Soil phosphorus fractions and adsorption as affected by organic and inorganic sources

The effect of organic and inorganic sources of phosphorus (P) on soil P fractions and P adsorption was studied in a field without plant growth on a Kandiudalf in western Kenya. A high-quality organic source, Tithonia diversifolia (Hemsley) A. Gray leaves, and a low-quality source, maize (Zea mays L.) stover, were applied alone or in combination with triple superphosphate (TSP). The P rate was kept constant at 15 kg P ha^-1. Soil extractable P (resin, bicarbonate and sodium hydroxide), microbial biomass P and C and P adsorption isotherms were determined during 16 weeks after application of treatments. Application of tithonia either alone or with TSP increased resin P, bicarbonate P, microbial P, and sodium hydroxide inorganic P. Tithonia alone reduced P adsorption at 2–16 weeks. Maize stover had no effect on any of the P fractions or P adsorption. At 8 weeks, the application of tithonia reduced microbial C-to-P ratio (20) as compared to maize stover, TSP and the control (31–34). The reduction in P adsorption by tithonia was accompanied by increases in all measured P fractions, the sum of P in those fractions (resin, bicarbonate and sodium hydroxide) being larger than the P added. The reduction in P adsorption apparently resulted from competition for adsorption sites, probably by organic anions produced during decomposition of the high quality tithonia. Integration of inorganic P (TSP) with organic materials had little added benefit compared to sole application of TSP, except that combination of tithonia with TSP increased microbial biomass. The results indicate that a high quality organic input can be comparable to or more effective than inorganic P in increasing P availability in the soil.     

成土母质和种植制度对土壤pH和交换性铝的影响

研究了我国南方 3种不同成土母质发育的酸性自然土壤的 p H与交换性铝含量状况和种植不同作物后它们的变化。研究结果表明 ,自然土壤的 p H平均值大小顺序为雷州半岛地区玄武岩发育砖红壤≤粤中花岗岩发育赤红壤 <粤北石灰岩发育红壤 ,土壤交换性铝含量的平均值的大小顺序为粤北石灰岩发育红壤 <雷州半岛地区玄武岩发育砖红壤 <粤中花岗岩发育赤红壤。种植茶树将使这 3种土壤的 p H显著降低 ,交换性铝的含量则将不同程度升高 ,最为明显的是种茶后石灰岩发育的茶园土的 p H在这 3种土壤中变为最低 ,交换性铝数量的增加幅度最大。种植水稻将提高土壤的 p H和交换性铝的含量。轮作花生后土壤的 p H也将上升 ,但受施用石灰的影响土壤交换性铝的含量将降低     

Nitrogen losses in puddled soils as affected by timing of water deficit and nitrogen fertilization

Erratic rainfall in rainfed lowlands and inadequate water supply in irrigated lowlands can results in alternate soil drying and flooding during a rice (Oryza sativa L.) cropping period. Effects of alternate soil drying and flooding on N loss by nitrification-denitrification have been inconsistent in previous field research. To determine the effects of water deficit and urea timing on soil NO₃ and NH₄, floodwater NO₃, and N loss from added ¹⁵N-labeled urea, a field experiment was conducted for 2 yr on an Andaqueptic Haplaquoll in the Philippines. Water regimes were continuously flooded, not irrigated from 15 to 35 d after transplanting (DT), or not irrigated from 41 to 63 DT. The nitrogen treatments in factorial combination with water regimes were no applied N and 80 kg urea-N ha^–1, either applied half basally and half at 37 DT or half at 11 DT and half at 65 DT. Water deficit at 15 to 35 DT and 41 to 63 DT, compared with continuous soil flooding, significantly reduced extractable NH₄ in the top 30-cm soil layer and resulted in significant but small (<1.0 kg N ha^–1) soil NO₃ accumulations. Soil NO₃, which accumulated during the water deficit, rapidly disappeared after reflooding. Water deficit at 15 to 35 DT, unlike that at 41 to 63 DT, increased the gaseous loss of added urea N as determined from unrecovered ¹⁵N in ¹⁵N balances. The results indicate that application of urea to young rice in saturated or flooded soil results in large, rapid losses of N (mean = 35% of applied N), presumably by NH₃ volatilization. Subsequent soil drying and flooding during the vegetative growth phase can result in additional N loss (mean = 14% of applied N), presumably by nitrification-denitrification. This additional N loss due to soil drying and flooding decreases with increasing crop age, apparently because of increased competition by rice with soil microorganisms for NH₄ and NO₃.     

