Assessment of P availability in heavily fertilized soils using the diffusive gradient in thin films (DGT) technique

Phosphorus-availability tests typically provide an indication of quantity of P available (Colwell bicarbonate-extractable P), or of the intensity of supply (0.01 M CaCl2-extractable P). The soil's capacity to buffer P is more difficult to assess, and is generally estimated using a P-adsorption curve. The diffusive gradient in thin films (DGT) approach may provide a simpler means of assessing a soil's ability to maintain soil solution P. Optimal extraction conditions were found to be 24 h exposure of DGT samplers to saturated soil. The DGT approach was evaluated on a range of 24 soils, some of which had high Colwell- (>100 mu g g(-1)) and Bray 1- (>30 mu g g(-1)) extractable P content, but showed a tomato (Lycopersicon esculentum Mill.) yield response to the addition of P fertilizer. The DGT approach provided an excellent separation of soils on which tomato showed a yield response, from those where fertilizer P did not increase dry-matter yield. Phosphorus accumulation was strongly correlated with soil solution P concentration and anion exchange resin-extractable P, but showed poor correlation with Colwell- or Bray 1-extractable P. The DGT P accumulation rate of 3.62 x 10(-7) to 4.79 x 10(-5) mol s(-1) m(-3) for the soils tested was comparable to the uptake rate of roots of tomato plants that were adequately supplied with P (2.25 x 10(-5) mol s(-1) m(-3)).

不同年限蔬菜温室土壤基本化学性质比较研究

本文对沈阳市郊大民屯镇不同年限蔬菜温室土壤化学性质进行研究与分析。得到主要结论如下： 蔬菜温室0～20 cm表层土壤有机质、全氮、速效磷、速效钾、铵态氮、硝态氮均处于较高的养分水平，并且随温室使用年限的延长，呈增加的趋势。土壤有酸化的趋势，土壤电导率呈升高态势。土壤有效态Fe、Mn、Cu、Zn含量分别为8.57～60.30 mg kg-1、2.69～22.43 mg kg-1、0.64～7.52 mg kg-1和0.56～9.29 mg kg-1，变异系数为50%左右；随着温室使用年限的增加，土壤有效态Fe、Mn、Cu、Zn含量总体上呈增加的趋势。土壤Ni、Cd的有效含量随种植年限的延长趋于增加，有效Pb呈现出下降的趋势，土壤重金属Cr的有效态含量与种植年限之间没有明显的相关性。 不同年限蔬菜温室土壤剖面有机质、全氮、速效磷及速效钾含量高于相邻的露地菜田土壤，并随种植年限的延长而增加，随土层深度的增加而下降。温室土壤中铵态氮的含量随温室种植年限的变化相对较小，在土壤剖面不同层次中变化也没有明显的规律性。与露地菜田土壤相比，温室土壤中有效态铁、锰含量下降，有效态铜、锌、铅、镍含量增加。0～30 cm土层土壤交换性Ca呈下降的趋势，交换性Mg呈上升的趋势，土壤Ca/Mg比值呈下降的趋势。

