不同还田方式下玉米秸秆腐解规律的研究

利用网袋模拟秸秆还田方式,研究不同还田方式不同阶段玉米秸秆氮、磷、钾养分释放特征。结果表明,经过150 d的分解,玉米秸秆生物量38.9%～66.3%被分解,埋于土壤的玉米秸秆分解速度明显高于露天处理。腐解后玉米秸秆从组织结构上变得松散。经150 d腐解后,玉米秸秆的氮、磷、钾养分释放率分别为51.1%～67.7%、76.0%～89.8%、76.9%～91.7%。     

还田方式对茶树修剪物腐解特征的影响

【目的】研究不同还田方式对茶树修剪物腐解特征的影响,为茶树修剪物的合理还田利用提供科学依据。【方法】试验设置4种还田方式：表层覆盖（T1）、深埋还田（T2）、调节碳氮比（T3）和添加腐解剂（T4）,通过连续培养取样,分析不同还田方式对茶树修剪物周年腐解率、养分释放率、碳氮比和木质素与纤维素比的影响。【结果】T2处理的茶树修剪物50%分解和95%分解所需的时间最短,分别为0.9年和3.5年。与T1相比,T2、T3和T4处理下茶树修剪物腐解率显著加快;腐解试验不同时期内,茶树修剪物腐解率均为T2处理最高,且T2处理360 d腐解率较其他处理提高1.8%～27.5%。腐解360 d后,T2～T4处理下的茶树修剪物碳养分释放率较T1处理显著提高了8.4%～19.6%;各时期的茶树修剪物氮养分释放率在T2处理下最快;腐解30、180、360 d时,T2处理下的茶树修剪物磷养分释放率较快,分别为49.0%、70.3%、85.1%;腐解360 d后,钾养分释放率接近释放完全,各处理的钾养分释放率为92.1%～93.7%。腐解360 d后,4种还田方式下茶树修剪物碳氮比大小依次为T2>T3>...     

不同水肥管理配施腐解剂对小麦秸秆腐解及养分释放的影响

为探寻促进还田秸秆腐解的有效管理措施,以农民常规水肥管理+秸秆还田为对照（CK）,设置常规水肥管理+秸秆还田+腐解剂（CKD）、滴灌+缓控释肥+秸秆还田（SS）、滴灌+缓控释肥+秸秆还田+腐解剂（SSD）、水肥一体+秸秆还田（SF）、水肥一体+秸秆还田+腐解剂（SFD）共5个处理,分析不同水肥管理配施秸秆腐解剂对小麦秸秆腐解率以及养分释放规律的影响。结果表明,（1）各处理秸秆腐解率均表现为前期快后期慢的变化趋势,CKD、SSD、SFD处理的秸秆腐解率在玉米收获期分别比对应的CK、SS、SF处理高2.1、4.4和4.2个百分点,其中SSD与SS处理间、SFD与SF处理间差异均达到显著水平;（2）各处理秸秆养分释放表现为钾>磷>氮,小麦生育期内养分释放规律与秸秆腐解变化趋势一致;SFD处理下的全磷投入量最多,为48.2 kg·hm^-2,而CKD处理下全钾和全氮投入量最高,分别为163.8和67.2 kg·hm^-2;（3）不同处理间, CK在0~20 cm土层的土壤速效养分含量最高,SSD和SFD处理的速效氮含量较对应的SS和SF处理分别增加了27.9%和19.5%,速效磷含量分别提升了42.9%和25.8%;（4）CKD处理的玉米产量最高,为10 387.9 kg·hm^-2,其次为SFD、SF、SSD处理,较CK分别提升了41.5%、31.0%、30.5%和0.8%,除SSD处理外,其余处理均与CK差异显著。综上,添加腐解剂不仅能有效促进小麦秸秆腐解和氮磷钾养分释放,提高玉米产量,还显著增加了水肥优化管理下土壤速效养分的含量,其中以水肥一体+秸秆还田+腐解剂、常规水肥管理+秸秆还田+腐解剂两处理效果最佳。     

