甘肃玉米镰孢茎腐病病原菌种群多样性分析

为了解甘肃玉米镰孢茎腐病致病菌的种群结构和数量,于2015和2017年在甘肃省10个市(州)采集玉米茎腐病样品42份,根据形态学特征和EF-1α (tef)基因序列分析进行病原菌的种类鉴定。结果表明,共获得10种镰孢菌,分别为禾谷镰孢菌复合种(Fusarium graminearum species complex, FGSC, 59.3%)、拟轮枝镰孢(F.verticillioides,11.5%)、木贼镰孢(F. equiseti,10.3%)、胶孢镰孢(F. subglutinans,5.9%)、层出镰孢(F. proliferatum, 4.7%)、变红镰孢(F. incarnatum, 4.0%)、三线镰孢(F. tricinctum, 1.9%)、温带镰孢(F. temperatum, 1.2%)、锐顶镰孢(F. acuminatum,0.8%)和尖孢镰孢(F. oxysporum, 0.4%),其中三线镰孢和锐顶镰孢作为玉米茎腐病新病原,属国内外首次发现。禾谷镰孢菌复合种、拟轮枝镰孢、木贼镰孢和胶孢镰孢在甘肃四大生态区(陇东地区、陇南地区、陇中地区和河西走廊)均有分布,其余种仅在1~3个生态区分布。利用镰孢菌的特异性引物EF-1α (tef)对甘肃玉米镰孢茎腐病优势病原菌禾谷镰孢复合种进行种群检测,共鉴定出布氏镰孢(F. boothii)和禾谷镰孢2个种群,其比例为2.75∶1。选用玉米品种甘宇301按照柯赫氏法则进行致病性测定,结果发现10种镰孢菌均可致病。本研究结果为甘肃玉米茎腐病的综合防控提供了科学依据。     

Do Collembola affect the competitive relationships among soil-borne plant pathogenic fungi?

The feeding preference of the collembolan Protaphorura armata in the presence of Fusarium culmorum and Gaeumannomyces graminis var. tritici, two soil-borne fungi pathogenic for winter cereals, was studied in a simplified experimental system including wheat seedlings. Analysis of gut content of all animals from microcosms containing inoculum of both fungi showed that F. culmorum was clearly preferred but that G. graminis var. tritici was also fed. At microscopic examination the majority of F. culmorum conidia present in the gut lacked cytoplasmic content, and only few conidial cells were intact. The feeding preference of P. armata favoured G. graminis var. tritici over F. culmorum in the competition for infection sites on wheat plants; in fact, the former resulted the prevalent cause of plant disease.

The viability of fungal propagules after passage through the gut of P. armata was also studied. No colonies of G. graminis var. tritici and only a few colonies of F. culmorum developed from faecal pellets set on agar medium. Fungal propagules dispersed by springtails were not sufficient to induce disease, as demonstrated by introducing animals, previously fed on fungal cultures separately, into microcosms containing a sterile substrate where wheat kernels were seeded.     

Food preferences of earthworms for soil fungi

Soil fungi are considered to be an important food source for earthworms. Selection experiments were carried out in order to study the preferences of earthworm species for a variety of soil fungi. Nine fungal species (Cladosporium cladosporioides, Rhizoctonia solani, Mucor sp., Trichoderma viride, Fusarium nivale, Phlebia radiata, Glaeophyllum trabeum, Coniophora puteana, Coriolus versicolor) were grown separately in centrifuge tubes on sterilized sand with potato dextrose. Tubes containing different fungal species, 8–9 per experiment, were arranged in a food choice arena. The preference for the fungi of 5 different earthworm species (Lumbricus terrestris, Lumbricus castaneus, Aporrectodea caliginosa, Aporrectodea rosea, Octolasion cyaneum) was tested by adding one specimen per chamber. Removal of sand from the tubes within 6 days was used as the indicator of preference by earthworms. The food preference of earthworms irrespective of ecological group followed a general pattern. F. nivale and C. cladosporioides were the preferred fungal species, followed by fast-growing species such as Mucor sp. and R. solani. In contrast, basidiomycetes were generally refused. The epigeic species L. rubellus had the strongest preference for a single fungal species, in contrast the endogeic species A. rosea fed more evenly on different fungal species. We conclude that early successional fungal species are used as cues by earthworms to detect fresh organic resources in soil.     

