不同草田轮作方式对土壤微生物和土壤酶活性的影响

10 a生苜蓿翻耕后,与马铃薯、玉米、高粱、谷子和荞麦进行草田轮作,对各轮作方式的土壤微生物数量和土壤酶活性进行测定和分析。结果表明：6-10月,土壤微生物总量呈先增加后减少的变化规律,细菌与放线菌数量呈先增加后减少的变化规律,真菌则呈增加的变化规律;同一时期不同草田轮作方式土壤微生物数量差异显著（P<0.05）,作物轮作方式的土壤微生物数量高于作物连作方式。土壤脲酶活性随着时间变化呈现先增加后降低的趋势,碱性磷酸酶、蔗糖酶及过氧化氢酶活性则呈现增加的趋势,玉米、高粱参与轮作方式的土壤酶活性高于作物连作方式及谷子、马铃薯参与轮作的方式。脲酶活性与微生物数量呈正相关（r=0.386）;草田轮作能提高土壤微生物数量和土壤酶活性。     

不同种植年限菜田土壤微生物区系的研究

采用稀释平板涂抹法对山东聊城周边地区不同种植年限的菜田土壤微生物数量、组成与养分状况及其相互关系进行了研究。结果表明：①该地区土壤微生物以细菌占绝对优势,其次为放线菌;②随着种菜年限的增加,土壤细菌和微生物总数表现出“低高低”的变化趋势,而真菌和放线菌则随种菜年限的增加而增加;③菜田土壤各类微生物主要集中在0～20cm的土层中,随着土层加深,其数量迅速减少;④菜田土壤放线菌组成复杂,共分离到了6个属的放线菌,但仍以链霉菌为主,其次为小单胞菌属和马杜拉放线菌属。链霉菌可分为9个类群,白孢类群占优势。种植1—2a的菜田土壤放线菌组成复杂,而链霉茼组成较简单;⑤蔬菜种类不同时,土壤微生物亦不同;⑥土壤养分含量与真菌和放线菌呈负相关,与细菌和微生物总数呈正相关。     

轮作与休闲对日光温室黄瓜连作土壤微生物和酶活性的影响

采用盆栽试验,研究了不同作物轮作和休闲方式对日光温室黄瓜连作土壤微生物数量、酶活性及后茬黄瓜生长和产量的影响.结果表明： 与连作相比,轮作有利于改善土壤微生物结构,增加细菌和放线菌数量,减少真菌数量;轮作与休闲有利于提高土壤转化酶、脲酶、过氧化氢酶和多酚氧化酶活性.在不同作物轮作和休闲方式下,后茬黄瓜结果期的细菌、放线菌数量和土壤转化酶活性均呈先升后降趋势,在盛瓜期达到最大值;真菌数量随生育期延长而增加;脲酶、过氧化氢酶和多酚氧化酶活性则随生育期延长而降低,在初瓜期最高.不同栽培模式下,以大葱-黄瓜轮作和糯玉米-黄瓜轮作的效果更佳,明显改善了后茬黄瓜的生长,提高了产量.     

蚯蚓对秸秆还田土壤细菌生理菌群数量和酶活性的影响

在连续7a稻麦轮作系统中,通过测定作物收获后表层土壤(0-20cm)中4种细菌生理菌群数量和4种酶活性的变化,研究接种蚯蚓(Metaphire guillelmi)对秸秆(表施或混施)还田土壤的细菌生理菌群数量和酶活性的影响。试验设5个处理:对照、秸秆表施、秸秆混施、秸秆表施且接种蚯蚓、秸秆混施且接种蚯蚓。结果表明,单独秸秆还田促进了土壤氨化细菌、固氮菌、纤维素分解菌和无机磷分解菌数量增加,且土壤酶活性显著地增强;在秸秆表施方式下,接种蚯蚓使得上述4种细菌生理菌群微生物的数量增加;秸秆混施方式下,接种蚯蚓增加氨化细菌和无机磷分解菌数量,且土壤蛋白酶和蔗糖酶活性显著地增强(P0.05)。另外,蚓粪中4种细菌生理菌群微生物数量和水解酶活性都远远高于其周围土壤。在秸秆还田的作物轮作系统中,蚯蚓活动进一步增加土壤微生物数量和酶活性,对改善农田土壤肥力有着重要意义。     

