Impact of agricultural land use on distribution of microbial biomass and activity within soil aggregates

The presence of aggregates of various sizes in the soil is an important condition for soil carbon sequestration. In this system, microbial biomass is a key link. This work was devoted to the study of the influence of land use systems on the distribution of SOС, MB-SIR, microbial activity and eco-physiological indices (qCO₂, QR, MB-SIR/SOС and qCO₂/SOС) in relation to the size of soil aggregates. The distribution of SOС, MB-SIR and mineralization activity among the aggregates was heterogeneous. In the soil of crop rotation, high mineralization activity and MB-SIR were found in the aggregates 0.5–0.1 mm, in the monoculture soil in aggregates <0.1 mm and in the control soil in the aggregates 1–0.25 mm. There was a general trend towards a decrease in microbial activity, MB-SIR and SOС availability with an increase in aggregate size. In agricultural soils, microbial activity was determined by large aggregates (>5 mm), while in the control soil, by the aggregates 5–1 mm. Depending on the type of site and the size of aggregates, the differences in microbial metabolism were revealed. The qCO₂ and QR values decreased, and the MB-SIR/SOС and qCO₂/SOС increased in the series: control soil > crop rotation > monoculture. In the control soil, the values of the eco-physiological indices decreased with decreasing aggregate size. And vice versa, in agricultural soils, these parameters were the highest in the microaggregates (<0.25 mm). The monoculture soil, in contrast to the control soil and crop rotation soil, turned out to be more energy efficient.     

Correlation among microbial biomass s,soil properties,and other biomass nutrients

The soil physicochemical characteristics and amounts of microbial biomass C, N, and S in 19 soils (10 grassland, 2 forest, and 7 arable soils) were investigated to clarify the S status in granitic regosols in Japan, in order to determine the relationships between biomass S and other soil characteristics and to estimate approximately the annual Sand N flux through the microbial biomass. Across the sites, the amount of biomass C ranged from 46 to 1,054, biomass N from 6 to 158, and biomass S from 0.81 to 13.44 mg kg_-1 soil with mean values of 438.8, 85.8, and 6.15 mg kg_-1 soil, respectively. Microbial biomass Nand S accounted for 3.4–7.7% and 1.1–4.0% of soil total Nand S, respectively. The biomass C: N, C : S, and N : S ratios varied considerably across the sites and ranged from 3.0–10.4, 32.5–87.7, and 5.0–18.8, respectively. Microbial biomass S was linearly related to biomass C and biomass N. The regression accounted for 96.6% for biomass C and 92.9% for biomass N of the variance in the data. The amounts of biomass C, N, and S were positively correlated with a number of soil properties, particularly with the contents of organic C, total N, SO₄-S, and electrical conductivity and among themselves. The soil properties, in various linear combinations showed a variability of 84–97% in the biomass nutrients. Stepwise multiple regression indicated that biomass C, N, and S were also dependent on SO₄-S as a second factor of significance which could limit microbial growth under the conditions prevailing at the study sites. Annual flux of Nand S was estimated through the biomass using the turnover rates of 0.67 for Nand 0.70 for S to be approximately 129 kg Nand 9.7 kg S ha^-1 y^-l, respectively, and was almost two times higher in grassland than arable soils.     

不同管理措施对西藏河谷农田土壤微生物量碳的影响

土壤微生物量碳(MBC)是反映农田土壤质量的重要指标。本研究以西藏河谷农田生态系统为对象,在中国科学院拉萨农业生态试验站长期施肥样地和农田撂荒地通过随机混合采样获取土壤样品,实验室内以氯仿熏蒸法测定土壤微生物量碳,探讨了不同施肥方式、不同除草方式对西藏河谷农田土壤质量的影响。从3个不同生育期的平均结果来看,施加羊粪样地的土壤微生物量碳比空白样地提高了56.1%,单纯施用化肥样地的微生物量碳比空白样地降低了14.0%,表明有机肥的施用对于提高西藏农田土壤质量具有显著的促进作用,而单纯施用化肥则会导致土壤质量的下降。在农田撂荒地试验中,自然撂荒样地(不除草)的土壤微生物量碳大约为85.2 mg/kg,而经常除草样地的土壤微生物量碳比不除草样地降低约1/4,从而进一步说明有机质输入对于提高高原农田土壤质量具有重要的作用。     

