MBN) And Phosphorus Research Articles

Application of organic manure as a potential strategy to alleviate the limitation of microbial resources in soybean rhizospheric and bulk soils

The development and vigor of soil microorganisms in terrestrial ecosystems are frequently constrained by the limited availability of essential elements such as carbon (C), nitrogen (N), and phosphorus (P). In this study, we investigated the impact of long-term application of varying levels of organic manure, low (7.5 Mg ha−1 yr−1), moderate (15.0 Mg ha−1 yr−1), and high (22.5 Mg ha−1 yr−1), on the stoichiometry of enzymes and the structures of the microbial communities in soybean rhizospheric and bulk soils. The main goal of this research was to examine how soil microbial resource limitations in the rhizosphere respond to different long-term fertilization strategies. The soil enzymatic activities were quantified, and the structure of the microbial community was assessed by analyzing phospholipid fatty acid profiles. When compared to the bulk soil, the rhizospheric soil had significant increases in microbial biomass carbon (MBC), nitrogen (MBN), and phosphorus (MBP), with MBC increasing by 54.19 to 72.86%, MBN by 47.30 to 48.17%, and MBP by 17.37 to 208.47%. Compared with the unfertilized control (CK), the total microbial biomasses of the rhizospheric (increased by 22.80 to 90.82%) and bulk soils (increased by 10.57 to 60.54%) both exhibited increases with the application of organic manure, and the rhizospheric biomass was higher than that of bulk soil. Compared with bulk soil, the activities of C-, N- and P-acquiring enzymes of rhizospheric soil increased by 22.49, 14.88, and 29.45% under high levels of organic manure, respectively. Analyses of vector length, vector angle, and scatter plots revealed that both rhizospheric and bulk soils exhibited limitations in terms of both carbon (C) and phosphorus (P) availability. The results of partial least-squares path modelling indicated that the rhizospheric soil exhibited a more pronounced response to the rate of manure application than the bulk soil. The varying reactions of rhizospheric and bulk soils to the extended application of organic manure underscore the crucial function of the rhizosphere in mitigating limitations related to microbial resources, particularly in the context of different organic manure application rates.

Rationalizing mineral gypsum use through microbially enriched municipal solid waste compost for amelioration and regaining productivity potential of degraded alkali soils

Reclamation of alkali soils to harness their productivity potential is more complex due to the presence of excess sodium ions, poor hydraulic conductivity and infiltration rate, resulting in poor plant growth and crop productivity. Sodic soil reclamation using inorganic ameliorants like mineral gypsum or phosphogypsum is beyond the reach of small and marginal farmers having alkali soils because of their higher market prices and shortage of availability. Conjoint use of inorganic and organic amendments can be a pragmatic solution for improving soil physico-chemical and biological properties and sustaining crop productivity. Municipal solid waste compost (MSWC) available in abundant quantity if enriched with the efficient halophilic microbial consortium and used in conjunction with a reduced dose of gypsum can be a cost-effective approach for sustainable reclamation of alkali soils and harnessing their productivity potential. Hence, a field experiment was conducted on a high alkali soil (pH2 9.2 ± 0.10), electrical conductivity (EC) 1.14 ± 0.12 dS m−1, exchangeable sodium percentage 48 ± 2.50 and organic carbon (0.30%) was conducted during 2018–19 to 2020–21 to study the combined effect inorganic and organic (enriched municipal solid waste compost (EMSWC)) amendments on amelioration of alkali soils and sustaining productivity of rice–wheat cropping system. Application of gypsum @ 25% GR + enriched MSW compost @ 10 t ha−1 (T6) showed significant improvement in soil physico-chemical and biological properties over the sole application of organic (T3 and T4), inorganic (T2) and control (T1). A significant improvement in soil fertility status in terms of available nitrogen and micronutrients as well as CO3, HCO3, Cl, Ca and Mg content were recorded with the combined application of organic and inorganic soil amendments (T5 and T6) over the sole application of mineral gypsum. Soil microbial biomass carbon (MBC), nitrogen (MBN) and phosphorus (MBP) improved significantly due to the application of EMSWC with gypsum over the application of gypsum only. Grain yield of rice and wheat increased significantly (P < 0.05) owing to the application of a reduced dose of gypsum (25% GR) and EMSWC @ 10 t ha−1 (T6) with values of 5.55 and 3.83 t ha−1, respectively over rest of the treatments. Three years economic analysis of the study revealed that treatments T6 and T5 gave the highest positive net return whereas it was lowest in treatment T1 and negative in treatment T2. The highest benefit-to-cost ratio (B:C) was obtained in treatments T6 and T5 which were significantly higher compared to the rest of the treatments.