Dynamics of bacterial communities in rice field soils as affected by different long-term fertilization practices

Fertilization and the response of the soil microbial community to the process significantly affect crop yield and the environment. In this study, the seasonal variation in the bacterial communities in rice field soil subjected to different fertilization treatments for more than 50 years was investigated using 16S rRNA sequencing. The simultaneous application of inorganic fertilizers and rice straw compost (CAPK) maintained the species richness of the bacterial communities at levels higher than that in the case of non-fertilization (NF) and application of inorganic fertilizers only (APK) in the initial period of rice growth. The seasonal variation in the bacterial community structure in the NF and APK plots showed cyclic behavior, suggesting that the effect of season was important; however, no such trend was observed in the CAPK plot. In the CAPK plot, the relative abundances of putative copiotrophs such as Bacteroidetes, Firmicutes, and Proteobacteria were higher and those of putative oligotrophs such as Acidobacteria and Plactomycetes were lower than those in the other plots. The relative abundances of organotrophs with respiratory metabolism, such as Actinobacteria, were lower and those of chemoautotrophs that oxidize reduced iron and sulfur compounds were higher in the CAPK plot, suggesting greater carbon storage in this plot. Increased methane emission and nitrogen deficiency, which were inferred from the higher abundances of Methylocystis and Bradyrhizobium in the CAPK plot, may be a negative effect of rice straw application; thus, a solution for these should be considered to increase the use of renewable resources in agricultural lands.     

Transformation of inorganic phosphorus in flooded soils under rice cropping

Summary The concentrations of water soluble and ammonium acetate extractable phosphorus in all the soils under investigation first increased and then decreased with time of submergence under rice cropping. The increase in soluble phosphorus in the three acid soils of Luisiana, Casiguran and Guadalupe was related to decrease in the concentration of iron, calcium and reductant soluble phosphates, while in slightly acidic Maahas clay, the increase was associated with decrease in iron and aluminium phosphates. But in the calcareous soil, the increase was due to decrease in the concentration of aluminium and reductant soluble phosphates. The decrease was due to the re-formation of insoluble aluminium, iron and calcium phosphates in Luisiana and Guadalupe clays, to the formation of aluminium and calcium phosphates in Maahas and to the formation of calcium phosphate only in Casiguran fine sand. The application of phosphorus at the rate of 100 pounds per acre produced better tillering, more penicles and higher straw and grain productions in Luisiana, Casiguran and Guadalupe only where the level of soluble phosphate was very low in pots where no phosphorus was applied. This study, thus, indicated the necessity of phosphorus fertilization in low land rice for soils which are low in phosphorus and high in active iron and aluminium.     

Metagenomic profiling of rhizosphere microbial community structure and diversity associated with maize plant as affected by cropping systems

International Microbiology - Soil microbial diversity is believed to be vital in maintaining soil quality and health. Limited knowledge exists on the impact of cropping systems (mono-cropping and...     

Bacterial diversity in agricultural soils during litter decomposition

Denaturing gradient gel electrophoresis (DGGE) of amplified fragments of genes coding for 16S rRNA was used to study the development of bacterial communities during decomposition of crop residues in agricultural soils. Ten strains were tested, and eight of these strains produced a single band. Furthermore, a mixture of strains yielded distinguishable bands. Thus, DGGE DNA band patterns were used to estimate bacterial diversity. A field experiment performed with litter in nylon bags was used to evaluate the bacterial diversity during the decomposition of readily degradable rye and more refractory wheat material in comparable luvisols and cambisols in northern, central, and southern Germany. The amount of bacterial DNA in the fresh litter was small. The DNA content increased rapidly after the litter was added to the soil, particularly in the rapidly decomposing rye material. Concurrently, diversity indices, such as the Shannon-Weaver index, evenness, and equitability, which were calculated from the number and relative abundance (intensity) of the bacterial DNA bands amplified from genes coding for 16S rRNA, increased during the course of decomposition. This general trend was not significant for evenness and equitability at any time. The indices were higher for the more degradation-resistant wheat straw than for the more easily decomposed rye grass. Thus, the DNA band patterns indicated that there was increasing bacterial diversity as decomposition proceeded and substrate quality decreased. The bacterial diversity differed for the sites in northern, central, and southern Germany, where the same litter material was buried in the soil. This shows that in addition to litter type climate, vegetation, and indigenous microbes in the surrounding soil affected the development of the bacterial communities in the litter.     

