不同碳氮比有机肥对有机农业土壤微生物生物量的影响

有机肥能提高土壤微生物活性, 改善土壤品质。碳氮比是影响有机肥肥效的重要因素。本试验以无肥处理为对照(CK), 设置4个有机肥碳氮比处理(20︰1、15︰1、10︰1、5︰1), 在温室中进行茄子盆栽试验, 定期采集土壤样品, 用熏蒸提取法测定土壤微生物生物量碳(SMBC)、氮(SMBN), 研究等氮条件下不同碳氮比有机肥料对土壤生物活性的影响。试验结果表明, 不同碳氮比的有机肥均能提高土壤的SMBC和SMBN含量, 具体表现为SMBC: 20︰1>10︰1≈15︰1>5︰1>CK, SMBN: 15︰1>10︰1>20︰1>5︰1>CK。SMBC/SMBN的比率反映土壤氮素生物活性, 其值越低, 生物活性越大, 氮素损失越少, 本试验SMBC/SMBN表现为: 15︰1<10︰1<20︰1≈5︰1相似文献   

不同施肥水平及玉米种植对土壤微生物生物量碳氮的影响

以裸地(不种植作物)和玉米种植的田间小区试验为平台,研究不同施肥水平及玉米种植对土壤微生物生物量碳氮的影响。结果表明,当不施肥时,土壤微生物生物量碳氮含量裸地平均值分别为175.98 mg/kg和26.04 mg/kg,种植玉米小区的平均值分别为161.65 mg/kg和22.70 mg/kg,土壤微生物生物量碳氮低于裸地;而施肥时,裸地的土壤微生物生物量碳氮平均值的变化范围分别为182.27~206.27 mg/kg和27.41~31.22 mg/kg,种植玉米小区的变化范围分别为194.70~235.58 mg/kg和35.76~44.66 mg/kg,土壤微生物生物量碳氮高于裸地,可见土壤碳氮的平衡对于土壤微生物生物量碳氮极为重要。裸地和玉米种植小区土壤微生物生物量碳氮均随着施肥量的增加呈现出先增加后降低的趋势,其施氮水平拐点分别为70 kg/hm2和150kg/hm2,表明施肥水平对土壤微生物生物量碳氮具有显著影响。另外,玉米各生育期间土壤微生物生物量碳氮也存在着显著差异,其中,土壤微生物生物量碳氮含量在拔节期处于最低,变动范围分别为154.46~229.09 mg/kg和18.84~31.44 mg/kg;抽雄期处于最高,变动范围分别为171.71~242.48 mg/kg和30.01~50.54 mg/kg。     

镉铅锌污染对红壤中微生物生物量碳氮磷的影响

用实验室培养法研究了不同镉、铅和锌化合物对红壤中微生物生物量碳、氮和磷的影响。引起微生物生物量碳显著减少的Cd、Pb和Zn(均为氯化物 )临界土壤含量水平分别为 30、4 50和 2 0 0mg/kg。以醋酸盐形式加入土壤中的Cd、Pb和Zn对土壤微生物生物量比氯化物有更大的毒性 ,可能与其较高的溶解度有关。不管施用何种化合物 ,Cd、Pb和Zn对微生物量的相对毒性依次为 :Cd Zn Pb。     

添加木醋液对沙地土壤微生物生物量和酶活性的影响

[目的]探讨沙地添加木醋液后土壤微生物生物量和酶活性的变化,为沙地土壤生物学质量的改良提供理论依据。[方法]采用盆栽植草培养法,以添加自来水为对照,对沙地添加不同稀释倍数(200,150,100,50,20)木醋液后的土壤可溶性有机碳、氮和酚,土壤微生物生物量碳氮以及土壤酶活性进行研究。[结果]向沙土添加木醋液可以显著降低土壤pH值,显著提高土壤易氧化碳、土壤水溶性碳氮、土壤可溶性酚以及无机氮的含量。在添加木醋液稀释高于50倍范围内,随木醋液稀释倍数降低,土壤微生物生物量碳氮增加以及β-糖苷酶、碱性磷酸酶和脱氢酶活性提高。添加稀释20倍的木醋液,导致土壤微生物生物量碳氮以及β-糖苷酶、碱性磷酸酶和脱氢酶活性有所降低。在高于20的稀释倍数范围内,随着施用木醋液稀释倍数的降低,α-糖苷酶、亮氨酸氨基肽酶、酸性磷酸酶和酚氧化酶的活性有显著增加的趋势。[结论]添加不同稀释倍数的木醋液会影响沙地土壤微生物生物量和酶活性。     

