玉米丝黑穗病发病条件的研究

试验主要研究土壤温度、湿度及播种期与玉米丝黑病发生的关系。结果表明,土壤温度为21℃,玉米丝黑穗的发病率最高为31.3%,17℃低温下发病率为10.9%～16.7%,温度在24℃时,发病率为3.7%～4.8%。从湿度对发病率的影响看,土壤含水量与病害侵染发病有较明显的关系。土壤湿度为15%时利于孢子萌发与侵染,发病率为31.1%,湿度为10%或20%时发病率仅为3.7%～8.8%,说明干旱与高湿条件下均不利于病菌孢子萌发,湿度是决定发病程度的主导因素。早播病害重,晚播病害轻,但玉米产量低,因此提倡适时播种。     

荔枝霜疫霉游动孢子及卵孢子生物学特性研究

为了更深入理解荔枝霜疫霉在果园内侵染流行规律,利用植物病理学方法,通过离体培养研究了环境因素对荔枝霜疫霉游动孢子释放、萌发及卵孢子萌发的影响。结果表明,在荔枝果肉培养基中,孢子囊萌发的温度等于或小于孢子囊形成的温度时,孢子囊主要以释放游动孢子的方式萌发,28℃是荔枝霜疫霉孢子囊释放游动孢子的临界温度。荔枝霜疫霉在荔枝果肉培养基中,于26℃下培养7 d后,游动孢子释放最适温度范围为12~20℃,最适pH值为5~7;游动孢子萌发的最适温度为20~24℃,最适pH值为7~9;孢子囊在水滴中才释放游动孢子,游动孢子在水滴中方可萌发。荔枝霜疫霉在荔枝果皮和叶片煎汁培养基中均可产生卵孢子。当温度为28℃,pH值为5,12 h光暗交替光照时,卵孢子的萌发率最高,可达到49.68%;温度是影响孢子囊萌发和萌发方式的主要因素,水是游动孢子释放和萌发的必要条件。卵孢子广泛存在于果园中,为翌年初侵染源;荔枝霜疫霉主要以游动孢子再次侵染寄主。     

新疆塔里木盆地覆膜棉田土壤温度变化规律

研究结果表明,覆膜可明显提高土壤温度。膜中土壤温度总是最高,垄沟土壤温度总是最低。土壤浅层温度增加较快且变幅大。不同土层温度呈现＂低-高-低＂的规律性变化：12：00之前,土壤温度较低且变化幅度不大,此后,随着时间的推移,土壤温度逐渐升高,至18：00,达到最高值,为25℃左右,18：00以后土壤温度开始下降。     

油菜菌核病菌子囊孢子对茎叶的直接侵染研究

为了解苗期发生油菜菌核病的致病机理,采用室内人工接种法,研究不同温度、接种浓度、接种方法、添加外源营养物等条件下核盘菌子囊孢子对甘蓝型油菜叶片和茎秆的直接侵染特性。结果表明,核盘菌子囊孢子在温度为10~30℃之间均可萌发,当温度为20~25℃时最适宜孢子萌发和芽管生长;在20~25℃子囊孢子接种油菜无伤或刺伤叶片、茎秆发病率最高;刺伤叶片或茎秆与无伤组织相比有利于子囊孢子侵染;与茎秆相比,子囊孢子更容易侵染油菜叶片;106/m L子囊孢子液及在子囊孢子液中添加2%蔗糖或葡萄糖有利于子囊孢子侵染油菜;用子囊孢子液接种油菜叶片和茎秆,其发病率显著低于菌丝块和带菌花瓣接种。     

依据土壤环境因子对油菜根肿病发生的风险评估

为了解土壤环境因子对根肿病发生的影响,2012年-2013年从我国油菜主产区采集土样12份,在实验室接种根肿菌(Plasmodiophora brassicae)后播种北京新三号(高感白菜品种)。实验结果发现:湖北随州和安徽巢湖土壤样品在根肿菌孢子接种量(按每克土壤中的孢子数量计算)为103接种时发病率达到76.7%;而湖北武昌和阳逻、青海西宁和互助、甘肃民乐等地土样在接种浓度为105时发病率仅为0~3.3%。说明湖北随州和安徽巢湖根肿病发生风险高,湖北阳逻和武昌、青海西宁和互助以及甘肃民乐根肿病发生风险小。土样灭菌后进行接种实验和对土样的理化性质和营养成分进行分析,初步明确在一些土壤中存在土壤生物因子抑制根肿病发生;使用SPSS软件进行路径分析发现,p H、速效钙、全磷、全钾和阳离子交换量(CEC)等因素对根肿病发病率具有抑制作用。     

