Short-term effects of biochar amendment on soil microbial community in humid tropics

Biochar is known to ameliorate soil fertility and improve crop production but information regarding soil microbiota responses on biochar amendment remains limited. The experiment was conducted to study the effect of biochars from palm kernel (pyrolysed at 400°C) and rice husk (gasified at 800°C) in a sandy loam Acrisol from Peninsular Malaysia. The soil was amended with palm kernel shell biochar (PK), rice husk biochar (RH), palm kernel biochar with fertilizer (FPK), rice husk biochar with fertilizer (FRH), fertilizer and control soil. Soil samples were taken during maize harvesting and were analysed for physico-chemical properties, microbial biomass, microbial abundance and microbial diversity. Increase in pH, moisture content, CEC, organic C, and labile C were recorded in all biochar amended soils. Microbial biomass C was 65% and 36% higher in RH and FRH, respectively, than control. Microbial biomass N was greatest in FPK and FRH with respective increment of 359% and 341% than control. β-glucosidase and xylanase activities were significantly increased in all biochar treated soils than control. A shift in microbial diversity was not detected. The biochar affects the microbial community by altering the soil environment and increasing labile active carbon sources in the short-term amendment.     

Differences in soil enzyme activities,microbial community structure and short-term nitrogen mineralisation resulting from farm management history and organic matter amendments

Changes in soil microbial biomass, enzyme activities, microbial community structure and nitrogen (N) dynamics resulting from organic matter amendments were determined in soils with different management histories to gain better understanding of the effects of long- and short-term management practices on soil microbial properties and key soil processes. Two soils that had been under either long-term organic or conventional management and that varied in microbial biomass and enzyme activity levels but had similar fertility levels were amended with organic material (dried lupin residue, Lupinus angustifolius L.) at amounts equivalent to 0, 4 and 8 t dry matter lupin ha^?1. Microbial biomass C and N, arginine deaminase activity, fluorescein diacetate hydrolysis, dehydrogenase enzyme activity and gross N mineralisation were measured in intervals over an 81-day period. The community structure of eubacteria and actinomycetes was examined using PCR–DGGE of 16S rDNA fragments. Results suggested that no direct relationships existed between microbial community structure, enzyme activities and N mineralisation. Microbial biomass and activity changed as a result of lupin amendment whereas the microbial community structure was more strongly influenced by farm management history. The addition of 4 t ha^?1 of lupin was sufficient to stimulate the microbial community in both soils, resulting in microbial biomass growth and increased enzyme activities and N mineralisation regardless of past management. Amendment with 8 t lupin ha^?1 did not result in an increase proportional to the extra amount added; levels of soil microbial properties were only 1.1–1.7 times higher than in the 4 t ha^?1 treatment. Microbial community structure differed significantly between the two soils, while no changes were detected in response to lupin amendment at either level during the short-term incubation. Correlation analyses for each treatment separately, however, revealed differences that were inconsistent with results obtained for soil biological properties suggesting that differences might exist in the structure or physiological properties of a microbial component that was not assessed in this study.     

Changes in nutrient content,enzymatic activities and microbial properties of lateritic soil due to application of different vermicomposts: a comparative study of ergosterol and chitin to determine fungal biomass in soil

In this experiment, vermicomposts, prepared from five different waste materials, were applied to acid lateritic soil under field conditions and soil samples were collected after 90 days to study the effect of vermicomposts on different chemical and biochemical. Results suggest that vermicompost prepared from paddy straw is most effective to improve nutrient content, enzymatic activities and microbial properties of lateritic soil. Vermicompost application significantly (P ≤ 0.05) increased the concentration of organic C, mineralizable N, available P and exchangeable K in soil. Amylase, protease, urease and acid phosphatase activities were also significantly (P ≤ 0.05) higher in vermicompost treated soils compared with the control. Both basal and substrate‐induced microbial respiration, microbial biomass C and N and fungal population in lateritic soil were increased due to vermicompost application. Ergosterol and chitin content were significantly (P ≤ 0.05) higher in vermicompost treated soils over the control. Application of vermicompost increased the proportion of fungal biomass in total soil microorganisms.     

