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Search Results: 1 - 10 of 7563 matches for " Alfredo Alvarado "
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AGRONOMíA COSTARRICENSE 35 A OS DESPUéS DE SU APARICIóN
Alfredo Alvarado
Agronomía Costarricense , 2012,
Abstract: ...
Effects of increasing soil acidity and decreasing nutrient availability on the growth of Vochysiafe""ginea a secondary rain forest of Northern Costa Rica
Bernal Herrera,Alfredo Alvarado
Agronomía Costarricense , 2001,
Abstract: Efecto del aumento en la acidez del sue- 10 y la disminucion en la disponibilidad de nu- trimentos sobre el crecimiento de Vochysiafe- rruginea en el bosque humedo de la region Norte de Costa Rica. En el presente trabajo se compara el crecimiento de la especie ~ ferrugi- varianea en 3 sitios del bosque humedo secundario de edad avanzada, ubicados en la zona norte de Costa Rica, bajo condiciones crecientes de aci- dez y de menor disponibilidad de nutrimentos en parael suelo. Se instalaron un total de 28 parcelas temporales de muestreo (20x20m), de tal forma que cubrieran toda la variacion del sustrato pre- sente en los sitios de estudio. Como parametros indicadores de la capacidad productiva del sitio bese utilizaron la altura esperada de un arbol a los 25 cm de dap (estimada en una investigacion condiprevia), el area basaVha y la altura total. Las comparaciones estadfsticas (P<0.05) mostraron diferencias significativas en cuanto a la produc- tividad de los sitios. Los sitios con mayor pro- ductividad presentaron el menor grado de pen- indiente, el mayor porcentaje de saturaci6n de AI, los mayores contenidos de Fe y P, asf como las menores concentraciones de bases intercambia-
Variación de la densidad aparente en órdenes de suelos de Costa Rica
Alfredo Alvarado,Warren Forsythe
Agronomía Costarricense , 2005,
Abstract: Este estudio se basa en la información de densidad aparente de 111 perfiles de suelos, representativos de los principales órdenes de suelo descritos por varios autores en Costa Rica. El ámbito de variación de la densidad aparente en los suelos estudiados es alto y osciló entre 0,53 y 2,00 Mg m-3. En general, los valores tendieron a aumentar con la profundidad del suelo debido a la reducción de la actividad biológica desarrollada en el horizonte A. Cuando no se encuentran capas compactadas, el horizonte enriquecido con arcilla eluviada (B2t) de Ultisoles y Alfisoles presenta un incremento de la densidad aparente. Los valores bajos de densidad aparente en Andisoles se relacionan con el origen del material parental y en el caso de los Vertisoles con la densidad de partículas de la fracción esmectítica dominante.
La saturación de acidez y el encalado sobre el crecimiento de la teca (tectona grandis l.f.) en suelos ácidos de Costa Rica
Alfredo Alvarado,Juan L. Fallas
Agronomía Costarricense , 2004,
Abstract: Las plantaciones de teca (Tectona grandis) en suelos ácidos de Costa Rica, en las zonas sur y norte del país, se encuentran principalmente en suelos rojos y arcillosos (Inceptisoles y Ultisoles) con diferentes grados de acidez. En el presente trabajo, se demuestra la sensibilidad de la teca a la saturación de acidez del suelo, donde valores del 3% reducen significativamente el incremento medio anual en altura; por otro lado, valores de saturación con calcio en el suelo superiores al 68%, favorecen su crecimiento significativamente. Bajo estas condiciones, la adición de 1 kg CaCO3 por árbol causó un incremento en la altura de los árboles del 59% y cuando se acompa ó la enmienda con 150 g de 14-22-15-4-5 (N-P2O5 K2O-MgO-S) por árbol, el incremento en altura de los árboles de un a o de edad fue del 216%.
Métodos de extracción de Boro y respuesta del Jaúl a su adición en Andisoles de Costa Rica
Segura,Manuel; Castillo,álvaro; Alvarado,Alfredo;
Agronomía Costarricense , 2010,
Abstract: abstract soil boron extraction methods and alder response to boron additions in andisols of costa rica. the effect of b to andisols on tree height, diameter and volume of 5 alnus acuminata plantations was studied. plantation initial ages in years were: 0.5 at hermanas callejas (hc), 1 at lechería experimental (le), 3 at rosa marta cubero (rmc), 5 at landelina (l) and 7 at carter (c); at the end of the experiment plantations were 3 years older. b was supplied as boronate and broadcasted at rates of 0, 2, 4, 6 and 8 kg.ha-1; the residual effect of fertilizer was determined 14 months after its application. the fertilizer added incremented b availability in the soils, as measured with pressurized hot water and mehlich 3 methods. r2 values obtained were higher with correlations obtained by the mehlich 3 procedure. the b applied did not cause increments of dasometric variables measured, except for a significant increase in volume of wood at landelina (8 year old plantation). the lack of response in growth variables to b addition are attributed to the initial b availability in the soils (0.19-1.00 mg.kg-1), most values above the critical value of 0.5 mg.kg-1 mentioned for crops in andisols, and the low requirement of b in alder. foliar concentration of b showed a slight tendency to increase with growing amounts of b applied to the soil, while n foliar concentration did not show any tendency after b addition to the soil.