长期免耕与施用有机肥对土壤微生物生物量碳、氮、磷的影响

通过设置在江苏省句容农科所的田间定位试验研究长期免耕及施用有机肥料对土壤微生物生物量碳、氮、磷的影响。结果表明 :经过 1 6年 32茬稻—麦水旱轮作后 ,表土层 ( 0～ 5cm)土壤微生物生物量碳、氮、磷含量比亚表层 ( 5～ 1 0cm)分别高 2 7.5 %、43.6%和1 1 %。与常规耕翻相比长期免耕处理表土层土壤微生物生物量碳、氮含量分别增加了2 5 .4%和 45 .4% ,而微生物生物量磷无明显变化规律 ;亚表层的土壤微生物生物量碳、氮、磷免耕与耕翻两种耕作方式间的差异不显著。尽管各施肥处理施用的氮、磷、钾数量完全相等 ,但土壤微生物生物量碳、氮、磷的含量却因肥料种类的不同而异。综合 0～ 5和 5～ 1 0cm土层 ,微生物生物量碳、磷为 :猪粪 化肥 >秸秆 化肥 >绿肥 化肥 >化肥 >不施肥 ,微生物生物量氮则为 :猪粪 化肥 >绿肥 化肥 >秸秆 化肥 >化肥 >不施肥。相关分析结果显示 ,土壤微生物生物量碳、氮与土壤有机碳、土壤全氮和土壤碱解氮之间均呈极显著的正相关 ,表明其与土壤肥力关系密切 ,可作为评价土壤肥力性状的生物学指标     

紫外分光光度法测定农田土壤微生物生物量氮可行性初探

采用氯仿熏蒸浸提-紫外分光光度法和消化法比较测定了田间定位试验不同施肥处理土壤、添加植物残体土壤、添加葡萄糖土壤的微生物生物量碳、氮(SMBC,SMBN)。结果表明,当土壤微生物生物量氮含量较高时(>20 mg kg-1),采用分光光度法与消化法测定的SMBN具有显著正相关关系(P<0.05),但当SMBN量较低时(<20 mg kg-1)时,分光光度法测定与消化法测定的SMBN没有显著相关性。当土壤中添加麦秸和玉米秸时,土壤浸提液颜色较深(黄色),不适合采用分光光度法测定SMBN。因此,熏蒸提取–分光光度法测定SMBN,仅适于土壤浸提液无色透明、且SMBN含量较高的土壤。     

免耕对旱作燕麦田耕层土壤微生物生物量碳、氮、磷的影响

2005～2008年,在内蒙古清水河县研究了免耕留低茬(NL)、免耕留高茬(NH)、免耕留低茬覆盖(NLS)、免耕留高茬覆盖(NHS)和常规耕作(T)5种耕作方式对旱坡地燕麦田耕层土壤微生物生物量碳、氮、磷的影响。结果表明:各处理土壤微生物生物量碳、氮、磷含量在不同年际间的变化趋势一致。土壤微生物生物量碳、氮含量均呈双峰曲线变化,其中,NHS和NLS处理土壤微生物生物量碳的峰值出现在拔节期和灌浆期,NH、NL和T处理的土壤微生物生物量碳的峰值出现在孕穗期和灌浆期,而土壤微生物生物量氮的峰值则出现在苗期和灌浆期。土壤微生物生物量磷呈单峰曲线变化,各处理的峰值均出现在灌浆期。不同年份间、不同生育期间,土壤微生物生物量碳、氮、磷含量的大小顺序为:NHS>NLS>NH>NL>T。其中,免耕各处理的燕麦产量相对常规耕作呈先降低后增加的趋势,以2008年为例,NHS、NLS、NH、NL燕麦产量分别较T增加了22%、17%、11%、5%。综上所述,免耕有利于提高土壤微生物生物量碳、氮、磷含量,而且可有效地增加作物产量,尤其是NHS和NLS处理比较明显。     