水稻种植模式与秸秆还田方式对土壤养分的影响

为探明水稻不同种植模式与还田方式下土壤养分含量的变化。以辽星21号为试验材料,在大田条件下,比较移栽与直播种植2种模式下秸秆还田、炭化还田和不还田3种方式土壤中有机碳、速效氮、速效磷、速效钾、全氮、全磷、全钾含量的差异。研究结果表明,直播种植模式较移栽方式土壤速效磷含量、速效钾含量和全磷含量增加0.9%、5.4%和7.1%,生物炭还田较不还田处理分别显著增加土壤有机碳含量、速效钾含量、全氮含量和全磷含量9.6%、20.1%、5.3%和8.1%。因此,直播种植结合生物炭还田可作为提高农田肥力、改善土壤养分的一项促进北方寒地稻田资源再利用有效措施。     

剑麻麻茎腐解及养分释放特征研究

应用网袋法研究剑麻茎秆在大田条件下的腐解及养分释放特征。结果表明:麻茎在覆土还田后的300 d内,鲜茎、干叶基、鲜叶基的腐解率分别达82.7%、57.9%、34.5%,氮素释放率分别为89.2%、81.3%、34.0%,磷素释放率分别达84.6%、53.8%、32.1%,钾素释放率分别为94.9%、86.5%、34.5%。麻茎还田300 d内,每667 m~2麻茎约释放氮(纯N)、磷(纯P)、钾(纯K)量分别为24.3、6.3、15.2 kg,相当于剑麻年平均施肥量所施入的化学氮、磷、钾肥养分量。麻茎完全腐解约需4年半,麻茎腐解和养分释放速率均表现为前期(30 d)快速而后期缓慢,不同部位顺序为鲜茎干叶基鲜叶基。通过麻茎还田,可以有效降低运输成本,减少肥料用量。     

甘蔗叶不同还田方式对土壤养分的影响

为减轻秸秆焚烧所带来的环境问题和充分利用甘蔗叶资源,在大田环境下动态监测甘蔗叶粉碎、焚烧和深埋3种还田方式对土壤养分的影响。结果表明:甘蔗叶粉碎还田和深埋还田有利于甘蔗叶中有机碳及氮、磷、钾养分的缓慢释放;甘蔗叶焚烧还田提高了土壤碱解氮含量5.6~20.9 mg/kg和速效磷含量0.8~4.0 mg/kg,促进土壤中氮磷向有效态转化,焚烧还田初期显著增加了土壤速效钾的含量12.3~18.3 mg/kg,但焚烧会损失部分甘蔗叶中碳氮元素,也造成环境污染。综合分析认为甘蔗叶粉碎还田是比较省工、方便的处理方式。     

不同秸秆还田方式对黑土土壤氮素和物理性状的影响

通过大田试验对不同秸秆还田方式下黑土农田生态系统土壤氮素和物理性状进行研究。结果表明,不同秸秆还田处理土壤容重降低0.09～0.19 g/cm3;土壤比重增加19.82%～29.49%;土壤总孔隙度增加18.23%～22.26%。过腹还田处理增加土壤全氮含量;秸秆直接还田处理和腐解还田处理土壤全氮含量低于常规栽培方式(对照)和无秸秆处理;不同秸秆还田处理增加了土壤铵态氮和微生物量氮含量;过腹还田处理降低了土壤硝态氮含量,提高了土壤可溶性有机氮含量;秸秆直接还田处理和腐解还田处理增加了土壤硝态氮含量,降低了土壤可溶性有机氮含量。因此,不同秸秆还田方式配施微生物菌剂,结合先进的栽培方式是增加土壤有效氮素的有效途径,有利于退化黑土的可持续利用。     

