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Paruelo J.M.,University of Buenos Aires | Pineiro G.,University of Buenos Aires | Baldi G.,National University of San Luis | Baeza S.,University of Montevideo | And 3 more authors.
Rangeland Ecology and Management

Grasslands are one of the most modified biomes on Earth. Land use changes had a large impact on carbon (C) stocks of grasslands. Understanding the impact of land use/land cover changes on C stocks and fluxes is critical to evaluate the potential of rangeland ecosystem as C sinks. In this article we analyze C stocks and fluxes across the environmental gradients of one of the most extensive temperate rangeland areas: the RÃ-o de la Plata Grasslands (RPG) in South America. The analysis summarizes information provided by field studies, remote sensing estimates, and modeling exercises. Average estimates of aboveground net primary production (ANPP) ranged from 240 to 316 g C·m-2·yr-1. Estimates of belowground NPP (BNPP) were more variable than ANPP and ranged from 264 to 568 g C·-2·yr-1. Total Carbon ranged from 5004 to 15008 g C·-2. Plant biomass contribution to Total Carbon averaged 13% and varied from 9.5% to 27% among sites. The largest plant C stock corresponded to belowground biomass. Aboveground green biomass represented less than 7% of the plant C. Soil organic carbon (SOC) was concentrated in the slow and passive compartments of the organic matter. Active soil pool represented only 6.7% of the SOC. The understanding of C dynamics and stocks in the RPG grasslands is still partial and incomplete. Field estimates of ANPP and BNPP are scarce, and they are not based on a common measurement protocol. Remotely sensed techniques have the potential to generate a coherent and spatially explicit database on ANPP. However, more work is needed to improve estimates of the spatial and temporal variability of radiation use efficiency. The absence of a flux tower network restricts the ability to track seasonal changes in C uptake and to understand fine-scale controls of C dynamics. © 2010 Society for Range Management. Source

Sotomayor-Ramirez D.,University of Puerto Rico at Mayaguez | Espinoza Y.,Instituto Nacional Of Investigaciones Agropecuarias
Journal of Agriculture of the University of Puerto Rico

Cultivation affects soil organic matter loss through decreased soil structural stability. Sparse information is available for highly weathered soils. The objective of this study was to evaluate the effects of soil order (Ultisols and Inceptisols) and land use (agriculture and forest) on the formation of water stable aggregates, concentration of aggregate-associated C, and quality of C In aggregates from selected soils in a humid tropical watershed. Ultisols and soils under forest had increased soil C as a result of increased C concentrations in aggregates. Nearly 90% of the soil C was found in macroaggregates of soils under forest and In Ultisols. In forest and agriculture land use, soil silt+clay content was an important determinant for C storage in the bulk soil but not in aggregates. Cultivation reduced the percentage of soil mass in large macroaggregates (>2,000 μm) relative to that in forest soils, whereas Ultisols had greater soil mass percentage in large macroaggregates than Inceptisols. Overall, macroaggregates have higher labile and stable C than microaggregates. Ultisols had greater amounts of labile C but similar proportions of stable C. As has been found in other soils dominated by mixed-mineralogy and 1:1 clays and oxides, aggregate-associated C is not the sole determinant for the formation of macroaggregates. Source

Sundry V.G.,Instituto Naciomnal Of Investigaciones Agricolas | Salazar E.,Instituto Naciomnal Of Investigaciones Agricolas | Dickson L.,Instituto Nacional Of Investigaciones Agropecuarias | Castro L.,Instituto Naciomnal Of Investigaciones Agricolas
Zootecnia Tropical

