Effect of Frequency and Intensity of Defoliation on Oat- Vetch Mixture

An experiment was conducted to evaluate the effect of different cutting regimes on productivity and complementarity between oat and vetch in a mixture. The treatments were allocated in a factorial design on a split-split-plot disposition: they were 3 cutting frequencies (each 35, 70 and 105 days), 3 cutting heights (2, 8 and 14 cm above ground) and 3 crops (oat, vetch and the 1:1 mixture). Forage production (dry matter per hectare) and complementarity between species Relative Yield Total (RYT) were evaluated. The highest forage production (p- 0.05) was obtained with a cutting height of 2 cm and a frequency of 70 days, both in mixture and pure crops. Mixture production was significantly higher than pure stands (p- 0.01) and RYT was higher than unity (p- 0.01) under all defoliation regimens. Defoliation treatments did not modify RYT. In these experimental conditions, cutting frequency and cutting height affected forage production but did not modify complementarity between species

Oat Grazing: Forage Composition and Supplementation Response

Oat forage (Avena sativa), which has low soluble carbohydrates (SC) and high soluble protein (SP) content, can reduce liveweight gain of grazing animals; supplementation with grain and low degradability protein may serve to counteract the effect. A grazing trial was carried out on two soils with different nitrogen (NO3 -) availability, from 16 April 1994 to 6 September 1994. Steers were randomly allocated to 3 treatments: low nitrogen (LN), high nitrogen (HN) and high nitrogen with supplementation (HNS). Forage of LN showed lower SP (p\u3c0.05) during the first month of grazing, and higher SC (p\u3c0.05), than HN during the first two months of the trial. Animal liveweight gain was: 892, 909 and 775 g/an/day for LN, HNS and HN, respectively, with animals in HN of significantly lower liveweight gain (p\u3c0.05). Under the conditions of this trial, animals grazing on oat forage with lower SC and higher SP had lower liveweight gain and responded to supplementation

Fertilización nitrogenada en trigo para la producción de forraje y grano en el sudoeste de la provincia de Buenos Aires (Argentina)

Cuando del cultivo de trigo (Triticum aestivum) se obtiene forraje y grano, i.e.cultivo doble propósito (DP), la disponibilidad de nitrógeno puede ser un aspecto clave para la expansión de esta alternativa. Se comparó la respuesta al N en trigo DP fertilizado en abril (DPF), en agosto (DPG), en ambas fechas(DPFG) y en el cultivo para grano (TC) en un experimento factorial con las dosis de N: 0, 40, 80, 120, y 160 kg ha-1, aplicado como urea al voleo. Se determinó el rendimiento de forraje y de grano y el contenido de N en cada producto.El rendimiento de forraje se incrementó en promedio en 10,3 kg MS kg-1 de Naplicado, hasta la dosis de 120 kg ha-1. El rendimiento de grano fue menor enlos DP, pero tuvo una mayor respuesta a N, incrementándose en 8,3, 7,3, 4,7, y4,7 kg kg-1 de N aplicado para DPG, DPFG, DPF y TC respectivamente. La eficiencia agronómica de la respuesta a N en el rendimiento de grano fue superior en los manejos de DP y estos resultados muestran una mayor conveniencia dela fertilización nitrogenada en estos que en TC

Fertilización nitrogenada en trigo para la producción de forraje y grano en el sudoeste de la provincia de Buenos Aires (Argentina)

Cuando del cultivo de trigo (Triticum aestivum) se obtiene forraje y grano, i.e. cultivo doble propósito (DP), la disponibilidad de nitrógeno puede ser un aspecto clave para la expansión de esta alternativa. Se comparó la respuesta al N en trigo DP fertilizado en abril (DPF), en agosto (DPG), en ambas fechas (DPFG) y en el cultivo para grano (TC) en un experimento factorial con las dosis de N: 0, 40, 80, 120, y 160 kg ha-1, aplicado como urea al voleo. Se determinó el rendimiento de forraje y de grano y el contenido de N en cada producto. El rendimiento de forraje se incrementó en promedio en 10,3 kg MS kg-1 de N aplicado, hasta la dosis de 120 kg ha-1. El rendimiento de grano fue menor en los DP, pero tuvo una mayor respuesta a N, incrementándose en 8,3, 7,3, 4,7, y 4,7 kg kg-1 de N aplicado para DPG, DPFG, DPF y TC respectivamente. La eficiencia agronómica de la respuesta a N en el rendimiento de grano fue superior en los manejos de DP y estos resultados muestran una mayor conveniencia de la fertilización nitrogenada en estos que en TC

Cretaceous and Eocene Rapid Cooling Phases in the Southern Andes (36\ub0\u201337\ub0S): Insights From Low-Temperature Thermochronology, U-Pb Geochronology, and Inverse Thermal Modeling From Domuyo Area, Argentina

The integration of inverse thermal history modeling of new geochronological data with structural analyses from the western flank of the Domuyo volcano ( 3c36\ub030\u2032S) allows us to propose a detailed cooling history of a key region in the Southern Andes. The Domuyo area is located in the northwestern part of the Chos Malal fold-and-thrust belt in the back-arc of the Southern Andes. Despite extensive geological investigations in this region, details about the early stages of Andean deformation remain poorly understood. The present study focuses on the interpretation and integration of new U-Pb, fission track, and (U-Th-Sm)/He data constraining the Cretaceous to Paleogene exhumation history of the Southern Andes at these latitudes. The results indicate two main episodes of rapid cooling during Albian-Campanian and Eocene times that can be related to exhumation driven by two main contractional pulses. The first event promoted basement cooling/exhumation associated with the uplift and erosion of a broad N-S striking antiform; whereas the Eocene episode triggered the inversion of the preexisting N-S striking Manchana Covunco normal fault and the deformation of the Mesozoic sedimentary cover. The two orogenic phases are separated by a potential period of orogenic quiescence during the Paleocene. These new insights highlight the importance of the initial compressional stages of mountain building in the Southern Andes at these latitudes