Field assessment of soil biological and chemical quality in response to crop management practices

Soil microbiological and chemical aspects were evaluated to determine the effects of conservation tillage and crop rotation on soil fertility over a 16-year period. A field trial was established to compare two cropping systems (continuous soybean and maize/soybean, soybean/maize rotation). In addition, maize (Zea mays L.) and soybean (Glycine max L., Merr) were grown in two different tillage systems: no tillage and reduced tillage. Soil populations of Trichoderma spp., Gliocladium spp. and total fungi were more abundant when maize or soybean were under conservation tillage and in the maize/soybean and soybean/maize rotation, than in continuous soybean. Furthermore, higher levels of microbial respiration and fluorescein diacetate hydrolysis (FDA), were recorded under no tillage systems. However, soil counts of Actinomycetes and Pythium spp., and Pythium diversity together with soil microbial biomass were not affected by the field treatments. To establish a correlation with soil biological factors, soil chemical parameters, such as pH, organic matter content, total N, electrical conductivity, N–NO₃ ⁻ and P were also quantified, most of the correlations being significantly positive. Under no tillage there was a clear increase of the amount of crop residues and the C and N soil content due to the presence of residues. Also the distribution of crop residues in surface soil due to zero tillage and the quality of these residues, depending on the crop rotation employed, improved on soil biological and chemical characteristics. Crop yield was also enhanced by zero tillage through the management of residues. Although yield values were not directly associated with the development of microorganisms, both yield and microorganisms were influenced by crop management. These results suggest that measuring soil properties over a long period helps to define effective management strategies in order to preserve soil conditions.     

湖北省不同花生轮作种植体系碳氮足迹

明确作物生产过程的主要碳氮排放环节,可为不同花生轮作种植体系实现高产高效与低碳氮排放的协同效益提供有效参考。本研究对湖北省黄冈市油菜-花生轮作、小麦-花生轮作、花生单作3种种植模式生产过程的农资投入和田间管理措施等进行实地调查,核算该3种种植模式的碳足迹和氮足迹。结果表明: 油菜-花生轮作较小麦-花生轮作单位面积碳排放降低7.8%、单位净现值碳排放降低36.9%、单位面积氮排放降低12.5%、单位净现值氮排放降低41.9%;油菜-花生轮作较花生单作单位净现值碳排放和氮排放分别降低19.6%和30.8%;油菜-花生轮作净收益是小麦-花生轮作的1.4倍、花生单作的2.4倍。表明油菜-花生轮作可实现高产高效与低碳氮排放的协同效益,有利于油料作物的绿色高质高效生产。     

耕作方式对紫色水稻土轻组有机碳的影响

以位于西南大学实验农场的长期免耕试验田为研究对象,通过0—60cm分层采集土壤样品的方法,探讨了不同耕作方式———冬水田平作(DP)、水旱轮作(SH)、垄作免耕(LM)及垄作翻耕(LF)对土壤轻组有机碳的影响。结果表明,重组有机碳是土壤总有机碳的主体,约占土壤总有机碳的69.56%—95.66%,在土壤剖面上随土壤深度的增加其分配比例逐渐升高;其次是自由轻组有机碳,约占土壤总有机碳的5.03%—26.43%,从土壤表层向下,其分配比例迅速下降;闭合轻组有机碳最低,仅占土壤总有机碳的1.37%—4.93%,其分配比例随土壤深度的变化不明显。在0—60 cm土壤深度内,不同耕作方式下自由轻组有机碳的平均含量为LM(4.36 g/kg)>DP(2.11 g/kg)>LF(1.74 g/kg)>SH(1.46 g/kg),相应的有机碳分配比例分别为17.1%、14.0%、12.2%和11.3%;闭合轻组有机碳的平均含量为LM(0.82 g/kg)>DP(0.51 g/kg)>LF(0.36 g/kg)>SH(0.34g/kg),相应的有机碳分配比例分别为3.36%、3.45%、2.71%和3.00%。因此,在西南地区紫色水稻土上实行垄作免耕能提高轻组有机碳的含量及其分配比例,从而改善土壤有机碳质量。另外,与土壤总有机碳、重组有机碳及闭合轻组有机碳相比,自由轻组有机碳对耕作方式的变化最敏感,是指示土壤有机碳变化的良好指标。     

