicates that even in the P-poor soils microorganisms mineralized organic P and took up more C than P from the organic compound. Thus, microbial mineralization of organic P was driven by microbial need for C rather than for P. In conclusion, our experiments showed that (i) the microbial biomass stoichiometry in the P-poor soils was more susceptible to additions of C, N and P than in the P-rich soils and that (ii) even in the P-poor soils, microorganisms were C-limited and the mineralization of organic P was mainly driven by microbial C demand.     

Development of microbial community during primary succession in areas degraded by mining activities

Together with plants, soil microbial communities play an essential role in the development of stable ecosystems on degraded lands, such as postmining spoil heaps. Our study addressed concurrent development of the vegetation and soil fungal and bacterial communities in the course of primary succession in a brown coal mine spoil deposit area in the Czech Republic across a chronosequence spanning 54 years. During succession, the plant communities changed from sparse plants over grassland and shrubland into a forest, becoming substantially more diverse with time. Microbial biomass increased until the 21st year of ecosystem development and later decreased. Although there was a close association between fungi and vegetation, with fungi mirroring the differences in plant community assemblages, the development of the bacterial community was different. The early succession community in the barren nonvegetated soil largely differed from that in the older sites, especially in its high abundance of autotrophic and free‐living N₂‐fixing bacteria. Later in succession, bacterial community changes were minor and reflected the chemical parameters of the soil, including pH, which also showed a minor change with time. Our results show that complex forest ecosystems developed over 54 years on the originally barren soil of the temperate zone and indicate an important role of bacteria in the initial stage of soil development. Although the arrival of vegetation affects substantially fungal as well as bacterial communities, it is mainly fungi that respond to the ongoing development of vegetation.     

Soil and microbial C:N:P stoichiometries play vital roles in regulating P transformation in agricultural ecosystems: A review

Stoichiometry plays a crucial role in biogeochemical cycles and can modulate soil nutrient availability and functions. In agricultural ecosystems,phosphorus(P) fertilizers(organic or chemical) are often applied to achieve high crop yields. However, P is readily fixed by soil particles, leading to low P use efficiency. Therefore, understanding the role of carbon:nitrogen:P stoichiometries of soil and microorganisms in soil P transformation is of great significance for P management in agriculture....     

不同施肥和耕作制度下土壤微生物多样性研究进展

本文主要介绍了运用Biolog GN、磷脂脂肪酸(PLFA)、核酸分析法进行土壤微生物群落分析的优缺点,综述了施肥、耕作两种农业措施对土壤微生物多样性影响的研究进展。指出不同施肥处理对微生物影响效果不同,合理施用有机肥有利于维持土壤微生物的多样性及活性;由于受其他环境因素(如土壤类型、农作制度、残茬量等)的影响,不同耕作措施对土壤微生物多样性影响有差异,但是大多试验结果显示免耕、少耕能增加微生物多样性和生物量,保持系统的稳定性。文章还指出了目前研究中存在的问题,并对今后的研究方向做了展望。     

Microalgal bioinoculants for sustainable agriculture and their interactions with soil biotic and abiotic components: A review

Modern agricultural practices have posed a detrimental impact on the environment due to their intensive use to meet the food demands of an ever-increasing population. In this context, microalgal bioinoculants, specifically cyanobacteria and green microalgae, have emerged as sustainable options for agricultural practices to improve soil organic carbon, nutrient availability, microbial quality, and plant productivity. An overview of current and future perspectives on the use of microalgal bioinoculants in agriculture practices is presented in this review, along with a discussion of their interactions with soil biotic and abiotic factors that affect soil fertility, plant health, and crop productivity. The benefits of microalgal bioinoculants include releasing agronomically important metabolites (exopolymers and phytohormones) as well as solubilizing soil nutrients. Furthermore, they function as biocontrol agents against soil-borne pathogens and facilitate the establishment of rhizosphere communities of agricultural importance. So far, very few studies have explored the basic mechanisms by which microalgal bioinoculants interact with soil biotic and abiotic factors. In recent years, advanced molecular techniques have contributed to a better understanding of these interactions.     