湘北红壤丘岗稻田土壤有机碳、养分及微生物生物量空间变异

通过对湘北典型红壤丘岗254个稻田耕层样(01～8.cm)进行分析,比较了微地形对稻田土壤有机碳、氮、磷和微生物生物量的影响。结果表明,丘岗底部稻田土壤有机碳、全氮、微生物生物量碳、微生物生物量氮、可溶性氮含量分别比丘岗中下部稻田高14.6%1、3.6%、24.6%、20.4%和95.8%,丘岗中下部稻田土壤Olsen-P含量比丘岗底部稻田高33.3%,差异均达极显著水平(P0.01)。不同部位稻田土壤全磷、微生物生物量磷含量和有效磷库(微生物生物量磷与Olsen-P之和)含量差异不显著。此外,丘岗底部稻田土壤碳磷比、微生物生物量碳磷比和微生物商比丘岗中下部稻田高12.7%,28.5%,8.2%,其差异达显著(P0.05)或极显著(P0.01)水平。但微生物生物量氮/全氮、微生物生物量磷/全磷、土壤碳氮比和微生物生物量碳氮比差异不显著。     

Influence of agricultural traffic and crop management on collembola and microbial biomass in arable soil

Collembola and microbial biomass C were investigated in a field experiment with controlled agricultural traffic and crop rotation over a period of 27 months. The wheel-induced compactive efforts were applied according to management practices within the crop rotation of sugar beet, winter wheat, and winter barley. Increasing wheel traffic produced increasing soil compaction, mainly due to a reduction in surface soil porosity. Increasing soil compaction was accompanied by a decrease in microbial biomass C and the density of collembola. The influence of soil compaction on microbial biomass C was smaller than that of the standing crop. However, for collembola, especially euedaphic species, a reduction in pore space appeared to be of more importance than the effects of a standing crop. Within the crop rotation, microbial biomass C and the density of collembola increased in the order sugar beet, winter wheat, and winter barley.     

不同土壤类型和农业用地方式对土壤微生物量碳的影响

通过野外调查与室内分析,研究了山东桓台县3种土壤类型(潮土、褐土和砂姜黑土)与农业用地方式(林地、菜地和粮田)对土壤表层(0—10.cm)微生物量碳的影响。结果表明,不同农业用地方式对微生物量碳的影响较大,3种利用方式的微生物量碳含量差异显著,依次为:粮田>菜地>林地;土壤类型不同,土壤微生物量碳含量也不相同。任何一种土壤,菜地的N、P、K含量都高于粮田和林地;有机质含量粮田>菜地>林地;pH值林地>粮田>菜地。全N、有机质与土壤微生物量碳呈极显著正相关,有效P与微生物量碳呈弱负相关,速效K、pH值和微生物量碳不相关。不同用地方式下土壤养分与微生物量碳的相关程度不同。秸秆还田和施用有机肥有利于提高土壤中微生物量碳水平,施用化肥在一定程度上能够增加微生物量碳。     

中国东南部红壤地区不同植被对土壤侵蚀和土壤养分的影响

The effect of different vegetation systems including bamboo plantation (BP), forest ecosystem (CF), citrus orchard (Ctr) and farmland (FL) on erosion and nutrients of red soil were investigated in hilly region of southeastern China to find effective control measures for soil erosion. The results showed that all the vegetation systems could significantly reduce soil erosion and nutrient losses compared to bare land (Br). The ability of different vegetation systems to conserve soil and water was in the order of Ctr > BP > CF > FL > Br. Vegetation could also improve soil fertility. The soil organic matter, total N and total P contents were much higher in all the vegetation systems than in bare land, especially for the top soils. Vegetation systems improved soil physical properties remarkably. Compared to the bare land, soil organic matter, TP, TK and available K, especially soil microbial biomass C, N and P, increased under all the vegetation covers. However, they were still much lower than expected, thus these biological measurements are still needed to be carried out continuously.     