生姜化感作用机理及其栽培模式研究

近年来，随着对作物重茬（连年种植）障碍原因的深入研究，植物的化感作用越来越受到国内外众多学者的重视。而作为重要调料和药用植物的生姜，其连作障碍也备受关注，系统地研究生姜化感作用将有助于理解和最终解决生姜连作障碍问题。本文通过研究生姜不同部位、不同浓度的水浸液对与其间作的两个物种（大豆和四季葱）种子的萌发及幼苗生长的影响，从而证明生姜化感作用的存在；并通过温室盆栽实验研究了生姜的自毒作用（即研究生姜不同部位、不同浓度的水浸液对其幼苗的形态、生理生化、光合作用、土壤酶、土壤微生物多样性及土壤养分的影响），从而揭示生姜退化和衰老的机制，并为生姜筛选出合适的间作物种提供科学依据，对生姜连作障碍提出科学的解决方法。主要研究结果如下： 1. 与对照相比，生姜所有部位（根茎、茎、叶）、所有浓度（10、20、40、 80 g l-1）的水浸液均抑制了大豆种子和葱籽的萌发率、幼苗生长、水分吸收和脂肪酶活性，并且其抑制程度随着水浸液浓度的增加而增强，其生姜各部位水浸液抑制效应的强弱顺序为茎＞叶＞根茎。这一结果表明生姜根茎、茎、叶含有能够抑制大豆种子和葱籽种子萌发和幼苗生长的水溶性化感物质。根茎是生姜的主要收获部位，而生姜的残株（主要是茎和叶）应该从大田中处理掉以减轻其抑制效应。生姜水浸液中主要化感成分包括：根茎水浸液中主要是丁香酸和伞花内脂；茎水浸液中主要是阿魏酸，且其含量最高为73.4 ug/g；叶水浸液中除了阿魏酸，其他六种物质均检测出来，但含量较高的主要有丁香酸、伞花内脂和香豆酸。 2. 生姜茎和叶不同浓度的水浸液均显著抑制了生姜幼苗的株高、每株叶片数和叶面积，其抑制程度随着水浸液浓度的增加而有所增强，而生姜幼苗每株分枝数差异不显著；同时生姜水浸液也极大程度地影响了生姜幼苗的生物量（包括地下生物量、地上生物量和总生物量，均为鲜重）。在同一浓度下，茎水浸液对生姜幼苗形态指标及生物量指标均显示出最强的抑制作用，叶水浸液次之，根茎水浸液最弱。与对照相比，低浓度的生姜根茎水浸液提高了生姜幼苗叶片内四种抗氧化酶（SOD、POD、CAT、APX）活性，高浓度的根茎水浸液抑制了四种抗氧化酶活性，而茎和叶水浸液均随着浓度的增加而抑制了四种抗氧化酶活性，三种水浸液均随着浓度的增加降低了生姜幼苗叶片内叶绿素的含量，而增加了生姜幼苗叶片的相对电导率和丙二醛含量。同时，三种水浸液均随着浓度的增加降低了生姜幼苗的光合参数（包括胞间CO2浓度、气孔导度、蒸腾速率及净光合速率）。 3. 三种生姜水浸液对所测六种土壤酶活性均产生了不同程度的影响，其中影响最大的是酸性磷酸酶和蔗糖酶，在10 g l-1 时就达到了显著水平，并且所有酶均有随着水浸液浓度增加而增大的趋势；相同部位的水浸液随着浓度的增加，细菌和真菌的数量呈增加趋势，而放线菌的数量呈减少趋势；三种生姜水浸液均随着浓度的增加降低了土壤中有机质的含量，加剧了土壤中硝态氮含量的积累，根茎水浸液对土壤有效磷、速效钾和铵态氮均显示出低浓度提高其含量而高浓度降低其含量的趋势，而茎和叶水浸液则随着浓度的增加均降低了其含量。 4. 与生姜单作相比，所有间作系统均在旺盛生长期和收获期不同程度地提高了土壤酶活性，同时也增加了土壤细菌数量及土壤微生物总数但不显著；所有间作系统在旺盛生长期和收获期均不同程度地影响了土壤真菌及放线菌数量（增加或减少），所有间作系统间的多样性指数差异不显著，除了旺盛生长期四种作物（生姜-大豆-四季葱-大蒜）的间作模式显著降低了多样性指数，其值仅为生姜单作的33.18%；生姜与大豆间作不仅提高了19.6%的生姜产量而且获得了较好的经济效益，并且，所有间作系统均显著抑制了生姜姜瘟病的发生。 5. 不同栽培模式不同程度地影响了收获期生姜的株高、分枝数、根茎产量及内在品质。其中处理2显著地促进了生姜的分枝（10.5%），同时处理2、3和4也促进了生姜的生长（株高分别增加了15.0%、11.4%和14.0%），并且这三个处理提高了生姜的产量；处理2和3能有效提高生姜块茎中维生素C（分别较单作生姜显著提高了3.29%和4.05%）、处理3显著提高了可溶性糖（8.2%）、姜辣素（4.6%）和蛋白质等有益物质的含量，降低硝酸盐有害物质的含量（处理2显著降低了14.0%），改善了姜块的外观和内在品质。并且，生姜与大豆间作具有最高的纯收入和产投比，分别较生姜单作提高了24.80%和8.8%。Recently, allelopathy has been more and more paid attentions by national and foreign scholars with profound research on reasons of crop replanted (continuous planted) obstacle. Ginger rhizome is valuable all over the world either as a spice or herbal medicine and ginger replanted obstacle is also paid attentions. Systematic research on ginger allelopathy will contribute to understanding and ultimate solving problem of ginger replanted obstacle. The effects of ginger aqueous extracts with different parts and concentrations on seed germination and early seedling growth of soybean and chive were studied in this article to testify that ginger existed allelopathy. Furthermore, ginger autotoxicity was also studied by pot experiment in greenhouse (namely research on effects of ginger aqueous extracts with different parts and concentrations on morphological indexes, physiological and biochemical indexes, photosynthesis, soil enzymes, soil microbial diversity and soil nutrients) to reveal mechanism of ginger degeneration and senescence, provide scientific basis for selecting appropriate intercropping species and put forward scientific resolvent for ginger replanted obstacle. The main results were as follows: 1. All aqueous extracts at all concentrations inhibited seed germination, seedling growth, water uptake and lipase activity of soybean and chive compared with the control, and the degree of inhibition increased with the incremental extracts concentration. The degree of toxicity of different ginger plant parts can be classified in order of decreasing inhibition as stem＞leaf＞rhizome. The results of this study suggested that rhizome, stem and leaf of ginger contained water soluble allelochemicals which could inhibit seed germination and seedling growth of soybean and chive. The rhizome is the main harvested part of ginger. The residue (mainly stems and leaves) of the ginger plant should be removed from the field so as to diminish its inhibitory effect. The main allelopathic components of three kind of aqueous extracts were as follows: Rhizome extract chiefly contained syringic acid and vmbelliferone and stem extract mainly contained frulic acid whose content was the highest (73.4 ug/g). The other six substances were detected except of frulic acid, but only contents of syringic acid, vmbelliferone and p-coumaric acid were higher. 