种植大豆对土壤磷、钾平衡的影响

以5个春大豆品种为材料,采用框栽方法对大豆秸秆还田与不还田时土壤磷、钾的盈亏量进行估算,研究了种植大豆对土壤磷、钾平衡的影响.结果表明:大豆成熟期有57.2％ ～70.1％的磷素、60.7％ ～ 74.7％的钾素转移到籽粒中,磷、钾的收获率较高.在大豆施磷酸氢二铵75 ～ 150 kg·hm-2和硫酸钾40～120 kg·hm-2水平下,土壤磷均有盈余,而土壤钾在施钾量低时亏损,高时盈余.大豆秸秆还田时,磷、钾的盈亏量分别为7.1～22.1 kg·hm-2、-7.6 ～25.6kg·hm-2;秸秆不还田时分别为6.0 ～21.0 kg·hm-2、-14.3 ～18.9 kg·hm-2.大豆秸秆还田时,维持土壤磷、钾平衡的临界磷、钾肥用量为P2O5 18.4 kg·hm-2、K2O 29.2 kg· hm-2;秸秆不还田时,磷、钾肥的临界用量为P2O5 20.9kg· hm-2、K2O 37.3 kg·hm-2.可见,优化肥料施用量和秸秆还田是保障土壤磷、钾素平衡的重要措施.     

石灰对红壤稻田油菜秸秆腐解、养分释放及早稻产量的短期效应

2018年早稻季在典型的酸性红壤双季稻田开展小区试验,探究石灰对红壤稻田油菜秸秆腐解、养分释放及早稻产量的影响。结果表明,施用石灰或油菜秸秆还田均显著提高早稻产量,且二者具有显著的互作效应。施用石灰显著促进了油菜秸秆还田后前中期的腐解和氮素释放,而对磷和钾元素的释放无显著影响。油菜秸秆还田并配施石灰能促进早稻分蘖成穗、地上部养分（氮、磷、钾）吸收及干物质积累,提高总颖花量,从而扩大有效穗数和每穗粒数。可见,在酸性红壤稻田,油菜秸秆还田并配施石灰可加速自身腐解与氮素释放,实现水稻增产。     

稻秆与紫云英协同还田对水稻产量和土壤有机碳的影响

为了阐明有机物料还田的作用和效果，探索合适的秸秆还田方式，为我国农业生态环境的保护和可持续发展提供科学依据，对稻秆和紫云英单独还田和协同还田对水稻产量和土壤有机碳的影响进行了比较分析。结果显示，有机物料与化肥混施不仅能促进土壤微生物分解、提高土壤中碳组分含量，还能为土壤提供新鲜有机物，增加微生物多糖，增强团聚体的稳定性，进而提高水稻产量。稻秆中碳和钾含量丰富、碳氮比值非常高，而紫云英中氮素含量很高、碳氮比值非常低，两者协同还田后能调优碳氮比值的平衡，更有利于作物吸收养分，不仅能提高早稻产量，对晚稻养分的存储也具有一定的后效作用。最后还指出了当前秸秆还田存在的问题，为探索有机物料科学还田方式提供借鉴和参考。     

Comparative Assessment of the Efficacy of Various Nitrogen Fertilizers

Summary

The efficiency of N fertilizers is usually poor; often less than 50% of the applied N is taken up by the crop. This review focuses on various N fertilizers with respect to the significance of different N loss pathways, namely (i) ammonia volatilization, (ii) dinitrogen and nitrogen oxide emissions, and (iii) nitrate leaching. Further, the significance of biological N immobilization, ammonium fixation and, finally, the impact of nitrate vs. ammonium uptake on crop yield are also discussed. The reviewed literature shows that N fertilizers may differ markedly in their susceptibility to losses. There is, however, considerable scope to improve N efficiency of each N source by proper N management practices.     

Studies on natural repellents against potato tuber moth (Phthorimaea operculella Zeller) in country stores

Summary The effects of the leaves of five plant species, one from each of the generaAmbrosia, Anemone, Eupatorium, Eucalyptus andLantana, on potato tuber moth were investigated under indigenous storage conditions at the Central Potato Research Station, Shillong (1800 m above sea level). Their action was compared with that of a biological insecticide (spores ofBacillus thuringiensis), a chemical insecticide (carbaryl), and an untreated control. The data collected after six months storage on tuber damage, sprout damage and the rotting indicated that the leaves ofLantana aculeata provided most protection to the tubers, reducing damage from over 70% in the check to below 5%, and sprout damage from over 45% to below 3%. Next best wasEucalyptus globulus followed byB. thuringiensis. They may be used on tubers stored for table use or for seed as they had no adverse effect on germination or on the yield of a subsequent crop.     

