Balanced Fertilization along with Farmyard Manures Enhances Abundance of Microbial Groups and Their Resistance and Resilience against Heat Stress in a Semi-arid Inceptisol

The impact of long-term (36-year) application of balanced fertilizers and farmyard manures (FYM) on the abundance of microbial groups (bacteria, fungi, actinomycetes, Pseudomonas, Azotobacter, ammonia-oxidizing bacteria) and their resistance and resilience against heat stress was investigated in a semi-arid Inceptisol at New Delhi, India. Surface soils from selected treatments [control, nitrogen (N), N and phosphorus (P), NP and potassium (K), NPK + FYM] under a maize crop were assessed immediately after sampling (0-day) and at 1, 14, 28, and 56 day(s) after heat stress (48 °C for 24 h). The heat stress significantly reduced the microbial groups by 20 to 80%. Recovery after stress was 60 to 100% within 56 days. Resistance and resilience of fungi and actinomycetes were greater than other groups of organisms. Ammonia-oxidizing bacteria (AOB) were found to be most sensitive with the lowest resistance index. Application of NPK + FYM was most effective in enhancing the resistance and resilience of soil microorganisms against heat stress.     

Nonexchangeable Potassium Displacement in Relation to Potassium Availability to Rainfed Maize under Nitrogen Fertilization

A study was conducted to evaluate the effect of nitrogen (N) application, through an easily available and cheap source urea, on potassium (K) displacement and its availability in K-deficient maize-growing soils of rainfed subtropics. The greatest amount of K was displaced (11.22 kg ha^?1) by N application at the rate of 80 kg N ha^?1 (treatment T₄). Amount of N fixed to displace K (11.10 kg ha^?1) was also greatest in the same treatment. Displaced K was positively related to nonexchangeable potassium (NEK) release. Nitrogen application through urea at 80 kg ha^?1 helped not only in meeting N requirement of maize crop in these N-deficient soils but can also satisfy the K requirements (as these soils are low in K) of these soils. Potassium displacement also increased the production efficiency of the maize crop by promoting its relative production efficiency index (RPEI) from suitability class V to class III.     

Nodulation Status and Nitrogenase Activity of Some Legume Tree Species in Bangladesh

Summary

A study was conducted to observe the nodulation status and measure nitrogenase activity of some important legume tree species in nursery. Of the thirteen species surveyed eight belong to Mimoceae, two Papilionaceae and three Caesalpiniaceae. All the species in Mimo-ceae and Papilionaceae were found nodulated whereas all the members of Caesalpiniaceae were non-nodulated. Among nodulated seedlings, highest number of nodules per seedling was recorded in Leucaena leucocephala (82) followed by Acacia auriculiformis (55), Acacia mangium (52), Albizia lebbeck (46), A. procera (41), Dalbergia sissoo (32) and Acacia catechu (29). Nitrogenase activity was highest in L. leucocephla (4913.59 nmole C₂H₄ h^?1) followed by Albizia procera (2080 nmole C₂H₄ h^?1). Seedling height, nodule fresh weight, root fresh weight and nitrogenase activity (per nodule per h, per gram nodule fresh weight per h, per gram root fresh weight per h and per gram root dry weight per h) were also highest in L. leucocephala.     

丙硫克百威生物活性及环境毒理研究进展

介绍了丙硫克百威在环境中的运动、代谢和降解过程，以及近年来对丙硫克百威农药的生物活性及其环境毒理的研究进展。     

PG1和PG6微生物在小麦根际的定殖对植物生长的影响

将对植物生长有促进作用的二个菌群ＰＧ１和ＰＧ６进行分离纯化，首先考察其中的单菌株生态学特性，然后在无菌条件下考察ＰＧ１和ＰＧ６菌群在沙－土试管中在小麦根际的定殖能力，并对根段显微观测以确定其定殖方式和密度及对小麦根形态的影响。同时对ＰＧ１和ＰＧ６微生物抗药标记，考察其温室条件下在土壤中的存活能力及对小麦根际土著细菌数量的影响。     

仓式好氧堆肥中影响有机物发酵降解的主要因素

在实验室条件下进行了仓式好氧堆肥实验,研究了城市有机固体废物堆肥物料种类、温度、含水率、固体颗粒粒度、碳氮比等因素对堆肥过程中有机物降解的影响．实验结果表明最佳堆肥实验条件为：温度40～50℃,含水率50％,粒径30mm,C/N质量比30：1．实验结果显示为了保证仓式好氧堆肥反应的顺利进行,上述几个因素应当被严格地控制在适当范围内．另外,通过正交实验对各影响因素进行了比较,发现在研究的4个主要影响因素中含水率的影响作用最大,C／N质量比其次,温度和物料的粒径所起的影响作用最小、     

不同退化程度“黑土滩”高山嵩草克隆生长特性

对不同退化程度“黑土滩”高山蒿草无性系分株构件和克隆生长进行了研究,结果表明,在一定退化程度下随着无性系面积的增大,高山蒿草营养分株、生殖分株数量及生物量均趋于增大,极度退化的草地中无性系变化无此规律。在轻度、中度和重度退化程度下,随着退化程度的增加,高山蒿草无性系营养分株能力加强,生殖分株能力减弱;极度退化的草地已呈现典型的“黑土滩”景观,高山蒿草的克隆生长维持在最低水平。高山蒿草分蘖节直径伴随着退化程度的加大有增加的趋势,分蘖节距离地面的高度变化不明显。     

作物种类对根际土壤中丁草胺降解的影响

研究了根际和非根际土壤中除草剂丁草胺的降解。结果表明,棉花、水稻、小麦和玉米的种植明显促进丁草胺的降解,15 mg/kg丁草胺的降解半衰期缩短26.6%~57.2%,这种促进作用与作物种类有关,玉米、小麦、水稻、棉花依次增强。50 mg/kg丁草胺的降解有所受抑制,但作物种植仍显示良好的促进作用。作物根际丁草胺降解菌的测定结果显示,根际土壤中丁草胺降解菌的数量大于非根际土壤,作物种植对丁草胺降解的促进作用源于根际丰富的降解菌。     

新型杀螨剂F1050优势降解菌(芽孢杆菌)的筛选及其鉴定

为探明土壤微生物对新农药F1050的降解能力,用平板稀释和富集培养法分离驯化土壤中F1050的优势降解细菌,并用合成培养基进行纯化培养,利用美国Biolog公司的细菌自动鉴定系统,初步筛选出5个菌株:ZJU.01为枯草芽孢杆菌(Bacillus subtilis,69％);ZJU.02为巨大芽孢杆菌(Bacillus megaterium,99％);ZJU.03为腊状芽孢杆菌(Bacillus cereus,86％);ZJU.04为腊状芽孢杆菌(Bacillus cereus,92％);ZJU.05为球形芽孢杆菌(Bacillus sphaericus,99％)。F1050添加浓度为50 mg/kg的液体培养和室内土壤模拟降解试验结果表明,ZJU.02、ZJU.04 和ZJU.05三个优势降解菌株对F1050表现出了较强的降解能力,50 mg/kg F1050的降解半衰期为6.41~6.74 d,而对照的灭菌和未灭菌土壤中的半衰期分别达72.20和29.88 d;不同菌株对F1050的降解能力没有显著差异。