Academic literature on the topic 'Acrisols'

L'évaluation des potentialités de stockage du carbone dans les agro-systèmes cultivés est à l'ordre du jour. Dans ce contexte, notre objectif de recherche est d'évaluer la dynamique des stocks de C dans le sol et de préciser les mécanismes en jeu, sous l'action de pratiques culturales, dans un Acrisol ferrique du Burkina Faso. Cette étude s'appuie sur des essais « longue durée» pour comprendre, quantifier et modéliser l'évolution des stocks de C sous l'action de pratiques culturales, usuelles, mais pouvant être optimisées. Les déterminations sont faites au champ et au laboratoire. Les résultats confirment que la mise en culture entraîne une diminution des stocks C par rapport à la jachère herbacée de départ, après 10,20 et 40 ans de culture continue avec labour, respectivement de 42, 44 et 68%. La modélisation des stocks de C à l'aide du modèle RothC (horizon 0-20 cm) nous conduit à admettre une cause jusque là insoupçonnée de pertes ou de transfert à partir du fumier, de l'ordre de 67%, qui n'entre donc pas dans l'amélioration des stocks de C du sol de l'horizon considéré, vraisemblablement liée au rôle de la macro faune du sol. Le fractionnement granulométrique montre l'importance des fractions 0-20 mm et soluble. Les fractions fines sont relativement stables alors que les fractions grossières enregistrent des variations importantes, notamment à la baisse en absence d'apport de MO. Lorsque le fumier est apporté simultanément à l'engrais N, il favorise un stockage préférentiel de C dans les fractions fines, attestant l'intérêt de cette pratique sur la stabilisation de la MOS. Une valeur critique de C dans le sol comprise entre 6 et 7 mg C g-1 est mesurée. En deçà de 6 mg Cg-1 les rendements chutent, au delà ils sont stabilisés. Cette étude conclut à la nécessité d'une prise en compte des activités macrofaunique et microbienne de ce sol en interaction avec les MO apportées<br>The evaluation of the potentialities of carbon storage in the cultivated agro-systems is on the agenda. In this respect, the objective of our research is to evaluate the stocks of C in the soil and show the mechanisms concemed, under the action of farming practices in a ferric Acrisol of Burkina Faso. This study is based on "long term" for understanding, quantifying and modelling the evolution of C stocks as a result of usual farming practices that can be optimised. Measurements and analyses are carried out in the field and in the laboratory. The results corroborate a decrease of the C stocks due to farming, in comparison with the initial herbaceous fallow, after 10, 20, and 40 years of continuous farming including ploughing of 42, 44 and 68%. The modellisation C stock with the RothC model (0-20 cm horizon) brings us to admit the existence of an unsuspected cause of loss or transfer from manure of about 67% which does not act on the improvement of C stock of the soil of the concemed horizon. This has seemingly something to do with the role of the soil's macrofauna. The importance of the 0-20 mm fraction and soluble is shown in the particle'size fractionation. The fine fractions are relatively stable whereas important variations are reported for the coarse fractions in case there is no input of organic matter. When there is a manure input together with nitrogen fertilizer, this situation is favourable for preferential storage of C in the fine fractions, thus showing the advantage of this practice in the stabilization of the SOM. A critical value of C in the soil, between 6 and 7 mg C g-1 is measured. The outputs decrease below 6 mg C g-1 and stabilize above this value. This study concludes on the necessity to take into account the macrofaunic and microbial activities of the given soil in interaction with the organic matter brought

As Terras Pretas de Índio (TPI) apresentam por definição o horizonte A antrópico, de cor escura, com presença de artefatos líticos e/ou cerâmicos oriundos do processo de ocupação humana na Amazônia. As áreas que ocorrem se diferenciam dos solos adjacentes por exibirem e manterem condições químicas do solo adequadas ao crescimento de plantas, mesmo após vários anos de cultivo. Essa pesquisa testa a hipótese que de que as TPI exibem condições físicas do solo adequadas ao crescimento de plantas e, mais adequadas que às encontradas nos solos adjacentes. O objetivo deste estudo foi avaliar as propriedades físicas dos horizontes antrópicos de duas TPI relacionando-as com as propriedades estruturais do solo que podem limitar o crescimento de plantas. Para a realização deste estudo foram amostradas duas áreas com horizonte A antrópico (TPI) e amostras do solo adjacente. A primeira área está localizada na estação experimental da Embrapa Amazônia Ocidental (Campo Experimental do Caldeirão) no município de Iranduba, Estado do Amazonas. O solo adjacente foi classificado como Argissolo Amarelo Tb Distrófico. A segunda área está localizada em uma pequena propriedade agrícola no município de Manacapuru, Estado do Amazonas. O solo adjacente foi classificado como Latossolo Amarelo Tb Distrófico. Para a caracterização das propriedades físicas do solo, coletaram-se 120 amostras de solo indeformadas na profundidade entre 0-0,05 m e oito amostras de solo com o formato de blocos (7,0 x 15 x 22 cm). As amostras coletadas foram utilizadas para determinar a curva de retenção da água no solo, a condutividade hidráulica saturada, a curva de resistência do solo à penetração, a densidade do solo, densidade de partículas, a porosidade total do solo, a estabilidade e a resistência tênsil de agregados e a friabilidade do solo. Além das propriedades físicas, o Intervalo Hídrico Ótimo (IHO) e o índice \"S\" foram utilizados como indicadores da qualidade física do solo. A hipótese da pesquisa foi parcialmente comprovada. Os índices de qualidade do solo constataram que as Terras Pretas de Índio apresentam condições físicas do solo adequadas ao crescimento de plantas, entretanto, as TPI não apresentam propriedades físicas mais adequadas ao crescimento de plantas que os horizontes superficiais adjacentes.<br>Amazonian Dark Earth (ADE) presents an Anthropic A horizon, with dark color and presence of lithic and ceramics sherds. Those topsoil characteristics resulted from old Indian settlements from the pre-Columbian time in the Amazon Basin. ADE shows differences from the surrounding soils by its very good soil chemical characteristics and that are still in the most sites very fertile and productive after long time of cultivation. In this study we tested the hypothesis that ADE presents good soil physical conditions to plant growth, and more appropriate than the surrounding soil. The objective of this study was to evaluate physical properties of Anthropic horizons of two sites with ADE. The soil physical properties were discussed concerning the potencial impacts on plant growth. The Anthropic horizons from two ADE sites were sampled and also the A horizon from the surrounding soil. The ADE sites sampled were located in the Amazonas State in Brazil, one at the Experimental Research Station of Embrapa Amazônia Ocidental (Campo Experimental do Caldeirão) - Iranduba, the surrounding soil was an Dystric Yellow Acrisol. The another site was located near the city of Manacapuru - AM in a private farm. The adjacent soil in this area was classified as Dystric Yellow Ferralsol. At the depth of 0-0,05 m, 120 soil cores were collected along with eight soil box (7,0 x 15 x 22 cm). At the laboratory, soil samples were analyzed to determine: soil water retention curve, saturated hydraulic conductivity, penetration resistance curve, bulk density, particle density, total porosity, aggregate stability, tensile strength and friability. The Least Limiting Water Range (LLWR) and S indexes were used as soil physical quality indicators. The hypothesis was partially proven. The soil quality indexes indicated that ADE presented appropriate soil physical conditions for plant growth; however, the ADE had no better soil physical quality than the surrounding soil.