磷供应对玉米根际微生物碳源利用和功能多样性的影响

磷有效性能够改变根分泌物的组成和数量,调节土壤微生物的群落结构和多样性,但磷添加如何影响土壤微生物碳源利用和功能多样性尚不清楚。本研究通过盆栽土培试验,设置2个磷处理[低磷5.7 mg(P)?kg?1和高磷200 mg(P)?kg?1],以生长35 d的玉米根际土壤为研究对象,采用Biolog微平板法,分别在培养后240 h内每隔24 h检测具有31种不同碳源的微孔溶液颜色变化,揭示磷供应对玉米根际微生物碳源利用模式和功能多样性的影响。结果表明:随着培养时间的延长,土壤微生物对土壤碳源的利用呈现增加的趋势,直至碳源消耗殆尽;高磷供应显著增加了玉米根际土壤微生物群落平均颜色变化率(average well color development,AWCD),提高了对糖类及其衍生物、氨基酸和代谢产物的利用,但没有显著提高对脂肪酸和脂类的利用;在培养前72 h内,高磷供应显著增加了玉米根际微生物多样性指数、优势度指数和均匀度指数,但培养72 h后,磷供应对其没有显著的影响。主成分分析结果表明,提取的前3个主成分解释了75.15%的碳源利用,高磷和低磷处理具有显著不同的土壤微生物碳源利用模式。总之,糖类及其衍生物、氨基酸和代谢产物是玉米根际土壤微生物利用的主要碳源,短期磷添加能够显著增加土壤微生物对碳源的利用,在一定程度上能够提高土壤微生物群落功能多样性。     

水稻根际和周围土壤中微生物功能基因丰度与碳、氮状况及其通量之间的关系

Rapid nitrogen（N） transformations and losses occur in the rice rhizosphere through root uptake and microbial activities. However,the relationships between rice roots and rhizosphere microbes for N utilization are still unclear. We analyzed different N forms（NH＋4,NO-3, and dissolved organic N）, microbial biomass N and C, dissolved organic C, CH4 and N2O emissions, and abundance of microbial functional genes in both rhizosphere and bulk soils after 37-d rice growth in a greenhouse pot experiment. Results showed that the dissolved organic C was significantly higher in the rhizosphere soil than in the non-rhizosphere bulk soil, but microbial biomass C showed no significant difference. The concentrations of NH＋4, dissolved organic N, and microbial biomass N in the rhizosphere soil were significantly lower than those of the bulk soil, whereas NO-3in the rhizosphere soil was comparable to that in the bulk soil. The CH4 and N2O fluxes from the rhizosphere soil were much higher than those from the bulk soil. Real-time polymerase chain reaction analysis showed that the abundance of seven selected genes, bacterial and archaeal 16 S rRNA genes, amoA genes of ammonia-oxidizing archaea and ammonia-oxidizing bacteria, nosZ gene, mcrA gene, and pmoA gene, was lower in the rhizosphere soil than in the bulk soil, which is contrary to the results of previous studies. The lower concentration of N in the rhizosphere soil indicated that the competition for N in the rhizosphere soil was very strong, thus having a negative effect on the numbers of microbes. We concluded that when N was limiting, the growth of rhizosphere microorganisms depended on their competitive abilities with rice roots for N.     

有机肥对水稻根际土壤中微生物和酶活性的影响

利用根际箱在红壤上研究了有机肥对水稻根际有效磷、根际微生物和土壤酶活性的影响。试验结果表明,有机肥明显地提高水稻根际和非根际土壤真菌、放线菌和细菌的数量及土壤有效磷的含量。根际土壤各类微生物的数量大于非根际土壤,表现出明显的根际效应。施用有机肥使根际效应增加,其效应为细菌 放线菌 真菌。有机肥还明显地促进水稻根际无机磷溶解菌和有机磷分解数量以及磷酸酶和脲酶的活性,同时对水稻根际土壤磷转化速率有明显的提高,从而加速了土壤养分的转化。     

磷影响下根际无机砷的形态分布及其对水稻生长的影响

两种有代表性的紫色土的水稻盆裁试验结果表明，磷的加入可减轻受砷污染的红紫泥中砷对水稻的毒害；但磷的加入会加剧受砷污染的红棕紫泥中砷对水稻的毒害。根际无机砷的形态分布研究表明：试验土壤上，根际砷各形态都比非根际高，砷在根际呈富集状态；在根际环境的作用下，红紫泥中，磷的加入加剧了砷由有效态砷（Al-As、Fe-As）向相对无效态砷（O－As）转化，砷对水稻的毒性减弱；红棕紫泥中，磷的加入加剧了砷由相对无效态砷Fe-As和Al-As向有效态砷Ca-As和A-As（表示水溶态砷及松结态砷）的转化，砷对水稻的毒性增强。     

