Soil degradation is a common occurrence in Haiti that is mainly caused by the cultivation of marginal lands and deforestation, which both contribute to the excessive erosion rate seen in the country today. The Central Plateau of Haiti is a mountainous region in which a majority of the population is rural and practices subsistence agriculture on hillsides and steeply-sloping land. Essential plant nutrients, such as nitrogen (N) and phosphorus (P), are commonly a limiting factor in crop production, yet fertilizer is unavailable or is too expensive for smallholder farmers to purchase. This study was conducted to a) evaluate organic matter and nutrient stocks of various soils in the Central Plateau region, along with other chemical and physical characteristics and b) to evaluate the phosphorus-scavenging ability of commonly-grown crops to isolate those that may benefit subsequent smallholder yields. Soils from four locations in the Central Plateau were assessed for organic matter in labile and non-labile fractions as well as for cation exchange capacity (CEC), total organic carbon (C) and N, pH, texture, and other characteristics. Results indicated that most of the soil (92%) was contained within aggregates, and organic matter was mainly present in stable, slowly-decomposing fractions. Seven species were evaluated in a controlled-environment pot experiment for bulk and rhizosphere soil P and pH, plant dry weight, and above- and below-ground P tissue content as indicators of the species' ability to solubilize P from the soil. Velvet bean (Mucuna pruriens (L.) DC) produced the most biomass and was able to take up the most P, though lablab (Lablab purpureous (L.) Sweet), took up comparable amounts of P. / Master of Science / LTRA-6 (A CAPS program for the Central Plateau of Haiti)

Submitted by Leticia Schettini (leticia@ufrrj.br) on 2016-10-03T15:58:13Z No. of bitstreams: 1 2011 - Paula Fernanda Chaves Soares.pdf: 2114719 bytes, checksum: 6297f456308144b9c0a8b946d61316f4 (MD5) / Made available in DSpace on 2016-10-03T15:58:13Z (GMT). No. of bitstreams: 1 2011 - Paula Fernanda Chaves Soares.pdf: 2114719 bytes, checksum: 6297f456308144b9c0a8b946d61316f4 (MD5) Previous issue date: 2011-02-15 / Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico - CNPQ / The Histosols are characterized by high organic content, distinguishing this class from others in the Brazilian System of Soil Clasification. Because of this characteristic they are more fragile in face of agricultural use and management than mineral soils. The agricultural drainage is the most important practice that changes soil properties and it is the cause of subsidence, which impacts on other attributes. On the other hand, Histosols are an important natural reservoir of carbon in the soil. However, there are few studies on the dynamics of carbon and nitrogen and potential contribution of greenhouse gases as a result of agricultural usage. The study aims to identify changes in edaphic attributes and dynamics of carbon and nitrogen of Histosols in a floodplain environment in State of Rio de Janeiro, according to types of land use and agricultural management. Three areas with different managements were selected. Two areas are located in Macae municipality, under pasture and annual crop rotation, and the third in Santa Cruz, in Rio de Janeiro city, cultivated with cassava (Manihot esculenta). They were evaluated: chemical and physical attributes, including aggregate stability and specific attributes of Histosols; content soil organic matter (SOM), carbon in the fractions - humin (HUM-C), humic acid (HAF-C) and fulvic acid (C-FAF); stocks of C and N; and flux of gases CO2 and N2O from soil to atmosphere. In general, the area cultivated with cassava had the highest values for the exchangeable cations at all depths; in the first sampling the H value varied from 32.1 to 33.2 cmolc kg-1, and Ca from 20.4 to 15.7 cmolc kg-1. In the second sampling K and P (5.16 to 4.36 cmol c kg-1, and 4 mg kg-1, respectively) were highest in the cassava crop area. The levels of (SOM) were highest in the pasture for the two sampling periods, with values ranging from 306.3 to 249.0 g kg-1 (WB method) and 297.8 to 278,5 g kg-1 (oven method) for the first sampling, and from 303.2 to 153.9 g kg-1 (WB) and 322.9 to 176.1 g kg-1 (oven) in the second period, indicating that this usage is less aggressive to the soil. The physical properties of Histosols may be used to indicate degree of subsidence. Thus, the high values of particle density and bulk density (1.9 and 0.8 Mg m-3); the total volume of pores that ranged from 54 to 60% with the lowest values in the two