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Showing items 1 through 9 of 21.
  1. Library Resource
    Journal Articles & Books
    November, 1999
    Brazil

    Resumen Han pasado más de diez años desde la realización del último censo agropecuario. Con la publicación del nuevo censo es posible hacer un primer análisis de los cambios estructurales observados en el sector en el transcurso del período en cuestión. En el presente libro se investigan en profundidad las principales modificaciones en la estructura productiva y en el empleo de los factores productivos, especialmente la mano de obra y la tierra. La organización agraria brasileña ha sufrido significativas alteraciones durante la última década.

  2. Library Resource
    Reports & Research
    December, 1999
    Brazil

    Esta tese examina o tema da recuperação de mais-valias fundiárias urbanas, situando-o como campo de investigação multidisciplinar e mapeando seu entendimento no contexto latinoamericano. O trabalho identifica relações entre o diagnóstico da debilidade na implementação de instrumentos de política urbana associados ao tema na América Latina e o das ambiguidades em sua interpretação, investigando a existência de um hiato entre o reconhecimento abstrato do tema e sua apropriação concreta na região.

  3. Library Resource
    Journal Articles & Books
    December, 1999
    Brazil, Central America, South America

    Intensive farming and grazing on Oxisols of the Brazilian savannas (also known as the Cerrados) are leading to loss of soil organic matter (SOM) and consequently to a decline in fertility and sustainability of the soils. Alternative land-use systems such as the introduction of legumes in pastures and the use of no-tillage systems can reverse this process.

  4. Library Resource
    Journal Articles & Books
    December, 1999
    Brazil, 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.

  5. Library Resource
    Journal Articles & Books
    December, 1999
    Brazil

    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).

  6. Library Resource
    Journal Articles & Books
    December, 1999
    Brazil, 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.

  7. Library Resource
    Journal Articles & Books
    December, 1999
    Brazil, Central America, South America

    The effect of land use on the availability of soil nitrogen (N) was studied by separating total soil N into one labile and one stable fraction by oxidation and extraction of labile N with potassium permanganate. The nitrogen management index (NMI) was calculated according to Blair et al. (1995) for the carbon management index. In all systems, labile N released by potassium permanganate was a better indicator for nitrogen availability than were total and stable N. The NMI was a good indicator for N availability but gave no information on the total amount of N.

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