Moisture conservation for rainfed wheat production with alternative mulches and conservation tillage in the hills of north-west India

In the hills of north–west India, maize (Zea mays L.)-wheat (Triticum aestivum L.) is the dominant cropping system. However, rainfed wheat suffers from lack of optimum moisture at sowing. Field experiments were conducted for 3 years on a silty clay loam (Typic Hapludalf) to evaluate the effectiveness of mulches and conservation tillage for rainfed wheat in mitigating this problem. The treatments were ten factorial combinations of five mulch-tillage practices and two nitrogen levels (N₆₀ and N₁₂₀ kg ha⁻¹). Mulch treatments consisted of application of 10 Mg ha⁻¹ (dry weight basis), to previous standing maize, of either wild sage (Lantana camara L.) or eupatorium (Eupatorium adenophorum Sprengel) in combination with either conventional or conservation (minium) tillage prior to wheat sowing. These alternative practices were compared to the conventional farmer practice of soil tillage after harvest of maize with no mulch. The application of these weed mulches to standing maize maintained friable soil structure owing to a five fold higher mean population of earthworms underneath mulch. Mulches resulted in 0.06–0.10 m³ m⁻³ higher moisture in the seed-zone when wheat was sown compared with the conventional farmer practice of soil tillage after maize harvest. Mulch-conservation tillage treatments favourably moderated the hydro-thermal regime for growing a wheat crop. The mean root mass density under these treatments at wheat flowering was higher by 1.27–1.40 times over the conventional farmer practice during the 3 year study. Conservation tillage holds promise because it does not require elaborate tillage and may ultimately reduce animal draught in the hilly regions. Recycling available organic materials having no fodder value coupled with conservation tillage may help enrich the soil environment in the long-term. The practice also offers gainful use of these obnoxious weeds that cause great menace in grass and forest lands in the region.     

Conservation tillage systems, fungal complexes and disease development in soybean and barley rhizospheres in Prince Edward Island

A potential for reduced soil macroporosity (below 12% soil volume) under direct drilling, with a concomitant increase in soil relative saturation, is associated with an increase in crown and root rots in Prince Edward Island field crops. Four long-term tillage systems (moldboard plowing, paraplowing-direct drilling, rotary cultivation and direct drilling) were compared in relation to the pathogenic fungal complexes formed in a two crop rotation in spring barley (Hordeum vulgare L.) and soybean (Glycine max L. Merrill) over a 3 year period in a cool humid region of eastern Canada. The principal phytopathogenic fungal complex of Rhizoctonia solani Kühn, Fusarium avenaceum (Fr.) Sacc. and F. oxysporum Schl. remained constant over the treatments. Tillage practice did not affect the number of colony forming units of R. solani in the rhizosphere. The recovery of R. solani from root tissues tended to be lower following conservation tillage and was attributed to antagonism associated with elevated numbers of saprophytic trash microflora concentrated at the soil surface. Disease levels in potato (Solanum tuberosum L.) plantlet bioassays were not influenced significantly by soil source or tillage regime. However, plantlet growth tended to be depressed following transplantation into soil from soybean plots in 1993. Under optimum soil physical conditions conservation tillage did not appear to influence disease levels in barley and soybean rotations.     

复配杀菌剂防治平菇尖孢镰刀菌病害的效果测定

为筛选应用于平菇栽培的高效低残留杀菌剂,本试验研究了复配杀菌剂(使百功+多菌灵、使百功+克霉灵、多菌灵+克霉灵)对尖孢镰刀菌与平菇菌丝生长的影响及其在平菇栽培中的应用效果。结果表明,3种复配杀菌剂抑制尖孢镰刀菌菌丝生长的EC₅₀值分别为3.67、4.51和7.01 mg·L^-1,均显著小于对应的单药杀菌剂;3种复配杀菌剂抑制平菇菌丝生长的EC₅₀值分别为156.41、121.97和237.38 mg·L^-1,是其抑制尖孢镰刀菌菌丝生长EC₅₀值的27~43倍。在平菇栽培发酵料中使用0.1%~0.3%的复配杀菌剂使百功+克霉灵,菌丝生长速度加快,生物学效率升高;与未添加杀菌剂处理相比,污染率降低6.1~8.8个百分点;与使百功处理相比,平菇子实体中的农药残留量降低71.8%~76.6%。综上,复配杀菌剂能有效降低平菇子实体中的农药残留,其中使百功+克霉灵复配杀菌剂效果最好,是一种高效低残留的平菇枯萎病防治药剂。     