花生根瘤菌数量效应与种床接种效果

本文报告了土壤中花生根瘤菌的群体数量与适宜接种量及接种方法。指出,在土壤中土著根瘤菌数每克干土>1G~4的情况下,每粒种子接种量不少于10~6活菌数和采用种床接种法是花生增产的有效技术。     

人参根疫病浸染规律的研究

作者探讨疫病菌的卯孢子和游动孢子在侵染人参根疫病侵染循环中的作用。接触侵染是人参根疫病发生的主要途径,试验证明:根疫病发生适宜温度为15—25℃,5℃和30℃根疫病停止发展,最适相对湿度为98％。当参床土壤5cm深的温度达17℃以上,1Ocm深土壤达10℃,土壤水势在200mb以下时,人参根疫病即可发生。     

玉米多堆柄锈菌的生物学特性

根据症状和夏孢子形状、大小和颜色等,将浙江省淳安县等地近年来流行的玉米锈病鉴定为由多堆柄锈菌(Puccinia polysora Underw)引起的玉米多堆锈病.该菌夏孢子发芽最适温度为26℃;夏孢子发芽还必须有水滴和空气.有自然光时夏孢子发芽率最高,其次为黑色和蓝色光,而黄、红、绿色光发芽最少.在适宜条件下,夏孢子经7h发芽率达最高.夏孢子存活期,在-15℃时不到5d,12～20℃时鲜病叶为10d,风干病为15～30d.喷雾毛笔刷、手指涂孢子悬浮液和手指擦干孢子粉4种接种方法的发病率、病情指数均相似.玉米苗期到乳熟期接种的发病率可达98%～100%,发病严重度和病害潜育期随生育期提高而减轻和延长。     

油菜菌核病菌(Sclerotinia sclerotiorum)菌核上寄生真菌研究

调查南方11个省市29个县土壤S.sclerotiorum菌核寄生真菌,分离到Trichoderma virid、T.harzianum、T.hamatum、T.polysporum、Gliocladium catenulatum、Coaiothyrium minitans、Fusarium spp.和Penicillium sp.等种类,以Trichoderma virid为优势种,占分离菌的40％。筛选出的T.virid 7个菌株,每克土壤接种100个孢子,能使90％以上菌核腐烂;在10—30℃温度范围内,温度愈高菌核腐烂愈快。     

油菜菌核病病原菌核的菌丝型萌发特性

近年来,在四川、湖北等地发现苗期油菜菌核病,可能由菌核萌发产生的菌丝侵染油菜茎基部所致。为此对菌核的菌丝型萌发特性进行研究。菌核在水中吸水迅速,2h左右接近饱和,其质量是吸水前的2.10倍。菌核吸水后在4d时开始萌发,11d左右萌发率达到100%。菌核在干燥土壤(-52kPa)萌发率极低,土壤湿度大有利于菌核的菌丝型萌发。菌核龄越小的菌核萌发较早,萌发率较高,9d后菌核的萌发率差异不显著。20.0℃~27.5℃适于菌丝型萌发,温度低于10.0℃和高于30.0℃都不利于菌核菌丝型萌发。pH在3.0~8.0范围内,4d时菌核萌发率随着pH值的增加而降低,pH值为3.0时萌发率最高。田间土壤接种发现,菌核萌发产生的菌丝可侵染油菜茎基部,在初花期引起苗期菌核病,发病率最高可达11.7%。     

Mapping soil micronutrients

Soils vary widely in their micronutrient content and in their ability to supply micronutrients in quantities sufficient for optimal crop growth. Soils deficient in their ability to supply micronutrients to crops are alarmingly widespread across the globe, and this problem is aggravated by the fact that many modern cultivars of major crops are highly sensitive to low micronutrient levels. Original geologic substrate and subsequent geochemical and pedogenic regimes determine total levels of micronutrients in soils. Total levels are rarely indicative of plant availability, however, because availability depends on soil pH, organic matter content, adsorptive surfaces, and other physical, chemical, and biological conditions in the rhizosphere. Micronutrient availability to plants can be measured in direct uptake experiments, or estimated with techniques that correlate quantities of micronutrients extracted chemically from soils to plant uptake and response to micronutrient fertilization. Rational management of micronutrient fertility and toxicity requires an understanding of how total and plant-available soil micronutrients vary across the land. A variety of approaches have been used to survey and map the geographic distribution of soil micronutrient content and availability at scales ranging from global to sites within single production fields. Soil micronutrient maps covering large areas improve our understanding of the nature and extent of micronutrient problems, and aid in determining their relationships with climate, soil properties, and soil genetic characteristics determined at similar scales, for example, Soil Taxonomy to the order, sub-order, or great group levels. Intermediate scale maps can be useful in delineating specific areas where deficiencies or toxicities are likely for agriculture, and in determining localized soil characteristics that may be associated with such problems. Highly detailed maps of soil micronutrient content and availability in individual fields are being developed for site-specific precision agriculture. Soil micronutrient maps have fostered discovery of relationships between soil micronutrient content and availability and some human and livestock health problems such as goiter, Keshan and Kaschin–Beck diseases, and cancer. Advances including the global positioning system (GPS), geographic information systems (GIS), inductively coupled plasma (ICP) spectrometry, geostatistics, and precision agriculture facilitate soil micronutrient mapping and provide quantitative support for decision and policy making to improve agricultural approaches to balanced micronutrient nutrition.     