2. Stem and leaf aqueous extracts of ginger with different concentrations significantly inhibited plant height, leaf numbers per plant and leaf area, and the degree of inhibition increased with the incremental extracts concentration. However, tiller number per plant of ginger seedling showed no significant difference. At the same time, ginger aqueous extracts also influenced biomass including under-ground biomass, above-ground biomass and total biomass (fresh weight) to a large extent. Under the same concentration, stem aqueous extract showed the mostly inhibitory effect on morphological indexes and biomass indexes of ginger seedling. Rhizome aqueous extract showed the leastly inhibitory effect and leaf aqueous extract was intervenient. Enhanced concentration of ginger aqueous extracts significantly reduced total chlorophyll content, accompanying with increases in memberane permeability (REL) and lipid peroxidation (MDA). Compared with the control, rhizome ginger aqueous extract of lower concentration (10 g l-1) increased the activities of major antioxidant enzymes (superoxide dismutase, SOD; peroxidase, POD; catalase, CAT; ascorbate peroxidase, APX) of ginger leaf tissue and higher concentration inhibited the activities of four antioxidant enzymes. However, stem and leaf aqueous extract inhibited the activities of four antioxidant enzymes with increase in concentration. Meanwhile, enhanced concentration of ginger aqueous extracts significantly reduced photo-parameters of ginger seedling (including CO2 concentration, stoma conductivity, net photosynthesis rate and transpiration rate). 3. Rhizome, stem and leaf ginger aqueous extract showed different effect on six soil enzyme activities, and acid phosphatase and invertase showed significant effect when aqueous extract concentration got 10 g l-1. Furthermore, six soil enzyme activities increased with increase in aqueous extract concentration. Bcterial and fungi number tended to increase while antinomyces tented to decrease with the increase in aqueous extract concentration of identical part. Ginger aqueous extracts reduced soil organic matter content with increased concentration, accompanying with NO3-—N accumulation in soil. Rhizome aqueous extract showed the same tendency for available P, available K and NH4+—N, namely lower concentration increased their contents in soil and higher concentration reduced their contents. While stem and leaf aqueous extracts reduced their contents with the increamental concentration. 4. All intercropping systems increased soil enzyme activities to different extent both at VGS and at HS compared to solo ginger. All intercropping systems increased the colony numbers of soil bacteria and total of soil microbe but not significantly either at VGS or at HS. All intercropping systems increased the colony numbers of soil fungi and actinomytes to a different extent (increase or decrease) both at VGS and at HS. For DI, difference between all cultivation patterns and S-G was not significant either at VGS or at HS except that G-S-C-G whose value was only 33.18% of S-G at VGS significantly decreased. G-S not only increased ginger yield by 19.6% but also obtained better economic benefit. Furthermore, all intercropping systems significantly inhibited occurrence of bacterial wilt of ginger. 5. Different cultivated pattern influenced plant height, tiller numbers, rhizome yields and intrinsic quality of ginger. Treatment 2 significantly facilitated tiller occurring (10.5%). Treatment 2, 3 and 4 promoted ginger growth (plant height respectively increased 15.0%、11.4% and 14.0%) and enhanced rhizome yields. Treatment 2 and 3 effectively increased vitamin C content (significantly increased 3.29% and 4.05% compared to solo ginger). Treatment 3 significantly increased contents of beneficial substances such as soluble sugar (8.2%), gingerols (4.6%) and protein. Treatment 2 significantly decreased contents of deleterious substance namely nitrate (14.0%) and improved appearance and intrinsic quality of ginger rhizome. Furthermore, treatment 2 (ginger/soybean intercropping) could obtain better economic benefit and showed the highest net income and ratio of benefit and cost whose values respectively increased by 24.80% and 8.8% compared to solo ginger.