Soil carbon and nutrient pools, microbial properties and gross nitrogen transformations in adjacent natural forest and hoop pine plantations of subtropical Australia

Background, Aims, and Scope  An improved understanding of important soil carbon (C) and nutrient pools as well as microbial activities in forest ecosystems is required for developing effective forest management regimes underpinning forest productivity and sustainability. Forest types and management practices can have significant impacts on soil C and nutrient pools as well as biological properties in forest ecosystems. Soil C and nutrient pools were assessed for adjacent natural forest (NF), first rotation (1R) (50-year-old), and second rotation (2R) (1-year-old) hoop pine (Araucaria cunninghamii Ait. ex D. Don) plantations in southeast Queensland of subtropical Australia. Materials and Methods  Five transects spaced 3 m apart with 9 sampling points along each transect were selected (9.6 m × 12.0 m each site), with 45 soil cores (7.5 cm in diameter) collected and separated into 0–10 and 10–20 cm depths. These soils were analysed for total C, total nitrogen (N), C (δ¹³C) and N (δ¹⁵N) isotope composition. The 0–10 cm soils were analysed for pH, CEC, exchangeable cations, total P and total K, and assayed for microbial biomass C and N, respiration, metabolic quotient, potential mineralizable N (PMN), gross N mineralization (M) and immobilization (I). Results  Total C and N in 0–10 cm soils were higher under NF and 1R plantation than under 2R plantation, while they were highest in 10–20 cm soils under NF, followed by the 1R and then 2R plantation. δ¹³C was lower under NF than under the plantations, while δ¹⁵N was higher under NF than under the plantations. Total P was the highest under NF, followed by the 1R and then 2R plantation, while total K was higher under the 2R plantation. No significant differences were detected for pH, CEC, exchangeable cations, microbial C and N, respiration and metabolic quotient among the 3 sites. PMN and M were higher under NF, while I was the highest under the 2R plantation, followed by the NF and then 1R plantation. Discussion  Soil total C and N in 0–10 cm depth were significantly lower under 2R hoop pine plantation than those under NF and 1R hoop pine plantation. There were significant reductions in soil total C and N from NF to 1R and from 1R to 2R hoop pine plantations in 10–20 cm depth. This highlights potential N deficiency in the 2R hoop pine plantations, and application of N fertilizers may be required to improve the productivity of 2R hoop pine plantations. There were no significant differences in other soil chemical and physical properties in 0–10 cm depth among the 3 sites under NF, 1R and 2R hoop pine plantations, except for soil total P and K. Soil microbial biomass C, CO₂ respiration and metabolic quotient did not differ among the 3 sites assessed, perhaps mainly due to these biological variables being too sensitive to variations in soil chemical and physical properties and thereby being associated with a larger variability in the soil biological properties. However, soil potential mineralizable N, gross N mineralization and immobilization were rather sensitive to the conversion of NF to hoop pine plantation and forest management practices. Conclusions  Total C and N in the top 20 cm soil were highest under NF, followed by 1R and then 2R hoop pine plantations, indicating that N deficiency may become a growth-limiting factor in the 2R hoop pine plantations and subsequent rotations of hoop pine plantation. The sample size for soil δ¹³C seems to be much smaller than those for soil total C and N as well as δ¹⁵N. The significant reductions in soil total P from NF to 1R and then from 1R to 2R hoop pine plantations highlight that P deficiency might become another growth-limiting factor in the second and subsequent rotations of hoop pine plantations. Soil microbial properties may be associated with large spatial variations due to these biological properties being too sensitive to the variations in soil chemical and physical properties in these forest ecosystems. Recommendations and Perspectives  Soil potential mineralizable N, gross N mineralization and immobilization were useful indices of soil N availability in response to forest types and management practices. The sampling size for soil δ¹³C was much smaller than the other soil chemical and biological properties due to the different patterns of spatial variation in these soil properties.     

Soil biochemical and microbial indices in wet tropical forests: Effects of deforestation and cultivation

Little information is available about the long‐term effects of deforestation and cultivation on biochemical and microbial properties in wet tropical forest soils. In this study, we evaluated the general and specific biochemical properties of soils under evergreen, semi‐evergreen, and moist deciduous forests and adjacent plantations of coconut, arecanut, and rubber, established by clear felling portions of these forests. We also examined the effects of change in land use on microbial indices and their interrelationships in soils. Significant differences between the sites occurred for the biochemical properties reflecting soil microbial activity. Microbial biomass C, biomass N, soil respiration, N mineralization capacity, ergosterol, levels of adenylates (ATP, AMP, ADP), and activities of dehydrogenase and catalase were, in general, significantly higher under the forests than under the plantations. Likewise, the activities of various hydrolytic enzymes such as acid phosphomonoesterase, phosphodiesterase, casein‐protease, BAA‐protease, β‐glucosidase, CM‐cellulase, invertase, urease, and arylsulfatase were significantly higher in the forest soils which suggested that deforestation and cultivation markedly reduced microbial activity, enzyme synthesis and accumulation due to decreased C turnover and nutrient availability. While the ratios of microbial biomass C : N and microbial biomass C : organic C did not vary significantly between the sites, the ratios of ergosterol : biomass C and ATP : biomass C, qCO2 and AEC (Adenylate Energy Charge) levels were significantly higher in the forest sites indicating high energy requirements of soil microbes at these sites.     

