种植模式与土壤管理制度对作物连作障碍的影响

连作障碍已经成为我国现阶段农业可持续发展的一个凾待解决的问题。本文从分析连作障碍产生的原因与造成的危害入手,比较全面系统的阐述了种植模式与土壤管理制度对作物连作障碍影响的特点,探讨了克服连作障碍的可能途径。认为推行多种作物混合种植结构、采用轮作与间作并举的复合种植模式、建立以菌根真菌接种为主导的土壤与种苗管理新制度是当前和今后解决连作障碍的主要方法。     

The Effect of a Substrate Containing Arbuscular Mycorrhizal Fungi and Rhizosphere Microorganisms (Trichoderma,Bacillus, Pseudomonas and Streptomyces) and Foliar Fertilization on Growth Response and Rhizosphere pH of Three Strawberry Cultivars

Abstract

Vegetatively propagated plants of three strawberry cultivars-‘Senga Sengana’, ‘Elsanta’ and ‘Kent’-were grown for 20 weeks in rhizoboxes filled with 1.85 kg of sterilized mineral soil. Ten plants were treated with an N-P-K foliar fertilizer (F, control), or inoculated with a substrate containing arbuscular mycorrhizal fungi, Trichoderma viride and rhizosphere bacteria (PGPR-Plant Growth Promoting Rhizobacteria) without any fertilization (M), or inoculated with the mixture of microorganisms and treated with the foliar fertilizer (MF). Total plant biomass was increased by the M treatment in all cultivars. M treatment resulted in higher total root length and number of root tips in ‘Senga Sengana’, whereas the other two cultivars showed different responses of root morphology. Shoot/root ratio was decreased by the M and MF treatments in comparison with control plants. Foliar fertilization of inoculated plants caused different growth responses in the three cultivars and a general decrease of root growth. After the MF treatment, the biomass of ‘Senga Sengana’ increased and the biomass of ‘Elsanta’ and ‘Kent’ decreased. Inoculation with the mycorrhiza-PGPR substrate increased rhizosphere pH irrespective of foliar fertilization. Plant mineral content was highly modified by the treatments in all the cultivars examined. In particular, changes were noted in N, P, K, Fe, B and Mn uptake. The results show an interaction between foliar fertilization and root inoculation with microorganisms, as well as genotype-dependent influences, on growth responses and rhizosphere pH of strawberry plants.     

Foraging strategies of the external mycelium of the arbuscular mycorrhizal fungi Glomus intraradices and Scutellospora calospora

The responsiveness of the external mycelium of Glomus intraradices and Scutellospora calospora was tested in a multiple-choice experimental system in which mycelium encountered patches amended with nitrogen (N) or phosphorus (P), either alone or in combination with a host plant. We hypothesised that only AMF mycelium with sufficient supply of photosynthate from an actively growing host would respond to the amendments provided. Mycelium was allowed to grow either 11 or 21 weeks before we analysed hyphal proliferation in amended patches introduced in mesh bags that were not reached by roots but by foraging mycelium only. Hyphal length, the AMF signature fatty acid 16:1w5, and root colonisation in new host plant seedlings were used to measure AMF growth and resource allocation in the patches. Mycelium from both fungal strains was able to colonise new host roots and sand in all patches but S. calospora was overall more responsive to the amendments than G. intraradices. G. intraradices grew equally into all patches, including the unamended control, whereas S. calospora produced significantly more hyphal length in the patch containing a host plant than in the rest of the patches. Both strains showed lower hyphal growth at the second harvest and mycelium of G. intraradices lost almost entirely its capacity to develop new mycelium in all choices presented. Lipid measurements showed this fungus did not use storage lipids to exploit the patches. S. calospora mycelium had reduced growth and colonisation ability but still showed some growth in the patches at the second harvest. A reduction in the content of NLFA 16:1w5 from the first to the second harvest suggested that S. calospora mycelium likely used storage lipids to sustain proliferation in the patches. The results indicated that S. calospora was more active and used more resources for foraging than G. intraradices and that external mycelium foraging was maintained mainly with recently acquired plant carbon (C). This supported in general our hypothesis but showed as well that the two AMF strains had different strategies and resource allocation to forage. The overall low response of both AMF to the choices presented suggested that the responsiveness of mycelium searching freely in the substrate is lower than that observed in experimental systems in which the amendments have been placed in close contact with actively growing mycelium fronts in close vicinity with host roots.     