黄土丘陵区仁用杏园不宜间作沙打旺

在陕北黄土丘陵沟壑区对清耕和问作沙打旺(Astragalus adsurgens)6年、4年、2年仁用杏园0～500cm土层土壤水分、有机质、全氮、全磷、速效氮、速效磷、速效钾含量及树体生长状况进行了测定,结果表明,间作沙打旺,除了在秋季提高了0～100cm土层土壤水分以外,在春季、夏季和秋季均显著降低了0～500cm土层土壤水分,且间作沙打旺年限越长,降低越显著。间作沙打旺提高了0～100cm土层土壤有机质和全氮含量,间作年限越长效果越显著,但对100cm土层以下的土壤有机质和全氮无显著影响。间作沙打旺对土壤全磷含量无显著影响。间作沙打旺显著降低了土壤速效养分含量,其中速效氮降低深度达500cm土层,速效磷、速效钾达300cm土层,且间作年限越长,降低越显著。间作沙打旺显著削弱了树体的长势,降低了坐果率和杏仁产量。间作沙打旺存在着与仁用杏争水争肥的矛盾,黄土丘陵沟壑区仁用杏园不宜间作沙打旺。

宁夏黄土区不同植物群落土地利用方式对土壤质量的影响

本文研究了宁夏南部山区典型植物群落土地不同利用方式下土壤质量的变化。结果表明:(1)典型长芒草群落土地,开垦地比封禁地土壤有机质、全氮、全磷、速效氮、速效磷、速效钾养分含量明显降低,降低幅度分别为19.5%、20.1%、17.6%1、3.0%、77.8%和47.5%。脲酶活性为开垦地>封禁地,蔗糖酶则表现为封禁地>开垦地,中性磷酸酶差异不明显。(2)铁杆蒿群落土地三种利用方式下:放牧地土壤有机质、全氮、全磷、速效钾等养分含量较封禁地与开垦地有一定幅度的增加;放牧地的土壤脲酶、蔗糖酶和中性磷酸酶活性均高于封禁和开垦的同土层土壤,封禁地的脲酶和蔗糖酶次之,开垦地的脲酶和蔗糖酶活性最小,开垦地的中性磷酸酶活性高于封禁地。脲酶活性在土层之间变化较小,最高为放牧地表层177.6 mg/(kg.h),最低为开垦地表下层114.5 mg/(kg.h),蔗糖酶活性层次之间变化明显,其中放牧地表层为表下层的3倍左右。长芒草群落土壤表层各级微团聚体表现为封禁地远大于开垦地,铁杆蒿群落土地不同利用方式下各级微团聚体表现不同,结构系数表现为表层>表下层,保持率则为表层<表下层。结构系数与保持率均表现为封禁地>放牧地>开垦地。(3)在...

