Impact of soybean cropping frequency on soil carbon storage in Mollisols and Vertisols

The high cropping frequency of soybean (Glycine max [L.] Merr.), mainly as a single annual crop, in the extensive agricultural systems of South America may adversely affect the soil organic carbon (SOC) storage, which may be different between soils depending on aggregation agents. The aim of this work was to evaluate the impact of the soybean cropping frequency on the SOC storage in different soil aggregate size classes in a Mollisol and in a Vertisol in the Northeastern Pampas of Argentina under no-tillage management. In each soil, the samples were collected at 0-5, 5-15 and 15-30 cm depths in eleven cropped and one uncropped fields. The number of months occupied with soybean in relation to the total number of months occupied with crops within crop sequences, over a 6-year period, was used to calculate the soybean cropping frequency. The SOC stocks in equivalent soil mass, the SOC concentration both in the whole sample and in different aggregate size classes, and the stratification ratio of the SOC stock and of the SOC concentration were determined. The increase in soybean cropping frequency reduced the SOC stock in both soils at 0-5 cm, and in the Vertisol at 5-15 and 0-30 cm but the change was evident only between the cropped and the uncropped situation. A decrease in soybean cropping frequency resulted in a higher amount of macroaggregates (> 250 um), a higher SOC concentration and a higher stratification ratio in the Mollisol at 0-5 cm, whereas in the Vertisol the soybean cropping frequency did not affect the stratification ratio or the aggregate distribution in any size class. The increase in soybean cropping frequency reduced SOC storage only in macroaggregates (> 250 µm) in both soils at 0-5 cm, particularly in the largest macroaggregates (> 2000 µm), and more in the Mollisol than in the Vertisol. Our results show that a high soybean cropping frequency may severely affect the SOC storage in the Mollisol, and suggest that in the Vertisol this effect may lead to a reduction in the SOC storage in the long term.Fil: Novelli, Leonardo Esteban. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Entre Ríos. Estación Experimental Agropecuaria Paraná; ArgentinaFil: Caviglia, Octavio Pedro. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Entre Ríos. Estación Experimental Agropecuaria Paraná; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Entre Ríos; ArgentinaFil: Melchiori, R. J. M.. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Entre Ríos. Estación Experimental Agropecuaria Paraná; Argentin

How digital is agriculture in a subset of countries from South America? Adoption and limitations

Digital agriculture (DA) can contribute solutions to meet an increase in healthy, nutritious, and affordable food demands in an efficient and sustainable way. South America (SA) is one of the main grain and protein producers in the world but the status of DA in the region is unknown. A systematic review and case studies from Brazil, Argentina, Uruguay, and Chile were conducted to address the following objectives: (1) quantify adoption of existing DA technologies, (2) identify limitations for DA adoption; and (3) summarise existing metrics to benchmark DA benefits. Level of DA adoption was led by Brazil and Argentina followed by Uruguay and at a slower rate, Chile. GPS guidance systems, mapping tools, mobile apps and remote sensing were the most adopted DA technologies in SA. The most reported limitations to adoption were technology cost, lack of training, limited number of companies providing services, and unclear benefits from DA. Across the case studies, there was no clear definition of DA. To mitigate some of these limitations, our findings suggest the need for a DA educational curriculum that can fulfill the demand for job skills such as data processing, analysis and interpretation. Regional efforts are needed to standardise these metrics. This will allow stakeholders to design targeted initiatives to promote DA towards sustainability of food production in the region

Could Only Fermions Be Elementary?

In standard Poincare and anti de Sitter SO(2,3) invariant theories, antiparticles are related to negative energy solutions of covariant equations while independent positive energy unitary irreducible representations (UIRs) of the symmetry group are used for describing both a particle and its antiparticle. Such an approach cannot be applied in de Sitter SO(1,4) invariant theory. We argue that it would be more natural to require that (*) one UIR should describe a particle and its antiparticle simultaneously. This would automatically explain the existence of antiparticles and show that a particle and its antiparticle are different states of the same object. If (*) is adopted then among the above groups only the SO(1,4) one can be a candidate for constructing elementary particle theory. It is shown that UIRs of the SO(1,4) group can be interpreted in the framework of (*) and cannot be interpreted in the standard way. By quantizing such UIRs and requiring that the energy should be positive in the Poincare approximation, we conclude that i) elementary particles can be only fermions. It is also shown that ii) C invariance is not exact even in the free massive theory and iii) elementary particles cannot be neutral. This gives a natural explanation of the fact that all observed neutral states are bosons.Comment: The paper is considerably revised and the following results are added: in the SO(1,4) invariant theory i) the C invariance is not exact even for free massive particles; ii) neutral particles cannot be elementar