samplings; and minimum residue and mineral material highest than other usages (0.49 to 0.44 cm and 85.1 cm-1 to 80.7%, respectively) in the cassava area point to the high subsidence ot these soil. As for SOM chemical fractionation, the C_HUM indicated that this fraction had highest expression in all areas. In the second sampling the cassava area showed the lowest values of C-HUM (79.05 to 76.27 g kg-1), followed by C_FAH (44.56 to 40.05 g kg-1) and C_FAF (20.37 to 14.36 g kg-1). The stocks of C and N were highest in the pasture area, indicating better preservation of SOM, with values from 72.93 to 117.12 mg kg-1 for C and from 8.35 to 2,67 mg kg-1 for N. The values of CO2-C flux were within the range of variation proposed by the IPCC, where the highest emission value corresponded to 0.09 Mg CO2 ha-1 day-1 in the pasture area. The values of N2O-N flux were lower than the emission rate proposed by the IPCC, with the highest value around 270 g N2O-N m-2 day-1 in the area with beans. In general, the area with pasture management stood up as management that caused the least damage to the Histosols properties, among the land use evaluated. / Os Organossolos caracterizam-se pelo alto teor de material org?nico, que distingue essa classe das demais no Sistema Brasileiro de Classifica??o de Solo. Ainda, por essa caracter?stica s?o solos mais fr?geis diante do uso e manejo agr?cola que solos com dom?nio de minerais. Dentre as pr?ticas que mais alteram as propriedades ed?ficas, a drenagem ? a mais importante e ? respons?vel pelo processo de subsid?ncia com impactos em v?rios atributos. Por outro lado, os Organossolos s?o importante reservat?rio natural de carbono no solo. Ainda assim s?o poucos os estudos sobre a din?mica de carbono e nitrog?nio e o potencial de contribui??o com gases de efeito estufa diante do manejo agr?cola. O estudo visa identificar altera??es nos atributos ed?ficos e na din?mica de carbono e nitrog?nio de Organossolos em ambiente de v?rzea no Estado do Rio de Janeiro, em fun??o de tipos de uso e manejo agr?cola. Foram selecionadas tr?s ?reas com manejos distintos. Duas ?reas localizam-se em Maca?, com pastagem e rota??o de culturas anuais, e a terceira em Santa Cruz, no Rio de Janeiro, com mandioca (Manihot esculenta). Foram avaliados: atributos qu?micos e f?sicos, incluindo estabilidade de agregados e atributos espec?ficos de Organossolos; teores de mat?ria org?nica do solo (MOS) e o teor de C nas fra??es humina (C-HUM), ?cido h?mico (C-FAH) e ?cido f?lvico (C-FAF); estoques de C e N; e fluxos dos gases CO2 e N2O do solo para a atmosfera. Em geral, a ?rea com mandioca apresentou os maiores valores para o complexo sortivo em todas as profundidades; na primeira coleta o H variou de 32,1 a 33,2 cmolc kg-1, e o Ca entre 20,4 e 15,7 cmolc kg-1. Na segunda coleta destacam-se os valores de K e P (5,16 e 4,36 cmolc kg-1 e 4 mg kg-1, respectivamente) tamb?m maiores na ?rea com mandioca. A MOS mostrou maior teor na ?rea de pastagem para as duas coletas, com valores variando entre 306,3 a 249,0 g kg-1 (m?todo WB) e 297,8 a 278,5 g kg-1 (m?todo da mufla) na primeira coleta, e para a segunda coleta de 303,2 a 153,9 g kg-1 (WB) e 322,9 a 176,1 g kg-1 (mufla), o que indica que esse manejo ? menos agressivo ao solo. As propriedades f?sicas dos Organossolos podem indicar o seu grau de subsid?ncia. Assim, os valores altos de densidade da part?cula e densidade do solo (em torno de 1,9 e 0,8 Mg m-3) mais o volume total de poros, que variou de 54 a 60% sendo os menores nas duas coletas, e o res?duo m?nimo e material mineral com valores maiores (0,49 a 0,44 cm cm-1 e 85,1 a 80,7%, respectivamente) indicam para a ?rea de mandioca maior grau de subsid?ncia. No fracionamento qu?mico da MOS o C_HUM indicou que essa fra??o teve maior express?o em todos as ?reas. Na segunda coleta a ?rea de mandioca apresentou os menores valores de CHUM (79,05 a 76,27 g kg-1) seguidos de C_FAH (44,56 a 40,05 g kg-1) e C_FAF (20,37 a 14,36 g kg-1). Os estoques de carbono e nitrog?nio foram mais altos no solo sob pastagem, indicando melhor conserva??o da MOS, com valores entre 117,12 e 72,93 Mg kg-1 para C e 8,35 e 2,67 Mg kg-1 para N. Os valores de fluxo de C-CO2 estiveram dentro da faixa de varia??o proposta pelo IPCC, em que o maior valor de emiss?o correspondeu a 0,09 Mg CO2 ha-1 dia-1 na ?rea de pastagem. Os valores de N-N2O foram menores que a taxa de emiss?o proposta pelo IPCC, com o valor mais elevado em torno de 270 ?g N-N2O m-2 dia-1 e na ?rea com feij?o. Em geral, a pastagem se destacou como o manejo que causou menor altera??o nas propriedades dos Organossolos, dentre as formas de uso da terra avaliadas.