High-affinity phosphate/arsenate transport in white lupin (Lupinus albus) is relatively insensitive to phosphate status

<p>The development of proteoid roots under phosphorus deficiency by white lupin (Lupinus albus) may result in increased arsenate uptake, as arsenate is a phosphate analogue. This, together with its high biomass production, rapid growth and ability to survive in soils with low phosphate and nitrogen contents, low pH and high metal contents make them an interesting species to investigate with respect to revegetation, and possibly also for long-term phytoremediation, of arsenic contaminated soils. Kinetic parameters for arsenate uptake for P-deficient and P-sufficient plants, as well as for proteoid and nonproteoid roots were obtained. Down-regulation of arsenate uptake by phosphate, as well as phosphate/arsenate competition for P-deficient and P-sufficient plants was studied. Arsenate uptake was reduced by phosphate, but small differences were found between P-deficient and P-sufficient plants. Arsenate uptake by proteoid roots was higher than for nonproteoid roots of P-deficient plants, with higher V_max and similar K_m values. Down-regulation of the high affinity phosphate/arsenate uptake system by phosphate does take place but seems to be slower than in other plants. This study suggests that the low sensitivity of the phosphate/arsenate uptake system to regulation by phosphate may be related to the adaptations of white lupin to low P available environments. Such adaptation are absent in plants unable to develop proteoid roots.p>

Asociación entre degeneración macular relacionada con la edad y la hipertensión arterial Bogotá 2014

Estudio Casos y Controles 1:1 que busca la relación entre la DMRE e HTA. Se estudian otras variables. Muestra de 400 pacientes, edad promedio 66,9 años +/-9,2 años. HTA y DM OR 2,315 y OR 4,626. Oclusión vascular OR 13,549 (IC 95% 3,023-60,724).

Impacto de las cirugías múltiples, en un solo tiempo quirúrgico, sobre el patrón de marcha en niños con parálisis cerebral

Introducción: La Parálisis Cerebral (PC) es la enfermedad neurológica más incapacitante en niños, su historia natural tiende al deterioro motor y funcional. Con este estudio se busca establecer sí las cirugías múltiples de miembros inferiores, en un tiempo quirúrgico, mantienen el nivel motor y funcional. Material y Método: Estudio analítico de cohortes. Se compara un grupo de pacientes sometidos a cirugías múltiples contra un grupo de pacientes no operados, en el Instituto de Ortopedia Infantil Roosevelt. Se evaluaron los pacientes con dos Laboratorios para el Análisis del Movimiento (LAM) y se midieron los desenlaces mediante el cambio en la puntuación del perfil de marcha (GPS) y el nivel funcional motor grueso (GMFCS). Resultados: 109 pacientes cumplieron con los criterios de selección, 67 pacientes fueron sometidos a cirugía y 42 pacientes no. Los pacientes operados mejoraron el GPS promedio (diferencia -1,94; p=0,002) comparado con los pacientes no operados (diferencia 1,74; p=0,001), indicando una mejoría significativa de la cinemática de la marcha. En un modelo de regresión logística predictivo, el paciente que es operado tiene una probabilidad del 78% de mantener su patrón de marcha, mientras que sí no se opera su probabilidad disminuye al 37%. El nivel funcional motor GMFCS no mostró cambios significativos entre los grupos. Discusión: Las cirugías múltiples de miembros inferiores mantienen de manera significativa el patrón de marcha en pacientes con PC. Se destaca el seguimiento de los pacientes mediante el LAM y se sugiere el uso del GPS para valorar resultados en este tipo de pacientes.

Factores perinatales para riesgo de sobrepeso y obesidad en niños de 4 a 5 años en Colombia 2010.