Developing disease-suppressive soils through crop rotation and tillage management practices

A field laboratory was established in Prince Edward Island, Canada, to determine the effects of 2- and 3-year crop rotations, with conventional and minimum tillage treatments, on the severity of soilborne diseases of potato. The 2-year rotation consisted of spring barley and potato (cv. ‘Russet Burbank’), and the 3-year rotation was barley (undersown with red clover), red clover and potato. Examination of potato stem, stolon, and tuber tissues revealed significantly (P=0.05) lower levels of canker and black scurf caused by Rhizoctonia solani, in plants grown in 3-year vs. 2-year rotations. The severity of dry rot (Fusarium spp.) and silver scurf (Helminthosporium solani) was significantly (P=0.05) lower in tubers from plots managed with 3-year rotations and minimum tillage practices. Potato tubers harvested from 3-year rotational soils were significantly (P=0.05) less diseased than those from 2-year rotational soils following inoculation with Phytophthora erythroseptica, causal agent of pink rot. In greenhouse experiments using field soils from 2- and 3-year rotations, we found that potato plants growing in 3-year rotational soils were significantly (P=0.05) less diseased than those growing in 2-year rotational soils following inoculation with P. erythroseptica. Analysis of root zone bacteria recovered from the rhizosphere (exoroot) and potato root tissues (endoroot) showed that the greatest antibiosis activity inhibiting the growth of soilborne pathogens in vitro occurred in bacterial isolates recovered from the endoroot tissues of 3-year rotation crops under minimum tillage management. Our evidence supports the view that soil agroecosystems can be modified through rotation and conservation tillage practices to improve disease suppression by enhancing the antibiosis abilities of endophytic and root zone bacteria (endo- and exoroot).     

华北典型区域土壤耕作方式对土壤特性和作物产量的影响

华北平原是我国重要的小麦玉米种植区,长期土壤旋耕免耕和秸秆全量还田带来耕层变浅、犁底层变厚和上移、土壤养分表聚等现象,通过耕作方式改变,解决上述问题对维持区域粮食生产有重要意义。试验以冬小麦-夏玉米轮作系统为研究对象,分别在代表华北平原高产区的栾城试验区和代表中低产区的南皮试验区进行,设置冬小麦播种前进行土壤深耕、深松、窄深松3种处理,以生产上常用的旋耕为对照。所有处理夏玉米季均采用土壤免耕播种,测定项目包括土壤容重、作物根系、作物产量和水分利用效率。结果表明,不同耕作方式对土壤特性和作物产量的影响具有区域差异。南皮试验区土壤深耕(松)显著地(P0.05)提高了作物产量,深耕、深松和窄深松处理的冬小麦产量比旋耕分别增加16.5%、19.3%和13.1%,夏玉米产量分别增加17.3%、16.2%和21.9%,周年产量分别增加16.9%、17.6%和17.8%;深耕、深松和窄深松处理间作物产量差异不显著。栾城试验区冬小麦、夏玉米产量和周年产量各处理之间差异不显著。土壤深耕、深松、窄深松和旋耕均能降低0～20 cm土层土壤紧实度和土壤容重。冬小麦播种后,与土壤耕作前比较,土壤深耕、深松和旋耕处理土壤紧实度南皮试验区分别平均降低71.6%和68.2%,栾城试验区分别降低88.8%和?7.7%,常用的旋耕模式在栾城试区没有降低土壤紧实度。小麦收获时不同耕作方式0～40cm土层的土壤容重均低于土壤耕作前的土壤容重,至夏玉米收获时不同耕作处理的土壤容重与耕作前基本一致,不同耕作处理对土壤容重的影响差异不显著。在南皮试验区, 3种耕作方式与旋耕相比,均显著提高了冬小麦和夏玉米水分利用效率;在栾城试验区,各处理冬小麦和夏玉米水分利用效率差异不显著。本研究结果显示在华北平原高产区连续实施土壤旋耕模式没有影响作物产量,而在中低产区实施土壤深耕或者深松模式更利于作物产量提高。     

Soil aggregation in a laboratory experiment: Interactions between earthworms, woodlice and litter palatability

