The role of cattle manure in enhancing on-farm productivity, macro- and micro-nutrient uptake, and profitability of maize in the Guinea savanna

An on-farm trial was conducted in the northern Guinea savanna of Nigeria, over a period of five years, with the objectives of quantifying the effects on maize of applying cattle manure in combination with synthetic fertilizer with regard to soil characteristics, yield, plant nutrition and profitability. Maize grain yield was significantly increased by the annual application of cattle manure, compared to maize receiving an equal amount of N through synthetic fertilizer, but only from the third year of the experiment. The application of manure resulted in higher soil Kjel N, Bray-I P and exchangeable K values, and an increased N utilization efficiency by maize, suggesting that yield-limiting factors other than N deficiencies were of lesser importance than in the treatment receiving sole inorganic fertilizer. Nutrients other than N applied via the manure, particularly P, K and/or B, may have contributed to the higher grain yields in treatments receiving manure. A partial budgeting analysis revealed that, over a 5-year period, investments in the application of manure, in combination with synthetic fertilizer, resulted in higher margins than the application of fertilizer alone. However, analyses of marginal rates of return of changes from low urea N to high urea N or additional manure applications suggested that it was more profitable to invest in additional urea than in organic manure in the first two years of the experiment. The results suggested that manure applications, even when applied at relatively high rates, did not serve as a quick fix to on-farm soil fertility problems, but over a longer period, manure applied in combination with synthetic fertilizers did provide a significant and profitable contribution to enhanced cereal production

Narrowband spectroscopy by all-optical correlation of broadband pulses

High peak power ultrafast lasers are widely used in nonlinear spectroscopy but often limit its spectral resolution because of the broad frequency bandwidth of ultrashort laser pulses. Improving the resolution by achieving spectrally narrow excitation of, or emission from, the resonant medium by means of multi-photon interferences has been the focus of many recent developments in ultrafast spectroscopy. We demonstrate an alternative approach, in which high resolution is exercised by detecting narrow spectral correlations between broadband excitation and emission optical fields. All-optical correlation analysis, easily incorporated into the traditional spectroscopic setup, enables direct, robust and simultaneous detection of multiple narrow resonances with a single femtosecond pulse.Comment: 5 pages, 4 figures, submitted to PR

Effect of light polarization on plasma distribution and filament formation

We show that, for 200 fs light pulses at 790 nm, the formation of filaments is strongly affected by the laser light polarization . Filamentation does not exist for a pure circularly polarized light, propagating in vacuum before focusing in air, while there is no difference for focusing the light in air or vacuum for linearly polarized light.Comment: 4pages 2 figure

EFECTO DE ENMIENDAS ORGANICAS E INORGANICAS SOBRE LAS PROPIEDADES FISICAS Y QUIMICAS DEL SUELO EN AGROECOSISTEMAS DE LA SABANA AFRICANA OCCIDENTAL

Long-term agroecosystem productivity has stirred up the need to develop and implement nutrient management strategies that maintain and protect soil resources. In an attempt to address this, the current study involved the incorporation of residues of Centrosema pascuorum, Lablab purpureus and Parkia biglobosa. In addition, an inorganic fertilizer amended soil and, a maize/Lablab purpureus intercrop, along with the control (no amendment) was included. The treatments were replicated three times and the site had been under continuous cultivation for eight years in a savanna Alfisol. Soil quality (physical and chemical) indicators were examined for treatments effects. Dry macroaggregate turnover increased by 7% under C. pascuorum amended soils. This same treatment had more water-stable large microaggregates and a 40% increase in aggregated silt and clay content. Soil bulk density and saturated hydraulic conductivity reduced in nutrient management practices involving residue incorporation. However, soil organic carbon, total soil nitrogen, exchangeable Ca2+ and Mg2+ concentration were highest with soil receiving C. pascuorum. Crop residue management practices involving incorporation of C. pascuorum significantly improved soil physical and chemical properties of the study area.La productividad a largo plazo de los agroecosistemas ha estimulado el desarrollo e implementación de estrategias de manejo de nutrientes que mantengan y protejan el suelo. Para contribuir a este objetivo, el presente estudio estudio la incorporación de residuos de Centrosema pascuorum, Lablab purpureus y Parkia biglobosa. Adicionalmente se estudió el empleo de fertilizante inorgánico, cultivo intercalado de maíz/Lablab purpureus, y un control. Los tratamientos se aplicaron en un área que había estado en cultivo contínuo por ocho años (Alfisol de savana). Se evaluaron las características físicas y químicas del suelo. El recambio de macroagregados  secos se incrementó 7% en los suelos con adición C. pascuorum. Este mismo tratamiento tuvó mayor cantidad de microagregados hidro-estables y un incremento de 40% en los agregados de arcilla y limo. La densidad del suelo y la conductividad hidraúlica saturada se redujó en las prácticas que involucraban incorporación de residuos. Sin embargo, el carbono orgánico del suelo, nitrógeno total, Ca2+ intercambiable y la concentración de Mg2+ fueron más altos en el suelo que recibió C. pascuorum. La prácticas de manejo de residuos involucrando la incorporación de C. pascuorum mejoraron significativamente las propiedades físicas y químicas del suelo del área de estudio

Resonance fluorescence in ultrafast and intense x-ray free-electron-laser pulses

The spectrum of resonance fluorescence is calculated for a two-level system excited by an intense, ultrashort x-ray pulse made available for instance by free-electron lasers such as the Linac Coherent Light Source. We allow for inner-shell hole decay widths and destruction of the system by further photoionization. This two-level description is employed to model neon cations strongly driven by x rays tuned to the 1s 2p-1 --> 1s-1 2p transition at 848 eV; the x rays induce Rabi oscillations which are so fast that they compete with Ne 1s-hole decay. We predict resonance fluorescence spectra for two different scenarios: first, chaotic pulses based on the self-amplified spontaneous emission principle, like those presently generated at x-ray free-electron-laser facilities and, second, Gaussian pulses which will become available in the foreseeable future with self-seeding techniques. As an example of the exciting opportunities derived from the use of seeding methods, we predict, in spite of above obstacles, the possibility to distinguish at x-ray frequencies a clear signature of Rabi flopping in the spectrum of resonance fluorescence.Comment: 17 pages, 13 figure

Recent visible light and metal free strategies in [2+2] and [4+2] photocycloadditions

When aiming to synthesize molecules with elevated molecular complexity starting from relatively simple starting materials, photochemical transformations represent an open avenue to circumvent analogous multistep procedures. Specifically, light-mediated cycloadditions remain as powerful tools to generate new bonds begotten from non-very intuitive disconnections, that alternative thermal protocols would not offer. In response to the current trend in both industrial and academic research pointing towards green and sustainable processes, several strategies that meet these requirements are currently available in the literature. This Minireview summarizes [2+2] and [4+2] photocycloadditions that do not require the use of metal photocatalysts by means of alternative strategies. It is segmented according to the cycloaddition type in order to give the reader a friendly approach and we primarily focus on the most recent developments in the field carried out using visible light, a general overview of the mechanism in each case is offered as wellFinancial support was provided by the European Research Council (ERC-CoG, Contract Number: 647550), the Spanish Government (RTI2018-095038-B-I00), the ‘Comunidad de Madrid’ and European Structural Funds (S2018/NMT-4367). R. I. R thanks Fundación Carolina for a graduate fellowshi