添加螯合剂对磷酸二铵溶解、固定及转化的影响

【目的】促进磷肥溶解、减少磷素固定是提高磷肥利用率的重要途径。本研究通过向磷酸二铵中添加羟基乙叉二膦酸和葡萄糖酸钠制备磷肥试验产品,研究其溶解和防固定性能及磷素肥际转化特征,为磷肥高效利用提供依据。【方法】选择羟基乙叉二膦酸（HEDP）和葡萄糖酸钠（SG）两种螯合剂,分别按0、0.5%、1%、3%、5%的添加比例与粉状磷酸二铵混匀并挤压造粒,制备出普通磷酸二铵（P）、HEDP_0.5%+P、HEDP_1%+P、HEDP_3%+P、HEDP_5%+P、SG_0.5%+P、SG_1%+P、SG_3%+P和SG_5%+P等9种颗粒磷酸二铵试验产品。分别采用水溶出率法和CaCl₂沉淀法分析比较不同磷酸二铵试验产品的水溶性磷的溶解速率和固定率,并利用土壤培养法研究其肥际移动和转化特征。【结果】（1）添加HEDP和SG的磷酸二铵平均溶解速率较普通磷酸二铵分别提高27.7%和20.0%;HEDP和SG在5%和0.5%添加量时溶解速率最高,分别达5.1%·min^-1和4.8%·min^-1,溶解15 min的溶出率分别为76.6%和72.6%,较普通磷酸二铵提高39.2%和32.6%。（2）添加HEDP和SG,磷酸二铵中水溶性磷固定率分别降低10.3%和6.6%,与普通磷酸二铵相比,HEDP和SG添加量分别为5%和3%时水溶性磷固定率最低,分别为58.1%和61.3%,较普通磷酸二铵降低17.0%和11.8%。（3）HEDP+P和SG+P处理肥际土壤有效磷含量较普通磷酸二铵分别显著提高39.5%和21.2%,以HEDP+P肥际土壤有效磷含量更高。HEDP和SG添加量均在3%时肥际微域有效磷含量最高,分别为2.9和2.5 g·kg^-1,较普通磷酸二铵提高53.3%和31.9%。（4）HEDP+P和SG+P处理肥际微域Ca₂-P含量较普通磷酸二铵分别提高38.2%和43.0%,均在螯合剂添加量为3%时最高;在施肥层上下5 mm肥际微域范围内,HEDP+P和SG+P的处理Ca₈-P含量较P处理分别降低33.6%和14.5%,HEDP和SG添加量分别在0.5%和3%时肥际微域Ca₈-P含量最低,分别为0.9和1.5 g·kg^-1,较P处理分别降低53.4%和25.8%。（5）肥际微域中有效磷和Ca₂-P含量与磷肥的溶解速率显著正相关,与水溶性磷固定率显著负相关（P<0.01）。【结论】添加羟基乙叉二膦酸和葡萄糖酸钠均可促进磷酸二铵溶解,有效减少磷素固定,其中羟基乙叉二膦酸的助溶解及防固定效果更好,且当其添加量为3%时能更显著地提高肥际土壤有效磷含量,并减少Ca₂-P向Ca₈-P的转化。     