改良剂对旱地红壤微生物量碳、氮及可溶性有机碳、氮的影响

基于室内模拟培养试验,研究改良剂(生物质炭、过氧化钙)对旱地红壤微生物量碳、氮及可溶性有机碳、氮的影响。试验设置4个处理,即CK、Ca(过氧化钙,1.72g/kg)、C(生物质炭,21.46g/kg)、C+Ca。结果表明:各处理土壤微生物量碳、氮以及可溶性有机碳具有相同的变化趋势,即前期(3d内)都增加较快,在第3天达到最大值,随试验进行有所下降,配施效果优于单施。各处理可溶性有机氮在21d内缓慢增加;第21天时,C+Ca、Ca、C相比CK分别显著增加了62.1%,55.5%,40.9%;35d以后,配施(C+Ca)与单施过氧化钙(Ca)的效果显著优于单施生物质炭(C)和对照(CK)。120d培养期内,配施(C+Ca)处理能够明显提高微生物量碳、氮以及可溶性有机碳、氮的平均含量;微生物量碳的平均含量大小顺序为C+CaCCKCa,微生物量氮的平均含量C+Ca处理显著高于其他处理;可溶性有机碳的平均含量大小顺序为C+CaCaCCK,可溶性有机氮的平均含量C+Ca、Ca处理显著高于CK、C处理。微生物量碳、氮以及可溶性有机碳之间互为极显著正相关(P0.01),而微生物量碳与可溶性有机氮之间呈极显著负相关。因此,生物质炭和过氧化钙能有效提高旱地红壤微生物量碳、氮及可溶性有机碳、氮,且生物质炭与过氧化钙配合施用更有助于土壤改良。     

Changes in enzyme activities and microbial biomass after “in situ” remediation of a heavy metal-contaminated soil

Microbial properties such as microbial biomass carbon (MBC), arylsulfatase, β-glucosidase and dehydrogenase activities, and microbial heterotrophic potential, together with several chemical properties such as pH, CaCl₂ soluble heavy metal concentrations, total organic carbon and hydrosoluble carbon were measured to evaluate changes in soil quality, after “in situ” remediation of a heavy metal-contaminated soil from the Aznalcóllar mine accident (Southern Spain, 1998). The experiment was carried out using containers, filled with soil from the affected area. Four organic amendments (a municipal waste compost, a biosolid compost, a leonardite and a litter) and an inorganic amendment (sugarbeet lime) were mixed with the top soil at the rate of 100 Mg ha⁻¹. Unamended soil was used as control. Agrostis stolonifera L. was sown in the containers. The soil was sampled twice: one month and six months after amendment application. In general, these amendments improved the soil chemical properties: soil pH, total organic carbon and hydrosoluble carbon increased in the amended soils, while soluble heavy metal concentrations diminished. At the same time, higher MBC, enzyme activities and maximum rate of glucose mineralization values were found in the organically amended soils. Plant cover was also important in restoring the soil chemical and microbial properties in all the soils, but mainly in those that were not amended organically. As a rule, remediation measures improved soil quality in the contaminated soils.     

Soil ameliorants alter physicochemical properties and fungal communities in saline-sodic soils of Northeast China

To understand the mechanisms of soil ameliorants affecting microbial communities is important for saline-sodic soils reclamation. High-throughput sequencing was used to characterize the fungal community in soils amended with four types of ameliorants over an 8-year period. Besides a control without any additional ameliorant (CK), other four treatments including 1) amendment with sandy soil (SS), 2) amendment with desulfurization gypsum (DG), 3) amendment with farm manure (FM), and 4) amendment with a mixture of SS, DG, and FM (M) were analyzed. Soil pH and electrical conductivity significantly decreased with the addition of soil ameliorants, whereas the soil organic carbon (SOC), total nitrogen (TN), and SOC/TN ratio (C/N) significantly increased in the FM and M treatments compared with the CK treatment. Fungal richness increased significantly with the mixed ameliorants addition (M). Distinct fungal community structures were observed in the treatments with soil ameliorants. The fungal community composition was significantly associated with the SOC, C/N, aggregate content with a diameter > 0.25 mm and geometric mean diameter. The changes in these soil characteristics were highly correlated with the ameliorants additions, suggesting that the impacts of ameliorants on the soil fungal community occurred indirectly as a result of alterations to soil physiochemical properties.     