Extracellular Enzyme Activity and Stoichiometry Reveal Nutrient Dynamics during Microbially-Mediated Plant Residue Transformation

Extracellular enzymes are the major mediators of plant residue and organic matter decomposition in soil, frequently associated with microbial metabolic processes and the biochemical cycling of nutrients in soil ecosystems. However, the dynamic trends and driving factors of extracellular enzymes and their stoichiometry during plant residue transformation remain to be further studied. Here, we investigated the dynamics of extracellular enzymes and enzymatic stoichiometry in the “litter-soil” transformation interface soil (TIS) layer, an essential occurrence layer for microbially-mediated C transformation. The results indicated an unbalanced relationship between substrate resource supply and microbial metabolic demand. Microbial metabolism was limited by C (C/N-acquiring enzymes &gt; 1) and P (N/P-acquiring enzymes &lt; 1) throughout the observed stages of plant residue transformation. The initially higher extracellular enzyme activity reflected the availability of the active components (dissolved carbon (DC), nitrogen (DN), microbial biomass carbon (MBC), nitrogen (MBN), and phosphorus (MBP)) in the substrate and the higher intensity of microbial metabolism. With the transformation of plant residues, the active fraction ceased to be the predominant microbial C source, forcing the secretion of C-acquiring enzymes and N-acquiring enzymes to obtain C sources and N nutrients from refractory substrates. Moreover, C/N-acquiring enzymes decreased, while C/P-acquiring enzymes and N/P-acquiring enzymes subsequently increased, which suggested that the microbial demand for N gradually increased and for P relatively decreased. Soil microorganisms can be forced into dormancy or intracellular mineralization due to the lack of substrate resources, so microbial biomass and extracellular enzyme activities decreased significantly compared to initial values. In summary, the results indicated that soil nutrients indirectly contribute to extracellular enzymes and their stoichiometry by affecting microbial activities. Furthermore, extracellular enzymes and their stoichiometry were more sensitive to the response of soil microbial biomass carbon.

Relationships between soil and microbial biomass properties and annual flux of nutrients in Central Himalaya forests, India

AbstractThe interrelationship among soil attributes and microbial biomass carbon (MBC), nitrogen (MBN), and phosphorus (MBP) of Indian Central Himalaya forest soils were analyzed. The forest ecosystem studied composed of chir pine (CPF), banj oak (BOF), and mixed oak‐pine forest (MOPF). This study reported 429–739 mg kg−1 MBC, 67–121 mg kg−1 MBN, and 18–63 mg kg−1 MBP. The contribution of MBC, MBN, and MBP appears to be 1.47–4.11 (X = 2.66%), 2.65–11.17 (5.93%), and 5.61–19.0 (X = 10.47%) of the soil organic carbon, total nitrogen (N) and phosphorus (P), respectively. Significant variations were observed in terms of C:N, C:P, and N:P ratios among various sites which ranged between 5.95 and 8.08, 11.73 and 26.42, and 1.92 and 3.72, respectively. The linear association between MBP with MBC and MBN was observed. Further, a positive correlation was recorded between MBC, MBN, and MBP with various soil characteristics. The annual flux of N and P estimated by microbial biomass using the turnover rates of 0.67 was approximately 100–181 kg N and 27–94 kg P ha−1 yr−l, respectively, which was twice the level for mixed oak‐pine forest (MOPF) than CPF soils. Our study reports a significant decrease in soil microbial biomass C, N, and P with change in forest type from BOF to CPF. So, MOPF can be an alternative for sustainable management of degraded forest ecosystems in the Central Himalaya belt.

The molecular composition of extractable soil microbial compounds and their contribution to soil organic matter vary with soil depth and tree species

Recent findings on soil organic matter (SOM) revealed that soil microorganisms are not only crucial for SOM formation through plant litter degradation but soil microbial biomass (SMB) may also directly contribute to SOM and its composition. However, the role and interactions of litter quality, microbial turnover and composition of SMB and SOM remain unclear. Hence, soil profiles (organic forest floor and mineral soil layers) at a recultivated and afforested post-mining site were investigated for the influence of litter quality from different tree species (Fagus sylvatica, Pseudotsuga menziesii, Pinus nigra) and soil depth – representing different degrees of organic matter (OM) turnover – on the molecular composition of chloroform fumigation extracted SMB-derived compounds in comparison with easily extractable (non-fumigated) SOM-derived compounds. The SMB extracts were analyzed for microbial biomass carbon (MBC), nitrogen (MBN) and phosphorus (MBP). The molecular composition of SMB and SOM compounds were determined by electrospray ionization Fourier transformation ion cyclotron resonance mass spectrometry (ESI-FT-ICR-MS) complemented by the determination of nine monosaccharides representing microbial or plant origin.Van Krevelen diagrams obtained from the ESI-FT-ICR mass spectra revealed the substantial contribution of microbial-derived compounds to extractable SOM that further increased with soil depth. Analysis of the easily extractable monosaccharides implied that >99% were of microbial origin. Microbial sugars as well as MBC, MBN and MBP explained best depth-related variations of extractable SMB compounds indicating that supply and availability of C-rich OM drive these parameters. Furthermore, the contribution of microbial sugar C to MBC increased with depth, suggesting that recycling of carbohydrates is an adaptation strategy of microorganisms in C-limited environments. The supply of tree species-specific substrates resulted in different chemical composition of SMB with largest differences between deciduous and coniferous stands and vice versa, microorganisms contributed to SOM resulting in large similarity in the composition of extractable SOM and SMB.