Interactions between soil invertebrate functional groups are still poorly understood. In this study, the effect of the soil dwelling earthworm Aporrectodea caliginosa and the woodlouse Porcellio scaber (litter inhabitant), alone or in combination, on soil aggregation was investigated in laboratory microcosms with litter of different quality (Quercus robur and Fagus sylvatica). After 4 months of incubation, the aggregate size distribution was measured using a dry-sieving method. A. caliginosa played an important role in the formation of large aggregates (>2 mm), whereas P. scaber greatly influenced litter disappearance. A. caliginosa individuals formed a greater number of large aggregates when fed with beech leaves compared to oak leaves even though they preferred the latter. In the presence of beech and P. scaber, A. caliginosa produced significantly fewer large aggregates than expected.     

A minimum data set for soil quality assessment of wheat and maize cropping in the highlands of Mexico

The objective was to establish a minimum soil quality dataset for a long-term tillage, residue management and rotation trial for wheat (Triticum aestivum L.) and maize (Zea mays L.) production systems. Based on this soil quality evaluation, sustainable management practices could be selected for transferring technologies to farmers in the region. A long-term experiment was conducted with 16 different crop management practices varying in: (1) rotation (continuous maize or wheat and both phases of the rotation of maize and wheat), (2) tillage (conventional and zero) and (3) crop residue management (full retention or removal for fodder). Superior soil quality was considered to represent the maintenance of high productivity without significant soil or environmental degradation. The pertinent, minimum soil quality data set included the following physical indicators: time-to-pond, aggregate stability, permanent wilting point, and topsoil penetration resistance. Chemical indicators were: soil C, N, K and Zn concentrations, measured in the 0–5 cm topsoil and C, N concentration in 5–20 cm. Multivariate analysis grouped the treatments into clusters: (1) zero tillage with retention of residue, (2) zero tillage with residue removal and (3) conventional tillage. Zero tillage combined with crop residue retention improved chemical and physical conditions of the soil. In contrast, zero tillage with removal of residues, led to high accumulation of Mn in the topsoil, low aggregate stability, high penetration resistance, surface slaking resulting in low time-to-pond values and high runoff. Finally, soil quality under conventional tillage was intermediate (irrespective of residue management), especially reflected in the physical status of the soil. The results provide a strong justification to promote zero tillage technology combined with appropriate residue management to farmers in the volcanic highlands of Central Mexico and other similar regions. The minimum data set and associated tools for careful monitoring and observation, will be essential for evaluating soil quality in farmer's fields.     

Tillage systems for a cotton–peanut rotation with winter-annual grazing: Impacts on soil carbon, nitrogen and physical properties

Integrating livestock with cotton (Gossypium hirsutum L.) and peanut (Arachis hypogaea L.) production systems by grazing winter-annuals can offer additional income for producers provided it does not result in yield-limiting soil compaction. We conducted a 3-year field study on a Dothan loamy sand (fine-loamy, kaolinitic, thermic plinthic kandiudults) in southern Alabama, USA to determine the influence of tillage system prior to cotton–peanut planting on soil properties following winter-annual grazing. Two winter-annual forages [oat (Avena sativa L.) and annual ryegrass (Lolium mutiflorum L.)] and four tillage practices [chisel + disk, non-inversion deep tillage (paratill) with and without disking and no-till] were evaluated in a strip-plot design of four replications. We evaluated cone index, bulk density, infiltration, soil organic carbon (SOC), and total nitrogen (N). Paratilling prior to cotton or peanut planting, especially without surface soil tillage, reduced compaction initially to 40 cm and residually to 30 cm through the grazing period in winter. There were no significant differences in cone index, bulk density, or infiltration between forage species. No-tillage resulted in the greatest bulk density (1.65 Mg m⁻³) and lowest infiltration (36% of water applied), while paratilling increased infiltration in no-tillage to 83%. After 3 years, paratilling increased SOC 38% and N 56% near the soil surface (0–5 cm), as compared to concentrations at the beginning of the experiment, suggesting an improvement in soil quality. For coastal plain soils, integrating winter-annual grazing in a cotton–peanut rotation using a conservation tillage system of non-inversion deep tillage (paratill) with no surface tillage can improve soil quality by reducing cone index, increasing infiltration, and increasing SOC in the soil surface.     