根际土壤微生物变化对西洋参种植的影响

以陕西产地不同年限西洋参根际土壤微生物（包括解钾、解磷及自生固氮菌）为研究对象,通过对根际土壤微生物进行分离、培养、计数和鉴定,并对比栽参后的玉米轮作根际土壤微生物数量和类群的变化特征,研究了根际土壤微生物的动态变化对西洋参连续种植的影响。结果表明：与轮作根际土壤相比,随西洋参生长期的增加其根际土壤中细菌数量的变化不明显,但优势细菌种类减少;放线菌数量及种类均有不同程度的减少;引起西洋参病害的霉菌类群明显增加;解磷、解钾、自生固氮菌的比例明显失调。此种变化可引起土壤理化性质的改变,进而影响西洋参的连续种植情况。     

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。     

不同草田轮作模式土壤养分及细菌群落组成特征

为研究不同草田轮作模式下土壤养分及细菌群落的组成特征,以5年紫花苜蓿-1年小麦(A5W1)、5年紫花苜蓿-1年玉米(A5C1)、5年紫花苜蓿-2年小麦(A5W2)和5年紫花苜蓿-2年玉米(A5C2)草田轮作模式为对象,测定了土壤有机质、全氮、全磷、全钾、碱解氮、速效磷和速效钾含量,在此基础上,基于16S rRNA基因序列扩增子测序研究了4种轮作模式下耕层土壤细菌群落组成特征。结果表明:轮作第2年各土壤养分含量较第1年显著下降。细菌组成研究结果显示,4种轮作模式下占优势的菌门为变形菌门、放线菌门和厚壁菌门。土壤细菌群落优势属以丙酸杆菌属(Propionibacterium)、芽孢杆菌属(Bacillus)、链球菌属(Streptococcus)以及奈瑟氏球菌属(Neisseria)为主。土壤细菌多样性以A5C2轮作处理最高,A5C1最低;聚类分析显示A5W1和A5C1的组成最接近,其次是A5C2,A5W2的组成与前两者相差较大。土壤养分含量与几种优势属之间呈显著相关性(P0.05 or P0.01)。研究结果揭示了河西走廊灌溉区种植紫花苜蓿多年后轮作小麦和玉米改善土壤肥力和防治某些土传植物病害微生物的机理。     

黄萎病不同发生程度棉田中土壤微生物多样性

作物根际土壤微生物群落对土壤生态及作物健康至关重要。以棉花黄萎病不同发生程度棉田的土壤为研究对象,采用理化分析、微生物纯培养及高通量测序技术对土壤理化性质及微生物数量、细菌丰度多样性进行综合分析。结果表明:在纯培养条件下,大丽轮枝菌无菌发酵滤液对细菌生长有明显的抑制作用;棉田接种大丽轮枝菌对土壤中细菌、真菌、放线菌的数量及细菌菌群丰度多样性未产生明显影响,不同采样时间的土壤中细菌菌群结构差异更大。土壤中大丽轮枝菌微菌核数量与棉花黄萎病的发生程度呈显著正相关。土壤肥力对土壤中微生物数量起主导作用,而水稻-棉花轮作能够使棉田有效降盐、减病、改善土壤肥力。通过生物防治、作物轮作、深翻等调控措施增加土壤中有益菌群数量、改善土壤生态、降低棉田土壤中大丽轮枝菌菌源数量是减轻棉花黄萎病危害的基础。     

轮作与施肥对滁菊连作土壤微生物特性的影响

为探讨轮作模式与生物有机肥施用对滁菊连作土壤微生物特性的影响,以滁菊、小麦为研究对象,采用田间试验,设置滁菊连作模式、常规滁菊小麦轮作模式和滁菊小麦轮作模式配施生物有机肥(200 kg·667 m-2)3种处理,测定土壤化学性状、土壤微生物量碳氮和土壤微生物数量指标.结果表明:与连作模式相比,常规菊麦轮作模式与菊麦轮作配施生物有机肥模式的土壤pH值,有机质、碱解氮、速效磷与速效钾含量,土壤微生物生物量氮(MBN)、碳(MBC)、微生物熵,以及土壤细菌、真菌和放线菌数量增加,土壤MBC/MBN值和真菌占三大菌群总量的比值降低.在试验条件下,以滁菊小麦轮作配施200 kg·667 m-2生物有机肥效果最佳,土壤有机质含量为15.62 g·kg-1,碱解氮、速效磷和速效钾含量分别达到为64.75、83.26和96.72 mg·kg-1,微生物生物量氮、碳为217.40和38.41 mg · kg-1,细菌、真菌、放线菌数量分别为22.31×106、56.36×103、15.90×105 cfu·g-1.合理轮作和增施生物有机肥可改善土壤酸化状况、土壤肥力和土壤微生物群落结构,增加土壤养分有效供给,对减轻连作障碍具有积极作用.     