菌根与间作对紫色土-水界面氮流失的削减效应

揭示土著丛枝菌根真菌(arbuscular mycorrhizal fungi,AMF)与间作对紫色土-水界面各形态氮流失的削减效应,可为保护水环境、减缓紫色土坡耕地氮流失带来的农业面源污染提供理论依据。通过自然降雨条件下的径流模拟试验,设置不同种植模式(单作玉米、玉米/大豆间作、单作大豆)和不同菌根处理(抑菌、未抑菌),在雨季不同时间采集7次径流和侧渗水样,分析比较各不同处理下径流及侧渗各氮形态变化迁移特征。研究结果表明,侧渗即壤中流为紫色土-水界面氮素流失的主要途径,硝态氮为紫色土-水界面氮素流失的主要形态。随取样时间后延,径流总氮、硝态氮浓度均呈现出波浪式上升的趋势,而铵态氮浓度整体表现出先上升再下降的趋势;侧渗总氮浓度趋势则呈现先下降后上升再下降的趋势,硝态氮浓度整体表现出下降后趋于平缓的趋势,铵态氮浓度则表现出先上升后下降并趋于平缓的趋势。所有复合处理中,未抑菌—间作处理的径流、侧渗及总流失量中总氮、铵态氮浓度均最低,且其径流、总流失量中硝态氮浓度也明显低于其他处理。在未抑菌处理下,与单作玉米、单作大豆处理相比,间作处理使径流和侧渗总氮浓度分别下降约13.4%、20.3%和56.5%、48.7%,总流失量中总氮浓度分别下降约50.1%和43.5%;使径流和总流失量中的硝态氮浓度分别降低约10.0%、16.7%和51.3%、42.9%;并使径流和总流失量中铵态氮浓度分别显著降低约10.5%、26.0%和21.7%、30.2%,侧渗铵态氮浓度也相应降低约29.6%和33.7%。可见土著菌根真菌与玉米/大豆间作体系对协同削减紫色土-水界面氮素的流失表现出了较大的潜力。     

Effects of tillage systems on soil characteristics, glomalin and mycorrhizal propagules in a Chilean Ultisol

Tillage affects the soil physical and chemical environment in which soil microorganisms live, thereby affecting their number, diversity and activity. However, soil disturbance generally has the greatest impact on biological properties, including both free and symbiotic fungal populations. Interest in more ecologically sustainable agricultural systems is rising with increasing recognition that agricultural intensification can adversely affect environmental quality. This paper discusses the effect of tillage system on some soil characteristics, such as pH, C, N and S levels, total and Olsen-P contents including some P forms associated with organic matter, glomalin contents and arbuscular mycorrhizae (AM) parameters, such as root colonization, spore number and total and active hyphal length. Measurements were in the sixth year of an on-going tillage-rotation experiment conducted on an Ultisol under no-till (NT), reduced tillage (RT) and conventional tillage with stubble mixed into the soil (CTS) or stubble burnt (CTB). Soil was sampled at two dates; after wheat (Triticum aestivum) harvest (autumn) and 6 months after subsequent grassland seeding (spring). Higher C, N, S, total P and fulvic acid-P concentrations and pH occurred under NT and RT than under CTS and CTB after wheat harvest. However, results at the second sampling were not consistent. AM spore number and active hyphal length were highest under NT having the greatest incidence on AM root colonization and P concentration in shoots of the pasture. Glomalin concentration was higher under NT and RT than under CTS and CTB but no differences in calculated glomalin to total C (ca. 5%) were found. It is concluded that a less disruptive effect of NT influences positively all soil characteristics and also increases P acquisition by the following crop in the rotation system.     

Genotypic variation for phosphorus uptake dinitrogen fixation in cowpea on low‐phosphorus soils of southern Cameroon

In cowpea, efficient N₂‐fixing genotypes are being selected to promote sustainable cropping systems in southern Cameroon (SC). However, N₂ fixation and growth of these genotypes are largely hampered by low levels of soil plant‐available P. To evaluate the genotypic variation in N₂ fixation and P uptake among cowpea (Vigna unguiculata L.) genotypes, field experiments were conducted over two years on two acid soils low in available P. The experiments were laid out in a split‐block design with four replications on typic (TK) and rhodic (RK) Kandiudult soils with seven cowpea genotypes. Phosphorus (P) fertilizers were applied on the main plots with 0 kg P, 30 kg P ha^–1 as triple superphosphate (TSP) and 90 kg P ha^–1 as Togo phosphate rock (PR). Nodule dry matter (DM), shoot DM, grain yield, and P uptake of cowpea significantly varied with site, P application, and genotype (p < 0.05). The N₂ fixation of the cowpea genotypes ranged from 29 to 51 kg N ha^–1 on both TK and RK soils and was significantly increased with P application. Significant genotypic variations in N₂ fixation were observed with superior ability of the genotypes IT89KD‐391 and IT90K‐59 to fix N₂. The harvest index (HI) did not significantly differ between soils and P application levels (p > 0.05). Four genotypes were selected to investigate root mechanisms responsible for efficient P acquisition in pot experiments. The results suggest that a better root infection by arbuscular mycorrhizal fungi (AMF) in genotype IT90K‐59 and root morphological and physiological characteristics in IT89KD‐391 were the most important factors for increasing P uptake.     