生物复混肥对土壤微生物群落功能多样性和微生物量的影响

在温室盆栽条件下,采用Biolog微平板法和氯仿熏蒸浸提法,研究了玉米施用等养分量的无机肥、有机无机复混肥和生物复混肥后土壤微生物群落功能多样性及土壤微生物量的变化。结果表明:生物复混肥处理的土壤微生物平均颜色变化率(AWCD)、微生物群落Shannon指数(H)和微生物群落丰富度指数(S)均最高;施用生物复混肥可明显提高土壤微生物对碳源的利用率,尤其是多酚化合物类和糖类;不同处理土壤微生物碳源利用特征有一定差异,生物复混肥在第1主成分上的得分值为正值,其他各处理在第1主成分上的得分值基本上为负值,起分异作用的主要碳源是糖类和羧酸类。在玉米生长期间各处理土壤微生物量大致呈先升高后逐渐平稳的趋势,且土壤微生物量碳、氮、磷的含量均以生物复混肥处理最高,最高值分别为333.21mg.kg 1、53.02 mg.kg 1和22.20 mg.kg 1。研究表明,生物复混肥的施用比等养分量的有机无机复混肥处理能显著提高土壤微生物群落碳源利用率、微生物群落丰富度和功能多样性,显著增加土壤微生物量碳、氮、磷的含量,有利于维持良好的土壤微生态环境。     

连续施用无害化污泥对沙质潮土土壤肥力和微生物学性质的影响

以小麦-玉米轮作体系下的沙质潮土为研究对象,选用经无害化处理后的城市污泥产物,通过2013~2015年田间定位试验,研究了不同城市污泥施用量对土壤肥力的影响,以期为城市污泥资源化利用提供理论基础和技术依据。设置单施化肥(CK)、CK+污泥15 t·hm~(-2)(CS1)、CK+污泥30 t·hm~(-2)(CS2)和CK+污泥45 t·hm~(-2)(CS3)共4个处理。主要研究结果如下:(1)连续定位试验结果表明,同一施用量污泥处理的土壤p H值随施用时间的增加呈下降趋势;土壤有机质(SOM)和养分含量如全氮(TN)、有效磷(AP)和速效钾(AK)随施用时间的增长呈上升趋势;(2)与CK比较,在2015年玉米季施用污泥各处理的土壤p H值显著降低了0.34~0.83个单位(P0.05),且与污泥施用量呈反比,以高施量污泥45 t·hm~(-2)下降最多;土壤SOM、TN、AP和AK分别显著提高了52.1%~166.9%、77.3%~177.8%、215.7%~486.3%和167.2%~379.0%(P0.05),且与污泥施用量呈正比,以高施量污泥45 t·hm~(-2)效果最显著;(3)试验所用污泥施用量范围内不会造成土壤和植物籽粒重金属污染,能够保持土壤环境健康;(4)与CK比较,施用污泥各处理土壤微生物量碳(MBC)、氮(MBN)含量均显著提高(P0.05),且与污泥施用量呈正比,并且季节不同也显著影响土壤MBC、MBN含量(P0.05);施用污泥能够显著提高土壤MBC/MBN(P0.05),说明施用污泥能够改变土壤微生物群落组成;(5)施用污泥,尤其是高施量污泥45 t·hm~(-2),在保证土壤和植物籽粒质量安全下,其土壤培肥效果最优。     

土壤微生物群落结构与多样性对农田集约化管理程度降低的响应

Using a scheme of agricultural fields with progressively less intensive management （deintensification）, different management practices in six agroecosystems located near Goldsboro, NC, USA were tested in a large-scale experiment, including two cash-grain cropping systems employing either tillage （CT） or no-tillage （NT）, an organic farming system （OR）, an integrated cropping system with animals （IN）, a successional field （SU）, and a plantation woodlot （WO）. Microbial phospholipid fatty acid （PLFA） profiles and substrate utilization patterns （BIOLOG ECO plates） were measured to examine the effects of deintensification on the structure and diversity of soil microbial communities. Principle component analyses of PLFA and BIOLOG data showed that the microbial community structure diverged among the soils of the six systems.Lower microbial diversity was found in lowly managed ecosystem than that in intensive and moderately managed agroecosystems, and both fungal contribution to the total identified PLFAs and the ratio of microbial biomass C/N increased along with agricultural deintensification. Significantly higher ratios of C/N （P 〈 0.05） were found in the WO and SU systems, and for fungal/bacterial PLFAs in the WO system （P 〈 0.05）. There were also significant decreases （P 〈 0.05） along with agricultural deintensification for contributions of total bacterial and gram positive （G＋） bacterial PLFAs.Agricultural deintensification could facilitate the development of microbial communities that favor soil fungi over bacteria.     