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。     

Effect of land use on soil nutrients in the loess hilly area of the Loess Plateau,China

Understanding the effects of land use change on soil properties is important for soil quality improvement and sustainable land use. In this study, six land use types including wasteland (WLD), cropland (CLD), abandoned land (ABD), artificial grassland (AGD), shrubland (SLD) and woodland (WOD) were selected to analyse the effects of land use types on soil nutrient in the Anjiapo catchment in the western part of the Loess Plateau in China. Significant differences were found in soil organic matter (SOM), total nitrogen (TN) and nitrate nitrogen (NON) (P < 0.01) between the six land use types. Our study also showed that land use types have different effects on soil nutrient storage, and vegetation restoration may improve soil nutrients and soil quality. While crop plantation can significantly decrease soil fertility, the trend can be reversed by cropland abandonment and afforestation. It is recommended that more C input, alternative cultivation practices, vegetation restoration and education and techniques training of local farmers could be used to improve soil conditions and to advance the sustainable land use and local development in the loess hilly area in the Loess Plateau of China. Copyright © 2005 John Wiley & Sons, Ltd.     

Influence of lanthanum on microbial biomass C,P and C- and P-cycling enzyme activities in tea garden soil

At present, reports of the effect of lanthanum on nitrogen cycling in the soil are very detailed, but information on carbon (C) and phosphorus (P) cycling is less reported. We present an investigation into the effects of lanthanum on the pH, microbial biomass C and P and enzyme activities (such as that of β-glucosidase, peroxidase, polyphenol oxidase, acid phosphomonoesterase, phosphodiesterase and phosphotriesterase) in soil in an indoor culture experiment. The results show that the application of lanthanum decreased the pH and had an inhibitory effect on microbial biomass C and P throughout the experiment. The application of lanthanum significantly inhibited most of enzyme activities at the 14th day of the experiment. However, soil samples treated with 100 mg kg^?1 of lanthanum significantly stimulated the activity of polyphenol oxidase at the 14th day, and the range 100–300 mg kg^?1 stimulated the activities during the 28th day to the 56th day. From the 42nd to the 56th day, the pH and all enzyme activities gradually increased. We inferred that the lanthanum had different effects on microbial biomass C and P and enzymes. We recommended that the amount of the rare earth element applied in a tea garden should be lower than 100 mg kg^?1.     

Effect of land‐use on soil nutrients and microbial biomass of an alpine region on the northeastern Tibetan plateau,China

Land‐use patterns affect the quantity and quality of soil nutrients as well as microbial biomass and respiration in soil. However, few studies have been done to assess the influence of land‐use on soil and microbial characteristics of the alpine region on the northeastern Tibetan plateau. In order to understand the effect of land‐use management, we examined the chemical properties and microbial biomass of soils under three land‐use types including natural grassland, crop‐field (50 + y of biennial cropping and fallow) and abandoned old‐field (10 y) in the area. The results showed that the losses of soil organic carbon (SOC) and total nitrogen (TN) were about 45 and 43 per cent, respectively, due to cultivation for more than 50 y comparing with natural grassland. Because of the abandonment of cultivation for about a decade, SOC and TN were increased by 27 and 23 per cent, respectively, in comparison with the crop field. Microbial carbon (ranging from 357·5 to 761·6 mg kg⁻¹ soil) in the old‐field was intermediate between the crop field and grassland. Microbial nitrogen (ranging from 29·9 to 106·7 mg kg⁻¹ soil) and respiration (ranging from 60·4 to 96·4 mg CO₂‐C g⁻¹ C_mic d⁻¹) were not significantly lower in the old‐field than those in the grassland. Thus it could be concluded that cultivation decreased the organic matter and microbial biomass in soils, while the adoption of abandonment has achieved some targets of grassland restoration in the alpine region of Gansu Province on the northeastern Tibetan plateau. Copyright © 2010 John Wiley & Sons, Ltd.     