双季稻田土壤微生物群落对连续5年施有机肥和石灰的响应差异

  目的  土壤微生物是土壤健康的敏感“指示器”,但不同的土壤微生物类群对连续施用有机肥和石灰的响应规律及不同指标的敏感性仍不明确。  方法  本文选取中亚热带双季稻区的紫泥田作为研究对象,研究连续5年施用有机肥或石灰后,土壤微生物“黑箱指标”（微生物生物量碳氮、微生物熵和土壤呼吸速率）和土壤活体微生物（PLFAs）组成的响应规律与差异。  结果  与对照相比,连续施用有机肥后,土壤微生物生物量碳（MBC）、氮（MBN）含量和土壤呼吸速率分别提高37%、28%和44% ~ 59%,微生物多样性也显著提高,土壤细菌结构发生改变,尤其是革兰氏阴性菌（G?）的PLFAs绝对量提高了100%,但真菌类群的响应不敏感。相反,连续施用石灰5年后,土壤微生物生物量碳、氮含量均呈下降趋势,微生物熵和土壤呼吸速率分别降低11%和26% ~ 52%,微生物多样性显著降低,细菌、放线菌和绝大多数真菌类群PLFAs绝对量下降30% ~ 58%。相关性分析结果表明,土壤有机质含量与土壤微生物总PLFAs和细菌PLFAs含量呈显著正相关关系;而土壤pH仅与Simpson多样性指数呈显著正相关关系。施有机肥显著提高了土壤有机质含量进而导致细菌MBC、MBN、G?和土壤呼吸速率显著增加;而施石灰后土壤微生物群落结构及活性降低与土壤pH有关。  结论  连续5年施用有机肥、石灰后,土壤微生物指标分别表现为正面、负面响应。与“黑箱指标”相比,某些特定微生物类群（如G?）的敏感性指数值更高,在土壤健康评价中极具应用潜力。     

微生物改良基质对新围垦海涂盐土改良的初步研究

海涂围垦区是陆海过渡带,围垦区土壤的传统洗盐和培肥技术易威胁近海生态环境,因此,探索新型、生态的盐土改良技术十分重要。该研究初步研究了新型微生物改良基质的盐土改良功能,结果表明微生物改良基质效果显著。相较于对照处理,微生物改良基质处理水稻产量增加了83.2%(P<0.05);土壤饱和含水率、田间持水量、总孔隙度、有机质、全氮、速效钾分别增加了13.80%、20.00%、6.80%、2.30倍、53.00%、31.00%(P<0.05);土壤容重降低了6.90%;土壤细菌、真菌和放线菌数量分别增加了10.30、11.20和3.18倍;水稻生育期累积灌溉水量减少了35.20%;0~10和>10~20cm土层可溶性盐质量分数分别降低了61.10%和54.40%。微生物改良基质能够在短期内加速盐分洗脱,提升土壤质量,是海涂新围垦区盐土改良的生态高效措施。     

Effects of copper on the decomposition of plant residues,microbial biomass,and β-glucosidase activity in soils