Novel food and non-food uses for sorghum and millets

Sorghum and millets have considerable potential in foods and beverages. As they are gluten-free they are suitable for coeliacs. Sorghum is also a potentially important source of nutraceuticals such antioxidant phenolics and cholesterol-lowering waxes. Cakes, cookies, pasta, a parboiled rice-like product and snack foods have been successfully produced from sorghum and, in some cases, millets. Wheat-free sorghum or millet bread remains the main challenge. Additives such as native and pre-gelatinised starches, hydrocolloids, fat, egg and rye pentosans improve bread quality. However, specific volumes are lower than those for wheat bread or gluten-free breads based on pure starches, and in many cases, breads tend to stale faster. Lager and stout beers with sorghum are brewed commercially. Sorghum's high-starch gelatinisation temperature and low beta-amylase activity remain problems with regard to complete substitution of barley malt with sorghum malt . The role of the sorghum endosperm matrix protein and cell wall components in limiting extract is a research focus. Brewing with millets is still at an experimental stage. Sorghum could be important for bioethanol and other bio-industrial products. Bioethanol research has focused on improving the economics of the process through cultivar selection, method development for low-quality grain and pre-processing to recover valuable by-products. Potential by-products such as the kafirin prolamin proteins and the pericarp wax have potential as bioplastic films and coatings for foods, primarily due to their hydrophobicity.     

In vitro antimicrobial activity of different accessions ofSolanum commersonii Dun. from Uruguay

Summary The in vitro antimicrobial activity of extracts from accessions ofSolanum commersonii Dun. collected in the south of Uruguay was investigated against five microorganisms including the pathogenRalstonia solanacearum. A total of 30 extracts corresponding to organic and aqueous extracts were studied. Interestingly, most of the positive results for growth inhibition were againstR. solanacearum. The extracts were also analyzed for the presence of glycoalkaloids and lectins. Six of the ten aqueous extracts showed lectin presence and a wide variation in the type and amounts of glycoalkaloids, was found. Results indicate that there is no clear relationship between the antimicrobial activity against the five microorganisms screened and the presence or amounts of lectins and glycoalkaloids, traditionally regarded as possible antimicrobial metabolites in theSolanum genus, which indicates the presence of as yet unidentified antimicrobial compounds.     

Extreme resistance to infection by potato virus X in genotypes of wild tuber-bearingSolanum species

Summary Clones derived from thirty-one different accessions (nineteen of Argentine origin) belonging to eightSolanum species were screened for resistance to infection by potato virus X strain cp (PVX cp) by mechanical inoculation of plantlets that had been micropropagated in vitro. Estimates of PVX multiplication obtained by enzyme linked immunosorbent assay and slot blot nucleic acid hybridization allowed the identification of resistant clones derived from five accessions belonging toS. commersonii S. oplocense, S. sparsipilum andS. tuberosum andigena. Resistant genotypes supported PVX concentrations 5 to 15 times smaller than did the susceptible control cultivar Spunta. Graft inoculation test confirmed the presence of extreme resistance similar to that conferred by the ‘immunity’ gene X¹ (also called RX_act).     

Cyanobacteria Secondary Metabolites as Biotechnological Ingredients in Natural Anti-Aging Cosmetics: Potential to Overcome Hyperpigmentation,Loss of Skin Density and UV Radiation-Deleterious Effects