小麦-甘薯轮作长期增施有机肥对碱性土壤固氮菌群落结构及多样性的影响

生物固氮为农业生态系统提供天然的氮素来源,探究长期增施有机肥对土壤固氮菌群落的影响,为合理增施有机肥和维持土壤固氮微生物群落多样性提供科学依据。选取小麦-甘薯轮作中连续37a不施肥对照(CK)、单施化肥(NPK)、化肥+有机肥(NPKM)处理的甘薯季碱性土壤样品为研究对象。采用Illumina MiSeq高通量测序技术,研究土壤固氮菌群落的组成、多样性及其与土壤特性的关系。结果表明:与对照和单施化肥相比,长期增施有机肥降低土壤固氮菌群落丰富度和多样性,且丰富度与土壤pH显著正相关,与有机碳、全氮和有效养分(硝态氮、有效磷和速效钾)显著负相关。主坐标分析表明长期施肥显著改变土壤固氮菌群落结构,与对照相比,增施有机肥比单施化肥对固氮菌群落结构的影响更大。冗余分析表明土壤有机碳和速效钾是影响固氮菌群落结构改变最主要的因素。长期增施有机肥显著降低变形菌门、蓝藻菌门、Beta-变形菌和固氮弧菌属的相对丰度,显著增加硝化螺旋菌门、酸杆菌门和硝化螺菌属的相对丰度,这与土壤pH、有机碳和有效养分显著相关。因此,在碱性土壤上长期增施有机肥对固氮菌群落结构的改变更大,对群落多样性的抑制作用更强。     

长期施肥对稻田土壤有机氮、微生物生物量及功能多样性的影响

以位于湖南省新化和宁乡县两个稻田肥力长期定位试验点的土样为材料,研究了不同施肥处理对稻田土壤有机氮组分、微生物生物量及功能多样性的影响.结果表明：与不施肥处理（CK）相比,化肥配施有机肥处理提高了稻田土壤酸解总氮（TAHN）及其组分中氨基糖氮（ASN）、氨基酸氮（AAN）和酸解氨态氮（AN）的含量,不同施肥处理对组分中酸解未知氮（HUN）的影响不尽相同.与CK相比,单施化肥处理对土壤微生物生物量碳、氮（MBC、MBN）含量的影响较小,化肥配施有机肥处理则显著提高了土壤MBC和MBN的含量.采用BIOLOG法对土壤微生物群落功能多样性进行测定,结果表明：中、高量有机肥处理提高了稻田土壤微生物的碳源利用率和微生物群落功能多样性;土壤微生物碳源利用的类型因长期不同施肥处理而产生差异.     

Effect of long-term fertilization and cropping on the potassium supplying capacity of soils

Soil samples from a long term field experiment, to study the K depletion pattern, were analysed for K. The values of supply parameters pK?1/2p (Ca+Mg) and free energy δG _r ⁰ were calculated using the data on water soluble and exchangeable cations. Correlation coefficient values between pK?1/2p (Ca+Mg) vs. total K removed, K removal by pearl millet in 1980 and soil available potassium were positive and statistically significant. This indicated that these soils have reached the stage where they would start responding to potassium application. Also, negative but significant correlation of δG _r ⁰ with pK?1/2p (Ca+Mg) and available K, were found. δG _r ⁰ values were positive indicating the affinity of such soils for K and the values, for K fertilized plots were lower in comparison to plots where no K was applied. pK?1/2p (Ca+Mg) parameter was found to be a better measure of K availability over δG _r ⁰ due to either fixation of K or greater contribution of nonexchangeable K fraction towards plant utilized K.     

施肥对麦田土壤可溶性有机氮的影响

利用长期定位试验,研究施肥和小麦生长对土壤可溶性有机氮(EON)的影响。长期不同施肥土壤包括不施肥(No-F)、施用化肥(NPK)和有机肥与化肥配施(MNPK)3种。EON含量范围为7.5—29.3 kg/hm~2,No-F、NPK和MNPK土壤中EON分别占可溶性总氮的40%、56%和56%。长期有机肥与化肥配施显著提高0—15 cm土层EON含量,但对30 cm以下土层EON含量无影响。在小麦开花期,可溶性有机氮的含量及其相对含量显著高于拔节期和收获期。虽然施用氮肥对当季EON含量无显著影响,但同位素示踪微区试验表明,土壤耕层(0—15 cm)中仍有0.4%—2.8%的可溶性有机氮来源于当季施入的肥料氮。可见,化学氮肥向可溶性有机氮的转化缓慢,但农田土壤中可溶性有机氮含量与矿质态氮含量相当,发生淋溶损失的风险大。     