Comparative Study on Soil Microbial Biomass in Tarai and Hill Sal (Shorearobusta Gaertn.) Forests of Tropical Region in Eastern Nepal

A comparative study was conducted to investigate the effect of altitudinal variation and seasonality on soil microbial biomass carbon (MB-C), nitrogen (MB-N), and phosphorus (MB-P) between Tarai Sal forest (TSF) and Hill Sal forest (HSF) of the tropical region in eastern Nepal. Soil microbial biomass was estimated by chloroform fumigation - extraction method in summer, rainy and winter seasons in the upper (0-15 cm) soil depth in both forests. Pre-conditioned soil samples were saturated with purified liquid chloroform, represented fumigated sample. Another set of soil samples without using chloroform, represented unfumigated samples and soil biomass was estimated from these samples. MB-C, MB-N, and MB-P were higher by 66%, 31%, and 9%, respectively, in HSF than TSF. Distinct seasonality was observed in soil microbial biomass. It was maximum in summer and minimum in rainy season in both the forest stands. The value decreased from summer to rainy season by 46 to 67% in HSF and by 32 to 80% in TSF. Higher soil microbial biomass in the summer season may be due to its accumulation in soil when the plant growth and nutrient demand are minimal. Analysis of variance suggested that MB-C, MB-N, and MB-P were significantly different for both sites and seasons (P &lt; 0.001). Soil organic carbon, TN, and TP were positively correlated with MB-C, MB-N, and MB-P in both the forests. In conclusion, the higher value of soil microbial biomass in HSF may be due to the higher concentration of soil organic matter and decreasing turnover rate of microbial biomass due to higher altitude. On the other hand, the lower value of microbial biomass at TSF may indicate its fast turnover rate due to lowland tropics to enhance the nutrient cycling process.

Ecological Stoichiometry of Microbial Biomass Carbon, Nitrogen and Phosphorus on Bauxite Residue Disposal Areas

Ecological succession by microbial activity on bauxite residue disposal areas (BRDAs) would accumulate nutrients and convert the residue into a soil-like material. However, the role of microorganisms in nutrient cycling remains elusive on BRDAs. Carbon (C), nitrogen (N) and phosphorus (P) ecological stoichiometry is a critical indicator of nutrient cycling in an ecosystem. In order to investigate the changes in nutrients following long-term natural weathering process, the contents of C, N, P, microbial biomass carbon (MBC), nitrogen (MBN), and phosphorus (MBP) were measured in chronological stacks of bauxite residue. Deeply, their ecological stoichiometric characteristics were analyzed. Compared to freshly stacked residue, organic carbon (OC), total nitrogen (TN) and available phosphorus (AP) have increased 89%, 1640%, and 369% after 20 years, respectively. The C/N in 20-year-old residue (BR20) is 12.41, which close to the mean range of soil C/N in China. Bauxite residue C/P and N/P increased significantly with the stacking age increased. MBC/MBN decreased from 6.75 to 4.52 after stacked for 5 years, whilst MBC/MBP increased from 23.74 to 59.16 with stacking age. Data analysis of C, N, P and MBC, MBN, MBP in bauxite residue correlated significantly, indicating that microbial biomass can be used as a biological indicator to evaluate bauxite residue quality. This study revealed that BRDAs ecosystem development reaches homeostasis gradually, whilst CNP and MBCNP substrate ratio can be used as an effective tool to explore the mechanism of nutrient cycling.

Assessment of the Microbial Biomass Carbon (MB-C), Nitrogen (MB-N) and Phosphorus (MB-P) in Soil Spiked with Pesticides (Carbofuran and Paraquat)

This study aimed at determining the impact of Carbofuran and Paraquat use on soil microbial biomass and microbial population as soil health index. Pot experiment, set-up as a randomized block design with replicates was done, with both pesticides applied at recommended rates for eight weeks. Twenty-four (24) soil samples were taken from the pesticides polluted soil as well as the unpolluted soil. These samples were used to assess the effect of pesticides on microbial biomass carbon (MB-C), nitrogen (MB-N) and phosphorus (MB-P). Also, microbial population (determined by aerobic spread plate count) of the pesticide-polluted soils was used as health index. The assessments were done weekly. The microbial biomass values increased from 273.48 µg/g to 293.15 µg/g (MB-C), 17.275 µg/g to 18.52 µg/g (MB-N) and 10.605 µg/g to 11.37 µg/g (MB-P) in carbofuran treated soil while increases from 277.26 µg/g to 288.365 µg/g (MB-C), 17.515 µg/g to 18.22 µg/g (MB-N) and 10.745 µg/g to 11.18 µg/g (MB-P) were observed in paraquat treated soil. The microbial counts in treated soils were within the ranges of 1.95 x 106 cfu/g to 1.03 x 107 cfu/g, 8.83 x 104 to 1.90 x 105 cfu/g, 1.08x 104 to 2.43 x 104, 1.15 x105 to 2.17 x 105 cfu/g, 1.38 x 105 to 2.22 x 105 cfu/g for total heterotrophic bacterial, fungal, actinomycetes, phosphate solubilizers, nitrifiers counts, respectively.&#x0D; The pesticides had no negative effects on the MB-C, MB-N, MB-P and soil microorganisms at recommended field rates, hence their use must be strictly based on these rates. These findings indicate that the relationship between soil nutrients and microbial biomass is significant in facilitating the use of microbial biomass as an important soil quality indicator.