Long-term impact of pulses crop rotation on soil fungal diversity in aerobic and wetland rice cultivation

Pulse crop rotation in rice cultivation is a widely accepted agronomic practice. Depending upon the water regime, rice cultivation has been classified into wetland and aerobic practices. However, no studies have been conducted so far to understand the impact of pulse crop rotation and rice mono-cropping on fungal diversity, particularly in aerobic soil. A targeted metagenomic study was conducted to compare the effects of crop rotations (rice-rice and rice-pulse) on fungal diversity in wetland and aerobic rice soils. Out of 445 OTUs, 41.80% was unknown and 58.20% were assigned to six phyla, namely Ascomycota (56.57%), Basidiomycota (1.32%), Zygomycota (0.22%), Chytridiomycota (0.04%), Glomeromycota (0.03%), and Blastocladiomycota (0.02%). Functional trait analysis found wetland rice-pulse rotation increased symbiotrophs (36.7%) and saprotrophs (62.1%) population, whereas higher pathotrophs were found in aerobic rice–rice (62.8%) and rice-pulse (61.4%) cropping system. Certain soil nutrients played a major role in shaping the fungal community; Ca had significant (p < 0.05) positive impact on saprotroph, symbiotroph and endophytes, whereas Cu had significant (p < 0.05) negative impact on pathotrophs. This study showed that rice-pulse crop rotation could enhance the saprophytic and symbiotic fungal diversity in wetland and reduce the population of pathogens in aerobic rice cultivation.     

The integration of crop rotation and tillage practices in the assessment of ecosystem services provision at the regional scale

The provision of ecosystem services at the landscape level can be significantly influenced by land management practices. Within an agriculturally dominated case study area in Saxony, Germany, a more detailed land use classification, which includes differentiated information on agricultural management practices, was utilized within the raster-based planning support tool GISCAME. “Management” refers to typical, regional crop rotations and soil tillage practices.The focus of this research was based on an indicator-based approach to assess ecosystem services and the development of land use change (LUC) and land management change (LMC) scenarios. The EuroMaps Land Cover data set was specifically developed for the case study and included remote sensing information for the general land use classification and terrestrial mapping information. Furthermore, statistical data on detailed regional agricultural land management were included. The raster-based planning support tool GISCAME was then used to simulate scenarios and visualize results. The LUC and LMC scenarios showed that the more detailed land use classification provided better output for the prioritization of planning alternatives. Further it enabled a refined assessment of the provisioning services (i) food and fodder provision, (ii) biomass provision, the regulation services, (iii) soil erosion protection, (iv) drought risk regulation, (v) flood regulation, (vi) returns from land-based production (i.e. the market value of biomass provision), and (vii) ecological integrity. The results of this study support the view that the application of improved management measures, such as conservation tillage, can significantly enhance the provision of ecosystem services (e.g. soil erosion protection and drought risk regulation) at the landscape level. The study also indicates that a combination of strategic LUC, such as afforestation and LMC, might be an effective way to enhance regulating services with acceptable trade-offs regarding provisioning services. Our approach presents a refined foundation for ecosystem services assessment, which is designed to better support regional planning and the provision of information to non-experts in the participatory processes. For transfer into other regions, standardized land use and land management classification will have to be defined.     

