Efeito do fraccionamento da fertilização azotada na cultura da batata

Durante os anos de 1996 a 1998 estudou-se o efeito do fraccionamento da aplicação de azoto na cultura da batata (cv. Desirée). Os ensaios decorreram em Bragança num Cambissolo êutrico. Foram usadas 7 modalidades de fertilização com as seguintes doses de N (fundo + cobertura). 0+0; 200+0; 0÷200; 100÷100; 100+o; 0+100; e 50+50 kg N ha na forma de ureia. Todas as modalidades fertilizadas apresentaram produções unitárias significativamente superiores à modalidade testemunha. Nas modalidades mais produtivas ultrapassaram-se Os 50 Mg ha de tubérculos de calibre comercial

Efficacy and limitations of Triticale as a nitrogen catch crop in a mediterranean environment

During 3 consecutive years (1996/97–1998/99) the efficacy was studied of Triticale as a nitrogen (N) catch crop sown after the harvest of the potato crop cultivated in the preceding summer season under several N fertilizer treatments. In October, shortly after the harvest of the potatoes, there were registered significative differences in the soil N–NO3− levels among N fertilizer treatments of the potato crop. The higher values were recorded on the plots corresponding to higher N doses. At the end of winter, the N status of plants and at the end of experiments (late in April), the N–NO3− in soil, the biomass yield and the N uptake by the catch crop did not reflect the differences registered before in the soil inorganic N. This comparison may suggest that Triticale is little effective in recovering the residual inorganic N of the preceding crop due either to the rainfall occurring in the autumn or to the poor vegetative development of the catch crop during the autumn/winter period. However, at the date of cut, the catch crop removed up to 80 kg N ha−1. At this time, the soil N–NO3− levels were significantly higher on the fallowed plots. This result shows that the crop was very effective in uptaking the N that is mineralized after the end of winter

Efficiency of organic nitrogen fertilization of potato in Northeast Portugal

The study was conducted over a 4 year period with the purpose of measuring N mineralization using an in situ incubation technique, following the application of farmyard manure, poultry manure or municipal solid waste. The results varied from –10 % (net immobilization) to +28 % (net mineralization) in relation to the total organic N applied. N fluxes were assessed through plant N analysis during the growing season and through determination of potato tuber dry weight (TDW), N uptake by tubers and the apparent N recovery (ANR) of added N at harvest. Organic material applications slightly increased TDW above the control treatment (9 to 25%), although the results indicate a shortage of N, where no N was added to the crop. The effect of organic fertilization on N uptake by tubers was also limited. Petiole nitrate concentration and estimated net N mineralization were in agreement with trends in TDW and N uptake by tubers, with no differences in soil N availability between the control and organic treatments. Values of ANR were particularly low, ranging from 4 to 23 %. The results suggest that caution is needed when judging the contribution of organic fertilization to N nutrition of crops, which have a short growing season. Synchronization between N release and plant uptake is discussed

Quantitative sidedress nitrogen recommendations for potatoes based upon crop nutritional indices

The quantification of sidedress N rate from in-season information on crop N nutritional status is extremely important in order to use only the necessary amount of nutrient to achieve maximum yields without significant N losses from soil. During three consecutive years (1996, 1997 and 1998) field N fertilizer experiments with irrigated potato (Solanum tuberosum L., cv. Désirée) were conducted in Bragança (NE Portugal). Eight preplant treatments (0, 50, 100, 200 and 300 kg urea-N/ha and poultry manure, farmyard manure and municipal solid waste in rates equivalent to 100 kg organic-N/ha) were arranged as main plots and five sidedress N rates (0, 25, 50, 100 and 200 kg urea-N/ha) included as subplots. Petiole nitrate concentration, determined by a laboratory method (PNLab, g NO3-N kg−1, dry weight basis) and by the portable RQflex reflectometer (PNRQflex, mg NO3 kg−1, from fresh tissues), and leaf N content (LeafN, g kg−1, dry weight basis) were used as N nutritional indices. From the five sidedress N rates applied over each of the preplant treatments, critical sidedress N rates were estimated for several different crop N nutritional status. This was achieved by establishing exponential asymptotic curves between sidedress N rates and tuber yields and solving the equations for 95% of maximum tuber yield. In a second step, multiple regression equations were established between the estimated critical sidedress N rates (SNrate, kg N/ha), as dependent variable, and each crop N nutritional indices (PNLab, PNRQflex or LeafN) and days after emergence (DAE). The equations obtained are: SNrate = 182.7 − 4.146 × PNLab −1.87 × DAE SNrate = 161.0 − 0.013 × PNRQflex −1.34 × DAE SNrate = 562.2 − 8.416 × LeafN −3.59 × DAE These equations provide quantitative sidedress N rates for any level of crop N nutritional indices and sampling dates from 10 to 48 days after emergence