施磷对灌耕风沙土磷含量及形态的影响

【目的】探究不同磷肥品种及施用方式对灌耕风沙土磷素形态及有效性的影响,为不同磷肥在土壤中的合理施用提供理论依据。【方法】利用灌耕风沙土进行为期120 d的室内土壤培养试验,试验共设6个处理,分别为不施磷肥对照(CK)、重过磷酸钙基施(TSP)、磷酸一铵基施(MAP-B)、聚磷酸铵基施(APP-B)、磷酸一铵滴施(MAP-D)和聚磷酸铵滴施(APP-D),分别测定不同处理土壤有效磷和各形态无机磷的含量,并分析120 d时土壤有效磷与各形态无机磷含量的相关性。【结果】在0~5 cm土层,磷肥滴施处理（MAP-D、APP-D）的土壤有效磷含量显著高于其他处理;而在5~10和10~20 cm土层,磷肥基施处理（TSP、MAP-B和APP-B）的土壤有效磷含量显著高于其他处理(P<0.05)。与CK和APP-D处理相比,TSP、MAP-B和APP-B处理均显著增加了0~20 cm土层有效磷含量,但这3种磷肥处理间无显著差异。与CK相比,施磷处理均能不同程度地增加各土层土壤无机磷总量。0~5 cm土层MAP-D和APP-D处理无机磷总量显著高于5~10和10~20 cm土层,而TSP、MAP-B和APP-B处理对0~20 cm土层土壤的无机磷总量无显著影响。磷肥滴施处理下,Ca₂-P、Ca₈-P和Al-P的比例随土层深度的增加而降低,而磷肥基施处理能显著提高耕层土壤中Ca₈-P和Al-P的比例。在0~5 cm土层,土壤有效磷含量与Ca₂-P、Ca₈-P、Al-P和Ca₁₀-P含量之间呈显著的正相关关系(P<0.05);在5~10和10~20 cm土层,土壤有效磷含量与Ca₂-P、Al-P和Fe-P含量之间呈显著的正相关关系(P<0.05)。【结论】在本试验土壤条件下,磷肥滴施处理后仅能显著提高0~5 cm土层土壤有效磷含量,而磷肥基施处理可以提高整个耕层（0~20 cm）土壤中的有效磷含量,建议滴灌棉田通过基施价格相对较低的重过磷酸钙,可以人为扩展磷肥在土壤中的分布深度。     

氮素形态对紫花苜蓿盛花期生长及结瘤固氮的影响

在完全营养液条件下,采用砂培法,研究了3种氮素形态配比NO3--N,NH4+-N和NO3--N∶NH4+-N为1∶1和0、105、210mg/L 3个氮素水平对紫花苜蓿盛花期生长及结瘤固氮的影响。结果表明:不同形态氮素处理下紫花苜蓿的株高、生物量、根瘤数、根瘤重、固氮酶活性和全氮含量均显著高于CK。同一氮素水平下,株高表现为NO3--N和NH4+-N混合培养下效果最好,NO3--N培养下次之,NH4+-N培养下最低;生物量、根瘤数、根瘤重、固氮酶活性和全氮含量NO3--N和NH4+-N混合培养下效果最好,NH4+-N培养下次之,NO3--N培养下最低;茎叶比则是NO3--N培养下最大,NH4+-N培养下次之,NO3--N和NH4+-N混合培养下的最低,各氮素形态处理间差异显著(P0.05)。随着氮素水平的增加,各形态配比下紫花苜蓿的株高、生物量、根瘤数、根瘤重、固氮酶活性和全氮含量呈现增加的变化趋势,茎叶比呈现减小的变化趋势。NO3--N+NH4+-N的浓度为210mg/L时,紫花苜蓿的株高、生物量、根瘤数、固氮酶活性和全氮含量取得最大值,茎叶比取得最小值,根瘤重则在NO3--N+NH4+-N的浓度为105mg/L时取得最大值,紫花苜蓿在混合态氮培养下生长最好。     

Renibacterium salmoninarum bar forms: characterization, occurrence, and evidence of a host response to a R. salmoninarum infection

Unique-staining Renibacterium salmoninarum (Rs) cells, termed bar forms, first observed in a coho salmon, Oncorhynchus kisutch (Walbaum), in 1983, could not be cultured, making their characterization difficult and significance obscure. They can be detected only by the fluorescent-antibody technique (FAT) and their numbers estimated only by a quantitative FAT (QFAT). Data collected over a 10-year period showed that bar forms were observed only in vivo and appeared associated with a host response. Bar forms were observed in 10 salmonid species from five countries and in fish from < 1 g to spawning adults. They were observed in 50.1% of kidney smears prepared from 10,061 Rs positive chinook, O. tshawytscha (Walbaum), coho, and Atlantic salmon, Salmo salar L. Bar forms were shown to be Rs cells based on absorption studies, their reaction with an Rs-specific FAT and enzyme-linked immunosorbent assay, and a transition from 'typical' Rs cells to bar forms in naturally and experimentally infected fish. Bar forms were determined to be non-virulent, damaged or dead Rs cells, based on fluorescence and electron microscopy observations, the inability to culture them, and mortality data. Bar forms appeared to represent visual markers of recovery from an Rs infection.     