不同耕作方式对稻田土壤动物、微生物及酶活性的影响研究

以长期定位试验为基本材料,研究了不同耕作方式对土壤动物、微生物及酶活性的影响．结果表明,0～20cm土壤层内大、中、小型土壤动物垄作免耕为14700个·m^-22,冬水免耕为10450个·m^-22水旱轮作为7950个·m^-22常规平作为6275个·m^-22,垄作免耕处理土壤动物的数量是常规平作的2．34倍．土壤微生物数量和土壤微生物生物量氮因季节而异,总体上是春秋多而夏季少,土壤酶活性表现出表层高,底层低．土壤微生物数量、土壤微生物生物量氮及土壤酶活性不同处理间仍是垄作免耕>水旱轮作>冬水免耕>常规平作,表明垄作免耕有利于改善稻田土壤生态环境。有利于土壤肥力的提高。     

Long-term tillage effects on soil organic carbon and dissolved organic carbon in a purple paddy soil of Southwest China

The impact of conservation tillage practices on soil carbon has been of great interest in recent years. Conservation tillage might have the potential to enhance soil carbon accumulation and alter the depth distribution of soil carbon compared to conventional tillage based systems. Changes in the soil organic carbon (SOC) as influenced by tillage, are more noticeable under long-term rather than short-term tillage practices. The objective of this study was to determine the impacts of long-term tillage on SOC and dissolved organic carbon (DOC) status after 19 years of four tillage treatments in a Hydragric Anthrosol. In this experiment four tillage systems included conventional tillage with rotation of rice and winter fallow system (CTF), conventional tillage with rotation of rice and rape system (CTR), no-till and ridge culture with rotation of rice and rape system (NT) and tillage and ridge culture with rotation of rice and rape system (TR). Soils were sampled in the spring of 2009 and sectioned into 0–10, 10–20, 20–30, 30–40, 40–50 and 50–60 cm depth, respectively.Tillage effect on SOC was observed, and SOC concentrations were much larger under NT than the other three tillage methods in all soil depths from 0 to 60 cm. The mean SOC concentration at 0–60 cm soil depth followed the sequence: NT (22.74 g kg^?1) > CTF (14.57 g kg^?1) > TR (13.10 g kg^?1) > CTR (11.92 g kg^?1). SOC concentrations under NT were significantly higher than TR and CTR (P < 0.01), and higher than CTF treatment (P < 0.05). The SOC storage was calculated on equivalent soil mass basis. Results showed that the highest SOC storage at 0–60 cm depth presented in NT, which was 158.52 Mg C ha^?1, followed by CTF (106.74 Mg C ha^?1), TR (93.11 Mg C ha^?1) and CTR (88.60 Mg C ha^?1). Compared with conventional tillage (CTF), the total SOC storage in NT increased by 48.51%, but decreased by 16.99% and 12.77% under CTR and TR treatments, respectively. The effect of tillage on DOC was significant at 0–10 cm soil layer, and DOC concentration was much higher under CTF than the other three treatments (P < 0.01). Throughout 0–60 cm soil depth, DOC concentrations were 32.92, 32.63, 26.79 and 22.10 mg kg^?1 under NT, CTF, CTR and TR, and the differences among the four treatments were not significant (P > 0.05). In conclusion, NT increased SOC concentration and storage compared to conventional tillage operation but not for DOC.     

不同轮作模式下设施土壤丛枝菌根真菌群落结构的季相变化

以番茄-甜瓜、番茄-豆角两种轮作模式为研究对象,采集番茄生长季(休耕期、花期、果期)的土壤样品,利用Illumina MiSeq高通量测序技术分析两种轮作模式下土壤AM真菌群落结构的差异特征,并探讨驱动AM真菌多样性和群落组成差异的关键因子。结果表明: 引入豆科作物的轮作模式显著改变了AM真菌的α多样性,与番茄-甜瓜相比,番茄-豆角土壤中AM真菌Shannon多样性和Pielou均匀度分别显著降低了24.9%和24.0%。AM真菌丰富度、Shannon多样性和系统发育多样性在番茄生育期(花期、果期)相比于休耕期分别显著下降了55.6%～67.5%、49.6%～51.5%及21.4%～23.7%。引入豆科作物的轮作模式在3个时期均提高了球囊霉属的相对丰度,降低了花期和果期类球囊霉属及原囊霉属的相对丰度。近明球囊霉属的相对丰度在休耕期表现为番茄-甜瓜>番茄-豆角,花期则相反。两性囊霉属、多孢囊霉属和盾巨孢囊霉属仅在花期番茄-豆角土壤中存在。置换多元方差分析(PERMANOVA)和非度量多维度分析(NMDS)结果表明,轮作模式和生长季均显著影响AM真菌群落结构,土壤湿度、pH、速效磷等是调控AM真菌群落结构和多样性的主要环境因子。结构方程模型(SEM)结果进一步表明,轮作模式和生长季主要通过影响土壤pH间接驱动AM真菌群落组成及多样性变化。     