Diffusion in plant cuticles as affected by temperature and size of organic solutes: similarity and diversity among species

Mobilities of lipophilic organic solutes in cuticular membranes (CM) isolated from mature leaves of Citrus aurantium L., Citrus grandis L., Hedera helix L., IIex aquifolium L., Ilex paraguariensis St.-Hil., Mains domestica Borkh., Prunus armeniaca L., Primus laurocerasus L., Pyrus communis L., Pyrus pyrifolia (Burm. f.) Nakai, Stephanotis florihunda Brongn. and Strophantus gratus Baill. were measured over a temperature range of 15–78°C. In this range, solute mobilities increased up to 1000-fold, which corresponds to temperature coefficients Q₁₀ of 3 (IAA in P. armeniaca) to 14 (cholesterol in H. helix). For most species, Arrhenius graphs showed good linearity up to 40°C, and up to 78°C for some species, while for others activation energies declined with increasing temperature. However, no distinct phase transitions caused by sudden structural changes in the CM were observed. In three species we examined whether heating to 70°C changed solute mobility irreversibly by comparing Arrhenius graphs for two successive experiments with the same CM. The two graphs were very similar for P. laurocerasus, while mobilities in the second graph were somewhat reduced for C. aurantium and greatly increased (at 25 and 35°C) for H. helix. This indicates rearrangements of at least some wax constituents when heated to high temperatures. The activation energies of diffusion (E_D) ranged from 75 to 189 KJ mol^?11 depending on species and solute size. Size selectivity and variability between cuticles decreased with increasing temperature, and this is caused by differences in (E_D). An excellent correlation between the pre-exponential factor of the Arrhenius equation and E_D was observed, which is evidence that organic solutes differing greatly in molecular size (130–349 cm³ mol^?1) and cuticle/water partition coefficient (25–10⁸) use similar diffusion paths in the CM of all 12 plant species tested. Diffusion occurs in regions with identical physicochemical properties and differs only in magnitude.     

Crop response to magnesium fertilization as affected by nitrogen supply

Background

Crop yield depends in large part on the availability and accessibility of nitrogen in the soil. For optimal yield, the soil nitrogen must be available at critical periods of crop development, and in a form that is accessible for plant uptake and use. Ancillary crop nutrients can alter the plant’s ability to access and utilize nitrogen. Therefore, crop fertilization with magnesium should focus on its effect on nitrogen management. This conceptual review aims to assess the present state of knowledge regarding the importance of magnesium in fulfilling both objectives.

Scope

The response to fertilizer magnesium of high-yielding wheat, maize, sugar beet and potato crops was evaluated using published and unpublished data on yield, yield components and nitrogen uptake. A simple, stepwise regression and path analysis was applied to explain the effect of fertilizer magnesium on yield and yield components.

Conclusions

The effect of soil or foliar applied magnesium on yield of crops was inconsistent due to (i) weather experienced during the growth season, (ii) rates of applied fertilizer nitrogen, and (iii) the (natural background levels of?) magnesium available in the soil. The yield increase due to magnesium application was related to the extra supply of nitrogen. In cereals, magnesium application resulted in a higher number of ears and/or thousand grain weight (TGW), stressing the magnesium-sensitive stages of yield formation. The increase of sugar beet yield was most pronounced in dry years. The main conclusion gleaned from the review underlines a positive effect of magnesium on nitrogen uptake efficiency. The optimal yield forming effect of fertilizer magnesium can generally occur under conditions of relatively low nitrogen supply (soil + fertilizer nitrogen), but high supply of magnesium. This phenomenon can best be described as “magnesium-induced nitrogen uptake”.     

Selenium distribution in ryegrass and its antioxidant role as affected by sulfur fertilization

Selenium (Se) essentiality to plants has not been demonstrated although evidence indicates that it plays a significant role as antioxidant in higher plants. Research concerning to the uptake and allocation of Se in plant tissues is reported in numerous works. However, the effect of sulfur (S) on both the distribution and the antioxidant ability of Se in selenite-treated plant remains unclear. In this work the effect of S application (0–100 mg S kg⁻¹ soil) on shoot Se concentration of Lolium perenne cv. Aries was studied. Se distribution into different fractions of plants supplied with selenite (2 mg Se kg⁻¹ soil) and the state of the antioxidative system were determined. Results showed that shoot Se concentration decreased at least 33% by S application. Plants supplied with S registered the lowest GSH-Px activity and the highest lipid peroxidation. Most of Se was incorporated into the organic fraction of the plant tissue irrespective of the S treatment. However, a significant decrease of both the soluble protein and the amino acid fraction occurred, and the residual Se fraction seemed to increase at expense of the organic-Se soluble fraction. Although no essential selenoproteins have been clearly identified in vascular plants, the decrease of the soluble protein fraction and the different pattern of protein synthesized (SDS-PAGE analysis) may explain the observed reduction of the GSH-Px activity.     