Abstract

Two types of soils (Brown Lowland soil and Ando soil), which were artificially enriched with different amounts of Cu, were incubated with or without pulverized orchard grass for 12 weeks at 25°C. For both soils with and without orchard grass amendment, the amount of CO₂ evolved over the 12-week period of incubation decreased by the enrichment with Cu at a concentration exceeding 1,000 mg kg^?1 soil. The decrease of the mineralization of added orchard grass in the Cu-enriched soil was conspicuous especially during the initial period of incubation. The amount of microbial biomass C at the end of the incubation was significantly reduced by the Cu enrichment regardless of the amendment with orchard grass. The relative decrease of the soil microbial biomass was much greater than that of the soil respiration. The amount of biomass C was negatively correlated with the amount of 0.1 M CaCl₂-extractable Cu as a logarithmic function. On the other hand, the β-glucosidase activity at the end of the incubation was not significantly affected by the presence of Cu in the soils without orchard grass amendment and increased with the increase in the amount of enriched Cu in the orchard grass-amended soils.     

土壤微生物体氮的季节性变化及其与土壤水分和温度的关系

以杨陵土垫旱耕人为土(中等肥力红油土)为供试土壤进行田间试验和室内培养试验,研究土壤微生物体氮的动态变化及其土壤含水量和温度的关系。结果表明,田间土壤微生物体氮的变化有明显的季节性;夏季最高,冬季最低,其它时期居中;且与土壤温度有显著或极显著的正相关性,相关系数在0.855以上;试验期间土壤水分含量在10%以上,基本能满足微生物活动所需,因而微生物体氮的变化与水分关系并不密切。应用培养试验结果进一步证明了田间试验结果,即在4～36℃范围内,微生物体氮与温度呈线性相关,而在土壤含水量为6.75%～23.23%范围内,与水分呈指数相关关系,当土壤水分小于10.87%时,水分对微生物体氮有突出结果,当超过10.87%后,几乎没有影响。频繁的干湿交替会使微生物体氮显著减少,但冻融交替却无明显影响。     

Influence of organic and mineral amendments on microbial soil properties and processes

Microbial diversity in soils is considered important for maintaining sustainability of agricultural production systems. However, the links between microbial diversity and ecosystem processes are not well understood. This study was designed to gain better understanding of the effects of short-term management practices on the microbial community and how changes in the microbial community affect key soil processes. The effects of different forms of nitrogen (N) on soil biology and N dynamics was determined in two soils with organic and conventional management histories that varied in soil microbial properties but had the same fertility. The soils were amended with equal amounts of N (100 kg ha⁻¹) in organic (lupin, Lupinus angustifolius L.) and mineral form (urea), respectively. Over a 91-day period, microbial biomass C and N, dehydrogenase enzyme activity, community structure of pseudomondas (sensu stricto), actinomycetes and α proteobacteria (by denaturing gradient gel electrophoresis (DGGE) following PCR amplification of 16S rDNA fragments) and N mineralisation were measured. Lupin amendment resulted in a two- to five-fold increase in microbial biomass and enzyme activity, while these parameters did not differ significantly between the urea and control treatments. The PCR–DGGE analysis showed that the addition of mineral and organic compounds had an influence on the microbial community composition in the short term (up to 10 days) but the effects were not sustained over the 91-day incubation period. Microbial community structure was strongly influenced by the presence or lack of substrate, while the type of amendment (organic or mineral) had an effect on microbial biomass size and activity. These findings show that the addition of green manures improved soil biology by increasing microbial biomass and activity irrespective of management history, that no direct relationship existed among microbial structure, enzyme activity and N mineralisation, and that microbial community structure (by PCR–DGGE) was more strongly influenced by inherent soil and environmental factors than by short-term management practices.     

