Relationship between readings of chlorophyll meter (Minolta SPAD 502) at differents crop corn stages and grain yield

Existe una estrecha asociación entre el contenido de nitrógeno (N) y clorofila en hojas de maíz. En consecuencia, el estado nutricional del cultivo puede ser evaluado a través de la medición del contenido de clorofila de la hoja. El objetivo de este trabajo fue determinar, durante el ciclo del cultivo de maíz, la relación existente entre las lecturas absolutas del clorofilómetro (Minolta SPAD® 502) y del índice de suficiencia de N (ISN) con el rendimiento en grano. El experimento fue realizado en Balcarce durante las campañas 1995/96 y 1996/97. En 1995/96 fue utilizado el híbrido Dekalb 636, mientras que en 1996/97 se utilizó el híbrido Dekalb 639. En ambos años, el cultivo no estuvo limitado por el abastecimiento de P ni de agua. Los tratamientos consistieron de distintos niveles de N y momentos de fertilización. Las lecturas fueron tomadas semanalmente desde el estadío de seis hojas (V6) hasta 15 días después de la floración. En el primer año se encontró una baja correlación entre los valores absolutos del SPAD al estadío V6 con el rendimiento del cultivo, mientras que en el segundo dicha correlación fue elevada. Sin embargo, en ambos años se observó una alta asociación de los valores SPAD y del ISN luego de V6 con el rendimiento del cultivo. En 1995/96, los valores óptimos para alcanzar el 95 % del rendimiento máximo oscilaron entre 51,5 y 61 unidades SPAD luego de V6, mientras que en 1996/97 los mismos variaron entre 47 y 54 unidades SPAD, para los mismos estadíos fenológicos. Cuando los datos de ambos años fueron analizados el 95 % del rendimiento máximo fue logrado con un ISN de 0,97-0,98. Se concluye que el medidor de clorofila constituye una herramienta apropiada para el monitoreo de la disponibilidad de N, especialmente en estadios avanzados del cultivo.There exists a close association between N content and chlorophyll content, and therefore, crop N status can be evaluated using a chlorophyll meter. The objective of this work was to determine the relationship between corn yield and either absolute readings of a chlorophyll meter (Minolta® SPAD 502) or N sufficiency index (ISN), along crop cycle. The experiment was carried on at Balcarce during 1995/96 and 1996/97, without water or P limitations and with different corn hybrids for each year. Treatments were made at different rates and moments of N fertilization. Chlorophyll meter readings were taken weekly since six-leaf stage (V6) until 15 d after flowering. The correlation between absolute meter readings at V6 and corn yield was low and high for the first and the second year, respectively. However, after V6 and in both years there was a high association between either meter readings after or ISN and crop yield. Threshold meter readings after V6 to get 95% of maximum yield were 51.5- 61 and 57-54 SPAD units for 1995/96 and 1996/97, respectively. For both years, 95% of maximum yield was reached when ISN was between 0.97 and 0.98. It is concluded that the chlorophyll meter is an appropriate tool to check N availability for corn, especially at advanced crop stages.Universidad Nacional de La Plata (UNLP) - Facultad de Ciencias Agrarias y Forestales (FCAF

Relationship between readings of chlorophyll meter (Minolta SPAD 502) at differents crop corn stages and grain yield