The loss of density and elasticity, the appearance of wrinkles and hyperpigmentation are among the first noticeable signs of skin aging. Beyond UV radiation and oxidative stress, matrix metalloproteinases (MMPs) assume a preponderant role in the process, since their deregulation results in the degradation of most extracellular matrix components. In this survey, four cyanobacteria strains were explored for their capacity to produce secondary metabolites with biotechnological potential for use in anti-aging formulations. Leptolyngbya boryana LEGE 15486 and Cephalothrix lacustris LEGE 15493 from freshwater ecosystems, and Leptolyngbya cf. ectocarpi LEGE 11479 and Nodosilinea nodulosa LEGE 06104 from marine habitats were sequentially extracted with acetone and water, and extracts were analyzed for their toxicity in cell lines with key roles in the skin context (HaCAT, 3T3L1, and hCMEC). The non-toxic extracts were chemically characterized in terms of proteins, carotenoids, phenols, and chlorophyll a, and their anti-aging potential was explored through their ability to scavenge the physiological free radical superoxide anion radical (O₂^•−), to reduce the activity of the MMPs elastase and hyaluronidase, to inhibit tyrosinase and thus avoid melanin production, and to block UV-B radiation (sun protection factor, SPF). Leptolyngbya species stood out for anti-aging purposes: L. boryana LEGE 15486 presented a remarkable SPF of 19 (at 200 µg/mL), being among the best species regarding O₂^•− scavenging, (IC₅₀ = 99.50 µg/mL) and also being able to inhibit tyrosinase (IC₂₅ = 784 µg/mL), proving to be promising against UV-induced skin-aging; L. ectocarpi LEGE 11479 was more efficient in inhibiting MMPs (hyaluronidase, IC₅₀ = 863 µg/mL; elastase, IC₅₀ = 391 µg/mL), thus being the choice to retard dermal density loss. Principal component analysis (PCA) of the data allowed the grouping of extracts into three groups, according to their chemical composition; the correlation of carotenoids and chlorophyll a with MMPs activity (p < 0.01), O₂^•− scavenging with phenolic compounds (p < 0.01), and phycocyanin and allophycocyanin with SPF, pointing to these compounds in particular as responsible for UV-B blockage. This original survey explores, for the first time, the biotechnological potential of these cyanobacteria strains in the field of skin aging, demonstrating the promising, innovative, and multifactorial nature of these microorganisms.     

Marine Pharmacology in 2009–2011: Marine Compounds with Antibacterial,Antidiabetic, Antifungal,Anti-Inflammatory,Antiprotozoal, Antituberculosis,and Antiviral Activities; Affecting the Immune and Nervous Systems,and other Miscellaneous Mechanisms of Action ?

The peer-reviewed marine pharmacology literature from 2009 to 2011 is presented in this review, following the format used in the 1998–2008 reviews of this series. The pharmacology of structurally-characterized compounds isolated from marine animals, algae, fungi and bacteria is discussed in a comprehensive manner. Antibacterial, antifungal, antiprotozoal, antituberculosis, and antiviral pharmacological activities were reported for 102 marine natural products. Additionally, 60 marine compounds were observed to affect the immune and nervous system as well as possess antidiabetic and anti-inflammatory effects. Finally, 68 marine metabolites were shown to interact with a variety of receptors and molecular targets, and thus will probably contribute to multiple pharmacological classes upon further mechanism of action studies. Marine pharmacology during 2009–2011 remained a global enterprise, with researchers from 35 countries, and the United States, contributing to the preclinical pharmacology of 262 marine compounds which are part of the preclinical pharmaceutical pipeline. Continued pharmacological research with marine natural products will contribute to enhance the marine pharmaceutical clinical pipeline, which in 2013 consisted of 17 marine natural products, analogs or derivatives targeting a limited number of disease categories.     

Recent Modifications of Chitosan for Adsorption Applications: A Critical and Systematic Review

Chitosan is considered to be one of the most promising and applicable materials in adsorption applications. The existence of amino and hydroxyl groups in its molecules contributes to many possible adsorption interactions between chitosan and pollutants (dyes, metals, ions, phenols, pharmaceuticals/drugs, pesticides, herbicides, etc.). These functional groups can help in establishing positions for modification. Based on the learning from previously published works in literature, researchers have achieved a modification of chitosan with a number of different functional groups. This work summarizes the published works of the last three years (2012–2014) regarding the modification reactions of chitosans (grafting, cross-linking, etc.) and their application to adsorption of different environmental pollutants (in liquid-phase).