薄层黑土微生物生物量碳氮对土壤侵蚀—沉积的响应

研究土壤侵蚀—沉积对土壤微生物生物量的影响可以为科学评估土壤侵蚀的环境效应提供依据。以典型薄层黑土区——黑龙江省宾州河流域为研究区,利用土壤137Cs含量估算侵蚀速率,通过分析流域不同位置和不同坡面部位土壤微生物生物量碳和氮含量以及土壤侵蚀强度的差异,揭示土壤微生物生物量对土壤侵蚀—沉积的响应规律。结果表明:流域不同位置和不同坡面部位土壤微生物生物量的分布存在明显差异,并呈现出与土壤侵蚀—沉积空间分布相反的变化趋势。土壤侵蚀速率在流域的分布为上游中游下游,在坡面的分布为坡中部坡上部坡下部;土壤微生物生物量碳(Microbial biomass carbon,MBC)和微生物生物量氮(Microbial biomass nitrogen,MBN)在流域表现为下游中游上游,在坡面表现为坡下部坡上部坡中部。回归分析表明,MBC、MBN、有机质(Organic matter,OM)和全氮(Total nitrogen,TN)含量随土壤侵蚀强度的增大而减少。土壤侵蚀对土壤微生物生物量的分布有重要影响,土壤侵蚀—沉积过程引起土壤养分的迁移和再分布是导致侵蚀区和沉积区土壤微生物生物量分布产生差异的重要原因。     

干旱绿洲长期微咸地下水灌溉对棉田土壤微生物量影响

由于淡水资源的缺乏,利用微咸地下水灌溉是干旱绿洲普遍采用的一种灌溉措施。该文对北疆棉区长期利用微咸地下水灌溉的土壤微生物和酶活性进行了研究。结果表明,长期微咸地下水灌溉土壤的含盐量比渠水灌溉上升61.5%,显著增加了棉田耕层土壤盐分（P＜0.05）,土壤可交换性钠百分率（ESP）升高3.2倍,并造成土壤碱化。微咸地下水灌溉纤维素酶、脲酶等、转化酶及过氧化氢酶4种酶活性分别降低了21.3%、50.9%、50.0%和10.5%,但在微咸地下水灌溉条件下多酚氧化酶和碱性磷酸酶的活性显著升高。微咸地下水灌溉对土壤微生物有明显抑制作用,长期微咸水灌溉使土壤微生物量碳、氮分别降低24.4%和42.4%,但对微生物量磷影响不显著。微生物量和酶活性与棉田土壤肥力密切相关,长期微咸地下水灌溉导致有机质、全氮分别降低26.8%和28.0%。长期微咸地下水灌溉影响了土壤生物质量,不利于绿洲农田土壤的持续利用。     

Effects of biochars produced from different feedstocks on soil properties and sunflower growth

The use of biochar as a soil amendment is gaining interest to mitigate climate change and improve soil fertility and crop productivity. However, studies to date show a great variability in the results depending on raw materials and pyrolysis conditions, soil characteristics, and plant species. In this study, we evaluated the effects of biochars produced from five agricultural and forestry wastes on the properties of an organic‐C‐poor, slightly acidic, and loamy sand soil and on sunflower (Helianthus annuus L.) growth. The addition of biochar, especially at high application rates, decreased soil bulk density and increased soil field capacity, which should impact positively on plant growth and water economy. Furthermore, biochar addition to soil increased dissolved organic C (wheat‐straw and olive‐tree‐pruning biochars), available P (wheat‐straw biochar), and seed germination, and decreased soil nitrate concentration in all cases. The effects of biochar addition on plant dry biomass were greatly dependent upon the biochar‐application rate and biochar type, mainly associated to its nutrient content due to the low fertility of the soil used. As a result, the addition of ash‐rich biochars (produced from wheat straw and olive‐tree pruning) increased total plant dry biomass. On the other hand, the addition of biochar increased the leaf biomass allocation and decreased the stem biomass allocation. Therefore, biochar can improve soil properties and increase crop production with a consequent benefit to agriculture. However, the use of biochar as an amendment to agricultural soils should take into account its high heterogeneity, particularly in terms of nutrient availability.     