Plant species diversity in remnant grasslands on arable soils in the cropping Pampa

In order to provide a baseline for management decisions, we evaluated vegetation heterogeneity among 38 remnant grasslands located on high agronomic potential soils along a five degree-east–west transect in the cropping Pampa. This extensive region has been cultivated for well over a century, small-scale traditional forms of agriculture were progressively replaced with large-scale industrial forms and its cropped area has more than doubled in the last 25 years, threatening the maintenance of biodiversity associated to productive soils. We characterized the diversity of this grassland patches, identified its main environmental drivers and searched for factors that favor their invasion by exotic plant species. Vegetation samples were analysed through Canonical Correspondence Analysis, proportional distribution of functional groups was compared and regression models were estimated to identify variables associated with exotic species importance. Water availability, determined by climate and soil characteristics, was the main driving factor of floristic heterogeneity in these grasslands. Exotic richness, mostly of Eurasian species, increases toward the east, related to proximity to the entrance port. The functional group of C₄ native grasses seems to be responsible for biotic resistance to invasion. More than 80% of the species recorded during the first vegetation registers in 1930 are still present, while the number of exotics was seven-fold increased. Despite covering small areas as isolated stands, these are hot spots of native biodiversity and must be the object of increasing attention for conservation and restoration in order to protect the biodiversity of an extensive agricultural landscape.     

鼎湖山不同演替阶段森林土壤细菌多样性

[目的]了解鼎湖山早、中、后3个演替阶段的3类森林(针叶林、混交林、阔叶林)土壤细菌群落结构及其多样性,为下一步研究不同演替阶段森林土壤微生物的功能及其与植物的相互作用提供依据.[方法]在代表性林区采集土样,从中提取总DNA,利用细菌通用引物27F和1492R PCR扩增16S rDNA并构建文库.从所构建的3个文库中各挑取150个阳性克隆子并对插入片段进行测序,利用Mothur软件对所得序列进行分析.[结果]从针叶林、混交林和阔叶林文库中分别得到122、118和120条有效16S rDNA序列,各代表70、64、72个OTUs(operational taxonomic units,以97％相似性为划分标准).分析结果显示,共检测到8个细菌门类,其中酸杆菌门(Acidobacteria)在针叶林、混交林和阔叶林土样中分别占53.3％,67.8％和60％ ;变形杆菌门(Proteobacteria)分别占29.5％,20.3％和32.5％ ;其它如厚壁菌,放线菌等均不超过10％.3类森林土壤细菌群落结构差异显著(P＜0.05),3者两两间共有的OTU数量占检测到的OTU总数的比例均低于25％,其中阔叶林土壤细菌有着最高的Chao指数(414.2)和Shannon指数(3.90),及最低的Simpson优势度指数(0.0249).[结论]鼎湖山针叶林、混交林和阔叶林3类林区土壤细菌在种群构成上差异显著,其中阔叶林土壤细菌丰富度及多样性相对较高,但3者在大类组成方面比较相似,均为酸杆菌占绝对优势,变形杆菌次之.     

Bacterial regeneration of ammonium and phosphate as affected by the carbon:nitrogen:phosphorus ratio of organic substrates

The effect of carbonnitrogenphosphorus (CNP) ratio of organic substrates on the regeneration of ammonium and phosphate was investigated by growing natural assemblages of freshwater bacteria in mineral media supplemented with the simple organic C, N, and P sources (glucose, asparagine, and sodium glycerophosphate, respectively) to give 25 different substrate CNP ratios. Both ammonium and phosphate were regenerated when CN and NP atomic ratios of organic substrates were 101 and 161, respectively. Only ammonium was regenerated when CN and NP ratios were 101 and 10–201, respectively. On the other hand, neither ammonium nor phosphate was regenerated when CN and NP ratios were 151 and 51, respectively. In no case was phosphate alone regenerated. As bacteria were able to alter widely the CNP ratio of their biomass, the growth yield of bacteria appeared primarily dependent on the substrate carbon concentration, irrespective of a wide variation in the substrate CNP ratio.     