Cattle Carora breed originated from empiricalcrossing of cattle breeds Criollo Amarillo deQuebarada Arriba and Brown Swiss. Carora is the creole cattle breed that makes the greatestcontribution to local cattle farming economy and itis part of a scarce number of local breeds that formVenezuela’s invaluable genetic patrimony. Theexhaustive knowledge of its genetic characteristicsis indispensable to contribute to its preservation.Main objective of present study was to undertakea genetic characterization, genetic variability determining and establishing of philo genetic relationships with its known ancestors. SinceCriollo Amarillo of Quebrada Arriba is extinct20 samples of closest relative Criollo Limonerowere used among 35 of Carora and 20 BrownSwiss blood samples. 10 DNA molecular markersre commended by FAO/ISAG microsatellites wereused to estimate a number of population genetic variables, test for Hardy and Weinberg, and todetect the formation of genetically distinct groups.Results show that the Carora breed possessesa high genetic variability. Five subtypes wereobserved. It can be concluded that despite of beinga hybrid product of at least two races, Carora cattlehas evolved and developed a proper identity. © 2014, Instituto Nacional de Investigaciones Agricolas (INIA). All rights reserved. Source

Morales-Salinas L.,University of Chile | Acevedo E.,University of Chile | Castellaro G.,University of Chile | Roman-Osorio L.,Instituto Nacional Of Investigaciones Agropecuarias | And 2 more authors.
Ciencia e Investigacion Agraria

In the past 20 years, different areas of research concerning native and exotic species, herbaceous crops and forest plantations have been oriented toward satisfying domestic, industrial and transportation energy requirements. Because bioenergy species constitute an important resource, it would be strategic for a country to have a method for identifying areas suitable for their cultivation to properly incorporate the establishment of energy crops into land use planning. In this study, we sought to define the suitable territories for 16 bioenergy species and their energy potential based on their soil and climate requirements in Central and Southern Chile. We used an adapted version of the FAO EcoCrop database implemented through DIVA-GIS software to predict the crop suitability of different geographical areas, and our results indicate that this method is a simple way to identify land suitable for the establishment of bioenergy species, which is information that can be used in land use planning. Furthermore, spatially explicit regression and ordinary kriging proved to be satisfactory tools for interpolating data from weather station networks through the generation of continuous climatic information grids. Land suitability is presented at a scale of 1:1,000,000 in a continuous digital format expressed in probabilistic terms. © 2015, Cien. Inv. Agr. All Rights Reserved. Source

Barrowclough M.,Virginia Polytechnic Institute and State University | Stehouwer R.,Pennsylvania State University | Alwang J.,Virginia Polytechnic Institute and State University | Barrera Mosquera V.H.,Instituto Nacional Of Investigaciones Agropecuarias | Dominguez J.M.,ESPOL Polytechnic University
Journal of Soil and Water Conservation

Small-scale farming in Ecuador's highlands is associated with excessive soil erosion, degradation of soil health, and agricultural productivity loss. Conservation agriculture (CA) offers promise in these areas. Minimum disruption of soil and maintenance of permanent groundcover, two CA pillars, reduce erosion and can increase soil health and productivity. Despite its promise, CA has not been widely adopted by Andean region farmers, and factors such as uncertainty about CA benefits, risk aversion, and high discount rates have been offered as explanations for lagging adoption. This paper combines an analysis of CA trial data from farmer fields and an analysis of two farm-household surveys to measure potential benefits from adoption and identify correlates of adoption. The analysis reveals actions to promote more widespread adoption of CA. Data are from a unique five-year research project in Bolivar Province, Ecuador. Yield and cost of production data from on-farm trials are used to estimate costs and benefits of CA, household data are used to analyze the determinants of CA adoption, and data from a choice experiment help estimate willingness to pay for CA attributes, such as increased yield and reduced erosion. We find that CA practices yield more and cost slightly less (over five years) than conventional practices, but differences are not large. The adoption analysis shows that farm size and labor access are not associated with adoption, but farmers who perceive soil loss on their farm to be severe are much more likely to adopt. This aversion to soil loss is examined in the choice experiment, which finds that farmers are most interested in economic considerations, such as increasing yields and saving increasingly costly labor. CA holds promise in such systems, but diffusion efforts must be carefully tailored to address farmer needs. Copyright © 2016 Soil and water Conservation Society All right reserved. Source

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