水稻根际土壤及根组织内外固氮微生物的遗传多样性分析

利用PCR—RFLP检测了水稻根际土壤及根组织内外固氮微生物的nifH基因。对54个阳性克隆的nifH 限制性内切酶Mnl I的RFLP图谱进行UPGMA聚类分析和最大似然法分析，结果表明了8对相似的带型(相似性> 50%)和2对同源性为100%的带型分别来源于水稻根际土壤及根组织内外，3种特有的带型均来源水稻根际土壤和3种特有带型来源于水稻根组织内外。证明了水稻根际土壤和水稻根组织的固氮微生物具有显著的多样性，也初步显示了土壤中某些固氮微生物能定植于水稻根内或根表。     

绿肥压青对南方春玉米根际土壤肥力的影响

采用黑麦草、毛叶苕子、紫云英3种绿肥材料进行玉米地压青试验,研究了绿肥压青对南方春玉米根际土壤肥力的影响.结果表明,与无绿肥压青比较,3种绿肥压青对春玉米根际土壤速效养分和有机质含量均有提高效应,其中黑麦草和毛叶苕子的增效最为显著;对玉米根际土壤速效养分而言,毛叶苕子增效好于黑麦草;就有机质而言,黑麦草和毛叶苕子增效相当.研究表明毛叶苕子和黑麦草可作为南方春玉米前茬地的优势绿肥品种.     

大气中臭氧浓度增加对根际和非根际土壤微生物的影响

在大田试验下,研究了冬小麦在不同的臭氧浓度下根际和非根际土壤细菌、真菌、放线菌数量的动态变化。结果表明,随着生育时期的推进,微生物数量呈现规律性的变化,其中微生物总量在抽穗期达最大。根际、非根际土壤细菌和真菌数量均随着生育期的推进呈先增大后降低的变化趋势,分别在抽穗期和孕穗期达最大。根际、非根际土壤放线菌数量随生育期呈下降的趋势,整个生育期内臭氧浓度的升高降低了土壤微生物的数量,不同的臭氧浓度处理间细菌数量差异达显著性水平,真菌数量差异只在成熟期达显著,放线菌差异不显著。     

两种母质的红壤性水稻土中微生物硫循环代谢途径特征

水稻土氧化还原交替频繁，使不同形态的硫元素转化的生物化学反应活跃，对水稻生产影响显著。本文以花岗岩和第四纪红色黏土母质发育的红壤性水稻土为研究对象，通过宏基因组测序以及生物信息学分析，研究了红壤性水稻土硫循环途径相关功能微生物特征，包括有机硫转化途径、其他（转运）途径、同化硫酸盐还原途径、硫氧化途径、异化硫酸盐还原途径以及硫歧化途径。结果表明：两种母质发育的红壤性水稻土具有相同的硫循环途径特征，即有机硫转化途径微生物功能基因丰度的发生频率最高，每百万个带注释的细菌序列平均检测到16000个有机硫转化的功能基因；硫歧化途径微生物功能基因丰度的发生频率最低，每百万个带注释的细菌序列平均仅检测到116个硫歧化途径功能基因。两种母质发育的红壤性水稻土中主导硫循环的微生物，在门分类水平上，微生物组成没有显著差异，都以变形菌门（Proteobacteria）、酸杆菌门（Acidobacteria）、绿弯菌门（Chloroflexi）为优势菌门，占比分别为55.19%、10.61%、7.18%等。在种水平分类上则差异显著，花岗岩母质发育的水稻土中硫循环途径微生物相对丰度更高，且所有途径的优势菌种都为Deltaproteobacteria bacterium、Acidobacteria bacterium、Betaproteobacteria bacterium，其丰度占花岗岩母质水稻土硫循环微生物丰度的40%以上；而在第四纪红色黏土母质发育的水稻土中参与硫循环每条途径的优势功能微生物更加丰富，如在有机硫转化途径中Gemmatirosa kalamazoonesis丰度最高，在其他（转运体）途径Azoarcus sp.的丰度最高，在同化硫酸盐还原途径丰度最高的微生物是Anaeromyxobacter sp.。研究结果表明：两种不同母质发育的红壤性水稻土中存在相同的硫循环途径特征，两种母质发育的红壤性水稻土中主导硫循环的微生物在门水平上没有显著差异，但在种水平分类上差异显著，表明不同母质中会存在着独特的优势硫转化功能菌群。     

氨基酸增值尿素对水稻苗期生长及根际微生物菌群的影响

[目的]研究氨基酸增值尿素(AU)对不同稻作水稻生长、根际养分与微生物群落的影响机制,以期为水稻早期水氮合理调控及氨基酸增值尿素合理施用提供依据.[方法]以'两优华6'水稻和氨基酸增值尿素(AU)为试材,开展了水作/旱作盆栽试验.试验共设旱作不施尿素(GCK)、旱作施普通尿素(GU)、旱作施氨基酸增值尿素(GAU)、水...     