Interacting entropy-corrected holographic dark energy with apparent horizon as an infrared cutoff

In this work we consider the entropy-corrected version of interacting holographic dark energy (HDE), in the non-flat universe enclosed by apparent horizon. Two corrections of entropy so-called logarithmic 'LEC' and power-law 'PLEC' in HDE model with apparent horizon as an IR-cutoff are studied. The ratio of dark matter to dark energy densities $u$, equation of state parameter $w_D$ and deceleration parameter $q$ are obtained. We show that the cosmic coincidence is satisfied for both interacting models. By studying the effect of interaction in EoS parameter, we see that the phantom divide may be crossed and also find that the interacting models can drive an acceleration expansion at the present and future, while in non-interacting case, this expansion can happen only at the early time. The graphs of deceleration parameter for interacting models, show that the present acceleration expansion is preceded by a sufficiently long period deceleration at past. Moreover, the thermodynamical interpretation of interaction between LECHDE and dark matter is described. We obtain a relation between the interaction term of dark components and thermal fluctuation in a non-flat universe, bounded by the apparent horizon. In limiting case, for ordinary HDE, the relation of interaction term versus thermal fluctuation is also calculated.Comment: 20 pages, 8 figures, figures changed, some Ref. is added, changed some sentences, accepted by General relativity and gravitation (GERG

How digital is agriculture in a subset of countries from South America? Adoption and limitations.

Abstract. Digital agriculture (DA) can contribute solutions to meet an increase in healthy, nutritious, and affordable food demands in an efficient and sustainable way. South America (SA) is one of the main grain and protein producers in the world but the status of DA in the region is unknown. A systematic review and case studies from Brazil, Argentina, Uruguay, and Chile were conducted to address the following objectives: (1) quantify adoption of existing DA technologies, (2) identify limitations for DA adoption; and (3) summarise existing metrics to benchmark DA benefits. Level of DA adoption was led by Brazil and Argentina followed by Uruguay and at a slower rate, Chile. GPS guidance systems, mapping tools, mobile apps and remote sensing were the most adopted DA technologies in SA. The most reported limitations to adoption were technology cost, lack of training, limited number of companies providing services, and unclear benefits from DA. Across the case studies, there was no clear definition of DA. To mitigate some of these limitations, our findings suggest the need for a DA educational curriculum that can fulfill the demand for job skills such as data processing, analysis and interpretation. Regional efforts are needed to standardise these metrics. This will allow stakeholders to design targeted initiatives to promote DA towards sustainability of food production in the region.Special issue

Unifying phantom inflation with late-time acceleration: scalar phantom-non-phantom transition model and generalized holographic dark energy

The unifying approach to early-time and late-time universe based on phantom cosmology is proposed. We consider gravity-scalar system which contains usual potential and scalar coupling function in front of kinetic term. As a result, the possibility of phantom-non-phantom transition appears in such a way that universe could have effectively phantom equation of state at early time as well as at late time. In fact, the oscillating universe may have several phantom and non-phantom phases. As a second model we suggest generalized holographic dark energy where infrared cutoff is identified with combination of FRW parameters: Hubble constant, particle and future horizons, cosmological constant and universe life-time (if finite). Depending on the specific choice of the model the number of interesting effects occur: the possibility to solve the coincidence problem, crossing of phantom divide and unification of early-time inflationary and late-time accelerating phantom universe. The bound for holographic entropy which decreases in phantom era is also discussed.Comment: 13 pages, clarifications/refs added, to match with published versio

Evidence-based Kernels: Fundamental Units of Behavioral Influence

This paper describes evidence-based kernels, fundamental units of behavioral influence that appear to underlie effective prevention and treatment for children, adults, and families. A kernel is a behavior–influence procedure shown through experimental analysis to affect a specific behavior and that is indivisible in the sense that removing any of its components would render it inert. Existing evidence shows that a variety of kernels can influence behavior in context, and some evidence suggests that frequent use or sufficient use of some kernels may produce longer lasting behavioral shifts. The analysis of kernels could contribute to an empirically based theory of behavioral influence, augment existing prevention or treatment efforts, facilitate the dissemination of effective prevention and treatment practices, clarify the active ingredients in existing interventions, and contribute to efficiently developing interventions that are more effective. Kernels involve one or more of the following mechanisms of behavior influence: reinforcement, altering antecedents, changing verbal relational responding, or changing physiological states directly. The paper describes 52 of these kernels, and details practical, theoretical, and research implications, including calling for a national database of kernels that influence human behavior