Characterization of acetylcholinesterase and its molecular forms in organs of five freshwater teleosts

The activity and molecular forms of acetylcholinesterase (AChE, EC 3.1.1.7) were characterized in the brain, heart, white skeletal muscle and liver of the Siberian sturgeon (Acipenser baeri), European eel (Anguilla anguilla), wels (Silurus glanis), common carp (Cyprinus carpio) and silver carp (Hypophthalmichthys molitrix), belonging in four families. The brain had the highest (between 183.2±10.6 and 1361.2±189.7 mU mg^-1 protein and between 4.7±0.4 and 23.5±2.7 U g^-1 wet tissue) and the liver the lowest (between 25.3±1.9 and 126.5±22.7 mU mg^-1 protein and between 1.0±0.1 and 4.5±0.5 U g^-1 wet tissue) activity in all these fish, with the exception of the wels, where the heart contained the smallest amount of AChE (26.2±7.5 mU mg^-1 protein and 1.2±0.3 U g^-1 wet tissue). The highest tissue AChE activity was found in the carp and lowest in the sturgeon. The solubility properties and molecular forms of AChE in the four tissues were studied by extraction in high-salt medium (1.0 M NaCl) with and without the detergent Triton X-100 (0.5%, v/v). The proportions of detergent-soluble (DS) and salt-soluble (SS) forms of AChE varied considerably from one species to another, but a general tendency could be observed: the proportion of DS AChE was generally higher in the brain (between 70.4±4.1 and 82.5±1.2%) and lower in the heart (between 12.0±2.0 and 51.3±2.3%) and skeletal muscle (between 16.0±2.0 and 64.4±0.7%). Velocity sedimentation centrifugation revealed that most tissues contained the G₄ or A₄ form. Three tissues (brain, heart, and liver) of the Siberian sturgeon contained a relatively high proportion of the G1 form (between 24.3±2.4 and 28.6±4.9%), while the skeletal muscle of the wels contained only the most complex type of AChE, i.e., A₁₂. Amongst the tissues studied, the brain and liver mostly contained amphiphilic globular forms of the G₄ type, while the heart and skeletal muscle were rich in asymmetric forms (A₄ and A₁₂). It was concluded that the differences revealed in the activities of AChE and in the distribution of its molecular forms may be connected with the variation in behavioral habits (feeding and swimming patterns), and the developmental stage of the nervous system.     

两种形态蛹虫草菌株子实体及有效成分比较

在蛹虫草资源调查中,发现两种子实体形态迥异的蛹虫草菌株T和G。栽培试验表明,T菌株子实体矮化膨大,G菌株子实体为棒状．两者子实体长度、直径和产量差异显著。有效成分测定结果表明,菌株T和G子实体中粗多糖的含量分别为1．75％,1．77％,虫草酸为2．81％,2．57％,超氧化物歧化酶（SOD）酶活分别为30．43U／mgprotein、53．49U／mgprotein,过氧化物酶（POD）分别为31．26U／mgprotein,33．49U／mgprotein,过氧化氢酶（CAT）分别为126．35U／mgprotein、137．46U／mgprotein。其中,虫草酸含量、SOD酶活两者差异均显著。     

多酶金缓释尿素对土壤氮素形态和含量及油菜产量的影响

采用盆栽试验和室内分析化验相结合的方法,研究了多酶金缓释尿素对油菜田土壤氮素及油菜植株全氮含量、氮肥利用率和土壤氮素依存率的影响。结果表明,多酶金缓释尿素在石灰性褐土中抑制尿素水解显著有效作用时间在油菜移栽后20 d以内,20 d以后多酶金缓释尿素处理的土壤铵态氮、硝态氮和无机氮分别为5.26,9.08,14.34 mg/kg,显著高于多酶金尿素和普尿;多酶金缓释尿素处理的土壤有机氮、全氮和植株全氮比多酶金尿素和普尿分别提高了13.55%,13.67%,9.85%和21.75%,21.82%,19.60%,且差异显著;多酶金缓释尿素处理的氮肥利用率最高,为45.19%,土壤氮素依存率和氮素损失最低,分别为40.13%和1.21 g/盆,而多酶金尿素处理的油菜产量比多酶金缓释尿素和普尿分别提高了5.38%,8.11%,这可能与肥料释放养分特点和油菜生长特性有关。     