Principal component analysis reveals microbial biomass carbon as an effective bioindicator of health status of petroleum-polluted agricultural soil

ABSTRACT We investigated a number of microbiological activities in the soil to serve as biomonitoring tools in assessing the ecotoxicity of diesel-contaminated soil samples during the different periods of bioremediation. Sawdust was used as the biostimulant for the biodegradation of artificial diesel-polluted soil samples. Soil microbial population, soil microbial enzymatic activities (catalase, lipase, dehydrogenase, urease, phosphatase and β-glucosidase), soil microbial biomass carbon (MBC), nitrogen (MBN) and phosphorus (MBP), soil microbial respirometric index and total petroleum hydrocarbon (TPH) concentration were monitored to evaluate the efficiency of the bioremediation process. After a period of 56 d, total petroleum hydrocarbon content reduced from 14,221 to 270 mg/kg. The parameter estimation using the nth-order kinetic model revealed that the first-order rate constants (k) for TPH removal were 4.417 d−1 and 0.2670 d−1 for sawdust-amended and unamended soil, respectively. This implied that, the sawdust amendment resulted in reaction rate 16.5 times faster than unamended soil. Thus, the biological indicators were generally more pronounced in biostimulated soil than the attenuated soil. However, to evaluate the efficiency of the sawdust-assisted bioremediation, principal component analysis, which was used in selecting the most sensitive bioindicators. It was observed that microbial biomass carbon, catalase, lipase and dehydrogenase were the most responsive bioparameters. A positive relationship between TPH removal and the four most sensitive bioparameters suggests that the use of four biological activities have proven to be effective monitoring tools for evaluating the efficiency of a bioremediation strategy.

Seasonal changes of soil microbial C, N, P and associated nutrient dynamics in a semiarid grassland of north China

Semiarid grasslands are widely distributed in northern China and characterized by marked seasonality. While the role of soil microbes in nutrient cycling is known to be crucial, the nutrient dynamics in relation to changes and turnover of microbial pools over the growth season in semiarid grasslands, are not well understood. In this study, three grasslands with long-term traditional managements (enclosure from sheep grazing for 31 or 18 years, or continuous free overgrazing) were selected to investigate the seasonal fluctuations of microbial biomass carbon (MBC), nitrogen (MBN), and phosphorus (MBP). In addition we calculated the turnover rates and fluxes of soil microbial biomass based on their seasonal fluctuations. Plant biomass and N, P uptakes were also assessed to reveal a potential relationship between plant and microbial nutrient pools. We found in this semiarid ecosystem approximately two times lower C:P and N:P ratios in microbial biomass (25:1 and 3:1, respectively) compared with global analysis (46:1 and 6:1, respectively). Enclosure from grazing increased MBC and MBN, while the change patterns of microbial pools were affected by season but not pasture management. Consequently, the turnover rates of microbial biomass as calculated from the seasonal fluctuations were similar in all treatments (around 1.5 year−1 for MBC and MBN, 3 year−1 for MBP). Lower mean stock in soil K2SO4-extractable N but similar in MBN compared with total plant N uptake were observed in all treatments, suggesting N deficiency in this region and the vital role soil microbes play as a stable nutrient pool for plant uptake. In contrast, both NaHCO3-extractable P and MBP stocks were much higher than total plant P uptake, suggesting no P deficiency under current N status.

Biochar-enhanced composts reduce the potential leaching of nutrients and heavy metals and suppress plant-parasitic nematodes in excessively fertilized cucumber soils.

Excessive fertilization is a common agricultural practice that has largely reduced soil nutrient retention capacity and led to nutrient leaching in China. To reduce nutrient leaching, in this study, we evaluated the application of biochar, compost, and biochar-compost on soil properties, leaching water quality, and cucumber plant growth in soils with different nutrient levels. In general, the concentrations of nutrients and heavy metals in leaching water were higher under high-nutrient conditions than under low-nutrient conditions. Both biochar and compost efficiently enhanced soil cation exchange capacity (CEC), water holding capacity (WHC), and microbial biomass carbon (MBC), nitrogen (MBN), and phosphorus (MBP), reduced the potential leaching of nutrients and heavy metals, and improved plant growth. The efficiency of biochar and compost in soil CEC, WHC, MBC, MBN, and MBP and plant growth was enhanced when applied jointly. In addition, biochar and biochar-enhanced compost efficiently suppressed plant-parasitic nematode infestation in a soil with high levels of both N and P. Our results suggest that biochar-enhanced compost can reduce the potential environmental risks in excessively fertilized vegetable soils.