Introducción: La OMS revela que en 2010 alrededor de 43 millones de niños menores de 5 años presentan sobrepeso. En Colombia según la Encuesta Nacional de Situación Nutricional en Colombia en su versión 2005, mostraba una prevalencia general de sobrepeso de 3.1% niños de 0 a 4 años. Es una condición de salud de origen multifactorial en la que interviene factores genéticos, ambientales, maternos y perinatales. Objetivo: Establecer la asociación de riesgo entre el bajo peso al nacer y el desarrollo de sobrepeso y obesidad en niños de 4 a 5 años. Metodología: Se realizó un estudio observacional descriptivo retrospectivo de corte transversal con los datos nutricionales, maternos y perinatales de la Encuesta Nacional de Demografía en Salud del año 2010 en Colombia. Se analizó la asociación entre la variable independiente bajo peso al nacer con el desenlace sobrepeso y obesidad en menores de 4 a 5 años, usando como medida el IMC según la edad. Se realizaron análisis univariados, bivariados y de regresión logística con un modelo de riesgo según las variables que inciden en el desenlace y la variable independiente. Resultados: La muestra obtenida para el estudio fue de 2166 niños de 4 a 5 años de edad quienes cumplían los criterios de inclusión. La prevalencia de sobrepeso u obesidad en la primera infancia fue de 21.8% (472) y el bajo peso al nacer. Los resultados sugieren la asociación de bajo peso y sobrepeso u obesidad es de ORajustado= 0.560 (0.356 – 0.881). Conclusiones: Los resultados sugieren que existe una asociación como factor protector entre el bajo peso y el sobrepeso u obesidad en la primera infancia. Sin embargo, debido al comportamiento de las variables consideradas en la muestra no hay suficiente información para rechazar completamente la hipótesis nula.

Phosphorus sorption and availability in soils amended with animal manures and sewage sludge

Soils that receive large applications of animal wastes and sewage sludge are vulnerable to releasing environmentally significant concentrations of dissolved P available to subsurface flow owing to the gradual saturation of the soil's P sorption capacity. This study evaluated P sorption (calculated from Langmuir isotherms) and availability of P (as CaCl2-P and resin P) in soils incubated for 20 d with poultry litter, poultry manure, cattle slurry, municipal sewage sludge, or KH2PO4, added on a P-equivalent basis (100 mg P kg(-1)). All the P sources had a marked negative effect on P sorption and a positive effect on P availability in all soils. In the cattle slurry- and KH2PO4- treated soils, the decreases in P sorption maximum (19-66%) and binding energy (25-89%) were consistently larger than the corresponding decreases (7-41% and 11-30%) in poultry litter-, poultry manure-, and sewage sludge-treated soils. The effects of cattle slurry and KH2PO4 on P availability were, in most cases, larger than those of the other P sources. In the poultry litter, poultry manure, and sewage sludge treatments, the increase in soil solution P was inversely related (R-2 = 0.75) to the input of Ca from these relatively high Ca (13.5-42 g kg(-1)) sources. Correlation analyses implied that the magnitude of the changes in P sorption and availability was not related to the water-extractable P content of the P sources. Future research on the sustainable application of organic wastes to agricultural soils needs to consider the non-P- as well as P-containing components of the waste.

Substitution of corn and soybean oil by cassava meal and African palm tree oil in diets of laying hens

Fourty-two White Leghorns laying hens, from the commercial Cuban hybrid L-33, were used for eight weeks during the laying peak (36 to 43 weeks of age), to assess the substitution of corn by cassava root meal (Manihot esculenta Crantz) and the crude soybean oil by crude oil of African palm tree (Elaeis guineensis J.) in the diets of laying hens. Analysis of variance was conducted, according to simple classification design, with three treatments and 14 repetitions (a cage with a hen). The treatments consisted of three diets (1- corn meal + soybean oil; 2- 25 % cassava meal + African palm tree oil; 3- 53 % cassava meal + African palm tree oil), with 15.71 % CP; 3.83 % Ca and 0.36 % P available. The viability was of 100 % in all treatments. No differences were found for laying (92.21, 92.09 and 91.59 %), which surpassed the potential of this hybrid during the laying peak (90 %), conversion (118g feedstuff/egg in the three treatments), egg mass produced (3066, 3114 and 3071 g/bird) and mass conversion (1.99, 1.95 y 1.98 feed consumed/egg mass). The pigmentation of the egg yolk was reduced as the level of cassava meal increased in the diets (6, 4 and 3 at Roche's scale), as well as the cost of the feed consumed in 56 d per hen (2.56, 2.15 and 1.83 USD/bird). The possibility of substituting, totally, corn meal by that of cassava and soybean oil by that of the African palm tree in the diets of laying hens during the laying peak was determined, with positive economic effect and without damaging the productive performance of birds.