退化红壤马尾松恢复林地土壤微生物生物量变化及其控制因素研究

退化土壤植被恢复后土壤质量在凋落物参与下提高,但恢复土壤理化性质与土壤微生物生物量间的相互作用尚不清楚。本研究目标是调查退化红壤马尾松恢复林地凋落物清除对土壤理化性质和微生物生物量的影响,分析影响土壤微生物生物量的控制因素。研究结果表明,与侵蚀裸地相比,无论凋落物清除与否,马尾松恢复林地的土壤孔隙度、水稳性团聚体比例、土壤有机碳、全氮、土壤微生物生物量均有较大提高;其提高幅度受土层深度和坡位影响,主要表现为表层土壤大于亚表层土壤,坡顶和坡底土壤大于坡中土壤。与凋落物保留林地相比,凋落物清除林地土壤各项指标提高幅度降低。通径分析的结果表明,影响微生物生物量最重要的因素是土壤有机碳含量,其次为土壤孔隙度;凋落物则是通过孔隙度和有机碳来间接影响土壤微生物生物量。本研究说明土壤物理结构恢复对土壤生物学性质的恢复有重要意义。     

不同农田生态系统土壤微生物生物量碳的变化研究

试验研究不同农田生态系统土壤微生物生物量碳的变化结果表明,长期单施N、P肥处理对土壤有机碳和微生物生物量碳的影响不明显,施有机肥处理土壤微生物生物量碳及微生物生物量碳/有机碳值均高于其他施肥处理,轮作中引入豆科作物或豆科连作均对土壤微生物生物量碳的积累有显著作用。     

长期施肥对土壤微生物生物量碳、氮及矿质态氮含量动态变化的影响

利用位于陕西杨凌的17年长期定位试验研究了长期不施肥(CK)、单施化肥(F)、化肥配施有机肥(F+M)和化肥加秸秆还田(F+S)处理对小麦-玉米轮作体系中作物不同生长时期土壤微生物生物量碳、氮(SMBC、SMBN)和矿质态氮含量的影响。结果表明,0—10 cm土层土壤SMBC、SMBN和矿质态氮含量的变化范围分别为264.8~752.2、37.51~14.8和3.83~8.5 mg/kg。不同处理相比,F+M处理中各采样时期(小麦苗期、拔节期、灌浆期及玉米播种期、大喇叭口期、灌浆期和收获后)土壤SMBC和SMBN含量均为最高,分别为不施肥对照的1.382~.65和1.892~.50倍;F+S处理矿质态氮含量最高,SMBC和SMBN也高于F和CK处理,大部分采样时期的差异达显著水平(P0.05);与CK相比,长期单施化肥也使各时期SMBC和SMBN含量提高。在小麦拔节期到灌浆期的旺盛生长阶段各施肥处理土壤SMBN含量均下降,而矿质态氮含量变化不大,处于较低水平;在玉米大喇叭口期到灌浆期的旺盛生长阶段,F+M、F+S和F处理土壤矿质态氮含量显著下降,而SMBN含量均有所升高。表明在土壤矿质态氮含量较高时,作物首先利用矿质态氮,而在土壤矿质态氮含量处于较低水平时,微生物固持的氮素可能会释放出来供作物吸收利用。     

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.     