Using lipid analysis and hyphal length to quantify AM and saprotrophic fungal abundance along a soil chronosequence

We evaluate the use of signature fatty acids and direct hyphal counts as tools to detect and quantify arbuscular mycorrhizal (AM) and saprotrophic fungal (SF) biomass in three Hawaiian soils along a natural soil fertility gradient. Phospholipids16:1ω5c and 18:2ω6,9c were used as an index of AM and saprotrophic fungal biomass, respectively. Both phospholipid analysis and hyphal length indicated that the biomass of AMF was greatest at the highest fertility site, and lowest where phosphorus limits plant growth. Saprotrophic fungal biomass did not vary. Hyphal length counts appeared to under-estimate SF abundance, while the phospholipid AMF:SF ratio was in line with expectations. This study indicates that phospholipids may be a valuable and reliable tool for studying the abundance, distribution, and interactions between AM and saprotrophic fungi in soil.     

设施大棚间作玉米对丛枝菌根网络形成及辣椒疫病防治的影响

丛枝菌根（Arbuscular mycorrhizal,AM）真菌对辣椒疫病等土传病害具有生防潜力,但由于难以纯培养而未能实现规模化生产应用,如能调动土著AM真菌的抑病功能则对实际生产具有重要指导意义。依托重庆石柱辣椒科技园,研究设施大棚中间作玉米对土著AM真菌生长及辣椒疫病防治的影响。结果表明,与辣椒单作相比,间作玉米处理辣椒根系AM真菌侵染率、根际AM真菌数量与土壤磷酸酶活性以及小区作物养分总吸收量均显著提高,辣椒疫病发病率与病情指数、单株辣椒的磷吸收量及果实生物量均显著下降,其中种植密度更高的等垄宽间作处理两种作物根系AM真菌侵染率、小区玉米产量及作物养分总吸收量均显著高于等行距间作处理,辣椒疫病发病率与之正好相反。设施环境下间作玉米或能通过促进AM真菌生长及其对辣椒根系的侵染来增强其对辣椒疫病的防治功效,其中等垄宽间作处理具有更好的经济效益。     

分室磷添加下菌根对滇池流域红壤间作玉米生长及磷素利用的影响

随着全球范围内磷矿资源短缺问题的日益严重,间作或菌根技术强化作物对土壤磷(P)的利用及增产增收的效应受到越来越多的关注。通过三室隔网盆栽模拟试验研究了分室磷处理[不添加磷(P0)、添加有机磷(OP50)、添加无机磷(IOP50)]和根室不接种(NM)、根室接种丛枝菌根真菌Glomus mosseae(GM)对与大豆间作的玉米的生长及磷素利用的影响。研究结果表明:所有复合处理中,以间作?GM?IOP50组合处理下的玉米根系最短和地上部生物量最高;OP50处理下,间作玉米的菌根侵染率显著高于单作处理。间作条件下,无论分室磷添加与否,接种GM处理的玉米地上部生物量明显高于NM处理;接种GM处理的玉米根系生物量和株高均显著高于NM处理,且根系生物量以间作?GM?OP50组合处理下最高。接种GM条件下,P0、IOP50、OP50处理下的间作植株生物量较单作处理分别提高45.98%、111.33%、33.56%。单作条件下,无论分室磷添加与否,接种GM处理的玉米地上部磷含量均显著高于NM处理;无论何种种植模式及分室磷添加与否,接种GM处理的植物根系磷含量均显著高于NM处理。无论磷添加与否,间作?GM组合条件下的玉米地上部磷吸收量均显著较高,其中IOP50处理下的地上部磷吸收量显著高于OP50处理。间作?GM组合条件下,IOP50处理玉米根系的磷吸收效率均显著高于OP50处理。可见,接种GM、分室磷添加和间作各自在一定程度上促进了玉米的生长。综合菌根侵染、生物量及磷含量与吸收量、磷吸收效率等指标,所有复合处理中以间作?GM?IOP50组合对玉米地上部的促生作用最好,玉米磷素吸收最多,可望有效强化滇池流域红壤坡耕地磷素的利用。