Response of soil physical, chemical and microbial biomass properties to land use changes in fixed desertified land

Fixed dunes are indicators of successful recovery of desertified land after several years of vegetation restoration. Land use profoundly influences soil properties; however, the effects of changes in land use, after the dunes are fixed, on soil physical, chemical and microbial biomass properties are still unclear. This study investigates the soil physical and chemical properties and soil microbial biomass in a desertified land located in the Xiaojihan desertification control station in northern Shaanxi province, where land use changed from shrub land to arboreal land, arable land and nursery garden. No significant changes in soil properties were found when shrubland was changed to arboreal land. However, changing the fixed desertified land from shrub land to arable land and nursery garden decreased soil porosity, but significantly increased soil bulk density (BD), soil organic matter (SOM), cation exchange capacity (CEC), total nitrogen (TN) and available nutrients (N, P, K). Soil microbial biomass carbon (MBC), nitrogen (MBN) and phosphorus (MBP), as well as microbial quotient (MBC/SOC, MBN/TN, MBP/TP), decreased significantly. No significant changes were detected in soil texture, total phosphorus (TP) and total potassium (TK). Results of this study indicated that agricultural land use can improve the fertility of fixed desertified land; however, soil microbial biomass could decrease. Therefore, conversion of fixed dunes to agricultural usage is full of risks.

连续施用保水材料对旱作条件下土壤特性及燕麦生长的影响

PDF HTML阅读 XML下载 导出引用 引用提醒 连续施用保水材料对旱作条件下土壤特性及燕麦生长的影响 DOI: 10.5846/stxb201604130676 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金项目（31160267）；国家科技支撑计划资助项目（2015BAD22B04）；全国农业科研杰出人才及其创新团队；内蒙古自治区燕麦种质资源创新与利用科技创新团队（20140401）；国家现代农业产业技术体系（CARS-08-B-5）资助 Effects of continuous application of water-retaining materials on soil characteristics and oat (Avena nuda L.) growth under dry-farming conditions Author: Affiliation: Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:以坝莜一号为材料，研究连续4a施用保水材料聚丙烯酰胺（PAM）与聚丙烯酸钾（PAM-K），对旱作农田不同土层土壤微生物量变化与相应土层土壤含水量、容重、电导率、养分及燕麦生长的影响。结果表明，旱区农田施用PAM-K和PAM的微生态效应存在时空差异，以连续施用4a效果最佳，其大小顺序表现为连续施用4a > 施用3a > 2a > 1a > 对照。连续施用4a PAM-K和PAM，0-60 cm土层土壤含水量平均增加了27.18%和34.40%；土壤容重、土壤电导率分别平均降低了2.33%和6.64%、29.50%和22.70%；相对显著增加了耕层土壤养分（有机质、碱解氮、有效磷、速效钾）含量；土壤微生物生物量碳、氮、磷增幅平均达24.11%、31.89%、46.52%和69.96%、35.21%、52.70%，尤其是连续施用4a PAM，10-20cm土层土壤微生物量氮增幅达98.95%及0-10cm、20-40cm土层土壤微生物生物量碳和土壤微生物量磷的增加最明显，增幅分别达31.13%和74.49%、62.27%和49.91%。连续施用4a PAM-K和PAM，植株鲜重、干重、株高、籽粒产量，分别增加了90.53%和146.91%、101.56%和128.13%、33.67%和76.39%、19.27%和22.40%。可见，连续多年施用PAM-K和PAM对施入层（0-20 cm）和近施入层（20-40 cm）改善效果显著；PAM对旱区土壤的适宜性优于PAM-K，可改善土壤质量，提高作物产量。 Abstract:A four-year experiment was conducted to investigate the effects of polyacrylamide (PAM) and potassium polyacrylate (PAM-K) application on the growth characteristics of oat (Avena nuda L.) and soil at different soil depths and in different years (2011, 2012, 2013, and 2014). The correlations between the growth characteristics of oat and soil microbial biomass, nutrients, moisture content, electrical conductivity, and bulk density at the respective soil layers in a dry land area of Inner Mongolia were also examined. PAM and PAM-K were applied at a rate of 75 kg/hm2 per year. The experiment consisted of a total of 8 treatments and a control. The application groups were as follows:conventional tillage (CK), (1) M1:PAM 2011, (2) M2:PAM 2011 and 2012, (3) M3:PAM 2011, 2012, and 2013, (4) M4:PAM 2011, 2012, 2013, and 2014, (5) A1:PAM-K 2011, (6) A2:PAM-K 2011 and 2012, (7) A3:PAM-K 2011, 2012, and 2013, and (8) A4:PAM-K 2011, 2012, 2013, and 2014. This was a two-factor experiment involving a randomized complete block design with three replications. Each treatment occupied a plot area of 4×5 m. Water-retaining materials were spread equally on the surface of the land and then incorporated into the soil by tilling. Oat seeds were sown on May 25 and harvested in late September during the four experimental years (2011, 2012, 2013, and 2014) at a rate of 3750000 plants per hectare with a row spacing of 25 cm and seeding depth of 3-5 cm. With increasing PAM and PAM-K application, differences in micro-ecological effects were observed at different times for the rain-fed farmland. The results showed the following superiority order:4 years > 3 years > 2 years > 1 year. At a depth of 0-60 cm soil, compared with the control, for the treatments administered continuously for four years (A4 and M4), soil moisture increased by an average of 27.18% in A4 and 34.40% in M4. A decreasing trend was observed for soil bulk density and soil electrical conductivity; soil bulk density decreased by 2.33% and 6.64%, while soil conductivity reduced by an average of 29.50% and 22.70% for A4 and M4, respectively. Soil nutrient content (available P, N, and K, organic matter) increased in both A4 and M4. Microbial biomass carbon (MBC), nitrogen (MBN), and phosphorus (MBP) showed an increasing trend; MBC increased by an average of 24.11% in A4 and 31.89% in M4, MBN increased by 46.52% in A4 and 69.96% in M4, and SMBP increased by 35.21% in A4 and 52.70% in M4. Interestingly, at a depth of 10-20 cm, MBN increased by 98.95% in M4, while at 0-10 cm, MBC increased significantly by 31.13% and MBP increased by 74.49% in M4, respectively. At a depth of 20-40 cm, MBC increased significantly by 62.27%, while MBP increased by 49.91% in M4, respectively. Additionally, the oat seedling aboveground fresh biomass increased for A4 and M4 by 90.53% and 146.91%; aboveground dry biomass increased by 101.56% and 128.13%, plant height increased by 33.67% and 76.39%, and grain yield increased by 19.27% and 22.40%. Significant improvement was observed with continuous application of PAM and PAM-K in the plowing layer (0-20 cm) and near the application layer (20-40 cm). We recommend PAM treatment, which is more suitable for yellow loamy soil, than PAM-K treatments, to improve soil quality and increase crop yield in dry farming areas. 参考文献 相似文献 引证文献