A microplate assay to measure soil microbial biomass phosphorus

Quantification of phosphorus (P) concentrations in microbial biomass is required to better understand how P immobilization and turnover in soils are controlled by environmental and anthropogenic factors. Soil microbial biomass P (MBP) is generally extracted using the chloroform fumigation-direct extraction procedure and then analysed for P using the ammonium molybdate-ascorbic acid method on a flow injection analysis (FIA) system. Our objective was to determine whether a microscale malachite green method on a microplate system would provide as accurate MBP analysis as the ascorbic acid method on an FIA system. Twelve soils were collected from agricultural fields in southwestern Quebec, fumigated with chloroform and extracted with 0.5 M NaHCO₃ (pH 8.5). The dissolved inorganic phosphorus (DIP) concentration in fumigated soils was not affected by the method of analysis, and results from the two systems of analysis were significantly correlated (r =0.998, P <0.05). The MBP concentrations in these agricultural soils were between 0.36 and 60.05 g P g^–1, consistent with other published values. Our results indicate that MBP can be assessed equally well with the malachite green method using a microplate system as with the ascorbic acid method on an FIA system. The microplate system is rapid and requires smaller volumes of samples and reagents than the FIA system, thus reducing the quantity of waste produced. We conclude that the microscale malachite green method could be applied to measure the MBP concentration in a wide range of soils with good sensitivity, reproducibility and accuracy.     

适宜的水氮处理提高稻基农田土壤酶活性和土壤微生物量碳氮

为探讨节水灌溉与氮肥施用对稻田土壤微生物特性的影响,该试验采用防雨棚池栽试验,研究2个灌溉模式（常规灌溉与控制灌溉）与3个水平施氮量（90、180和270 kg/hm2））对稻基农田土壤脲酶活性、土壤过氧化氢酶活性、土壤磷酸酶活性、土壤转化酶活性、土壤微生物量碳及土壤微生物量氮的影响。研究结果表明,随着施氮水平增加,土壤脲酶活性和土壤微生物量氮增加,土壤过氧化氢酶活性、土壤磷酸酶活性、土壤转化酶活性、土壤微生物量碳、土壤微生物量碳与土壤微生物量氮的比值、土壤微生物熵均呈先增加后降低趋势;与常规灌溉相比,控制灌溉显著提高稻基农田土壤脲酶活性、土壤过氧化氢酶活性、土壤磷酸酶活性、土壤转化酶活性、土壤中微生物量碳、土壤微生物量氮、土壤微生物熵,降低土壤微生物量碳与土壤微生物量氮的比值。在该试验条件下,以控制灌溉模式下施氮量180 kg/hm2可获得最优的生物环境,土壤脲酶活性、土壤过氧化氢酶活性、土壤磷酸酶活性、土壤转化酶活性、土壤中微生物量碳、土壤微生物量氮分别达到3.02×10-2 mg/g、0.93 mL/g、5.70 mg/g、10.08 mL/g、237.58 mg/kg、52.60 m/kg。该研究对认识稻基农田水氮耦合关系、指导江淮丘陵季节性干旱区水稻优质节水高产高效栽培实践提供理论依据。     

黄土高原典型土壤全氮和微生物氮剖面分布特征研究

为阐明黄土高原典型土壤全氮和微生物氮含量随土壤类型、土层和土地利用方式变化规律,研究了从北向南依次分布的干润砂质新成土(神木)、黄土正常新成土(延安)和土垫旱耕人为土(杨陵)等典型土壤的全氮和微生物氮含量的变化特征。结果表明,不同土壤类型、不同土层全氮和微生物氮含量存在显著差异。从南到北,全氮和微生物氮含量显著下降(P0.05)。对同一土壤类型,全氮和微生物氮含量在060.cm随土层深度增加下降很明显,60120.cm有轻微下降,120.cm以下低而稳定。微生物氮含量随土壤类型的变化趋势与全氮完全相同,其与土壤全氮、有机碳及微生物碳含量均存在极显著正相关关系(P0.01)。土壤微生物氮与全氮比值变化在0.42%9～.44%之间。虽然土地利用对土壤全氮和C/N比影响不显著,但却显著影响微生物氮含量和微生物氮与全氮的比值;与农田土壤相比,草地土壤微生物氮含量和微生物氮与全氮比值均明显增加。这一结果说明微生物氮含量和微生物氮与全氮比值更能有效、快速地反映土壤质量的变化。     

长期施肥与地膜覆盖对土壤微生物量碳氮的影响

通过田间定位试验研究长期施肥与地膜覆盖对土壤微生物量C、N的影响。结果表明，长期施肥与地膜覆盖提高了土壤微生物量C、N含量，长期施有机肥和有机无机肥配施，土壤微生物量C、N显著高于单施化肥和不施肥。相关分析表明，土壤微生物量C、N与土壤有机C、全N均呈极显著的正相关。土壤微生物量C、N可作为指示土壤肥力的重要指标。本试验土壤微生物量C占有机C的比例平均为9．95％，微生物量N占全N的比例平均为10．78％。     