不同轮作模式对桔梗生长、根际土壤微生物及土壤酶活性的影响

为研究不同轮作模式对桔梗根际土壤微生物及土壤酶活性的影响,从土壤微生态角度探寻一种无公害防治桔梗连作障碍的方式,以二年生桔梗为试材,采用盆栽试验的方法,以桔梗-桔梗（JG-JG）为对照,研究了桔梗-北沙参（JG-SS）、桔梗-玉米（JG-YM）、桔梗-防风（JG-FF）和桔梗-牛膝（JG-NX）不同轮作模式下对桔梗生长及土壤微生物和土壤酶活性的影响,分析筛选出桔梗的最优轮作模式。研究发现,JG-YM和JG-NX轮作模式下桔梗各生物量指标均优于其他处理;通过不同轮作种植模式对桔梗根际土壤微生物数量的影响研究发现,JG-SS、JG-YM、JG-NX、JG-FF细菌数量高于桔梗连作处理;JG-YM和JG-FF整体放线菌数量变化高于桔梗连作处理;JG-YM和JG-NX真菌数量与桔梗连作处理相比增长最为缓慢。通过不同轮作种植模式对桔梗根际土壤酶活性的影响研究发现,JG-NX的脲酶、蔗糖酶和纤维素酶活性高于其他四种处理。通过测定不同轮作模式下的桔梗生物量、桔梗根际土壤微生物数量和土壤酶活性,表明桔梗与牛膝或玉米轮作种植能改善种植土壤环境,缓解桔梗的连作障碍,可为桔梗的规范化种植奠定基础。     

Contribution of above‐ and belowground bioenergy crop residues to soil carbon

GHG mitigation by bioenergy crops depends on crop type, management practices, and the input of residue carbon (C) to the soil. Perennial grasses may increase soil C compared to annual crops because of more extensive root systems, but it is less clear how much soil C is derived from above‐ vs. belowground inputs. The objective of this study was to synthesize the existing knowledge regarding soil C inputs from above‐ and belowground crop residues in regions cultivated with sugarcane, corn, and miscanthus, and to predict the impact of residue removal and tillage on soil C stocks. The literature review showed that aboveground inputs to soil C (to 1‐m depth) ranged from 70% to 81% for sugarcane and corn vs. 40% for miscanthus. Modeled aboveground C inputs (to 30 cm depth) ranged from 54% to 82% for sugarcane, but were 67% for miscanthus. Because 50% of observed miscanthus belowground biomass is below 30 cm depth, it may be necessary to increase the depth of modeled soil C dynamics to reconcile modeled belowground C inputs with measured. Modeled removal of aboveground corn residue (25–100%) resulted in C stock reduction in areas of corn–corn–soybean rotation under conventional tillage, while no‐till management lessoned this impact. In sugarcane, soil C stocks were reduced when total aboveground residue was removed at one site, while partial removal of sugarcane residue did not reduce soil C stocks in either area. This study suggests that aboveground crop residues were the main C‐residue source to the soil in the current bioethanol sector (corn and sugarcane) and the indiscriminate removal of crop residues to produce cellulosic biofuels can reduce soil C stocks and reduce the environmental benefits of bioenergy. Moreover, a switch to feedstocks such as miscanthus with more allocation to belowground C could increase soil C stocks at a much faster rate.     