Fertilización nitrogenada en fechas de siembra tempranas y tardías de maíz

Los cambios en el cultivo, como los nuevos eventos biotecnológicos incorporados han permitido retrasar la fecha de siembra, priorizando mejorar la estabilidad en el rendimiento a expensas de un menor rendimiento potencial. La siembra en fechas tempranas a inicios de la primavera (septiembre-octubre) permiten lograr altos rendimientos (Otegui et al., 1995) y reducir la incidencia de adversidades bióticas con mayor prevalencia en los meses estivales (por ejemplo barrenador del tallo, gusano cogollero y enfermedades como tizón foliar). Sin embargo, las siembras tempranas presentan un mayor riesgo productivo asociado a un mayor desbalance hídrico próximo a floración (Maddonni, 2012), mientras que siembras tardías reducen el riesgo del cultivo dando una mayor estabilidad de rendimientos debido a un balance hídrico más equilibrado (Maddonni, 2012; Mercau y Otegui, 2014). Mientras que la posibilidad de un periodo de barbecho más largo, y una siembra en época con mayores temperaturas incrementa la disponibilidad de N en el suelo para los maíces en siembras tardías, por otra parte, el periodo más crítico del maíz alrededor de floración transcurre en el mes de febrero con niveles decrecientes de radiación solar y temperatura que limitan el rendimiento potencial respecto a siembras tempranas.La disponibilidad de nitrógeno (N) es uno de los factores limitantes en la producción de maíz. En términos generales las recomendaciones para la fertilización nitrogenada para el cultivo en la región pampeana Argentina está relacionada con el N disponible (N de nitratos disponible en el suelo más N de fertilizante) al momento de la siembra, con umbrales que varían entre 137 y 161 kg N ha-1 en el caso de los maíces tempranos (Echeverría y col., 2014). Algunas referencias evaluaron la respuesta a la fertilización con N en maíz tardío (Diaz Valdez et al., 2014), y reportaron menor eficiencia de uso del N (EUN) (Papucci et al., 2016). Adicionalmente, Melchiori et al. (2004) determinaron interacción significativa de fecha de siembra x N, con una mayor respuesta al agregado de N en los maíces tempranos respecto a los de siembra tardía, sin embargo no se dispone de comparaciones de umbrales de N disponible para distintas fechas de siembra. En efecto, debido al menor rendimiento potencial y la mayor disponibilidad de N de las fechas tardías puede esperarse una menor eficiencia de uso del N de fertilizantes. En virtud de esto, es útil generar información sobre la eficiencia agronómica de uso del N (EUNa), complementaria a las recomendaciones de fertilización. En relación con lo planteado, se plantea como objetivo de este trabajo comparar la respuesta en rendimiento al agregado de N, los umbrales de respuesta y la EUNa en fechas de siembras tempranas y tardías de maíz. Los resultados reportados demuestran que los rendimientos promedios del cultivo de maíz fueron menores cuando la fecha de siembra fue retrasada. Aunque no se detectaron diferencias en los umbrales de respuesta a la fertilización, los maíces tempranos presentaron una mayor respuesta al agregado de fertilizante nitrogenado comparado con los maíces tardíos y una mayor EUNa. Finalmente, el amplio set de datos utilizado generado en diversas condiciones ambientales en la región reafirma la utilidad de los umbrales determinados como herramientas de guía para la recomendación de fertilización nitrogenada en maíz.Fil: Pautasso J. M.. Instituto Nacional de Tecnologia Agropecuaria. Centro Regional Entre Rios. Estacion Experimental Agropecuaria Parana. Agencia de Extension Rural Diamante.; ArgentinaFil: Maltese, Nicolás Elías. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Entre Ríos. Estación Experimental Agropecuaria Paraná; ArgentinaFil: Melchiori, R. J. M.. Instituto Nacional de Tecnologia Agropecuaria. Centro Regional Entre Rios. Estacion Experimental Agropecuaria Parana. Agencia de Extension Rural Diamante.; Argentin