Eficiência de utilização do azoto pelas plantas

A eficiência com que as plantas absorvem e utilizam o azoto aplicado como fertilizante tem importantes implicações económicas e pode ter consequências adversas na saúde pública e no meio ambiente. Neste trabalho, são considerados os aspectos teóricos relacionados com a eficiência de uso do azoto, designadamente o metabolismo do nutriente e a sua dinâmica nos solos. São também revistos os diferentes métodos de avaliar a eficiência de uso do azoto pelas plantas e descritas as intervenções fitotécnicas susceptíveis de aumentar a percentagem de azoto recuperado. The theoretical aspects related to nitrogen utilization efficiency are considered, namely the plant nitrogen metabolism and the dynamic of the nutrient in soils. The different methods of nitrogen efficiency evaluation and the management techniques to be able to enhance the nitrogen recovery by plants are then outlined

Solid-liquid phase equilibrium of trans-cinnamic acid, p-coumaric acid and ferulic acid in water and organic solvents: Experimental and modelling studies

The solubility of the trans isomers of cinnamic acid, p-coumaric acid and ferulic acid was measured in water and seven organic solvents (methanol, ethanol, 1-propanol, 2-propanol, 2-butanone, ethyl acetate and acetonitrile), at 298.2 K and 313.2 K, using the analytical shake-flask technique. The melting temperatures and enthalpies of the solutes were studied by differential scanning calorimetry, while solute solid structures were identified by powder and single X-ray diffraction. The NRTL-SAC model was applied to calculate the solubility of trans-cinnamic acid and trans-ferulic acid in pure solvents. For trans-p-coumaric acid, the NRTL-SAC was combined with the Reference Solvent Approach, as the solute melting properties could not be determined. The global average relative deviations (ARD) were 32% and 41%, in the correlation and prediction stages, respectively. The Abraham solvation model was also applied. The global ARD were 20% for correlation and 29% for predictions, which can be considered very satisfactory results for these semi-predictive models.This work was developed within the scope of the project CICECO-Aveiro Institute of Materials, UIDB/50011/2020 & UIDP/ 50011/2020, and CIMO-Mountain Research Center, UIDB/00690/ 2020, both financed by national funds through the Portuguese Foundation for Science and Technology/MCTES. We also acknowledge the support of the projects “AIProcMat@N2020 - Advanced Industrial Processes and Materials for a Sustainable Northern Region of Portugal 2020”, with the reference NORTE-01-0145-FEDER- 000006, supported by Norte Portugal Regional Operational Programme (NORTE 2020), under the Portugal 2020 Partnership Agreement, through the European Regional Development Fund (ERDF); and project AllNat - POCI-01-0145-FEDER-030463, funded by the European Regional Development Fund (ERDF) through the Competitiveness and Internationalization Operational Program (COMPETE2020-POCI) and national funding from the Foundation for Science and Technology (FCT, Portugal). S. M. Vilas-Boas thanks the financial support provided by FCT PhD grant (SFRH/BD/138149/ 2018).info:eu-repo/semantics/publishedVersio

Influencia de la distancia de plantación y selección de genotipos de mani (Arachis hypogaea L.) resistentes a Cercosporidium personatum (Berk & Curt.)Deigh. y Puccinia arachidis Speg.

La mancha negra y la roya, causadas respectivamente por los hongos Cercosporidium  personatum y Puccinia arachidis, constituyen las principales enfermedades del maní en el  N.E. brasilero. Buscando contribuir al manejo integrado de esas enfermedades, 15 genotipos de maní  fueron analizados con respecto a los niveles de resistencia bajo condiciones naturales de infección.El diseño se efectuó en bloques completos al azar, con 5 repeticiones. La evaluación fue efectuada a los 85 días después de la siembra, midiendose la incidencia y la severidad de las enfermedades en 45 folíolos por parcela.Los genotipos BR-1, L2IAC2, CNPA Senegal y CNPA 125 AM, se destacaron de los demas al evidenciar los menores niveles de severidad de la mancha negra, mientras en la incidencia de la roya se destacó CNPA Senegal y CNPA Havana. El efecto de los tipos de espacimientos de siembra fueron de 0,3, 0,5 y 0,7 m entre líneas con 5, 10 y 15 plantas/m lineal. Los niveles de severidad de las enfermedades fueron analizados utilizándose el cultivar IAC Tupa.  La evaluación fue efectuada 90 días después de fa siembra, en 45 folíolos de la línea central de cada parcela. Los reslIltados no evidenciaron un efecto significativo de los tipos de espacimientos en la severidad de la mancha negra y de la roya

Bound Chains of Tilted Dipoles in Layered Systems

Ultracold polar molecules in multilayered systems have been experimentally realized very recently. While experiments study these systems almost exclusively through their chemical reactivity, the outlook for creating and manipulating exotic few- and many-body physics in dipolar systems is fascinating. Here we concentrate on few-body states in a multilayered setup. We exploit the geometry of the interlayer potential to calculate the two- and three-body chains with one molecule in each layer. The focus is on dipoles that are aligned at some angle with respect to the layer planes by means of an external eletric field. The binding energy and the spatial structure of the bound states are studied in several different ways using analytical approaches. The results are compared to stochastic variational calculations and very good agreement is found. We conclude that approximations based on harmonic oscillator potentials are accurate even for tilted dipoles when the geometry of the potential landscape is taken into account.Comment: 10 pages, 6 figures. Submitted to Few-body Systems special issue on Critical Stability, revised versio