Soil microbial community structure and activity in a 100-year-old fertilization and crop rotation experiment

Aims Nitrogen (N) fertilization and lime addition may affect soil microbial and nematode communities and ecosystem functions through changing environmental conditions, such as soil pH and soil organic carbon. The objectives of this experiment were to examine the impact of N input and liming on soil microbial and nematode communities and to identify the key environmental determinant of community composition in a century-old fertilization and crop rotation experiment.Methods The field experiment consisting of a 3-year crop rotation regime was established in 1911 in southeastern USA. Four treatments, (i) no-input control, (ii) NPK with winter legume, (iii) PK with legume and lime and (iv) NPK with legume and lime, were included in this study. Soil samples collected at the 0–5cm depth were used to determine the bacterial growth rate by the 3 H-thymidine incorporation technique. Incorporation of 13 C into neutral lipids, glycolipids and phospholipid fatty acids (PLFAs) was measured after incubation of soil with 13 C-labeled acetate for 24h. Free-living nematodes in fresh soil were extracted using a density sucrose centrifugal flotation method and identified to trophic group level.Important findings Liming resulted in a 10-fold increase in bacterial growth rates compared with the no-input control, whereas N fertilization had no significant effect. Multivariate analysis of PLFA profiles showed that soil microbial community composition was different among the four treatments; the difference was primarily driven by soil pH. PLFAs indicative of Gram-negative bacteria covaried with soil pH, but not those of fungi and actinobacteria. Liming enhanced 13 C incorporation into neutral lipids, glycolipids and phospholipids by 2–15 times. In addition, 13 C incorporation into 16:0, 16:1ω9, 18:1ω9, 18:1ω7 and 18:2ω6 were greater than other PLFAs, suggesting that Gram-negative bacteria and fungi were more active and sensitive to simple C input. Bacterivorous nematodes were the dominant trophic group in the soil, but no significant differences in nematode communities were found among the treatments. Our results suggest that soil pH had a greater impact than N fertilization on soil microbial community composition and activity in a crop rotation system including legumes.     

Effects of biocides and rotation breaks on soil organisms associated with the poor early growth of sugarcane in continuous monoculture

Glasshouse and field experiments were conducted to determine the effects of biocides and rotation breaks on deleterious soil organisms associated with the poor early growth and subsequent yield decline of sugarcane grown in continuous monoculture. Fumigation of a soil that had been under sugarcane monoculture with minimal breaks for more than 30 years markedly improved the health and growth of the sugarcane sett and shoot root systems, increased the growth of the primary shoot and stimulated more and larger secondary shoots. It also reduced populations of culturable fungi in the rhizosphere of the sett roots and reduced colonization of the sett and shoot roots by lesion nematode (Pratylenchus zeae). Exposure of the developing sett root system for 14 days to mono-cultured sugarcane soil was sufficient to significantly retard subsequent plant growth. In field experiments, fungicide and nematicide (mancozeb + aldicarb), when applied together to land under sugarcane monoculture, was as effective as fumigation in improving early sugarcane growth and increasing sugarcane yields. Rotation breaks (alternate crops, sown pasture, bare fallow) that were in place for 54 months, increased sugarcane establishment and increased sugarcane yields to levels similar to that obtained following fumigation of land under sugarcane monoculture. Fumigation of land that had been under the rotation breaks gave plant growth responses that were in addition to that achieved by the breaks alone. A mancozeb + aldicarb treatment was as effective as fumigation in increasing sugarcane yields after a bare fallow break but accounted for only a portion of the fumigation response following the crop and pasture breaks. Improved plant nutrition may be a factor in the fumigation response following the crop and pasture breaks. Plant growth responses to fumigation and the manocozeb + aldicarb treatments that were manifested in final sugarcane yields (after one years growth) were evident as plant growth responses (sett root, shoot root and primary shoot dry weight) measured 54 days after planting. The experimental results support the concept that when sugarcane is grown as a monoculture, deleterious fungi and nematodes retard plant establishment and early plant growth and that this leads to reduced sugarcane yields.     

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.     

半干旱黄土区苜蓿草地轮作农田土壤氮、磷和有机质变化

大田试验研究了多年生苜蓿草地轮作农田2年内的耕层土壤氮、磷养分和有机质变化.结果表明,与苜蓿连作相比,苜蓿草地轮作成农田后,土壤N和有机质消耗增加,2年中耕层土壤全氮含量平均分别下降了5.4%和19.5%、有机质下降了46.8%和28.2%,土壤全磷无显著变化;轮作提高了土壤氮、磷养分有效性及其活化率,土壤硝态氮含量2年分别提高了15.5%和159.1%、速效磷含量提高了44.5%和48.0%,差异显著.不同轮作方式对土壤养分变化有显著影响.苜蓿草地轮作后第2年,种植春小麦与种植玉米相比差异显著,种植马铃薯和休闲处理土壤养分变化幅度处于二者之间.种植春小麦能够维持农田土壤肥力生长季平衡,种植玉米增加了对土壤全氮、有机质和速效磷的消耗,土壤养分含量出现季节性下降,C/N和C/P降低.在半干旱地区多年生苜蓿草地向农田转变过程中,以轮作春小麦为宜,应避免种植玉米作物,以维持农田肥力平衡.     