Capacidad de las tierras para uso agrícola en la subcuenca media-alta del río Pirrís, los Santos, Costa Rica
Chinchilla,Miguel; Alvarado,Alfredo; Mata,Rafael;
Agronomía Costarricense , 2011,
Abstract: land capability for agricultural use in the middle-upper pirrís river watershed is mainly determined by altitude belts. between 1075 and 1700 m asl, coffee production is the main agricultural activity on clayey ultisols with important erosion manifestations. from 1700 to 3100 m natural forest, highland fruit trees, flowers, fish ponds, pastures, some vegetables, mountain cabins, and charcoal production are the main activities on predominant andisol, inceptisol, and entisol soil orders. the area consists of mountains of steep (30-60%) slopes, and a few low-relief deep valleys with recent alluvial terraces. visible features on agricultural lands allowed to estimate that 60% of this land suffers moderate erosion (laminar and reel); 18% of this land suffers severe erosion, to very severe not considering linear erosion due to poorly-designed secondary roads, no road drainage, excavations for infrastructure, and active landslides that cause large scale soil loses. forty four % of the soils are deep, while 38% are moderately deep, and 17% are shallow to superficial. fertility characteristics observed on peats all over the region show that 33% the soils are of low fertility and 52% of very low fertility. considering relief features, suffered erosion, soil fertility, and soil depth, land use capability for agricultural activities in the watershed are: 1% class iii, 2% class v, 8% class viii, 26% class vii, and 63% classes iv and vi.
Caracterización y clasificación de algunos Ultisoles de la Región de los Santos, Talamanca, Costa Rica
Chinchilla,Miguel; Mata,Rafael; Alvarado,Alfredo;
Agronomía Costarricense , 2011,
Abstract: twenty-six soil profiles were characterized and classified as ultisols in the middle-upper watershed of pirrís river. these soils developed on pleistocene to oligocene undulated to strongly undulated mountainous landscapes, on: 1) marine sediments, 2) volcanic andesitic-basaltic materials and 3) colluvial materials, all of them covered by natural vegetation of wet to very wet tropical forest in an ustic soil moisture regime. the soils are deep, possess an argillic horizon and are of fine to very fine texture. soil reaction is acid to strongly acid and may possess a horizon high in manganese concretions associated to ancient water levels of the pirrís river watershed, on geologic materials high in manganese content. clay content, cec, particle density and bulk density of the soils vary with parent material, while base content and phosphorus fixation are not so related. according to soil taxonomy, 2 suborders were recognized: humults and ustults. five great groups: haplustults, paleustults, haplohumults, palehumults, rhodustults; and 9 subgroups: typic haplustults, aquic haplustults, typic paleustults, andic haplohumults, aquic haplohumults, aquandic haplohumults, ustic haplohumults, andic palehumults, typic rhodustults. the andic and aquandic subgroups exhibit, in superficial horizons, depositions of volcanic ash materials dated around 700 years of age. buried clayey subsoils of talamanca ultisols are much older than their over laying horizon, being dated as old as 9000 to 65 000 years of age.
Factores formadores y distribución de suelos de la subcuenca del Río Pirrís, Talamanca, Costa Rica
Chinchilla,Miguel; Alvarado,Alfredo; Mata,Rafael;
Agronomía Costarricense , 2011,
Abstract: this study emphasizes on the soil-forming factors and soils distribution of the middle-upper pirrís river watershed, talamanca, costa rica, a region locally known as los santos. this area covers around 25 000 ha, at elevations from 1078 to 3140 m, and a range of yearly average rainfall from 1954 to 2233 mm. geologically, rocks of the area represent a period span from holocene to oligocene. four major soil units were identified: 1) recent soils developed from volcanic ash (high elevation sections); 2) soils developed from old geologic parent materials of the talamanca range and the brunque?a hills (middle elevation sections); 3) soils developed on and around intrusive volcanic buildings (medium to high elevation sections of the landscape); and 4) soils developed from recent alluvial materials deposited on valley floors (lower positions of the landscape). soils developed on the older materials from the pliocene to the oligocene, present an argillic horizon as a final result of weathering and soil formation. soils from pleistocene to upper miocene intrusive materials, present a higher quartz content. soils developed from recent alluvial deposits present a cambic horizon, but not an argillic horizon and the volcanic ash materials may present a cambic horizon or a buried argillic horizon. six soil consociations and 22 soil associations were described in the area. mayor soil orders in the region are ultisols, andisols, inceptisols and entisols, including 4 suborders, 6 great groups, 12 subgroups and 9 soil families.