Role of soil mesofauna in dispersal of Coniothyrium minitans: transmission to sclerotia of Sclerotinia sclerotiorum

Coniothyrium minitans Campbell is a mycoparasite with proven biocontrol activity against Sclerotinia sclerotiorum (Lib.) de Bary in the field and glasshouse. It is known to spread from sites of application but the mechanisms of dispersal are unclear. As C. minitans has been recovered from collembolans collected during glasshouse trials, and numerous mites and insects are often associated with decaying S. sclerotiorum-infected plant material in the glasshouse, the mite Acarus siro L. and the collembolan Folsomia candida Willem were used to investigate the potential of soil mesofauna to disperse C. minitans. In an initial investigation, A. siro was found to transmit the mycoparasite from infected to uninfected sclerotia of S. sclerotiorum in moist sterile sand and non-sterile soil. Subsequently, a simple assay system to monitor transfer of C. minitans from colonised wheat grains to uninfected sclerotia of S. sclerotiorum was developed. Both A. siro and F. candida transmitted C. minitans at least 55 mm to sclerotia in soil at water potentials ranging from saturation to −3.6 MPa. Transmission by A. siro was greater in drier conditions (−0.25 to −3.6 MPa) as mites survived poorly in saturated soil. However, water potentials between saturation to −3.6 MPa had no effect on transmission by F. candida, although collembolans died after 18 d at water potentials of −5.4 MPa or drier. Generally, maximum dispersal occurred within 2 weeks. In soil lacking added arthropods, negligible spread of the mycoparasite was observed. These results suggest that soil mesofauna may be important in the dissemination of C. minitans.     

Saprophytic survival of the take-all fungus and its antagonist, Gaeumannomyces graminis var. graminis under conventional and no-tillage

The saprophytic survival of the take-all fungus, Gaeumannomyces graminis var. tritici, and its antagonist, G. graminis var. graminis, was studied over 9-month periods in 1982 and 1983 under conventional and no-tillage cultivation. In 1982, when the rainfall for the 9-month period was 30.4% below the long-term average, the survival of the fungi was comparable under the two tillage systems. However, the survival of G. graminis var. graminis was significantly greater (P 0.05) than that of G. graminis var. tritici at each sampling time. In 1983, when the rainfall for the 9-month period was 25.1% above the long-term average, the survival of both fungi was significantly greater under no-tillage than under conventional tillage. The survival of the two isolates of G. graminis var. graminis after 3 months was significantly greater (P 0.05) than that of the two isolates of the pathogen. The implications for the greater survival of the fungal antagonist compared to the take-all fungus under no-tillage are discussed in relation to the biological control of take-all.     

Tillage and crop management effects on soil erosion in central Croatia

Soil erosion continues to be a primary cause for soil degradation and the loss of soil quality throughout the world. Our objectives were to quantify soil erosion (referred to as erosional drift) and to assign erosion risk to six tillage and crop management treatments evaluated from 1995 to 1999 for a 5-year maize (Zea mays L.), soybean (Glycine hyspida L.), winter wheat (Triticum aestivum L.), oil-seed rape (Brassica napus var. oleifera L.), and spring barley (Hordeum vulgare L.) plus double-crop soybean rotation on Stagnic Luvisols in central Croatia. Standard black fallow (tilled, unsown, and without any vegetative cover) Universal Soil Loss Equation (USLE) plots were used to establish the erosion potential associated with the rainfall pattern for each year. Soil loss from the check plots was several times greater than the T value, which is estimated to be 10 t ha⁻¹ per year. During the 2 years when spring seeded maize or soybean were grown (1995 and 1996) erosion risk was extremely high, especially for treatments where tillage and planting (row direction) were up and down the slope. When autumn seeded winter wheat or oil-seed rape were grown (1996/1997 or 1997/1998), soil erosion was insignificant. Also, except when plowing and sowing were up and down slope, erosion loss for the spring barley plus double-crop soybean crops in 1999 was insignificant. With no-tillage, soil erosion from the maize and soybean crops was reduced 40 and 65% compared to plowing up and down slope, even though the planting direction was still up and down the slope. With the exception of maize in 1995, erosion losses were moderate to insignificant when plowing and planting were performed across the slope. We conclude that erosion risk can be used as a reliable indicator of sustainable land management and that using no-tillage or plowing and planting perpendicular to the predominant slope are effective soil conservation practices for this region.     