Bacterial diversity in microcosms of soils with various humidity]

The succession analysis of bacterial diversity in the A horizons (rich in organic matter) of three contrasting types of soil--burozem, soddy gley soil, and chernozem--showed that the bacterial diversity of soil microcosms in humid regions can be adequately evaluated only if soil samples are incubated at different soil moisture contents. A complete account of actinobacteria and proteobacteria requires the levels of soil moisture corresponding to the maximum capillary-sorption moisture and capillary moisture, respectively. The bacterial diversity, whose value was maximum on the 40th day of succession, was higher in soddy gley soil than in burozem. The taxonomic structures of the bacterial communities of these two types of soil were different. After wetting chernozem samples from arid regions, the soil bacterial community changed insignificantly with time and drastically differed from that of soils from humid regions. The difference in the bacterial diversity of soils was the most distinct when it was evaluated by measuring the proportion between proteobacteria and actino-bacteria.     

Seasonal variation in organic and inorganic phosphorus fractions of temperate-climate sandy soils

Soils from an arable plot, a grassland plot and pasture plot were sampled over an 18-month period. Inorganic (P_i) and organic (P_o) soil phosphorus fractions were extracted sequentially with resin, NaHCO₃, and NaOH. Soil solution was sampled on the arable plot and pasture plot during 12 months with teflon suction cups, and the contents of P_i and P_o were determined.The patterns of the variation for all soil fractions were similar for the three plots. All soil P_i fractions were at minimum in the cool moist winter period. The soil P_o fractions varied less systematically than P_i fractions. The sum of P_o fractions had a winter maximum and a spring minimum. For all soil P fractions temporal variation was highly significant (p<0.0001). The magnitude of change in P_i and P_o soil fractions was 4–40 times greater than what would be expected from the magnitude of new N mineralization.The content of P in the inorganic soil P fractions was negatively correlated with soil moisture. The variation in organic soil P could not be explained by any single factor, but it is suggested that the variation is caused by changes in solubility rather than by biological transformations. Thus, physicochemical processes masked the impact of biological transformations on the temporal variation of soil phosphorus fractions.Both soil solution P_i and P_o varied significantly with time on field scale. In contrast to soil P_i fractions, solution P_i was initially low in the early autumn, increased by a factor 4 during the following 6 weeks, and thereafter decreased to a low level by the end of the sampling period. Soil solution P_o had several fluctuations during the sampling period.     

玉米连作及其施肥对土壤微生物群落功能多样性的影响

采用Biolog技术,借助吉林农业大学1984年建立的长期定位试验,以撂荒和非玉米连作(当季作物为芸豆)为对照,研究玉米连作及其不同施肥措施对土壤微生物功能多样性的影响。结果表明,反映土壤微生物活性的平均颜色变化率(AWCD)呈现出以下变化规律:撂荒(UC)非玉米连作(NCC)玉米连作不施肥(CK);玉米连作配施秸秆(S、SN、SNPK)玉米连作配施NPK(NPK)玉米连作不施肥(CK)玉米连作单施N(N)。微生物培养72h活性旺盛,各处理AWCD在0.395—0.732之间,其中撂荒AWCD显著高于非玉米连作和玉米连作不施肥(P0.05);玉米连作配施秸秆明显提高微生物活性,玉米连作配施秸秆(S、SN、SNPK)AWCD是玉米连作不施肥和单施化肥(N、NPK)的1.26—1.62倍。玉米连作不施肥土壤微生物群落多样性指数(H、E、S)低于撂荒处理,但高于非玉米连作处理,非玉米连作提高了土壤微生物优势度指数。玉米连作配施秸秆土壤微生物物种丰富度指数和均匀度指数高于玉米连作不施肥和玉米连作施化肥,玉米连作单施氮肥优势度指数较高,其它多样性指数降低。主成分分析结果表明,不同处理土壤微生物碳源利用特征出现分异:撂荒和玉米连作配施秸秆处理集中在第1主成分正方向,得分系数在2.39—4.17之间,土壤微生物碳源利用特征相似;玉米连作不施肥、玉米连作单施化肥和非玉米连作处理分布在第1主成分负方向,得分系数在-5.43—-1.59之间。土壤微生物利用的碳源主要是糖类、羧酸类、氨基酸和聚合物。玉米连作配施秸秆和撂荒有利于提高土壤微生物代谢活性和土壤微生物群落功能多样性,玉米连作单施化肥尤其单施氮肥土壤微生物活性和功能多样性下降。