甘蔗间作玉米对甘蔗根际微生物代谢功能多样性的影响

为探讨甘蔗间作玉米种植对甘蔗根际土壤微生物群落功能多样性的影响,在云南元江和陇川甘蔗种植区设置甘蔗间作玉米和单作甘蔗田间小区试验,采用Biolog技术研究了甘蔗间作玉米对甘蔗根际微生物代谢功能的影响。结果表明:陇川试验点甘蔗间作玉米田土壤微生物代谢功能多样性指数Shannon多样性指数、Simpson指数、Mc Intosh指数、Shannon均匀度指数和Mc Intosh均匀度指数分别比甘蔗单作田提高7.08%、11.25%、63.16%、1.31%和2.26%;元江试验点,甘蔗间作玉米田土壤微生物代谢功能多样性指数Shannon多样性指数、Simpson指数、Mc Intosh指数、Shannon均匀度指数和Mc Intosh均匀度指数分别比甘蔗单作田提高10.58%、48.40%、43.42%、0.20%和1.65%。由此表明甘蔗间作玉米种植提高了甘蔗根际土壤微生物的多样性。甘蔗间作玉米种植提高了甘蔗根际微生物对碳源的利用率,且元江甘蔗根际土壤微生物对碳源的利用效率低于陇川。与单作甘蔗相比,元江试验点间作甘蔗根际碳水化合物类、氨基酸类、多聚物类、胺类、羧酸类和酚酸类利用率分别提高141.71%、50.53%、62.38%、92.82%、43.21%和6.30%,陇川试验点分别提高42.90%、51.50%、33.30%、42.64%、16.72%和24.47%。其中,两个试验区间作田甘蔗根际土壤微生物对碳源D-纤维二糖、D,L-a-甘油、D-半乳糖-γ-内酯、L-丝氨酸、甘氨酰-L-谷氨酸和2-羟苯甲酸的利用率比单作显著提高100%以上。通过主成分分析,发现甘蔗与玉米间作改变了甘蔗根际微生物的群落组成及其代谢功能,且碳水化合物类、羧酸类和氨基酸这3类碳源是区分甘蔗单作和间作处理间差异的敏感碳源。陇川试验点,对土壤微生物代谢功能影响较大的碳源主要包括2种多聚化合物、6种碳水化合物、2种羧酸类化合物、4种氨基酸和1种酚酸;元江试验点,对土壤微生物代谢功能影响较大的碳源主要包括1种多聚化合物、5种碳水化合物、3种羧酸类化合物、4种氨基酸和2种胺类化合物。综上所述,宿根甘蔗间作玉米提高了甘蔗根际微生物群落的多样性,增加了根际微生物的活性,改变了微生物群落的代谢功能。研究结果可为作物间作对土壤微生物多样性分析及增产机理研究提供新的思路和理论基础。     

不等量翻压紫云英处理下黄泥田土壤磷组分的变化

黄泥田是我国南方主要的中低产水稻土类型之一,采用定位试验的方法,研究了单施化肥(NPK)、化肥+紫云英(12 000、24 000、36 000、48 000 kg·hm-2)5个处理下土壤磷组分的变化。结果表明,与单施化肥相比,紫云英翻压与化肥配施的土壤有效磷增幅达10.23%～22.69%,全磷含量增加3.09%～13.31%,以化肥配施24 000 kg·hm-2紫云英(NPK+MV2)增幅最为明显;其中,有机磷占总磷含量的36.52%～43.14%,无机磷占56.86%～63.48%;无机磷组分主要以Fe-P和O-P为主,不等量紫云英翻压与化肥配施土壤无机磷组分含量与NPK相比都有所增加,当翻压量小于NPK+MV2处理时,增加幅度均表现为显著水平,大于NPK+MV2处理时,则差异不显著;紫云英翻压与化肥配施处理水稻产量较NPK增产达12.51%～23.01%,以NPK+MV2处理增产最为明显,增产1 345.7 kg·hm-2。表明在黄泥田中紫云英翻压配施化肥比单施化肥能提高土壤磷组分及其含量,水稻产量与土壤磷含量密切相关,以翻压紫云英24 000 kg·hm-2与化肥配施为较适宜的施肥模式。     