长期冬种绿肥改变红壤稻田土壤微生物生物量特性

以进行了31年的双季稻-冬绿肥长期定位试验的红壤性水稻土为对象,研究了长期冬种绿肥条件下土壤微生物生物量特性的季节变化,为阐释冬绿肥措施在稻田生态系统土壤碳氮转化中的作用机制提供理论基础。试验包括双季稻-紫云英(RRV)、双季稻-冬油菜(RRP)、双季稻-黑麦草(RRG)及双季稻-冬闲(RRF)4个处理,在典型时期(绿肥盛花期、绿肥翻压后、早稻成熟期、晚稻收获后)采集土壤样品,分析土壤微生物生物量碳氮及微生物商等方面的变化。结果表明,3种冬绿肥均提高了土壤微生物生物量碳(SMBC)、微生物生物量氮(SMBN)和微生物商,在土壤性质相对稳定的晚稻收获后均显著高于对照处理,全年平均值也多显著高于对照处理。豆科绿肥紫云英对SMBC和SMBN的提高作用最显著,晚稻收获后相对冬闲分别提高了21.12%和98.45%,全年平均值分别提高了15.92%和36.49%。取样时期对SMBC、SMBN和微生物商有较大的影响,但变化趋势基本一致,即绿肥翻压前后无明显变化,早稻成熟期降至最低,至晚稻收获后再次上升。SMBC/SMBN比值在不同绿肥处理间差异不大,但有明显的季节变化,早稻成熟期较高而晚稻收获后降低。因此,南方稻田冬种绿肥后土壤微生物特性明显改善,冬种绿肥是提升稻田土壤肥力的高效措施。     

Effect of land degradation on soil microbial biomass in a hilly area of south Sumatra,Indonesia

We investigated the impact of land-use changes on the soil biomass at several soil sites in Indonesia under different types of land-use (primary forest, secondary forest, coffee plantation, traditional orchard, and deforested area), located within a small geographical area with similar parent material and climatic conditions. Various parameters of soil microbial biomass (biomass C, biomass N, content of anthrone-reactive carbohydrate carbon, and soil ergosterol content) were examined. Our results suggested that the removal of the natural plant cover did not cause any appreciable decrease in the amount of microbial biomass; on the contrary it led to a short-time increase in the amount of microbial biomass which may be due to the availability of readily decomposable dead roots and higher sensitivity to the decomposition of residual litter in recently deforested soils. However, the amount of microbial biomass tended to decrease in proportion to the duration of the land history in coffee plantation soils. This may be ascribed to the effect of the loss of available substrates associated with soil erosion in the long term. Lower ergosterol contents in recently deforested areas reflected a reduction in the amount of fungal biomass which may be due to the destruction of the hyphal network by the slash and burn practice. On the other hand, the higher soil ergosterol content at the sites under bush regrowth indicated that microbial biomass was able to recover rapidly with the occurrence of a new plant cover.     

Effects of exclosure on soil nutrients,vegetation diversity and biomass production in hilly rangelands

Livestock grazing is one of the most important factors influencing the soil nutrients, soil surface, vegetation diversity, and the above-ground biomass production in a natural rangeland ecosystem. An experiment was conducted to evaluate the influence of the long-term grazing on soil pH, electrical conductivity (EC), total organic carbon (TOC), total nitrogen (TN), available phosphorus (Available P), exchangeable potassium (Exchangeable K), diversity and the above-ground biomass production. This study was conducted in Maraveh Tapeh hilly rangelands of Golestan province, Iran. Soil and vegetation samplings were conducted based on the randomized systematic method. Three 150 m transects were positioned randomly within each grazing management practice. Soil samples were systematically taken every 3 m along each transect. Thirty (30) randomly chosen quadrats were sampled in each transect for vegetation diversity and biomass assessment. The effects of grazing management practices and aspect on soil nutrients, vegetation diversity, and biomass production were detected by analysis of variance (ANOVA) (at α = 0.05). Results of this study indicated, Exclosure north aspects had the maximum soil pH. There were significant differences found between soil electrical conductivity values in the grazed south aspect and the other treatments. Soil TOC, TN, available P and exchangeable K values increased significantly in the exclosure north aspects. Shannon diversity index and the above-ground biomass production had highest values in the exclosure north aspects.     