Existe una estrecha asociación entre el contenido de nitrógeno (N) y clorofila en hojas de maíz. En consecuencia, el estado nutricional del cultivo puede ser evaluado a través de la medición del contenido de clorofila de la hoja. El objetivo de este trabajo fue determinar, durante el ciclo del cultivo de maíz, la relación existente entre las lecturas absolutas del clorofilómetro (Minolta SPAD® 502) y del índice de suficiencia de N (ISN) con el rendimiento en grano. El experimento fue realizado en Balcarce durante las campañas 1995/96 y 1996/97. En 1995/96 fue utilizado el híbrido Dekalb 636, mientras que en 1996/97 se utilizó el híbrido Dekalb 639. En ambos años, el cultivo no estuvo limitado por el abastecimiento de P ni de agua. Los tratamientos consistieron de distintos niveles de N y momentos de fertilización. Las lecturas fueron tomadas semanalmente desde el estadío de seis hojas (V6) hasta 15 días después de la floración. En el primer año se encontró una baja correlación entre los valores absolutos del SPAD al estadío V6 con el rendimiento del cultivo, mientras que en el segundo dicha correlación fue elevada. Sin embargo, en ambos años se observó una alta asociación de los valores SPAD y del ISN luego de V6 con el rendimiento del cultivo. En 1995/96, los valores óptimos para alcanzar el 95 % del rendimiento máximo oscilaron entre 51,5 y 61 unidades SPAD luego de V6, mientras que en 1996/97 los mismos variaron entre 47 y 54 unidades SPAD, para los mismos estadíos fenológicos. Cuando los datos de ambos años fueron analizados el 95 % del rendimiento máximo fue logrado con un ISN de 0,97-0,98. Se concluye que el medidor de clorofila constituye una herramienta apropiada para el monitoreo de la disponibilidad de N, especialmente en estadios avanzados del cultivo.There exists a close association between N content and chlorophyll content, and therefore, crop N status can be evaluated using a chlorophyll meter. The objective of this work was to determine the relationship between corn yield and either absolute readings of a chlorophyll meter (Minolta® SPAD 502) or N sufficiency index (ISN), along crop cycle. The experiment was carried on at Balcarce during 1995/96 and 1996/97, without water or P limitations and with different corn hybrids for each year. Treatments were made at different rates and moments of N fertilization. Chlorophyll meter readings were taken weekly since six-leaf stage (V6) until 15 d after flowering. The correlation between absolute meter readings at V6 and corn yield was low and high for the first and the second year, respectively. However, after V6 and in both years there was a high association between either meter readings after or ISN and crop yield. Threshold meter readings after V6 to get 95% of maximum yield were 51.5- 61 and 57-54 SPAD units for 1995/96 and 1996/97, respectively. For both years, 95% of maximum yield was reached when ISN was between 0.97 and 0.98. It is concluded that the chlorophyll meter is an appropriate tool to check N availability for corn, especially at advanced crop stages.Universidad Nacional de La Plata (UNLP) - Facultad de Ciencias Agrarias y Forestales (FCAF

Multivector Field Formulation of Hamiltonian Field Theories: Equations and Symmetries

We state the intrinsic form of the Hamiltonian equations of first-order Classical Field theories in three equivalent geometrical ways: using multivector fields, jet fields and connections. Thus, these equations are given in a form similar to that in which the Hamiltonian equations of mechanics are usually given. Then, using multivector fields, we study several aspects of these equations, such as the existence and non-uniqueness of solutions, and the integrability problem. In particular, these problems are analyzed for the case of Hamiltonian systems defined in a submanifold of the multimomentum bundle. Furthermore, the existence of first integrals of these Hamiltonian equations is considered, and the relation between {\sl Cartan-Noether symmetries} and {\sl general symmetries} of the system is discussed. Noether's theorem is also stated in this context, both the ``classical'' version and its generalization to include higher-order Cartan-Noether symmetries. Finally, the equivalence between the Lagrangian and Hamiltonian formalisms is also discussed.Comment: Some minor mistakes are corrected. Bibliography is updated. To be published in J. Phys. A: Mathematical and Genera

Global, Regional, and National Trends of Chagas Disease from 1990 to 2019: Comprehensive Analysis of the Global Burden of Disease Study.

Background Chagas disease (CD) is a neglected tropical disease, endemic in Latin America, but due to migration and environmental changes it has become a global public health issue. Objectives To assess the global prevalence and disability-adjusted life years due to CD using findings from the Global Burden of Disease Study 2019. Methods The Global Burden of Disease data was obtained from the Global Burden of Disease Collaborative Network; results were provided by the Institute for Health Metrics and Evaluation. The prevalence and disability-adjusted life-years (DALYs) were described at a global, regional, and national level, including data from 1990 to 2019. Results Globally, CD prevalence decreased by 11.3% during the study period, from 7,292,889 cases estimated in 1990 to 6,469,283 in 2019. Moreover, the global DALY rate of CD decreased by 23.7% during the evaluated period, from 360,872 in 1990 to 275,377 in 2019. In addition, significant differences in the burden by sex, being men the most affected, age, with the elderly having the highest burden of the disease, and sociodemographic index (SDI), with countries with the lowest SDI values having the highest prevalence of the disease, were observed. Finally, the prevalence trends have followed different patterns according to the region, with a sustained decrease in Latin America, compared to an increasing trend in North America and Europe until 2010. Conclusion The global burden of CD has changed in recent decades, with a sustained decline in the number of cases. Although the majority of cases remain concentrated in Latin America, the increase observed in countries in North America and Europe highlights the importance of screening at-risk populations and raising awareness of this neglected tropical disease