Predicting soil moisture condition in arbitrary agricultural lands using the digital soil map and soil physical properties database

To predict soil moisture condition in arbitral agricultural lands by taking spatial distribution of soil type in a watershed into account, we investigated the possible proper methods of determining the soil hydrological parameters using available soil physical properties database of Japanese soils, “SolphyJ”, and the digital soil map. In this study, simulation of soil moisture was conducted at three neighboring locations, including monitoring sites each in Toyama and Fukui cities. The simulated results of soil moisture appeared to be improved when hydraulic parameters were obtained by fitting water retention data of SolphyJ compared to the parameters estimated by neural network with soil texture and dry bulk density data. It is probably because peculiar soil structure in each field could affect the hydraulic properties more than the soil texture. Simulation results also indicated that soil moistures are much different even if they are located in neighbors (<5 km). We concluded that combination of these two databases is useful for estimating soil hydraulic parameters and to predict soil moisture condition in arbitrary agricultural lands.     

湘西植烟土壤养分变化趋势分析

通过对比湘西自治州2010年295个与1999年453个植烟土壤样品养分含量,分析养分含量变化趋势,结果表明：湘西州植烟土壤pH值基本没有变化,有机质含量有下降的趋势;大量元素养分全氮、碱解氮、速效磷含量有上升的趋势,全磷含量有下降的趋势,全钾、速效钾变化不明显;中量、微量元素养分,除有效锰含量有下降的趋势外,其他都有升高的趋势。同时速效氮、速效钾含量的平均值随着海拔升高而升高。针对湘西州植烟土壤养分含量特点,建议控氮、稳磷、增钾。     

多环芳烃对土壤线虫和微生物生物量的影响

通过向土壤中添加不同浓度的3种多环芳烃（PAHs）蒽、2-甲基蒽和7,12-二甲基苯并[a]蒽,研究PAHs对土壤微生物生物量碳和土壤线虫的影响。结果表明,土壤微生物生物量碳随PAHs浓度增加而呈指数下降,说明PAHs可抑制土壤微生物活性。土壤线虫总数随PAHs浓度不同而变化,低浓度和高浓度条件下土壤线虫总数增加,中等浓度对土壤线虫总数无影响。土壤线虫中食植物线虫和食细菌线虫占总数的81.8%,PAHs加入后此两类线虫仍占绝对优势,占总数的77.0%-92.8%。但线虫营养类群发生变化,食植物线虫和杂食性线虫比例增高,而食细菌线虫和食真菌线虫比例趋于降低,这主要由PAHs对土壤微生物的影响所致。     

蔗区土壤肥力现状与甘蔗测土配方施肥

本文对南宁市和崇左市蔗区主要土壤养分抽样调查,针对蔗田土壤酸化加重、有机质含量低,有效磷钾含量中等偏低、速效钾后备贮量供给较低的现状,提出蔗田土壤改良、氮磷钾平衡施肥和加大中量元素的开发与应用的建议。     

广西主要蔗区宿根蔗根际土壤微生物群落结构分析

探讨了广西主要蔗区宿根蔗根际土壤微生物的分布情况,结果表明：宿根蔗根际土壤微生物数量总体上表现为：细菌〉真菌〉放线菌。但宜州市和北海市土壤中真菌数量〉放线菌;崇左市土壤中真菌和放线菌相当。     

施用白云石粉对黄红壤 酸度和油菜产量的影响

田间试验结果表明,酸性黄红壤上施用白云石粉显著降低了土壤交互性铝含量和提高了土壤pH值,其 降酸作用与白云石粉用量呈正相关。适当施用白云石粉能够极显著提高油菜产量。白云石粉用量在1 600kg/hm2 时,油菜达到最高产量2 518kg/hm2。此外,施用白云石粉改善了土壤的养分状况,提高了油菜植株的养分含量和 养分吸收量。