Effects of colored polyethylene film mulch on pest populations,plant growth and yield of peanut in Northern China

Polyethylene film mulching is commonly used in peanut (Arachis hypogaea L.) production, an important oil crop. Clear polyethylene film (CLEF) has previously been the only choice for all growing conditions. However, colored polyethylene film has been applied to the cultivation of crops in recent years, so testing the effects of colored film mulches on peanuts is necessary. In this study, we observed the effects of eight colored polyethylene films on devastating pest abundance, plant growth and yield, and soil conditions in peanut fields. The results showed that light-silver-gray film (LSGF), silver-black on both sides film (SGBF), and black film (BLAF) mulches were more effective in reducing the pest population (aphids, thrips, and mites) compared to plants mulched with other films. In addition, SGBF and LSGF mulching accelerated seeding emergence and benefited peanut growth, and the yield increased by about 20% compared to peanuts mulched with CLEF. The soil temperature and humidity under the LSGF and SGBF treatment were more suitable for peanut growth compared to the other film treatments. In conclusion, LSGF and SGBF mulches were appropriate choices for managing pests, maintaining optimum soil conditions, and increasing yield in peanut production.     

Effects of fertilization rate and crop rotation on diazotrophic cyanobacteria in paddy field

Application of chemical fertilizers at the recommended level (medium fertility) or lower stimulated growth of the diazotrophic cyanobacterial population and nitrogenase activity in a paddy field. High fertilizer levels proved to be inhibitory to nitrogen-fixing cyanobacteria indicating that indiscriminate use of chemical fertilizers for a longer period drastically disturbed the natural ecological balance. The rice–mustard–moong (RMM) crop rotation was observed to be more suitable for cyanobacterial nitrogen fixation than rice–wheat–maize rotation. The cropped plots had higher nitrogenase activity than fallow plots. The low fertility coupled with RMM rotation were found to be best suited for promoting nitrogen fixation by cyanobacteria to supply the rice plants. A top dressing of chemical nitrogenous fertilizer drastically suppressed the cyanobacterial nitrogenase activity (ARA) within 12 h; the magnitude of inhibition varied with respect to the cropping system. The inhibition was overcome by the 10th day and the ARA value reached the preapplication value or even higher in the case of low fertility and medium fertility level plots. A regression equation was established to predict nitrogen fixation in a given soil ecosystem.     

Evaluation of some fungal diseases and yield of groundnut in groundnut-based cropping systems

A study on the evaluation of some fungal diseases and yield of groundnut in groundnut-based cropping systems was conducted in 2002 and 2003 planting seasons. Analysis of variance indicated that intercropping was highly significant on leaf spot disease severity 0.76; 0.75, rust 2.75; 2.69, as well as percentage defoliation 78.42%; 78.10% in 2002 and 2003, respectively. Plant population was significant on leaf spot severity 4.52, 4.60 rust 2.76; 366 and defoliation 226.5; 441.1 fungal as well as yield, while interactions were not significant on the fungal diseases and yield. Sole groundnut recorded significantly high severity of the fungal diseases investigated but low yield, when groundnut was intercropped with maize and melon and recorded the lowest yield in 2002 and 2003 respectively. 250,000 plants/ha recorded the lowest severity of the diseases investigated, while 444,444 plants/ha recorded the highest. Sole groundnut also recorded the highest percentage defoliation 79.37%, 79.25% when groundnut was intercropped with maize recorded the lowest 77.06%; 77.60%. 250,000 plants/ha had the lowest defoliation when 444,444 plants/ha had the highest 80.75% 82.13% in 2002 and 2003, respectively. Sole groundnut recorded the lowest in the majority of yields when intercropped with maize and with melon recorded a high yield and yield components in 2002 and 2003, respectively. The microorganisms identified were Cercospora spp., Aspergillus linked and Blastomyces.     