Effects of vegetation on soil microbial C, N, and P dynamics in a tropical forest and savanna of Central Africa

The forest–savanna transition zone is widely distributed on nutrient-poor oxisols in Central Africa. To reveal and compare the nutrient cycle in relation to soil microbes for forest and savanna vegetation in this area, we evaluated seasonal fluctuations in microbial biomass carbon (MBC), nitrogen (MBN), and phosphorus (MBP) for 13 months as well as soil moisture, temperature, soil pH levels, and nutrients for both vegetation types in eastern Cameroon. Soil pH was significantly lower in forest (4.3) than in savanna (5.6), and soil N availability was greater in forest (87.1mgNkg−1 soil) than in savanna (32.9mgNkg−1 soil). We found a significant positive correlation between soil moisture and MBP in forest, indicating the importance of organic P mineralization for MBP, whereas in savanna, we found a significant positive correlation between soil N availability and MBP, indicating N limitation for MBP. These results suggest that for soil microbes, forest is an N-saturated and P-limited ecosystem, whereas savanna is an N-limited ecosystem. Additionally, we observed a significantly lower MBN and larger MB C:N ratio in forest (50.7mgNkg−1 soil and 8.6, respectively) than in savanna (60.0mgNkg−1 soil and 6.5, respectively) during the experimental period, despite the rich soil N condition in forest. This may be due to the significantly lower soil pH in forest, which influences the different soil microbial communities (fungi-to-bacteria ratio) in forest versus savanna, and therefore, our results indicate that, in terms of microbial N dynamics, soil pH rather than soil substrate conditions controls the soil microbial communities in this area. Further studies should be focused on soil microbial community, such as PLFA, which was not evaluated in the present study.

Cultivation impacts soil microbial dynamics in dry tropical forest ecosystem in India

We studied for two years the seasonal changes in plant available nitrate and ammonium nitrogen (N), nitrification, N-mineralization, microbial biomass carbon (MBC), nitrogen (MBN) and phosphorus (MBP) in two forest and three cropland sites, derived from a tropical forest ecosystem of India. Results indicated that seasonal values of nitrate N, ammonium N and phosphate P ranged from 7.33–12.99, 5.1–10.22 and 4.0–7.8μgg−1 in forest and 4.13–9.26, 9.35–14.46 and 2.8–5.8μgg−1 in cropland ecosystems, respectively, with maximum values in summer and minimum in rainy seasons. Nitrification and N-mineralization values varied from 6–28 and 4–26μgg−1mo−1 in forest and 3–14μgg−1mo−1 and 4–17μgg−1mo−1 in cropland, with maximum values in rainy season and minimum in summer season.MBC, MBN MBP ranged from 393–753, 34–80 and 16–36μgg−1 in forests and 186–414, 21–41 and 11–22μgg−1 in croplands, being maximum in summer and minimum in rainy seasons. There was gradual increase in the values of inorganic N, nitrification, N-mineralization and MBC, MBN and MBP along the age of cropland. Analysis of variance indicated significant difference in the concentration of inorganic N, nitrification and N-mineralization and MBC, MBN and MBP due to sites and seasons.Cultivation caused decline in the mean annual organic C, N and P by 42%, 29% and 13%. The values of nitrate N were decreased by 23–38%, while ammonium N was increased by 39–74%. Nitrification and N-mineralization values were reduced by 39–63% and 40–60%, respectively. Microbial C, N and P were reduced by 44–54%, 41–50% and 28–44%, respectively. Nonetheless, the contribution of soil microbial biomass reflected in total N was enhanced from 4.76% in forest to 5.03% in cropland ecosystem. Enhancement of plant available ammonium-N and microbial contribution in total N are an indicator of natural conserving mechanism to check the nitrogen loss from the nutrient poor agro-ecosystem.