Influence of erosion on soil microbial biomass,abundance and community diversity

This study aimed to determine microbial biomass carbon and microbial abundance immediately after, and two years after, forest soil erosion, so as to estimate the degree of damage, including the rate of recovery of microorganisms, in each area. It also aimed to determine the community diversity, and to establish relationships between microbial biomass, microbial abundance and the physico‐chemical properties of the soil. Three different study areas in Hiroshima Prefecture, Japan, were used. One undisturbed area and two eroded areas (one immediately after and one two years after erosion). The analysis of variance showed a highly significant difference in microbial biomass carbon and abundance between the study areas. The undisturbed area showed the highest value, followed by the area eroded two years ago, then lastly the area studied immediately after the erosion. The biomass carbon was highly correlated with gram positive bacteria with r² = 0·983, p < 0·01. The biomass carbon and microbial population were shown to be significantly correlated to the soil's physico‐chemical properties, such as pH, moisture content, water‐holding capacity and CN ratio. However, CN ratio proved to be closely correlated to biomass carbon with r² = −0·978, p < 0·01, to Gram‐positive bacteria with r² = −0·977, p < 0·01, to Gram‐negative bacteria with r² = −0·989, p < 0·01 and to fungi with r² = −0·977, p < 0·01. The undisturbed area showed a highly diverse community in both of the restriction enzymes used, followed by the area affected by erosion two years ago, then the area immediately after erosion. Copyright © 2004 John Wiley & Sons, Ltd.     

Impact of soil fumigation practices on soil nematodes and microbial biomass

This study was designed to understand the impact of methyl bromide (MB) (CHaBr) and its alternatives on both free-living and root-knot nematodes in the soil. A randomized complete block experiment with six treatments and 4 replicates (each replicate in a separate greenhouse) was established in Qingzhou, Shandong Province, China. In addition to MB and untreated control (CK) treatments there were four alternative soil fumigation practices including MB virtually impermeable films (VIF), metam sodium (MS), MS VIF and soil solarization combined with selected biological control agents (SS BCA). Two tomato (Lycopersicum esculentum Mill.) cultivars, cv. Maofen-802 from the Xian Institute of Vegetable Science, China, and cv. AF179 Brillante from the Israeli Hazera Quality Seeds, were selected as test crops. The results indicated that Rhabditidae was the most dominant population with percentage abundance as high as 85% of the total number of identified free-living nematodes, followed by that of Cephalobidae. Methyl bromide and its alternatives except for the non-chemical SS BCA treatment controlled the target pest, root-knot nematodes. Also, the impact of the three chemical alternatives on free-living nematode number and functional group abundance was similar to the impact associated with a typical methyl bromide application. Chemical fumigation practices, especially that with MB, significantly reduced the number of nematodes in the soil and simultaneously significantly reduced the number of nematode genera thereby reducing nematode diversity. All the four soil chemical fumigation activities decreased soil microbial biomass and had an obvious initial impact on microorganism biomass. Furthermore, both plant-parasitic and fungivore nematodes were positively correlated with soil microbial biomass.     

PH对红壤微生物生物量碳和生物量磷的影响

The impact of pH changes on microbial biomass carbon (Cmic) and microbial biomass phosphorus (Pmic) were examined for 3 red soils under citrus production with different lengths of cultivation. Soil pH significantly affected Cmic and Pmic. The Cmie and Pmic changes, as a function of soil pH, appeared to follow a normal distribution with the original soil pH value at the apex and as pH increased or decreased compared to the original soil pH, Cmic and Pmic declined. Moreover, there were critical pH values at both extremes (3.0 on the acidic side and 8.0 to 8.5 on the alkaline side), beyond which most of microorganisms could never survive. The effect of pH on Cmic and Pmic was also related to the original soil pH. The higher the original soil pH was, the less Cmic or Pmic were affected by pH change. It is suggested that soil microorganisms that grow in a soil environment with a more neutral soil pH range (i.e. pH 5.5-7.5) may have a greater tolerance to pH changes than those growing in more acidic or more alkaline soil pH conditions.     