Non-standard connections in classical mechanics

In the jet-bundle description of first-order classical field theories there are some elements, such as the lagrangian energy and the construction of the hamiltonian formalism, which require the prior choice of a connection. Bearing these facts in mind, we analyze the situation in the jet-bundle description of time-dependent classical mechanics. So we prove that this connection-dependence also occurs in this case, although it is usually hidden by the use of the ``natural'' connection given by the trivial bundle structure of the phase spaces in consideration. However, we also prove that this dependence is dynamically irrelevant, except where the dynamical variation of the energy is concerned. In addition, the relationship between first integrals and connections is shown for a large enough class of lagrangians.Comment: 17 pages, Latex fil

Invariant Forms and Automorphisms of Locally Homogeneous Multisymplectic Manifolds

It is shown that the geometry of locally homogeneous multisymplectic manifolds (that is, smooth manifolds equipped with a closed nondegenerate form of degree > 1, which is locally homogeneous of degree k with respect to a local Euler field) is characterized by their automorphisms. Thus, locally homogeneous multisymplectic manifolds extend the family of classical geometries possessing a similar property: symplectic, volume and contact. The proof of the first result relies on the characterization of invariant differential forms with respect to the graded Lie algebra of infinitesimal automorphisms, and on the study of the local properties of Hamiltonian vector fields on locally multisymplectic manifolds. In particular it is proved that the group of multisymplectic diffeomorphisms acts (strongly locally) transitively on the manifold. It is also shown that the graded Lie algebra of infinitesimal automorphisms of a locally homogeneous multisymplectic manifold characterizes their multisymplectic diffeomorphisms.Comment: 25 p.; LaTeX file. The paper has been partially rewritten. Some terminology has been changed. The proof of some theorems and lemmas have been revised. The title and the abstract are slightly modified. An appendix is added. The bibliography is update

Classical field theory on Lie algebroids: Variational aspects

The variational formalism for classical field theories is extended to the setting of Lie algebroids. Given a Lagrangian function we study the problem of finding critical points of the action functional when we restrict the fields to be morphisms of Lie algebroids. In addition to the standard case, our formalism includes as particular examples the case of systems with symmetry (covariant Euler-Poincare and Lagrange Poincare cases), Sigma models or Chern-Simons theories.Comment: Talk deliverd at the 9th International Conference on Differential Geometry and its Applications, Prague, September 2004. References adde

Effect of urease inhibitor and moment of fertilization on corn nitrogen absorption and yield in no-till

La siembra directa puede afectar la eficiencia con que el nitrógeno (N) del fertilizante es utilizado, sobre todo, cuando este es a base de urea. Por ende, el objetivo del presente estudio fue evaluar la absorción de N, acumulación de materia seca y el rendimiento en grano y sus componentes del cultivo de maíz, en función de dosis de N, presencia de un inhibidor de la actividad ureásica como el N-n-butil-triamida tiofosforica (nBTPT), y momento de fertilización. Se evaluaron las dosis de 35, 70, 140 kg N.ha-1, con y sin nBTPT, aplicadas en dos momentos del ciclo del cultivo, a la siembra y al estadío vegetativo de 6 hojas. El aumento en la disponibilidad de N generado por los distintos niveles de fertilización y por la aplicación de N al estadío V6 del cultivo produjeron un aumento significativo en el rendimiento, fundamentalmente a través del número de granos por unidad de superficie. La fertilización en V6 incrementó el rendimiento al aumentar la recuperación de N desde el fertilizante en madurez fisiológica. La recuperación de N desde el fertilizante y el rendimiento del cultivo no se incrementaron cuando la urea fue tratada con nBTPTNo-tillage can affect the use efficiency of N fertilizer, specially when it is urea based. Therefore, the objective of this study was to evaluate the effect of N fertilizer rate, presence of nBTPT and moment application on plant N uptake, plant dry matter accumulation, and grain yield and its components of corn under no-tillage. Treatments were different doses N (35, 70, and 140 kg N.ha-1 as urea), with and without nBTPT, and moment of N application (sowing and V6). The increase of availability due to N and to a moment of fertilization (V6) increased grain yield due to an increase in kernels number per unit area. Fertilization at V6 increased grain yield due to improved N fertilizer recovery at phisiological maturity. Recovery of N fertilizer and grain yield did not increase by urea+nBTPTFacultad de Ciencias Agrarias y Forestale