Applications of reduced tillage in hills of central Nepal

Conventional tillage practices on steep and fragile landscape of Himalayan hills result in significant loss of topsoil during rainy season. Soil erosion in Nepal mid-hills is the most critical during pre-monsoon season. Many reviews argue that reduced tillage could be an option to tackle this problem. However, very few field experiments to evaluate reduced tillage systems have to date been conducted in this region. Thus, a field experiment was initiated in factorial randomized complete block design on acidic sandy loam soil (Lithic Dystochrept) during the summer season of 2001 at Kathmandu University (1500 masl) to assess the effects of tillage and cropping patterns on soil and nutrient losses, crop yield and soil fertility. Two main treatments viz. conventional and reduced till, and two sub-treatments viz. sole maize (Zea mays) and maize + soybean (Glycine max) were considered. Soil organic carbon (OC), total nitrogen (N), plant available phosphorus (P) and exchangeable potassium (K) were determined for the original soil and eroded sediment using standard methods. Two years of data indicated annual soil and nutrient losses to be significantly lowered by reduced till as compared to conventional till. Total annual soil loss from conventional and reduced till was 16.6 and 11.1 Mg/ha, respectively. Similarly, annual nutrient losses associated with the eroded sediment were 188 kg OC/ha, 18.8 kg N/ha, <1 kg P/ha and 3.8 kg K/ha for conventional till and 126 kg OC/ha, 11.8 kg N/ha, <1 kg P/ha and 2.4 kg K/ha for reduced till. Soil OC and N losses were significantly higher in conventional till and this may be one of the major causes of fertility depletion in the Nepalese hills. Soil chemical properties did not differ due to tillage and cropping systems; however, over years pH, N and P were increased irrespective of treatments. Although treatments were at par for maize grain yield, conventional till + soybean produced highest grain yield (4.0 Mg/ha) followed by reduced till + soybean (3.9 Mg/ha) and conventional till sole maize (3.8 Mg/ha). Mixed cropping of legumes and maize do not help conserve soil and nutrient loss in hills of central Nepal. Thus, reduced till could be a viable option for minimizing soil and nutrient losses without sacrificing economic yields in central hills of Nepal.     

Soil macropore dynamics affected by tillage and irrigation for a silty loam alluvial soil in southern Portugal

Soil tillage can have a significant effect on soil porosity and water infiltration. This study reports field measurements of near saturated hydraulic conductivity in an undisturbed soil under two tillage treatments, conventional tillage (CT) and minimum tillage (MT). The objective was to determine effective macro and mesoporosities, porosity dynamics during the irrigation season, and their contribution to water flow. Field observations were performed during the 1998 maize (Zea mays L.) cropping season in an Eutric Fluvisol with a silty loam texture, located in the Sorraia River Watershed in the south of Portugal. Infiltration measurements were done with a tension infiltrometer. At each location an infiltration sequence was performed corresponding to water tensions (φ) of 0, 3, 6 and 15 cm. Five sets of infiltration measurements were taken in both treatments in the top soil layer between May and September. One set of measurements was done at the depth of 30 cm at the bottom of the plowed layer in the CT plot. After 5 years of continuous tillage treatments the results show that regardless of the tillage treatment, saturated conductivity values K(φ₀) were several times larger than near saturation conductivity K(φ₃). This indicates that subsurface networks of water conducting soil pores can exist in both CT and MT maize production systems. In CT, the moldboard plow created macro and mesoporosity in the top soil layer while breaking pore continuity at 30 cm depth. This porosity was partially disrupted by the first irrigation, resulting in a significant decrease of 45% in the macropore contribution to flow. Later in the season, the irrigation effect was overlaid by the root development effect creating new channels or continuity between existing pores. In MT macroporosity contribution to flow did not show significant differences in time, representing 85% of the total flow. In both the treatments, macropores were the main contributing pores to the total flow, in spite of the very low macroporosity volumes.     