Impact of deforestation on soil physicochemical characteristics,microbial biomass and microbial activity of tropical soil

The study dealt with the assessment of the impact of deforestation on tropical soil through a comparative analysis of physicochemical and microbiological parameters of natural forest and a deforested barren site. With significant decline in clay, texturally the soil of the deforested barren site was observed to be different from that of natural forest. Bulk density and porosity data revealed structural deterioration of deforested barren soil. The soil hydrological regime was also adversely affected by the deforestation. Levels of soil organic carbon, total nitrogen, microbial biomass C, N and microfungal biomass also exhibited significant decline in deforested site. Analysis of microbial respiratory quotient (q CO₂) was also observed to be impaired in the deforested site. Copyright © 2001 John Wiley & Sons, Ltd.     

连年翻压绿肥对植烟土壤微生物量及酶活性的影响

通过3年田间定位试验,研究连年翻压绿肥对植烟土壤微生物量碳、氮及酶活性的影响。结果表明,连年翻压绿肥能提高土壤微生物量碳、氮及土壤脲酶、酸性磷酸酶、蔗糖酶、过氧化氢酶的活性,且随翻压年限的增加而增加。整个生育期,翻压3年绿肥的处理与对照相比微生物量碳、氮分别提高31.0%~67.1%、23.0%~145.1%;土壤脲酶、酸性磷酸酶、蔗糖酶、过氧化氢酶活性分别提高34.4%~51.9%、11.0%~18.6%、58.0%~172.7%、24.0%~50.0%,表明翻压绿肥后土壤生物过程活跃,利于有机物质的转化和烤烟正常生长所需的营养供应。动态变化特征表明,翻压绿肥1、2、3年的各处理微生物量碳、氮均在团棵期出现峰值,土壤脲酶、酸性磷酸酶、过氧化氢酶均在旺长期出现峰值。在出现峰值时翻压3年的处理与对照相比微生物量碳、氮分别提高67.1%、60.7%;土壤脲酶、酸性磷酸酶、过氧化氢酶活性分别提高51.9%、14.2%、30.6%。此时正值生育旺期,利于烟株生长发育,说明连年翻压绿肥后培肥土壤效果显著。土壤微生物量C、N和酶活性能灵敏反映土壤肥力的变化,可作为评价土壤质量的生物学指标。     

聚丙烯酸盐类土壤改良剂对燕麦土壤微生物量氮及酶活性的影响

以燕麦田土壤为研究对象,探讨了聚丙烯酸盐类土壤改良剂及其复配(聚丙烯酸钾、聚丙烯酰胺、腐植酸钾、聚丙烯酸钾+腐植酸钾、聚丙烯酰胺+腐植酸钾)对燕麦田土壤微生物量氮及土壤酶活性的影响。结果表明,不同土壤改良剂均能提高土壤有机质、碱解氮、速效磷和速效钾的含量,各指标分别比对照增加了8.24%～30.22%、7.60%～19.29%、5.15%～29.45%和27.86%～68.86%;土壤改良剂能促使燕麦全生育期内0～10、10～20和20～40 cm各土层的土壤微生物量氮含量显著提高,聚丙烯酸钾+腐植酸钾和聚丙烯酰胺+腐植酸钾复配处理较其各单施效果显著,随土壤深度的增加土壤微生物量氮逐层递减;与对照相比,土壤改良剂能显著提高燕麦全生育期各土层过氧化氢酶活性,在抽穗期活性最高,且以聚丙烯酸钾+腐植酸钾较高;但对于脲酶,聚丙烯酸钾+腐植酸钾、聚丙烯酰胺+腐植酸钾和腐植酸钾3个处理在苗期显著低于对照,在抽穗期和成熟期高于对照,两种酶活性均随土壤深度的增加逐渐降低。