发酵肥与秸杆还田对土壤微生物区系与作物产量的影响

土壤中施入不发酵新鲜粪肥时土壤细菌与放线菌数量明显增加,当施入发酵肥时对土壤微生物活性影响较小;在施发酵肥基础上再进行秸杆还田,土壤微生物活性明显提高,作物获得持续丰产。单一秸杆还田也能提高土壤微生物活性,但当年无增产效果,在秸杆还田时喷雾接种木霉（Ｔｒｉｃｈｏｄｅｍａｋｏｎｉｎｇｉ）４５６—２与固氮菌（Ａｚ．ｖｉｎｅｌａｎｄｉｉ）２３０,当年获得增产效果。     

不同土壤类型下甘蔗根系AM真菌多样性及与土壤因子关系

甘蔗是广西重要的糖料作物,本研究通过建立克隆文库、土壤养分分析和根样染色等方法测定了33个采样点3种土壤类型(赤红壤,红壤,砖红壤)下甘蔗根系AM真菌多样性及其与土壤因子的关系。结果表明,3种土壤类型的甘蔗根系共鉴定出6科6属11种AM真菌,AM真菌各属频度存在明显差异,其中球囊霉属的频度值最高,在33个根系样品中有32个存在该属,为广西甘蔗根系AM真菌的优势属,而类球囊霉属、无梗囊霉属、近明球囊霉属、多样孢囊霉属和盾巨孢囊霉属5个属为稀有属。3种土壤类型的甘蔗根系均发现有球囊霉属和盾巨孢囊霉属;近明球囊霉属、无梗囊霉属和类球囊霉属仅在赤红壤的甘蔗根系中出现;而多样孢囊霉属仅在在赤红壤和砖红壤的甘蔗根系中出现。土壤的pH与AM菌根侵染率呈显著正相关,而有机质、总N、有效P、交换性Mg2+与AM菌根侵染率均呈负相关。本研究表明,自然条件下甘蔗根系具有相对丰富的AM真菌类群,这些AM真菌可能在甘蔗生长过程中发挥着重要的生态功能。     

间作大豆对甘蔗根际土壤细菌及固氮菌多样性的影响

为探讨间作大豆(Glycine max)对甘蔗(Saccharum officinarum)根际土壤细菌及固氮细菌多样性的影响, 收集和开发固氮菌资源, 筛选高效甘蔗联合固氮体系, 选用3个甘蔗栽培品种‘ROC22’、‘GT21’、‘B8’与大豆品种‘Guizao 2’进行间种栽培, 采用巢式PCR特异扩增细菌16S rRNA基因片段和固氮细菌nifH基因片段, 并结合变性梯度凝胶电泳(DGGE)技术, 对间作大豆的甘蔗根际土壤细菌及固氮细菌进行系统演化和多样性分析。聚类分析结果显示, 间作大豆改变了甘蔗根际土壤细菌及固氮细菌原来的群落组成结构, 尤其对固氮菌群落组成的改变更大, 但对群落物种的优势度影响较小。Shannon-Wiener多样性指数和Simpson多样性指数分析结果表明, 甘蔗-大豆间作显著影响甘蔗根际土壤中细菌和固氮菌的多样性, 其中对固氮细菌多样性的影响较大。不同甘蔗品种的根际土壤细菌和固氮菌在间作大豆条件下表现出不同的多样性, ‘ROC22’和‘GT21’间作处理甘蔗根际土壤固氮细菌的Shannon-Wiener多样性指数显著高于单作处理, 而‘ROC22’与大豆间作处理的甘蔗根际土壤固氮菌多样性最为丰富。在大豆生长盛期, 间作处理的甘蔗根际土壤细菌多样性最为丰富, 不同处理间的差异也最大, 随后下降。总体来看, 甘蔗-大豆间作显著地影响根际土壤细菌和固氮菌的群落结构和群落多样性, 有助于对甘蔗合理间作栽培模式的认识和筛选高效甘蔗联合固氮体系。     