The effects of stubble retention and tillage practices on surface soil structure and hydraulic conductivity of a loess soil

The current cropping system of excessive tillage and stubble removal in the northwestern Loess Plateau of China is clearly unsustainable. A better understanding of tillage and stubble management on surface soil structure is vital for the development of effective soil conservation practices in the long term. Changes in surface soil structure and hydraulic properties were measured after 4 years of stubble management (stubble retained vs. stubble removed) under contrasting tillage practices (no-tillage vs. conventional tillage) in a silt loam soil (Los Orthic Entisol) in Dingxi, Gansu, the northwestern Loess Plateau, China. Our results indicated that after 4 years small but significant changes in soil properties were observed amongst the different tillage and stubble treatments. Surface soil (0–5 cm) under no-tillage with stubble retention had the highest water stability of macroaggregates (>250 μm), soil organic carbon (SOC) and saturated hydraulic conductivity. Significant correlation was found between water stable macro-aggregates and soil organic carbon content, indicating the importance of the latter on soil structural stability. The improvement in soil structure and stability was confirmed by higher soil hydraulic conductivity measurements. Consistently higher K_sat was detected in the no tillage with stubble retained soil compared to other treatments. Therefore, no-tillage with stubble retention practice is an effective management technique for improving physical quality of this fragile soil in the long term.     

The effects of stubble retention and tillage practices on surface soil structure and hydraulic conductivity of a loess soil

The current cropping system of excessive tillage and stubble removal in the northwestern Loess Plateau of China is clearly unsustainable. A better understanding of tillage and stubble management on surface soil structure is vital for the development of effective soil conservation practices in the long term. Changes in surface soil structure and hydraulic properties were measured after 4 years of stubble management (stubble retained vs. stubble removed) under contrasting tillage practices (no-tillage vs. conventional tillage) in a silt loam soil (Los Orthic Entisol) in Dingxi, Gansu, the northwestern Loess Plateau, China. Our results indicated that after 4 years small but significant changes in soil properties were observed amongst the different tillage and stubble treatments. Surface soil (0–5 cm) under no-tillage with stubble retention had the highest water stability of macroaggregates (>250 μm), soil organic carbon (SOC) and saturated hydraulic conductivity. Significant correlation was found between water stable macro-aggregates and soil organic carbon content, indicating the importance of the latter on soil structural stability. The improvement in soil structure and stability was confirmed by higher soil hydraulic conductivity measurements. Consistently higher K_sat was detected in the no tillage with stubble retained soil compared to other treatments. Therefore, no-tillage with stubble retention practice is an effective management technique for improving physical quality of this fragile soil in the long term.     

Yield and yield components of maize and soil physical properties as affected by tillage practices and organic mulching

Maize (Zea mays L.) is an important grains cereal crop. Lots of farmers using tillage and mulching practices influence the final yield, to maintain up with the growing demand for food, fuel and feed. Field experiments were conducted to investigate the effects of tillage practices (i.e. conventional tillage CT, reduced tillage RT, deep tillage DT) and wheat straw mulching (i.e. no mulch and wheat straw mulch of 4, 8 and 12 Mg ha⁻¹, SM0, SM1, SM2 and SM3 respectively) on the growth, yield and yield components of maize and some of soil physical properties. The results showed that compared with RT, DT and CT decreased soil bulk density, as well as led to increase soil water content. Application of mulch treatments increased soil water content. DT and CT have been associated with greater plant height, yield components, grain and biomass yield than RT treatment. Plant height, yield components, grain and biomass yield as well as soil water content increased following mulching treatments. Mulching treatment of SM2 had the largest positive effects on maize yield. DT and CT that have potential to break the compacted zone in soil leading to a better soil environment and crop yield. The application of wheat straw mulch could be an efficient soil management practice for corn production in arid subtropical climate region.     