不同耕作方式下玉米农田土壤养分及土壤微生物活性变化

通过连续3年的野外调查与室内分析试验,研究了不同耕作方式（翻耕、旋耕、免耕）对玉米农田土壤养分及土壤微生物活性的影响。结果表明,不同耕作方式下土壤pH值略显酸性,土壤容重与土壤总孔隙度变化趋势相反;土壤容重基本表现为:免耕 > 翻耕 > 旋耕;土壤总孔隙度TSP基本表现为:翻耕 > 旋耕 > 免耕,不同耕作方式差异均显著（p<0.05）。不同耕作方式下土壤养分（有机碳、全氮含量）和有效养分（有效磷、铵态氮和硝态氮）均呈现出一致性规律,大致表现为翻耕 > 旋耕 > 免耕,不同耕作方式下土壤全磷含量差异均不显著（p > 0.05）;与免耕相比,土壤微生物量碳和氮、土壤微生物数量（细菌、真菌、放线菌、固氮菌和纤维素菌）均有明显的增加,大致表现为:翻耕 > 旋耕 > 免耕。土壤微生物活度的变化范围为0.38~0.69,依次表现为翻耕 > 旋耕 > 免耕,不同耕作方式下土壤微生物活度差异均显著（p<0.05）。不同耕作方式下土壤微生物量碳周转率高于氮周转率,说明微生物量碳更新比微生物量氮快,其中翻耕处理下土壤微生物量碳和氮更新较旋耕和免耕快。通径分析发现,不同土壤环境因子对土壤微生物活度产生直接和间接负作用,其中有机碳、全氮、硝态氮、铵态氮、细菌数量对土壤微生物活度产生直接效应;土壤微生物量碳、微生物量氮、真菌数量和固氮菌数量对土壤微生物活度产生间接效应。     

Nitrogen immobilization/remineralization in legume‐amended soils as influenced by texture and compaction

Abstract

The role of intrinsic soil properties and management induced changes in bulk density on legume shoot biomass‐nitrogen (N) turnover to soil mineral N [nitrate (NO₃) plus ammonium (NH₄)], SMN, through soil microorganisms is poorly understood. In this study, the influence of intrinsic soil properties and changes in bulk density in soils amended with red clover (Trifolium pratense L.) on N immobilization/remineralization was investigated. Time in incubation, soil type, bulk density, and legume amendment had significant influence on the amounts of microbial biomass carbon (C) (MBC), N (MBN), and the SMN measured during incubation. During the first 32 days in incubation, MBC and MBN in the legume‐amended soils were higher than the control whereas an opposite trend existed for SMN. The SMN measured at the end of incubation, i.e., 70 days after incubation, was significantly higher than the unamended control. The ratio of SMN to MBN (SMN:MBN) was < 1.0, in general, during the first 32 days in incubation in legume amended soils, indicating N immobilization in microbial biomass during this period. Forty‐two days after incubation, the SMN:MBN ratios in the legume amended soils were >1.0, indicating remineralization of the immobilized N, derived, at least partially, from the legume. In the unamended control, these ratios were > 1.0 throughout the incubation. Over time, 63% to 76% of the variability in N‐immobilization/remineralization (SMN:MBN) was accounted for clay content, water (WFP) and air (AFP) filled porosities, volume fraction of pores (VFP) <1.5 μm, total N, C to N ratios in soils, bulk density, and legume amendment. The results indicate the influence of intrinsic soil properties and bulk density on microbially mediated legume N turnover to SMN changed over time.     

Carbon and nitrogen limitation to microbial respiration and biomass in an acidic solfatara field

The solfatara field is a unique ecosystem characterized by harsh conditions such as acidic soils. We examined the respiration rate and phospholipid fatty acid (PLFA) content of solfatara soils and their responses to carbon and nitrogen addition to determine whether soil microbial respiration and biomass in a solfatara field are limited by substrate availability. Soil samples were collected from locations along a transect across a solfatara field in Oita Prefecture, Japan. The soil in the central part of the solfatara field was highly acidic (pH 2.4) and contained low amounts of carbon and nitrogen. Low basal respiration rates were detected in these soil samples. Measurements of substrate-induced respiration (SIR) and PLFA contents suggested that it was partly attributable to low microbial biomass. Addition of a carbon source (glucose) to the solfatara soil engendered a marked increase in the microbial respiration rate, whereas the nitrogen source (ammonium nitrate) application had no marked effect. Addition of both carbon and nitrogen caused a nearly eightfold increase in the microbial respiration rate and a threefold increase in the total PLFA contents. These results suggest that some acidophilic and/or acid-tolerant microorganisms exist in solfatara soil, but that their respiration and biomass are limited by low substrate availability.     