黄土丘陵区植被类型对土壤微生物量碳氮磷的影响

The Loess Plateau is an important site for many ecological restoration studies in China. Different vegetation types change the soil environment to different extents,influencing the biogeochemical cycles of materials such as soil microbial biomass carbon,nitrogen and phosphorus. Determining the relationship between soil physicochemical properties and soil microbial biomass under different vegetation types can provide useful information for vegetation restoration in the Loess Plateau. Soil profiles under four typical vegetation types( natural grassland,artificial shrub land,artificial timber forest and crop land) were collected in the Yanhe River catchment in a hilly area of the Loess Plateau. The Yanhe River catchment( 36°23'—37°17' N,108°45'—110°28' E) is situated in the north of the Shaanxi Province. It belongs to the continental monsoon climate. The basic soil physicochemical properties and microbial biomass carbon( MBC),nitrogen( MBN),and phosphorus( MBP) were measured. The results indicated that the MBC of natural grassland,artificial shrub land,artificial timber forest and crop land ranged from 315. 15—400. 89,246. 56—321. 25,267. 76—347. 05 and 118. 96—245. 14 mg /kg,respectively and the MBN ranged from 35. 87—47. 63,27. 63—42. 89,24. 66—36. 20 and 15. 64—22. 56 mg / kg,respectively and the MBP ranged from 14. 14—22. 96,12. 89—19. 75,11. 54—14. 40 and 7. 23—11. 59 mg / kg,respectively. Natural grassland showed the highest soil microbial biomass,followed by artificial timber forest,artificial shrub land and crop land,indicating that returning crop land to forests or grassland had a significant promoting impact on the soil microbial biomass. Under the different types of vegetation,the MBC / MBN ranged from 7. 49 to 10. 87,and the MBC / MBP ranged from 16. 27 to 24. 11. The ratio of MBC / soil organic C was 2. 70% —4. 85%,the ratio of MBN / total N was 2. 56% —4. 45% and the ratio of MBP / total P was 2. 08% —5. 34%. The MBC / MBN and MBC / MBP of natural grassland,artificial timber forests and crop land were all significantly less than the artificial shrub land( P 0. 05),but the MBC / soil organic C showed no significant differences between vegetation types. The MBN / total N and MBP / total P of natural grasslands were significantly more than the artificial shrub land,followed by the artificial timber forest and the crop land( P 0. 05). The soil microbial biomass correlated or significantly correlated with soil organic C,total N and soil moisture,but negatively correlated with the soil pH. This showed that the vegetation types had a significant impact on the physical and chemical properties of soil that are closely associated with the soil microbial biomass.

Does Soil Disturbance Affect Soil Phosphorus Fractions?

Increased turnover of organic matter as a result of soil disturbance (e.g. by soil tillage) is described in principle, but the direct influence of soil disturbance on soil P turnover especially for organic farming systems has not been sufficiently proven. The objective of the study was to evaluate the short term effect of soil disturbance on different soil P fractions in a soil shaking experiment. Four soils were incubated for 10 days in the dark with three different disturbance treatments: 1) no disturbance, 2) overhead shaking for 2 h at the beginning of the experiment and 3) continuous overhead shaking at 5 r. p. m. The four investigated soils were: 1) a silty loam soil with long term bio-compost application and 2) the corresponding soil without bio-compost application, 3) a long-term organically managed clay loam soil and 4) a clay loam soil with long time application of pig manure, all not and from Baden-Wurttemberg, Germany. We determined NaHCO3-, NaOH- and H2SO4-extractable inorganic and organic P fractions (Pi and Po, resp.) in a sequential extraction. Furthermore, the potentially plant available P as Calcium-acetate-lactate-extractable P (CAL-P) and P extractable by electro-ultra-filtration (EUF-P), and aqua regia extractable total P (PT) were determined. Furthermore, we determined microbial biomass carbon (MBC), nitrogen (MBN) and phosphorus (MBP), and acid phosphatase activity in soil. The organically managed soil had the highest PT contents (1300 mg·kg-1). The soil with pig manure application had the smallest potentially labile P fractions (NaHCO3-Pi and -Po and NaOH-Pi). The ecologically managed soil had the biggest organic P fractions (114 mg·kg-1 NaHCO3-Po and 463 mg·kg-1 NaOH-Po), but, this soil was the lowest in CAL-P (5 mg·kg-1). Short term soil disturbance had effects on labile organic P fractions of two of the four analyzed soils, but inorganic P was rather unaffected. In the compost amended COMP(+) soil, there was an incorporation of P from the less available NaOH-P fractions into the more available NaHCO3-Po fraction. However, if taking all investigated soils and treatments into account, the effects of soil disturbance were limited and not consistent.