Adsorção e disponibilidade de fósforo para o crescimento inicial de mamoneira em solos com diferentes classes texturais

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Níveis de cálcio, fósforo, lipídeo e proteína na dieta inerte do camarão-da-malásia Macrobrachium rosenbergii, na fase larval

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Phosphorus components, CaCO3 and biogenic opal in sediments from ODP Leg 167 sites

The ocean history of reactive phosphorus (P) (i.e., dissolved P available to fuel oceanic primary productivity) is of interest because of the role of P as a biolimiting nutrient, and knowledge of P burial in marine sediments is key to testing hypotheses about temporal changes in P input or output fluxes. Our understanding of the history of the P cycle over the Cenozoic has increased substantially with temporal records of reactive P mass accumulation rates from open-ocean Pacific and Atlantic equatorial sites. However, questions about the relative importance of nutrient burial in ocean-margin sediments relative to burial in open-ocean sediments and about the extent of P remobilization in organic-rich, reducing environments characteristic of margin sediments remain unresolved. Nutrient burial in oceanic boundary current systems has been suggested to have a controlling role in oceanic nutrient budgets in certain time intervals (Vincent and Berger, 1985, doi:10.1029/GM032p0455), with higher sediment accumulation rates balancing the limited spatial extent of these sediments. Some investigators suggest that remobilization of P from reducing sediments in margin settings is a significant positive feedback to primary productivity (e.g., Van Cappellan and Ingall, 1994, doi:10.1029/94PA01455), whereas other results indicate that both P uptake and P release may occur in these settings depending on the balance of organic carbon and iron supply to the sediments and on the oxygenation of bottom waters (McManus et al., 1997, doi:10.1016/S0016-7037(97)00138-5). It is important to quantitatively understand the geochemistry of reactive P in margin sediments, where productivity and delivery of organic-rich material to the sediments in relatively shallow-water settings is often sufficient to promote anoxia in interstitial waters. To address these questions, we determined the P concentrations and geochemistry in sediment samples from eight sites drilled during Ocean Drilling Program (ODP) Leg 167, California margin (Sites 1010-1012, 1014, 1016-1017, and 1021-1022). These results are the first records of reactive P concentrations on long time scales-required for the calculation of P accumulation rates-for sediments from a highly productive eastern boundary current setting. In addition, we determined calcium carbonate contents and biogenic silica concentrations to define the environments of sedimentary production, burial, and diagenesis.

Métodos de extração de fósforo e micronutrientes em latossolos com uso de energia ultrassônica

Assessing the soil nutrient availability to plants under lab conditions is one of the main challenges to Soil Fertility and Chemistry, due to the complex behavior and the interaction of the soil properties. Many extractant solutions associated with mechanical forms of agitation have been proposed, showing different correlations with plant growth and nutrients absorption. Using ultrasonic energy is a agitation procedure of the soil:extractant solution suspension (based on the cavitation phenomenon). It allows the establishment of relations between the amount of extracted nutrient and the ultrasonic energy level. Thus, this work aims: to evaluate the effect of cavitation intensity on the extraction of P, Zn, Cu, Mn and Fe in soil samples from five Latosols under different uses around Uberlândia and Uberaba, Minas Gerais State; to obtain extracting curves as function of ultrasonic energy levels; and to obtain an index from extracting curves to expresses the nutrient retention by the soil solid phase. A soil-solution suspension (ratio 1:10) was sonicated using a probe ultrasound equipment under different combinations of power and time: i) 30 W for 35, 70, 140 and 280 s; ii) 50 W for 21, 42, 84 and 168 s; and iii) 70 W for 15, 30, 60 and 120 s. The extractant solutions used were Mehlich-1 (for all elements), Olsen and distilled water for P. After each sonication, P concentration was quantified by molybdenum blue colorimetric method and Zn, Cu, Mn and Fe by flame atomic absorption spectrophotometry. The cavitation intensity did not affect the P extraction, only the total energy applied. The P extraction was influenced by extractant solution, decreasing as follows: Mehlich-1>Olsen>water. In cultivated Latosols, the P extraction increased linearly with ultrasonic energy, and the slope of the 1:1 linear regression reflects the P retention in the soil. The Zn and Fe extractions were influenced only by total energy applied. Mn and Cu extractions were influenced by both cavitation intensity and total ultrasonic energy. Soils containing similar amounts of P, Cu, Zn, Mn, and Fe may have a different extraction rate. Likewise, soils containing different amounts of those elements may have the same extraction rate.