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Showing items 1 through 9 of 74.-
Library ResourceReports & ResearchDecember, 1988Ecuador, Bolivia, Peru, Brazil, Guatemala, South America, Central America
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Library ResourceReports & ResearchDecember, 1983Ecuador, Bolivia, Peru, Brazil, Guatemala, South America, Central America
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Library ResourceJournal Articles & BooksDecember, 1995Brazil, Central America, South America
Numbers of plant species and individuals were examined relative to land use in an agricultural settlement in the Brasilian Amazon. Land uses were forest, cropped after forest, fallows, cropped after fallow, and pasture. These uses corresponded roughly to farmers` land use changes over time. As expected, species diversity was high in forest. Diversity was also high, however, in fallows of 3-5 years--as a result of both survival/reestablishment of forest species and appearance of plants not found in forest.
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Library ResourceJournal Articles & BooksDecember, 1999Brazil, Central America, South America
We examined whole-soil samples and particle-size fractions to study the distribution of different phosphorus (P) fractions after land-use change from native savanna to crops, pasture, and reforestation on clayey and loamy Oxisols of the Brazilian savannas. Phosphorus was extracted sequentially, according to a modified Hedley procedure, into inorganic and organic P (NaOH-extractable Pi and Po, respectively), and recalcitrant P (P HCl and P res). Under natural conditions of strong P deficiency, over 60% of NaOH-extractable P was organic, reflecting the high contribution of P.
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Library ResourceJournal Articles & BooksDecember, 1999Brazil
This study assessed the influence of land use (continuous cropping, CC; tree plantations, F; pasture, PG; and native savanna, NS) on P concentrations and partitioning in bulk soil and two aggregate size fractions of two Oxisols, one loamy and one clayey. The quantity and quality of physically protected P within aggregates were also determined. Total P in bulk soil and macroaggregates (0.25-2 mm and 2-8 mm) was partitioned into inorganic and organic P fractions (P, and P., respectively) after sequential extraction, using NaHCO, (Olsen), NaOH, HCl, and H2SO4 (residual).
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Library ResourceReports & ResearchDecember, 1996Colombia, Ecuador, Peru, Brazil, Honduras, Nicaragua, South America, Central America
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Library ResourceJournal Articles & BooksDecember, 1999Brazil, Central America, South America
In the Brazilian savannas, or Cerrados the rapid advance in agriculture and cattle ranching is affecting soils through, for example, accelerated erosion and depletion of soil organic matter (SOM). Changes in soil microbial biomass are good indicators of changes in SOM. We therefore assessed the effects of agricultural and pastoral use of a clayey Oxisol in the Cerrados on soil microbial biomass, and evaluated the usefulness of this parameter in studying SOM dynamics in savanna ecosystems.
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Library ResourceReports & ResearchDecember, 1981Colombia, Venezuela, Brazil, South America, Central America
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Library ResourceReports & ResearchDecember, 1985Colombia, Venezuela, Brazil, South America, Central America
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Library ResourceConference Papers & ReportsDecember, 2003Colombia, Brazil, Bolivia, Asia, Africa
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