厌氧土壤灭菌不同添加物对日光温室土壤性质及微生物群落的影响

厌氧土壤灭菌(ASD)作为替代化学农药熏蒸灭菌技术在各地逐渐推广,但不同土壤类型、不同添加物厌氧土壤灭菌效果具有较大差异,田间条件下明确当地不同添加物厌氧灭菌对土壤性质及微生物群落效应,为日光温室绿色环保的土壤灭菌方法提供科学依据。结果表明:(1)除添加碳酸氢铵(AB)处理外,其他处理均可以显著降低0—20 cm土层电导率(EC),但仅灌水不添加物料(CK)处理20—40 cm土层NO_3~--N和EC显著增加,且AB处理显著增加0—20 cm土层NH_4~+-N及20—40 cm土层NO_3~--N;添加鸡粪(CM)处理0—20 cm土层NH_4~+-N极显著增加,NO_3~--N极显著降低,EC显著降低,土壤有机质、全氮和有效养分亦显著增加。(2)添加鸡粪(CM)显著降低细菌丰富度和均匀度,但土壤中植物促生菌(PGPR)芽孢杆菌属(Bacillus)及假单胞菌属(Pseudomonas)的相对丰度极显著增加。对真菌群落,不同处理真菌丰富度和均匀度与处理前差异均不显著,但添加碳酸氢铵(AB)、木醋液(PS)和鸡粪(CM)处理病原菌-镰刀菌属(Fusarium)的相对丰度均显著降低;同时,鸡粪(CM)处理有益属曲霉属(Aspergillus)丰度显著增加。(3)综合土壤理化性质、细菌和真菌群落变化,鸡粪作为有机碳源添加厌氧土壤灭菌效果较好,既可以厌氧灭菌同时也腐熟鸡粪,且各地原料来源方便,可同时实现化肥农药双减。     

有机肥施用对植烟土壤氮素矿化及土壤酶和微生物群落的影响

为探索不同有机肥对植烟土壤氮素矿化及土壤微生态的影响。在等氮(100 mg/kg)投入和30℃条件下对施入不同有机肥(植物源有机肥、芝麻饼肥、生物质炭有机肥)的土壤进行室内培养，分析不同时期土壤NO3–-N和NH4+-N含量、土壤酶活性及细菌群落多样性的变化。结果表明：施用不同有机肥均可提高土壤矿质氮含量，在培养前期以饼肥矿化量最高，矿化速率最快，而后期为生物质炭有机肥处理的氮素矿化量、矿化速率高于其他处理；施用生物质炭有机肥、植物源有机肥均可显著提高土壤脲酶、硝酸还原酶活性，芝麻饼肥对蛋白酶、蔗糖酶活性有显著的提升作用；相较不施有机肥处理，添加不同有机肥的土壤细菌多样性明显提升。优势菌门为变形菌门、酸杆菌门、拟杆菌门、浮霉菌门，优势菌属为Sphingomonas、RB41,Sphingomonas在不施有机肥处理中最高，RB41在生物质炭有机肥处理中最高。Sphingomonas与蔗糖酶活性呈正相关关系，与脲酶、硝酸还原酶均呈负相关关系；PCA分析显示，生物质炭有机肥处理的细菌群落结构与其他处理相比差异较大。施用芝麻饼肥有利于促进早期氮素矿化，提高矿化量，而生物质炭有机肥后期矿化量较...     

蚯蚓活动和秸秆施用方式对土壤生物学性质的动态影响

通过实验室短期培养研究接种蚯蚓和有机物不同施用方式(混施与表施)对土壤微生物类群、土壤微生物量以及呼吸强度等土壤生物学性质的影响。结果表明,接种蚯蚓对土壤可培养酵母菌、细菌数量和土壤底物诱导呼吸强度有明显促进作用。最高增幅分别达到相应未接种蚯蚓处理的5.18,8.88,2.50倍。蚯蚓活动对土壤微生物量及真菌数量的影响受到秸秆施用的影响:在混施和不施秸秆的处理(SRME、SE)中显著抑制丝状真菌数量;在混施秸秆处理中蚯蚓活动降低了SMBC含量。秸秆的施用方式对土壤微生物性状也有较大影响。混施秸秆处理中,土壤酵母菌、细菌数量、土壤微生物量和土壤呼吸强度增加也最为明显,而丝状真菌数量的增加幅度却不如表施秸秆处理。各处理土壤微生物量碳随时间变化趋势比较一致,呈现先降(第4周)后增的变化趋势,其他测定项目没有一致的随时间变化的规律。方差分析表明秸秆施用对土壤微生物量氮和可培养微生物数量变化的贡献最大,分别达到96.5%(SMBN)、77.9%(细菌)、69.4%(酵母菌)和85.3%(丝状真菌)。并且时间、秸秆和蚯蚓因子间存在强烈交互作用。