Andisoles, inceptisoles y entisoles de la subcuenca del río Pirrís, Región de los Santos, Talamanca, Costa Rica
Chinchilla,Miguel; Mata,Rafael; Alvarado,Alfredo;
Agronomía Costarricense , 2011,
Abstract: eight soil profiles were described and classified on volcanic ash deposits at the upper pirrís river watershed. the soils were classified as andisols and inceptisols of the suborders ustands, udands and ustepts; at the great group level the soils were classified as haplustands, placudands and dystrustepts, belonging to the subgroups dystric haplustands, humic haplustands, aquic haplustands, typic placudands and andic dystrustepts. the topsoil characteristics of many of these soils are fragile, vulnerable to erosion and landslides. in general, these soils are acid, of low fertility status and present recent surface horizons (holocene), but could be underlain by argillic horizons formed during the pleistocene. on recent alluvial terraces from the holocene, another group of seven soil profiles were described. these showlittle morphological development; major soilforming processes in these positions include detachment in the highlands and deposition of particles through river flooding in the lowlands. these soils were classified in the orders entisols and inceptisols, suborders fluvents y ustepts, great groups ustifluvents, dystrustepts and haplustepts, finally belonging to the subgroups typic ustifluvents, fluventic dystrustepts, fluventic haplustepts and humic dystrustepts. most entisols present coarse textures (sandy loam) while in the inceptisols the clay content is dominant (clay loam, sandy clay loam and clayey textures). a third group of soils were described in a rim around intrusive materials of miocene to pleistocene origin, dated to be 8 to 11 ma. on these metamorphic materials inceptisols were formed, showing high rock and stone contents. most of these soils are shallow, acid and of yellowish colors, due to the illuviation, lixiviation, humus formation, weathering and erosion dominating soil forming processes in this area.
CAPACIDAD DE LAS TIERRAS PARA USO AGRíCOLA EN LA SUBCUENCA MEDIA-ALTA DEL RíO PIRRíS, LOS SANTOS, COSTA RICA
Miguel Chinchilla,Alfredo Alvarado,Rafael Mata
Agronomía Costarricense , 2011,
Abstract: El uso de la tierra en la subcuenca mediaalta del río Pirrís, está diferenciado por la altitud sobre el nivel del mar. Entre los 1075 y 1700 m de elevación, la principal actividad agrícola es el cultivo del café, desarrollado sobre suelos arcillosos del orden de los Ultisoles con importantes manifestaciones de erosión. Por encima de los 1700 m y hasta los 3100 m dominan los Andisoles, Inceptisoles y Entisoles, utilizados con bosques, pastos, frutales de altura, algo de hortalizas, floricultura, piscicultura, hoteles de monta a, producción de carbón en trincheras y donde existe menor pérdida de suelo. En general, el área se caracteriza por las tierras monta osas con fuerte pendiente (30 a 60%) y unos pocos relieves suaves que ocupan valles profundos con terrazas recientes. Rasgos visibles permitieron estimar que en suelos agropecuarios hay un 60% de erosión moderada (laminar y en surcos) y un 18% de severa a muy severa, sin considerar una erosión lineal que se presenta por caminos mal dise ados, ausencia de cunetas, excavaciones para infraestructura y deslizamientos activos que provocan remociones de suelo en grandes proporciones. En cuanto a profundidad efectiva, los suelos profundos significan el 44% del área, mientras que un 38% son moderadamente profundos y el 17% son poco profundos a superficiales. Las calicatas localizadas en la parte media alta de la subcuenca se alan un 33% de suelos con fertilidad baja y 52% de fertilidad muy baja. Considerando los factores pendiente, erosión actual visible, fertilidad y profundidad de suelos, la capacidad de uso de las tierras agrícolas en el área estudiada, revela que 1% de las tierras son clase III; 2% clase V; 8% clase VIII; 26% clase VII y 63% de clases IV y VI
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