982 resultados para Cultivation of coca


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Emergence and persistence characteristics of Phalaris paradoxa seeds in no- and minimum-till situations and at different burial depths were studied in a sub-tropical environment. Three experiments were carried out using naturally shed seeds. In the first experiment, seedlings emerged from May through to September each year, although the majority of seedlings emerged in July. In the second experiment with greater seed density, cultivation in March of each year stimulated seedling emergence, altered the periodicity of emergence and accelerated the decline of seeds in the seedbank compared with plots that received no cultivation. The majority of seedlings in the cultivated plots emerged in May whereas the majority of seedlings in the undisturbed plots emerged in July. Emergence accounted for only 4-19% of the seedbank in both experiments over 2 years. Seed persistence was short in both field experiments, with less than 1% remaining 2 years after seed shed. In the third experiment, burial depth and soil disturbance significantly influenced seedling emergence and persistence of seed. Seedlings emerged most from seed mixed in the top 10 cm when subjected to annual soil disturbance, and from seed buried at 2.5 and 5.0 cm depths in undisturbed soil. Emergence was least from seed on the soil surface, and buried at 10 and 15 cm depths in undisturbed soil. Seeds persisted longest when shed onto the soil surface and persisted least when the soil was tilled. These results suggest that strategic cultivation may be a useful management tool, as it will alter the periodicity of emergence allowing use of more effective control options and will deplete the soil seedbank more rapidly.

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The irrigation of pasture with saline, Na-contaminated industrial wastewater typically results in an increase in soil ESP. From current knowledge (derived largely from cultivated agricultural soils), although these sodic soils are likely to remain stable whilst irrigated with effluent (due to the effluent’s large electrolyte concentration), during rainfall periods of low electrolyte concentration these soils would be expected to disperse. However, effluent irrigated pasture soils have been observed to maintain their structure even during intense rainfall events. Three soil types were collected (Sodosol, Vertosol and Dermosol), each with a cultivated/non-cultivated pair. The soils were equilibrated with various SAR solutions and then leached with deionised water to allow the measurement of saturated hydraulic conductivity (Ksat). At low SARs, Ksat tended to be greater in non-cultivated than cultivated soils and is attributable to a loss of structure associated with cultivation. In addition, as SAR increased, the reduction in relative Ksat tended to be significantly greater in cultivated than non-cultivated soils. The relatively rapid saturated hydraulic conductivity in the non-cultivated soils at large SARs is due to a greater aggregate stability due to greater soil C content. For the sustainable disposal of saline effluent, it is therefore necessary to ensure that soils remain undisturbed and preferably under pasture, thus maximising soil structural stability and hydraulic conductivity.

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Oil palm has increasingly been established on peatlands throughout Indonesia. One of the concerns is that the drainage required for cultivating oil palm in peatlands leads to soil subsidence, potentially increasing future flood risks. This study analyzes the hydrological and economic effects of oil palm production in a peat landscape in Central Kalimantan. We examine two land use scenarios, one involving conversion of the complete landscape including a large peat area to oil palm plantations, and another involving mixed land use including oil palm plantations, jelutung (jungle rubber; (Dyera spp.) plantations, and natural forest. The hydrological effect was analyzed through flood risk modeling using a high-resolution digital elevation model. For the economic analysis, we analyzed four ecosystem services: oil palm production, jelutung production, carbon sequestration, and orangutan habitat. This study shows that after 100 years, in the oil palm scenario, about 67% of peat in the study area will be subject to regular flooding. The flood-prone area will be unsuitable for oil palm and other crops requiring drained soils. The oil palm scenario is the most profitable only in the short term and when the externalities of oil palm production, i.e., the costs of CO2 emissions, are not considered. In the examined scenarios, the social costs of carbon emissions exceed the private benefits from oil palm plantations in peat. Depending upon the local hydrology, income from jelutung, which can sustainably be grown in undrained conditions and does not lead to soil subsidence, outweighs that from oil palm after several decades. These findings illustrate the trade-offs faced at present in Indonesian peatland management and point to economic advantages of an approach that involves expansion of oil palm on mineral lands while conserving natural peat forests and using degraded peat for crops that do not require drainage.

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Das im Rahmen des DFG-Schwerpunktprogramms „Kompetenzmodelle“ durchgeführte Projekt „Conditions and Consequences of Classroom Assessment“ (Co²CA) geht in vier Teilstudien der Frage nach, wie formatives Assessment im Unterricht gestaltet werden kann, um sowohl eine präzise Leistungsmessung zu ermöglichen als auch positive Wirkungen auf den Lehr-Lernprozess zu erreichen. Das Project Co²CA leistet damit einen wichtigen Beitrag zur Erforschung zweier Kernelemente formativen Assessments – der detaillierten Diagnose von Schülerleistungen und der Nutzung der gewonnenen Informationen in Form lernförderlichen Feedbacks. Zentrale Idee von formativem Assessment (Lernbegleitende Leistungsbeurteilung und –rückmeldung) ist es mit Hilfe von Leistungsmessungen Informationen über den Lernstand der Schülerinnen und Schüler zu gewinnen und diese Informationen für die Gestaltung des weiteren Lehr- und Lernprozess zu nutzen. Den Lernenden kann auf Basis der Leistungsbeurteilung lernförderliches Feedback gegeben werden, um so die Diskrepanz zwischen Lernstand und Lernziel zu verringern. Die Kernelemente formativem Assessments bestehen also aus einer detaillierten Diagnose des Lernstandes und der Nutzung der gewonnen Informationen – z.B. in Form von Feedback. [...] Das vorliegende Skalenhandbuch dokumentiert die in der Unterrichtsstudie eingesetzten Befragungsinstrumente für Schülerinnen und Schüler sowie für Lehrkräfte. (DIPF/Autor)