Seasonal variation of microbial biomass, activity, and community structure in soil under different tillage and phosphorus management practices

No-tillage systems contribute to physical, chemical and biological changes in the soil. The effects of different tillage practices and phosphorus (P) fertilization on soil microbial biomass, activity, and community structure were studied during the maize growing season in a maize–soybean rotation established for 18 years in eastern Canada. Soil samples were collected at two depths (0–10 and 10–20 cm) under mouldboard plow (MP) and no-till (NT) management and fertilized with 0, 17.5, and 35 kg P ha^?1. Results show that the duration of the growing season had a greater effect on soil microbiota properties than soil tillage or P fertilization at both soil depths. Seasonal fluctuations in soil microbial biomass carbon (SMB-C) and nitrogen (SMB-N), in dehydrogenase and alkaline phosphomonoesterase activities, and in total phospholipids fatty acid (PLFA) level, were greater under NT than MP management. The PLFA biomarkers separated treatments primarily by sampling date and secondly by tillage management, but were not significantly affected by P fertilization. The abundance of arbuscular mycorrhizal fungi (AMF; C16:1ω5) and fungi (C18:2ω6,9) was lower under NT than MP at the 10–20-cm soil depth in July. Phosphorus fertilization increased soil microbial biomass phosphorus (SMB-P) and Mehlich-3 extractable P, but had a limited impact on the other soil properties. In conclusion, soil environmental factors and tillage had a greater effect on microorganisms (biomass and activity) and community structure than P fertilization.     

Tillage and mulch effects on soil physical environment, root growth, nutrient uptake and yield of maize and wheat on an Alfisol in north-west India

Field experiments were conducted for 6 years on a silty clay loam to study the effect of soil management on soil physical properties, root growth, nutrient uptake and yield of rainfed maize (Zea mays L.) and wheat (Triticum aestivum L.) grown in a sequence. Treatments were: no-tillage (NT), NT+pine needle mulch at a rate of 10 t ha⁻¹ (NT+M), conventional tillage (CT), CT+pine needle mulch at a rate of 10 t ha⁻¹ (CT+M) and deep tillage (DT). The soil is classified as a Typic Hapludalf and has compact sub-surface layers. The NT treatment increased the bulk density of the surface layer but this problem was not observed in the no-tilled treatment having mulch at the surface (NT+M). The CT+M and NT+M treatments favourably moderated the hydro-theregime resulting in greater root growth, nutrient uptake and grain yields of maize and wheat. The DT treatment, imposed only once, at the beginning of the study, also enhanced root growth and grain yields. The yields were similar to the mulched treatments for maize and somewhat less than the mulched treatments for wheat. Mulched treatments generally showed significantly greater total uptake of N, P and K than corresponding unmulched ones. Since NT+M was comparable to CT for maize and superior for wheat, the latter is preferable since it does not require ellaborate tillage.     

不同耕作措施对土壤水分和青贮夏玉米水分生产率的影响

适宜的耕作与覆盖措施可在不同程度节约农业用水。本文选用了翻耕处理、燃茬免耕处理和覆盖免耕处理为主要耕作措施,开展了为期2a的田间试验,研究不同措施对农田土壤含水量、土面蒸发、夏玉米生长指标、产量和水分生产率的影响。研究结果表明在降雨较少年份(2010年),覆盖免耕处理0～20cm土壤含水量均高于其他2处理,2a试验期间覆盖免耕处理0～120cm土壤贮水量一直高于其他2处理,且其土面蒸发量最小。2a试验期间,覆盖免耕青贮夏玉米产量较翻耕和燃茬免耕分别提高了11%和9%,青贮夏玉米水分生产率分别提高了11.7%和14.8%。覆盖免耕能减少土面蒸发和提高水分生产率,因此建议在北京地区夏玉米种植采用覆盖免耕措施。     

玉米秸秆还田对盐碱地土壤真菌多样性的影响

为揭示盐碱地秸秆还田改良中土壤真菌群落结构及其多样性变化,以未开垦盐碱地(ZH1)、非盐碱连作玉米田(ZH2)和秸秆还田盐碱玉米田(ZH3)为材料,在玉米吐丝期,利用高通量测序技术与相关生物信息学分析结合,研究表层土壤真菌群落丰富度、多样性和群落结构的变化。结果表明,3个处理土壤真菌群落结构和丰度差异大,已知菌属中ZH1的优势属为马拉色菌,ZH2优势属为暗球腔菌属,ZH3优势属为链格孢属。玉米秸秆还田对盐碱地土壤真菌多样性的影响较大,两年玉米秸秆还田盐碱土壤真菌多样性和物种丰度与未开垦盐碱地比较均有所下降。