保护性耕作对麦药轮作土壤酶活性和微生物数量的影响

以传统耕作(T)为对照,研究了免耕(NT)和免耕+秸秆覆盖(NTS)保护性耕作对麦药轮作后土壤脲酶、碱性磷酸酶、蔗糖酶和过氧化氢酶活性与细菌、真菌和放线菌数量的影响。试验结果表明:麦药轮作后,从T、NT至NTS,0-5cm、5-10cm和10-30cm同层土壤各种酶活性均逐渐增强,以NTS处理效果最好。表层土壤水解酶活性变化最明显,NTS较T菘蓝土壤表层脲酶、碱性磷酸酶和蔗糖酶活性分别提高38.53%、39.65%和110.00%,小麦土壤分别提高28.10%、19.71%和75.00%,均对蔗糖酶活性影响最大;过氧化氢酶均为深层土壤变化最明显,菘蓝和小麦土壤分别提高9.09%和18.91%。麦药轮作后菘蓝T、NT至NTS同层土壤各种微生物数量和总数逐渐升高,NTS处理效果最好,而小麦土壤表层和中层微生物数量逐渐增加,NTS处理效果最好,但深层土壤细菌、真菌数量和微生物总数呈T低,NT升高,NTS又降低的趋势,土壤放线菌数量则逐渐升高。菘蓝0-5cm土壤细菌、真菌、放线菌数量和微生物总数NTS较T分别提高22.81%、55.56%、67.14%和22.81%,小麦土壤分别提高62.84%、92.86%、14.29%和66.67%。麦药轮作后菘蓝不同耕作处理土壤细菌数量和微生物总数较小麦土壤减少了10倍左右。     

Microbial community responses to soil tillage and crop rotation in a corn/soybean agroecosystem

The acreage planted in corn and soybean crops is vast, and these crops contribute substantially to the world economy. The agricultural practices employed for farming these crops have major effects on ecosystem health at a worldwide scale. The microbial communities living in agricultural soils significantly contribute to nutrient uptake and cycling and can have both positive and negative impacts on the crops growing with them. In this study, we examined the impact of the crop planted and soil tillage on nutrient levels, microbial communities, and the biochemical pathways present in the soil. We found that farming practice, that is conventional tillage versus no‐till, had a much greater impact on nearly everything measured compared to the crop planted. No‐till fields tended to have higher nutrient levels and distinct microbial communities. Moreover, no‐till fields had more DNA sequences associated with key nitrogen cycle processes, suggesting that the microbial communities were more active in cycling nitrogen. Our results indicate that tilling of agricultural soil may magnify the degree of nutrient waste and runoff by altering nutrient cycles through changes to microbial communities. Currently, a minority of acreage is maintained without tillage despite clear benefits to soil nutrient levels, and a decrease in nutrient runoff—both of which have ecosystem‐level effects and both direct and indirect effects on humans and other organisms.     

The effects of crop rotation and fertilization on soil xylanase activity in a soil of the southeastern United States

Summary Xylanase activity was determined in soils from a 3-year rotation with corn, (Zea mays L.), cotton (Gossypium hirsutum L.), and soybean (Glycine max (L) Merr.) as summer crops at Auburn, Alabama, in the southeastern U.S.A. Winter wheat (Triticum aestivum L.) followed corn and a period of winter fallow as maintained after soybeans. A combination of common vetch (vicia sativa L.) and crimson clover (Trifolium incarnatum Gibelli & Belli) followed cotton during the winter months to serve as green manure. Highest xylanase activity was detected after soybeans and lowest after cotton among the summer crops. The culture of wheat and winter legumes resulted in increased soil xylanase activity wheareas winter fallowing reduced the activity. The effect of various fertilization schemes superimeposed on the rotation on soil xylanase activity was also studied. Seasonal fluctuations in soil xylanase activity were not affected by the fertilization regimes and highest xylanase activities were observed during crop periods and with fertilization treatments that resulted in high root densities but not necessarily in high yields.     