Altering soil carbon and nitrogen stocks in intensively tilled two-year rotations

Information is needed on the ability of different crop management factors to maintain or increase soil C and N pools, especially in intensively tilled short crop rotations. Soil samples from field experiments in Maine were used to assess the effect of cover crop, green manure (GM) crop, and intermittent or annual amendment on soil C and N pools. These field experiments, of 6–13 years duration, were all characterized by a 2-year rotation with either sweet corn ( Zea mays L.) or potato ( Solanum tuberosum L.), and primary tillage each year. Total, particulate organic matter (POM), and soil microbial biomass (SMB)-C and -N pools were assessed for each experiment. Total C and N stocks were not affected by red clover ( Trifolium pratense L.) cover crop or legume GM, but were increased by 25–53% via a single application of papermill sludge or an annual manure and/or compost amendment. With the exception of continuous potato production which dramatically reduced the SMB-C and SMB-N concentration, SMB-C and -N were minimally affected by changes in cropping sequence, but were quite sensitive to amendments, even those that were primarily C. POM-C and -N, associated with the coarse mineral fraction (53–2,000 µm), were more responsive to management factors compared to total C and N in soil. The change in soil C fractions was a linear function of increasing C supply, across all experiments and treatments. Within these intensively tilled, 2-year crop rotations, substantial C and N inputs from amendments are needed to significantly alter soil C and N pools, although cropping sequence changes can influence more labile pools responsible for nutrient cycling.     

Effects of long-term litter manipulation on soil carbon,nitrogen, and phosphorus in a temperate deciduous forest

Changes in above-ground litterfall can influence below-ground biogeochemical processes in forests. In order to examine how above-ground litter inputs affect soil carbon (C), nitrogen (N) and phosphorus (P) in a temperate deciduous forest, we studied a 14-year-old small-scale litter manipulation experiment that included control, litter exclusion, and doubled litter addition at a mature Fagus sylvatica L. site. Total organic C (TOC), total N (TN) and total P (TP), total organic P (TOP), bioavailable inorganic P (Pi), microbial C, N and P, soil respiration and fine root biomass were analyzed in the A and in two B horizons. Our results showed that litter manipulation had no significant effect on TOC in the mineral soil. Litter addition increased the bioavailable Pi in the A horizon but had no significant effect on N in the mineral soil. Litter exclusion decreased TN and TP in the B horizon to a depth of 10 cm. In the A horizon of the litter exclusion treatment, TP, TOP and bioavailable Pi were increased, which is most likely due to the higher root biomass in this treatment. The high fine root biomass seems to have counteracted the effects of the excluded aboveground litter. In conclusion, our study indicates that aboveground litter is not an important source for C in the mineral soil and that P recycling from root litter might be more important than from above-ground litter.     

Substrate inputs and pH as factors controlling microbial biomass, activity and community structure in an arable soil

Our aim was to determine whether the smaller biomasses generally found in low pH compared to high pH arable soils under similar management are due principally to the decreased inputs of substrate or whether some factor(s) associated with pH are also important. This was tested in a soil incubation experiment using wheat straw as substrate and soils of different pHs (8.09, 6.61, 4.65 and 4.17). Microbial biomass ninhydrin-N, and microbial community structure evaluated by phospholipid fatty acids (PLFAs), were measured at 0 (control soil only), 5, 25 and 50 days and CO₂ evolution up to 100 days. Straw addition increased biomass ninhydrin-N, CO₂ evolution and total PLFA concentrations at all soil pH values. The positive effect of straw addition on biomass ninhydrin-N was less in soils of pH 4.17 and 4.65. Similarly total PLFA concentrations were smallest at the lowest pH. This indicated that there is a direct pH effect as well as effects related to different substrate availabilities on microbial biomass and community structure. In the control soils, the fatty acids 16:1ω5, 16:1ω7c, 18:1ω7c&9t and i17:0 had significant and positive linear relationships with soil pH. In contrast, the fatty acids i15:0, a15:0, i16:0 and br17:0, 16:02OH, 18:2ω6,9, 17:0, 19:0, 17:0c9,10 and 19:0c9,10 were greatest in control soils at the lowest pHs. In soils given straw, the fatty acids 16:1ω5, 16:1ω7c, 15:0 and 18:0 had significant and positive linear relationships with pH, but the concentration of the monounsaturated 18:1ω9 PLFA decreased at the highest pHs. The PLFA profiles indicative of Gram-positive bacteria were more abundant than Gram-negative ones at the lowest pH in control soils, but in soils given straw these trends were reversed. In contrast, straw addition changed the microbial community structures least at pH 6.61. The ratio: [fungal PLFA 18:2w6,9]/[total PLFAs indicative of bacteria] indicated that fungal PLFAs were more dominant in the microbial communities of the lowest pH soil. In summary, this work shows that soil pH has marked effects on microbial biomass, community structure, and response to substrate addition.     