池塘网箱清洁养殖对水环境的影响

通过对池塘网箱清洁养殖淡水鱼的水环境进行研究,分析了流水网箱养殖模式对水质、藻类和粪便残留的影响,结果表明,流水浮式网箱养殖模式能够有效地降低淡水鱼养殖水环境中氮、磷以及固形物的含量,同时可以有效地降低粪便的残积速度,进而加速了水环境的净化.说明流水浮式网箱养殖模式是一种先进的现代淡水鱼类养殖模式,并为流水网箱养殖模式的进一步研究和推广提供了参考.     

不同硫浓度下叶面施硒对水稻幼苗镉的亚细胞分布及化学形态的影响

采用水培的方式,通过叶面喷施硒(Se),根部施加硫(S)与镉(Cd),研究了不同硫浓度下叶面施硒对水稻幼苗体内Cd的亚细胞分布和化学形态的影响。结果表明,在不同处理条件下,细胞壁组分所占比例均为Cd10Cd1(Cd10代表浓度为10 mg·L-1的Cd,下同)。随着S的增加以及叶面施Se可溶性组分中Cd的比例有所升高,表明S与Se的供应能促进Cd向液泡转移。NaCl提取态所占比例趋势为S720S48S0、Se500Se0,而乙醇和去离子水等活性较高的提取态所占比例有所下降,说明S的添加以及叶面施Se能够促使Cd向活性较低的提取态转移。然而相对于无S,在高浓度S情况下,施Se并未显著增加Cd在液泡中以及FNaCl提取态的比例,推测S与Se之间相互竞争,从而未产生协同作用。     

Phosphorus utilization in rainbow trout (Oncorhynchus mykiss) fed practical diets and its consequences on effluent phosphorus levels

Excessive dietary phosphorous (P) concentrations in effluents from aquaculture present a major environmental problem. We therefore studied the effect of dietary P and vitamin D₃ on P utilization by rainbow trout-fed practical diets and on P concentrations in the soluble, particulate and settleable components of the effluent from fish tanks. Rainbow trout (average weight: 78 g, initial biomass: 13 kg in 0.7 m³ tanks) were fed for 11 weeks, practical diets that varied in total P, available P, and vitamin D₃ concentrations. Soluble, particulate (10–200 μm) and settleable (>200 μm) P in the effluent were sampled every 0.5–6 h for 1–3 days in the third and eleventh weeks of the experiment. Trout in all diets more than doubled their weight after 11 weeks. Increasing the concentrations of available dietary P from 0.24% to 0.88% modestly enhanced growth rate. Feed conversion ratio (FCR) and biomass gain per gram P consumed decreased as dietary P concentrations increased. Carcass P, daily P gain, and plasma P concentrations were lower in fish fed with low P diets. Soluble P concentrations in the effluent peaked immediately after and again 4–6 h after feeding, and is a linear function of available dietary P. No soluble P would be produced during consumption of diets containing less than 0.22±0.02% available P. Above this dietary concentration, soluble P would be excreted at 6.9±0.4 mg/day/kg for each 0.1% increase in available dietary P. Particulate P concentrations in the effluent were independent of dietary P concentrations. Settleable, presumably fecal, P concentrations tended to increase with dietary P concentrations. In trout fed with low P (0.24% available P, 0.6% total P) diets, 60% of total dietary P were retained by the fish and the remaining 40% were excreted in the effluent as settleable P (20–30%) and particulate or soluble P (10–20%). In trout fed with high P (0.59–0.88% available P; 0.9–1.2% total P) diets, 30–55% of total dietary P was retained by fish, and the remaining 15–25% appeared in the effluent as settleable P, 20–55% as soluble P, and 5–10% as particulate P. Vitamin D₃ did not affect fish growth nor effluent P levels. Physicochemical management of aquaculture effluents should consider the effect of diets on partitioning of effluent P, the peaks of soluble P concentration following feeding, and the contributions of particulate P to total P in the effluent. Increasing our understanding of how dietary P is utilized and is subsequently partitioned in the effluent can contribute significantly towards alleviating this important environmental and industry problem.