轮作模式对植烟土壤酶活性及真菌群落的影响

种植模式显著影响土壤理化生物学性质,并与作物土传真菌病害的发生密切相关。试验选择云南省具有代表性的红壤,设置烤烟-休闲-玉米(T-B-M)、烤烟-油菜-玉米(T-C-M)、烤烟-油菜-水稻(T-C-R)和烤烟-苕子-水稻(T-V-R)等4种轮作模式,利用化学、酶学分析及454高通量测序技术,研究了土壤养分、酶活性及真菌群落结构,旨在为烤烟的合理轮作提供科学依据。经16a的不同轮作种植后,土壤p H变化于5.6—6.4之间,仍然适合种植水稻、玉米、油菜和烤烟等多种作物。在T-V-R处理的土壤中,烤烟产量、烟叶产值和上中等烟比例最高,有机质比原初提高45.11%,碱解氮、有效磷和微生物量碳氮显著增加,蔗糖酶、脱氢酶、脲酶、磷酸酶和过氧化氢酶活性也显著高于其它轮作模式,说明T-V-R改善了土壤生态环境,促进了微生物繁衍,数量增加,活性增强。土壤真菌的18S r DNA读数依次为13097(T-B-M)、11345(T-C-M)、12939(T-C-R)和13763(T-V-R),分别代表530、378、395和581种(类)的真菌,由子囊菌门、担子菌门、接合菌门、壶菌门和尚待鉴定的真菌等构成,其中尚待鉴定的真菌属种和子囊菌门占绝大部分。在不同轮作处理的土壤中,前15种优势真菌的丰富度变化于29.46%—62.86%之间,优势菌株的相似性极低,说明土壤真菌的种群结构因轮作模式不同而异。T-V-R处理土壤中的真菌多样性指数最高,优势度指数最低,说明T-V-R轮作的土壤适合多种真菌的繁殖生长,种群数量增加。多种真菌共同存在,互相制约,可防止病原真菌过度繁殖,降低作物发生真菌病害几率。从作物产量和产值、土壤有机质、养分和真菌种群结构看,T-V-R优于其它3种轮作模式,值得推广应用。     

The effect of season and crop rotation on the abundance of spores of vesicular-arbuscular (V-A) mycorrhizal endophytes

Summary Spores of V-A mycorrhizal endophytes were extracted and counted from three different soils under three different rotations; continuous wheat, annual pasture and an alternating crop: pasture rotation.High V-A spore abundance in the autumn fell at the onset of plant growth. Spore abundance remained low under wheat but recovered under pasture regimes in the spring, coincidently with host maturation in all except one of the experiments sampled.Weak positive correlations were found between V-A spore abundance and components of pasture biomass while wheat biomass was negatively correlated with V-A spore numbers.     

耕作方式对玉-豆轮作地表节肢动物多样性及其营养结构的影响

为阐明长期不同耕作方式对轮作种植模式黑土农田地表节肢动物多样性及其营养结构的影响,2015年5月至9月间,利用陷阱法对连续13年玉米大豆轮作模式的定位试验站三种耕作方式(免耕、垄作、秋翻)的地表节肢动物群落进行了调查。共捕获动物1002只,隶属于3纲11目29科37个类群,凹唇蚁、玉米毛蚁和直角通缘步甲为优势类群。免耕(NT,no tillage)有利于增加蜘蛛类群密度,垄作(RT,ridge tillage)和秋翻(MP,mould board plough)显著增加了玉米毛蚁密度。耕作方式仅对群落密度有显著影响显著影响(P0.05),而大豆不同生育阶段显著或极显著的影响地表节肢动物群落组成特征(P0.05; P0.001)。长期玉米大豆轮作种植的地表节肢动物群落营养功能群在不同耕作方式中所占比例不同,保护性耕作方式(NT、RT)更有利于捕食性和植食性动物的生存和繁殖,常规耕作(MP)则是杂食性动物占据优势,明显呈现对不稳定环境的适应。大豆不同生育期,各功能群的个体数与类群数的动态变化不尽一致,不具有明显的规律性。研究结果表明,免耕轮作对维持地表节肢动物群落内部物种间的关系及其营养结构有着较为重要的作用,保护性耕作和轮作种植模式相结合可维持农田生态系统平衡。