3,099 research outputs found
Taking Indigenous Technology seriously: The Case of Inter?cropping Techniques in East Africa
SUMMARY Although inter?cropping (IC) is widely practised in rainfed tropical small?scale agriculture, agricultural research scientists have not systematically explored the rationale for it and have rarely attempted to improve it. instead, they have concentrated on planting crops in pure stands and extension advice has been to replace IC with pure stands. This has reduced the impact of research and extension activities. A review of East African experience from the 1930s considers reasons for the research concentration on pure stand planting and reveals two phases when formal experiments on IC were carried out. Despite generally favourable results, neither of these led to including IC in extension advice to farmers. IC can contribute to one or more of five common objectives of small?scale farmers, but the standard design of agronomic experiments at best takes account of only one of these, so that benefits are underestimated and erroneous policy conclusions drawn. The paper advocates, inter alia , multidisciplinary research for small?scale agriculture and active participation by farmers themselves. RESUME Prendre la technologie indigène au sérieux: le cas des techniques d'association des cultures en Afrique orientale Bien que l'association des cultures (IC) soit très répandue dans l'agriculture pluviale intensive, les agronomes n'ont pas étudié systématiquement leur bien?fondé, et ont rarement tenté de l'améliorer. Ils se sont au contraire attachés à encourager les cultures ‘propres’, certains même conseillant aux exploitants de remplacer les cultures associées par des cultures ‘propres’. Une étude de l'expérience est?africaine depuis les années trente étudie les raisons de cette démarche et révèle qu'il y a eu deux phases au cours desquelles ont été officiellement effectuées des expériences sur les cultures associées. Malgré ses résultats généralement favorables, cette technique n'a pas été conseillée aux agriculteurs. L'association des cultures permet d'atteindre un ou plusieurs des cinq objectifs communs des petites exploitations agricoles, mais les modalités standards des expériences agronomiques ne font entrer en jeu que l'un d'entre eux, d'où une sous?estimation des résultats et des conclusions erronées. L'article conseille entre autres d'effectuer des études multidisciplinaires pour les petites exploitations, avec participation active des agriculteurs. RESUMEN Cómo se toma seriamente la tecnologÃa indÃgena: el caso de las técnicas de las cosechas asociadas en Africa Oriental Aunque las cosechas asociadas (CA) están muy extendidas en los paÃses tropicales de lluvias torrenciales con agricultura en pequeña escala, los hombres de ciencia e investigadores agrÃcolas todavÃa no han explorado de manera sistemática su explicación racional y rara vez se ha tratado de mejoraria. En su lugar, se han concentrado en plantar cosechas de cultivos únicos, lo cual ha reducido las repercusiones de las actividades de investigación y extensión. En un estudio de la experiencia adquirida en Africa Oriental desde el decenio de 1930 se analizan los motivos para concentrar la investigación en los cultivos únicos y revela dos fases en que se realizaron experimentos oficiales sobre CA. A pesar de los resultados, que en general fueron favorables, ninguno de estos experimentos condujo a que se incluyeran las CA en el asesoramiento de ampliación a los agricultores. Las CA pueden contribuir a uno o más de cinco objetivos comunes de los agricultores en pequeña escala, pero la concepción normal de los experimentos agronómicos tienen en cuenta uno solamente de éstos, en el mejor de los casos, de manera que se subestiman los beneficios y se llega a conclusiones erróneas de polÃtica. El artÃculo aboga, entre otras cosas, por la investigación en múltiples disciplinas para la agricultura en pequeña escala y la participación activa de los agricultores mismos
Implications of a New Aff. Hippopotamus Karumensis Mandible From the Koobi Fora Formation, Turkana Basin, Kenya
The phylogeny of the East African Hippopotamidae is problematic. A particularly controversial relationship is that between aff. Hippopotamus protamphibius and aff. Hippopotamus karumensis from the Pliocene and Pleistocene of the Turkana Basin (Kenya and Ethiopia). Various hypotheses have been proposed, including (1) that the species are sister taxa derived from a common ancestral hexaprotodont species, (2) that they are time-successive segments of a single anagenetic evolutionary lineage, and (3) that aff. Hippopotamus karumensis represents a branch of an evolving aff. Hippopotamus protamphibius lineage. A major obstacle to determining which of these evolutionary scenarios is the most parsimonious is the unknown degree to which the two species co-occurred. Here we describe a new aff. Hippopotamus karumensis mandible from the Upper Burgi Member of Koobi Fora Formation, east of Lake Turkana (Kenya), that represents the earliest occurrence of this species yet to be documented. The presence of aff. Hippopotamus karumensis in this member implies a lengthy period of sympatry with aff. Hippopotamus protamphibius that makes an anagenetic relationship between these species improbable. It is also unlikely that the species derived from a common hexaprotodont since there is currently a lengthy time gap between the earliest occurrences of the two species. The most parsimonious interpretation is that aff. Hippopotamus karumensis represents a branch of an evolving aff. Hippopotamus protamphibius lineag
Will photosynthesis of maize (Zea mays) in the US corn belt increase in future [CO2] rich atmospheres? An analysis of diurnal courses of [CO2] uptake under Free-Air Concentration Enrichmnent (FACE).
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L'herència dels primats en l'origen de l'home
Què sabem dels primers éssers que podem considerar els nostres primers avantpassats
Body weight estimation of Bovidae and Plio-Pleistocene faunal change, Turkana Basin, Kenya
Plio-Pleistocene mammalian faunal evolution has been causally linked to global climate change. This study investigates the extent to which climate affected the faunal representation of large mammals in the fossil assemblages from the Turkana Basin, in East Africa during the Plio-Pleistocene. The research project involved the collection and study of both modem and fossil specimens Relative abundances of fossil mammalian families and the Bovidae are explored. To interpret climatically driven faunal change, comparisons are made with fossil faunas from the Nachukui, Shungura and Koobi Fora Formations. The combined relative abundances of bovid tribes through time are used to infer changes in habitat representation. The reduncines, wet habitats indicators, are abundant around 2.5 ma in contrast to the Shungura Formation represented by closed-dry habitats. This suggests that local rather than global scale climatic influences are affecting habitat representation. At 1.7 ma the inferred habitat in the Nachukui Formation shows similarity with more distant localities, namely the Olduvai Basin in Tanzania, where more arid and open environments become increasingly dominant. In a second part of this study, data were collected from modem antelope remains to develop new body weight estimation equations, essential for the estimation of body weights of fossil antelopes from the Nachukui Formation assemblage. Dental remains are less accurate estimators of body weight than are postcranial remains. The body weight estimation equations developed in this study are more accurate than published estimation equations when compared. The body weights of Nachukui Formation fossil bovids were estimated using the equations developed in this study. Variation in body weight representation of bovid tribes through time, in the context of changing habitats, and the use of bovid body weights in taxonomic identification of isolated teeth are explored for the Nachukui Formation
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