Growth,phosphorus uptake,and rhizosphere microbial‐community composition of a phosphorus‐efficient wheat cultivar in soils differing in pH

In a pot experiment, the P‐efficient wheat (Triticum aestivum L.) cultivar Goldmark was grown in ten soils from South Australia covering a wide range of pH (four acidic, two neutral, and four alkaline soils) with low to moderate P availability. Phosphorus (100 mg P kg^–1) was supplied as FePO₄ to acidic soils, CaHPO₄ to alkaline, and 1:1 mixture of FePO₄ and CaHPO₄ to neutral soils. Phosphorus uptake was correlated with P availability measured by anion‐exchange resin and microbial biomass P in the rhizosphere. Growth and P uptake were best in the neutral soils, lower in the acidic, and poorest in the alkaline soils. The good growth in the neutral soils could be explained by a combination of extensive soil exploitation by the roots and high phosphatase activity in the rhizosphere, indicating microbial facilitation of organic‐P mineralization. The plant effect (soil exploitation by roots) appeared to dominate in the acidic soils. Alkaline phosphatase and diesterase activities in acidic soils were lower than in neutral soils, but strongly increased in the rhizosphere compared with the bulk soil, suggesting that microorganisms contribute to P uptake in these acidic soils. Shoot and root growth and P uptake per unit root length were lowest in the alkaline soils. Despite high alkaline phosphatase and diesterase activities in the alkaline soils, microbial biomass P was low, suggesting that the enzymes could not mineralize sufficient organic P to meet the demands of plants and microorganisms. Microbial‐community composition, assessed by fatty acid methylester (FAME) analysis, was strongly dependent on soil pH, whereas other soil properties (organic‐C or CaCO₃ content) were less important or not important at all (soil texture).     

半干旱区不同围封年限对草地土壤和微生物碳氮含量的影响

[目的]探究半干旱区草地根际土壤碳氮及土壤微生物量碳氮对不同封禁年限响应特征,为半干旱草地生态系统物质循环研究以及生态系统养分限制判定等提供依据,并为确定合理围封年限提供科学参考.[方法]以宁夏回族自治区固原市云雾山国家级自然保护区半干旱草原为研究对象,应用生态化学计量学方法对比分析放牧地与围封10,25,35 a样地...     

Soil microbiological and biochemical properties for assessing the effect of agricultural management practices in Estonian cultivated soils

A set of soil microbiological and biochemical properties was used to assess the influence of agricultural practices such as rotation, usage of pesticides, and fertilizers on the three most widespread soil types (Calcaric Regosols, Calcaric Cambisols and Stagnic Luvisols) in the fields of horticultural farms throughout Estonia. Microbial biomass, dehydrogenase and alkaline phosphatase activity were significantly higher in Calcaric Regosols, whereas measured soil chemical parameters showed practically no difference among soil types. Multivariate exploratory analysis of soil biochemical and microbiological parameters clearly distinguished soils with different management practices when the effect of soil type was taken into account in data analysis. Activity of dehydrogenase, potential nitrification, N-mineralisation, and microbial biomass contributed most strongly to the differentiation of soils from differently managed fields. Soils managed according to organic farming principles were generally characterized by elevated microbiological parameter values, but at the same time the variation of those parameters among soils from these fields was also highest. The application of organic manure positively affected microbial biomass, N-mineralisation, potential nitrification, dehydrogenase and acidic phosphatase activity. Data analysis indicated that the amount of mineral nitrogen fertilizers added over time has a stronger effect on microbial biomass than the amount added in a given year. Legume-based crop rotation increased soil respiration and microbial biomass.