不同蔬菜与番茄轮作对设施土壤微生物多样性、酶活性及土壤理化性质的影响

【目的】番茄是一种受连作障碍影响明显的蔬菜作物,本试验旨在研究不同蔬菜作物与番茄轮作后对设施土壤微生物多样性、酶活性及土壤理化性质的影响,以期筛选出适宜与番茄轮作的蔬菜作物,为从设施栽培模式选择角度缓解或避免番茄连作障碍提供理论依据。【方法】试验以连续两茬种植番茄后分别种植大白菜(A)、黄瓜(B)、辣椒(C)、茄子(E)、秋葵(F)、西葫芦(G)6种作物为不同处理,以继续种植番茄(D)和休耕闲置土壤(H)为对照,采用16S rRNA和真菌ITS区测序、同时测定土壤酶活性、pH值、有机质含量、速效氮、磷、钾含量,研究不同蔬菜作物与番茄轮作对土壤微生物多样性、酶活性及土壤理化性质的影响。【结果】种植作物土壤细菌和真菌多样性指数均显著高于闲置土壤(H);番茄连作与轮作土壤中的细菌门水平群落结构比较固定,但不同物种的丰度差异较大。真菌对于环境变化的响应比细菌更加敏感,轮作各样本间真菌群落结构差异明显大于细菌群落结构,在物种丰度和门水平上均存在较大差异;轮作茄子和大白菜显著增加了土壤中硝化细菌[亚硝化单胞菌属(Nitrosomonas)、亚硝化螺菌属(Nitrosospira)]的丰度;PCA分析表明轮作茄子和空白闲置土壤细菌和真菌的群落结构与其他处理的差异较大;轮作不同作物土壤酶活性差异显著,但变化规律不明显。轮作大白菜、黄瓜和空白闲置土壤过氧化氢酶活性显著高于番茄连作和轮作其他作物。不同蔬菜轮作土壤肥力主成分分析结果表明土壤pH值、有机质、速效氮与速效磷是主要贡献因子,综合肥力排名第一的为空白土样,其次为轮作黄瓜的土样,综合肥力最低的为轮作茄子土样。【结论】种植作物可以显著提高土壤微生物多样性;轮作茄子和大白菜显著增加了土壤中硝化细菌的丰度,有利于土壤中氮素代谢和利用;轮作黄瓜和大白菜,显著提高土壤中过氧化氢酶的活性,有利于降低番茄连作产生的自毒作用。因此综合分析认为,茄子、黄瓜和大白菜是避免或缓解番茄连作障碍的潜在优势轮作作物。     

The effects of wheat-pea mixed intercropping on biocontrol potential of generalist predators in a long-term experimental trial

Arthropod generalist predators can be effective natural control agents of pests and weeds in agroecosystems. Their activity and contribution to biocontrol may increase in response to more complex agricultural habitats. In this study, we investigated the effects of winter wheat-pea mixed intercropping on the biocontrol potential of generalist predators compared with the respective mono-crops. We evaluated not only the effects during the intercropping season but also the pre-crop values of the mixture for the subsequent barley crop. Furthermore, we evaluated the influence of different long-term soil organic carbon and fertility management regimes on activity and biocontrol potential of predators. Field work was conducted over two seasons in a field experiment located in Gembloux, Belgium. A set of proxies for ecosystem functions were measured using the Rapid Ecosystem Function Assessment approach. We measured attack and predation rates of sentinel prey and weed seeds artificially placed in the field. Furthermore, we assessed activity density of the main groups of generalist predators during the exposure of the baits. Our results showed that crop type affected activity and biocontrol potential of predators. Predation rates were much lower in wheat than pea and wheat-pea. The mixture wheat-pea had a positive effect on predator activity density compared to wheat mono-crop, while pea supported an intermediate activity of epigeal predators. In the second season of the field work, we found the highest biocontrol potential by predators in barley plots cultivated after pea. Finally, our results failed to find any differences in biocontrol potential of predators between long-term soil organic carbon and fertilisation management strategies. These results suggest that crop type has a major relevance in influencing the activity of generalist predators, and the mixed intercropping wheat-pea may represent a valid strategy to enhance biological pest control in comparison to wheat cultivated as mono-crop. Furthermore, we show that the cultivation of pea as mono-crop may have an important pre-crop value within the rotation increasing the provision of ecosystem services such as biocontrol.