不同施肥模式对设施菜田土壤微生物量碳、氮的影响

【目的】 本文利用天津日光温室蔬菜不同施肥模式定位试验,研究了不同施肥模式对设施菜田土壤微生物量碳、氮含量的影响,为设施蔬菜高效施肥和菜田土壤可持续利用提供依据。 【方法】 调查在第 9 茬蔬菜 (秋冬茬芹菜) 和第 10 茬蔬菜 (春茬番茄) 进行。定位试验设 8 个处理,分别为:1) 不施氮;2) 全部施用化肥氮 (4/4CN);3) 3/4 化肥氮 + 1/4 猪粪氮 (3/4CN + 1/4PN);4) 2/4 化肥氮 + 2/4 猪粪氮 (2/4CN + 2/4PN);5) 1/4 化肥氮 + 3/4 猪粪氮( 1/4CN + 3/4PN);6) 2/4 化肥氮 + 1/4 猪粪氮 + 1/4 秸秆氮 (2/4CN + 1/4PN + 1/4SN);7) 2/4 化肥氮 + 2/4 秸秆氮 (2/4CN + 2/4SN);8) 农民习惯施肥 (CF),除不施氮肥和农民习惯施肥外,其余处理为等氮磷钾处理。在不同生育时期,采 0—20 cm 土壤样品,测定土壤微生物量碳、氮含量,并分析其与蔬菜产量之间的关系。 【结果】 两茬蔬菜不同施肥模式土壤微生物量碳、氮含量总体上均随生育期的推进呈先增后降的趋势。芹菜季较高土壤微生物量碳含量出现在定植后 90 d,土壤微生物量氮较高含量出现在定植后 60 d;番茄季分别出现在定植后 20～80 d 和 60 d。芹菜季 5 个有机无机肥料配施模式土壤微生物量碳、氮含量分别在 185.0～514.6 和 34.3～79.1 mg/kg 之间,较化肥(4/4CN)模式平均分别增加 15.1%～81.7% 和 24.5%～100.0%,其中以配施秸秆模式土壤微生物量碳、氮含量相对较高,平均分别增加 62.0%～81.7% 和 81.1%～100.0%;番茄季 5 个有机无机肥料配施模式土壤微生物量碳、氮含量分别在 120.7～338.0 和 25.5～68.8 mg/kg 之间,较 4/4CN 模式平均分别增加 16.9%～86.9% 和 12.2%～109.3%,又以配施秸秆模式土壤微生物量碳、氮含量最高,平均分别增加 61.4%～86.9% 和 78.2%～109.3%。两季蔬菜不同生育期土壤微生物量碳、氮含量与当季蔬菜产量和定位试验开始以来蔬菜总产量之间均呈极显著正相关关系。 【结论】 同等养分投入量下,有机无机肥料配合施用提高土壤微生物量碳、氮的效果显著好于单施化肥,又以化肥配施秸秆效果更佳;土壤微生物量碳、氮含量与设施蔬菜产量之间呈极显著正相关关系。证明有机无机肥配施,特别是配施一定量的秸秆可有效提高土壤微生物量碳、氮含量,维持较高的菜田土壤肥力,有利于设施蔬菜的可持续和高效生产。      

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.