Microbial biomass phosphorus and alkaline phosphomonoesterase activity in the rhizosphere of different wheat cultivars as influenced by inorganic phosphorus and farmyard manure

Wheat cultivars C 306, PBW 175, HD 1553, and HD 2329 were grown in an alkaline soil with and without inorganic P fertilizer and/or farmyard manure in a pot culture experiment. Microbial biomass P (MBP) and alkaline phosphomonoesterase (APM) activities were studied in rhizosphere soils of the above wheat cultivars at different physiological stages. Root weight and P uptake were also estimated simultaneously. Higher microbial biomass P was observed at crown root initiation (CRI) stage while APM activities were higher at panicle initiation (PI) stage. The HD cultivars showed higher MBP and APM activities at PI stage, while at CRI stage, the reverse was true. Though the application of inorganic P apparently showed higher APM activity, the ratio of APM activity and microbial biomass P (APM to MBP) decreased in the presence of inorganic fertilizer P. Inorganic P compared to FYM was the more dominant factor in reducing the APM to MBP ratio. Root weight did not correlate with grain yield. From step-wise regression analysis, it was revealed that microbial biomass P at both CRI and PI stages was a significant factor in influencing the P uptake in relation to grain yield of wheat.     

Phosphine-induced phosphorus mobilization in the rhizosphere of rice seedlings

Purpose

The aim of this study was to evaluate the role of phosphine in the mobilization of phosphorus in the rhizosphere soil of rice seedlings and to determine the relative efficiency of phosphine in plant P acquisition.

Materials and methods

An indoor simulation experiment was conducted and the matrix-bound phosphine (MBP), phosphorus fractions, and phosphatase activity in the rhizosphere soil samples from rice cultivation, biomass, the plant P, and the root system activity were measured under different phosphine concentrations (0, 1.4, 4.2, and 7.0 mg m^?3) for a period of 30 days.

Results and discussion

The results indicated that phosphine treatments enhanced MBP, inorganic P (resin–P_i, NaHCO₃–P_i, and NaOH–P_i), and phosphatase activity, as well as the root system activity, and the content of P in the rice seedlings was stimulated with increasing phosphine concentrations. However, organic P (NaHCO₃–P_o and NaOH–P_o) accumulation occurred in the rhizosphere of the rice seedlings. In addition, the content of organic P in the soil samples decreased with increased phosphine concentration.

Conclusions

Therefore, relatively high concentrations of phosphine in paddy field could have a positive impact on the effectiveness of phosphorus in rice plants via influencing the rhizosphere properties.

     

Soil phosphorus mobilization in the rhizosphere of cover crops has little effect on phosphorus cycling in California agricultural soils

Phosphorus (P) is a key limiting factor in many terrestrial ecosystems because most soil P is bound to soil minerals or organic matter. Increasing P cycling rates can increase P availability, including in agricultural soils that receive external P inputs. For example, cover crops may increase P cycling rates via plant uptake and P release during microbial decomposition. Cover crops and associated microbes may also change rhizosphere properties and stimulate soil P mobilization. We studied the potential of legume – fava bean (Vicia faba), vetches (Vicia dasycarpa, Vicia sativa, Vicia benghalensis) pea (Pisum sativum) – and cereal – rye (Secale cereale), wheat (Triticum aestivum), oat (Avena sativa) – cover crops to stimulate P cycling across management practices in two long-term systems trials in California. We measured cover crop biomass and nutrient content, P-mobilizing capacity (pH, organic acids, phosphatase activity) and soil P fraction changes in the rhizosphere. Cereals generally produced more biomass with similar P content compared to legumes, but higher C:P in cereal residues could favor microbial immobilization, delay residue mineralization and reduce P cycling rates. Legumes, especially fava bean, had the largest effect on rhizosphere properties by reducing pH and increasing organic acids concentrations and phosphatase activity. However, these changes in rhizosphere properties had a modest impact on soil P and did not increase soil P availability. Furthermore, we found no strong effect of management practices or soil P concentrations on soil P mobilization. Our results suggest that P mobilization in the rhizosphere of legumes is unlikely to increase P cycling rates in these soils, whereas P uptake and release in cereal biomass could have stronger effects.     