Impact of Savannization on Nitrogen Mineralization in an Indian Tropical Forest

The effects of conversion of an Indian dry tropical forest ecosystem into savanna, on mineral nitrogen (N), net N-mineralization rate and microbial biomass carbon (MBC), nitrogen (MBN) and phosphorus (MBP) in soil were studied for two years. There was a marked seasonal variation in all the above parameters at both (upper, 0-10 cm and lower, 10-20 cm) the soil depths of forest and savanna ecosystems. In forest ecosystems the mean annual values of mineral N, net nitrification rate, net N-mineralization rate, MBC, MBN and MBP at both depths were 17.41 and 13.2 µg g -1 , 18.76 and 10.96 µg g -1 mo -1 , 23.54 and 12.83 µg g -1 mo -1 , 623 and 195µg g -1 , 116 and 29µg g -1 , 16 and 9µg g -1 , respectively; while in savanna ecosystems the values were 20.15 and 15.73 µg g-1, 10.74 and 6.29 µg g-1mo-1, 16.59 and 10.11 µg g -1 mo -1 , 453 and 150µg g -1 , 79 and 21.7µg g -1 , 13 and 6µg g -1 , respectively. The soil microbial biomass was positively related to root biomass and total plant biomass (i.e., above- and below-ground biomass). Interestingly, seasonal soil moisture and temperature are reciprocally related to microbial biomass and mineral N and directly related to nitrification and N-mineralization. The microbial biomass, nitrification and N-mineralization are negatively related to clay content. Savannization caused significant loss of soil mean organic carbon (OC), total N (TN) total mean annual nitrification, N-mineralization, MBC, MBN and MBP by 40, 42, 27, 27, 29 and 7%, respectively at upper soil depth and 18, 21, 42, 29 and 22%, respectively at lower soil depth. The reflectances of soil microbial biomass to OC were 1.22 and 1.06 folds at upper and lower soil depths, respectively. Thus, conversion of dry tropical forests into savanna affects remarkably the soil N transformation; microbial biomass and loss of soil organic C which adds to the environmental pollution.

高山森林三种细根分解初期微生物生物量动态

Microorganism plays an essential role in the decomposition of litter and senesced fine root,as a consequence of which more and more attentions have been paid to the microbial biomass dynamics in litter and soil in the past two decades.Moreover,increasingly studies have also demonstrated that lots of litter mass lost in cold winter in the seasonal freeze-thaw area.However,little information has been available on the dynamics of microbial biomass during litter decomposition in wintertime,far less for fine roots decomposition.In order to character the dynamics of microbial biomass during fine roots decomposition in a alpine forest over the growing season and freeze-thaw season,microbial biomass carbon(MBC),nitrogen(MBN) and phosphorus(MBP) were measured using the litterbag method from November 11,2009 to November 11,2010.The fine roots of Picea asperata,Abies faxoniana and Betula albosinensi were selected which are three representative tree species in the alpine and subalpine forest of Western China.Microbial biomass C(MBC) displayed a sharp decline tendency before the soil frozen as soil temperature decreased,and significantly increased utile to soil thawing,but continually declined as temperature increased after the middle stage of soil thawing,and then a increased tendency was observed.However,the changed time of MBC was different in the fine root decomposition of different species.The peak values of MBC during the decomposition of spruce and fir fine roots were observed in the late stage of growing season,but which of birch was detected in the early stage of soil frozen.MBN displayed the similar dynamics pattern during the fine roots decomposition for all three species,which rapidly decreased until soil completely frozen,and showed little changes during the whole freeze-thaw season,but obviously increased to a peak value in the later stage of growing season.In addition,MBP during the decomposition of spruce and fir fine roots were increased as the decomposition proceeded,although which of birch displayed its maximum value in the later stage of soil thawing,another peak value in the middle stage of growing season,and then obviously declined in the later stage of growing season.The results indicated that large quantities microorganisms could be available even in winter,which could do great contributions to the litter decomposition.Nevertheless,the microbial biomass could be significantly affected by fine root quality,temperature and other climate conditions.

Spatial variability of soil microbial biomass carbon, nitrogen and phosphorus in a hilly red soil landscape in subtropical China

Soil microbial biomass (SMB) is considered to be an important indicator of soil fertility and biological quality, and it presents strong spatial heterogeneity in relation to soil properties (e.g. soil texture, organic carbon, total nitrogen) and topography at various spatial and temporal scales. In the present study, geostatistics were used to analyze the spatial variability of soil microbial biomass carbon (MBC), nitrogen (MBN) and phosphorus (MBP) in a hilly red soil landscape (446 ha) in subtropical China. Five hundred and twenty-three soil samples at a soil depth of 0–20 cm were randomly collected from paddy fields, dry lands, orchards and wood lands in the study region. Significant negative correlations (r = −0.69 to −0.54) of MBC, MBN and MBP with elevation were observed. The Stein's Matérn, Spherical and Gaussian models with effective ranges of 157, 252 and 213 m were best-fitted to the sample semivariograms of original MBC, MBN and MBP variables, respectively. All three SMB variables exhibited moderate spatial dependence. After detrending the elevation impact, the normal score transformed MBC and MBP still retained their moderate spatial autocorrelations with slightly decreased effective ranges, whereas the normal score transformed MBN demonstrated a very strong spatial dependence with a much shorter effective range of 70 m. Spatial distributions of the three SMB variables were estimated using both ordinary kriging (OK) and regression kriging (RK) with elevation as the predictor. The kriging predictions showed that soil MBC, MBN and MBP had overlapping spatial patterns, and furthermore the RK interpolations showed more details in space than the OK interpolations, with improved prediction accuracy. The spatial distribution of soil MBN demonstrated more hotspots than the other two SMB variables, implying that MBN might be more sensitive to environmental disturbances (such as fertilization, tillage and crop rotations).