水稻栽后施绿肥对其生长发育及土壤肥力的影响

水稻栽后在行间施绿肥，既保持了深施绿肥培肥土壤的作用，又克服了栽前常规施绿肥影响水稻生长发育，甚至造成当季减产的弊端。     

Adaptation of green manure legumes to adverse conditions in rice lowlands

Poor adoption of sustainable pre-rice green manure technology by lowland farmers is frequently associated with unreliable legume performance under adverse environmental conditions such as marginal soils, short photoperiod, and unfavorable hydrology. A series of field and microplot experiments were conducted at the International Rice Research Institute (IRRI) in 1991 and 1992 to screen and evaluate 12 promising flood-tolerant legumes for adaptation (N accumulation and biological N₂ fixation) to a range of environmental stresses, frequently encountered in rice lowlands. Legumes belonging to the genera Sesbania and Aeschynomene were grown for 8 weeks at 10×10 cm spacing: (1) in a fertile control soil and in four marginally productive irrigated lowland rice soils (sandy Entisol, P-deficient Inceptisol, acid Ultisol, and saline Mollisol); (2) during short- (11.7h) and long-day (12.3 h) seasons in a favorable irrigated lowland soil; and (3) in an aerobic soil (drought-prone rain-fed lowland) and a deep-flood-prone lowland soil (1 week seedling submergence). A large variability in N accumulation was obsersed among legume species and across different environments, ranging from less than 1 to over 70 mg N plant^-1. The nitrogen derived from the atmosphere (Ndfa) accounted on average for 82% of total N accumulation. Sesbania virgata was least affected by unfavorable soil conditions but its Ndfa was the lowest among the tested species (less than 60%). Stem nodule formation did not convey a significant advantage to legumes grown under adverse soil conditions. However, flooding reduced N₂ fixation less in stem-nodulating than in solely root-nodulating species. Most species drastically reduced N accumulation under short-day conditions. Aeschynomene afraspera and S. speciosa were least affected by photoperiod. The considerable genetic variability in the germplasm screened allows the selection of potentially appropriate legumes to most conditions studied, thus increasing N accumulation in green manures.     

Lead availability and soil microbial community composition in rice rhizosphere affected by thiosulfate addition

A pot experiment was carried out to study the sulfur (S) and lead (Pb) interaction and its impact on soil microbial community composition in rice rhizosphere soil under flooded conditions. Paddy soil was treated with a Pb gradient with and without thiosulfate addition and then planted with rice. The increasing addition of Pb resulted in plant yield reduction and high, phytotoxic concentrations of Pb in roots with relatively low concentration of Pb in shoots. Under the impact of thiosulfate, Pb uptake in plants and NH₄OAc extractable Pb did not increase dramatically. PCR-DGGE experiment suggested that S action led to new bands. Specific clones (T3 and T6) found in S addition soils had high similarity to Thiobacillus, which indicated relatively high rates of potential S oxidation. S addition did not affect the availability Pb and the composition of soil microbial community. S addition is not a suitable amendatory tool of phytoremediation for Pb polluted soil.     

Impact of monoculture of poplar on rhizosphere microbial communities over time

To date, research on the adverse effects of continuous cropping has focused on field crops; forest plantations, despite their very significant economic and ecological value, have received less attention. The evolution of microbial community in the rhizosphere of forest plantations, in particular, has rarely been examined. In this study, changes in the size, composition, and structure of bacterial and fungal communities in the rhizosphere of different generations of poplar (Populus deltoides) plantations were studied using real-time polymerase chain reaction (PCR) and PCR-denaturing gradient gel electrophoresis and compared with the composition of the microbial community in a bare land (control) adjacent to the plantation sites through sequencing analysis and by constructing phylogenetic trees. The numbers of bacteria and fungi increased significantly with successive poplar generations, although the increases in the two groups were not parallel. When compared with the control, the bacterial community increased greatly in the second generation, and the most significant increase occurred in the third generation. In contrast, the most significant increase in the fungal community occurred in the first generation, and the increase in the third generation was insignificant. In terms of community composition, the first generation showed little change in either community; however, the second generation showed remarkable changes in the bacterial community, and the third in the fungal community. The numbers of Gammaproteobacteria, Alphaproteobacteria, and Actinobacteria increased by 10.92%, 7.38%, and 5.46%, respectively, whereas those of Acidobacteria decreased by 18.38% in the second generation. These changes in the number and composition of microbial communities in the rhizosphere could be one of the reasons for the decline in yield and quality associated with long-term monoculture.     

浅析油菜作为绿肥的应用优势

油菜是可以作为绿肥广泛应用的作物。在总结油菜绿肥土壤培肥性状的基础上,从病虫害生物防治、土壤难溶性磷活化、土壤重金属污染治理3个方面总结归纳了油菜作为绿肥在我国可持续农业发展中的应用优势。     

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.