Restoration of abandoned, nonnative species-dominated agricultural lands provides opportunities for conserving declining shrubland and grassland ecosystems. Land-use legacies, such as elevated soil fertility and pH from agricultural amendments, often persist for years and can favor nonnative species at the expense of native species. Understanding the factors that limit native species establishment on abandoned agricultural lands can provide important insights for restoration and conservation of native species on human-modified lands. I conducted two field experiments on abandoned agricultural lands: a former pasture on Martha’s Vineyard, MA and a former citrus grove at Merritt Island National Wildlife Refuge (MINWR) in Titusville, FL. In these experiments I tested how soil chemical properties affect native and nonnative species abundance and how different methods of removing nonnative, invasive species affect native and nonnative species abundance. In the first experiment, specifically I tested how restoration treatments affect competition between existing nonnative agricultural plant species and native plant species that are targets for sandplain grassland restoration on Martha’s Vineyard, MA. At MINWR, I examined how lowering soil fertility with carbon additions and lowering soil pH by applying sulfur affects nonnative species richness and cover (in two former citrus groves that were historically scrub/ scrubby flatwoods. Overall, I found that biotic factors, such as competition with nonnative species, play a stronger role in limiting native species establishment than soil chemical properties. Likewise, control of nonnative, invasive species is most effective with mechanical treatments to physically reduce cover, rather than altering soil chemical properties

Thesis (MScAgric)--University of Stellenbosch, 2001. / ENGLISH ABSTRACT: Protein and oilseed production in the winter rainfall region of South Africa (primarily the Southern and Western Cape) is well below the potential for the area. One possible method of increasing production is to convince producers that the inclusion of protein and oilseed rotational crops will enhance the sustainability of wheat production systems. A project to investigate, quantify and elucidate the effect of canola (Brassica napus), lupins (Lupinus angustifolius) and medics (Medicago spp.) on subsequent wheat (Triticum aestivum) production as well as their influence on soil fertility in respect to nitrogen was initiated in 1999. The long- term rotational crop system experiment on Langgewens experimental farm near Malmesbury, provided the infrastructure for the project. During the 1999 and 2000 wheat-growing seasons, 50m2 plots were demarcated in wheat fields where wheat, lupins, canola or medics were produced in 1998 and 1999 respectively. Each plot was cleared of all vegetation and received no fertilizer N. In these fallow plots, soil samples were collected at three to four week intervals and the available nitrate-N and ammonium-N content of the topsoil (0-15cm depth) and the subsoil (15-30cm depth) were determined. Additional soil samples were also taken from the topsoil on 09/03/2000 after a summer fallow period. These samples were taken on plots that were subjected to a wheat crop in 1999, but were preceded by either wheat, canola, lupins or medics in 1998. The soil samples were then subjected to a 60-day incubation period at 15°C while being maintained at 75% of their water holding capacity. Mineral N was determined after 0, 3, 7, 15, 30, 45 and 60 days of incubation. Large variation in the nitrogen contents observed made it difficult to always obtain significant differences. The results of the soil investigations however indicate that the inclusion of lupins and medics in wheat cropping systems in the Swartland could help to limit the decline of mineral N in the soil profile, experienced within a growing season. This will therefore enable farmers to reduce fertilizer inputs without facing soil mineral N depletion. Plant samples were also collected from wheat plots during the 1999 growing season on three occasions (23/06/99 (growth stage 5), 5/08/99 (growth stage 15), 14/09/99 (growth stage 23)). Plots were selected to represent the same treatments as in the soil sampling procedure during the growing season of 1999 as described above. Plant and tiller numbers of a 0.25m2 sub sample from each plot were counted and leaf area was determined, whereafter the dry material was weighed. The percentage nitrogen content in the leaves and stems were subsequently determined using Near Infra-Red Spectroscopy. In terms of vegetative growth, little difference was observed. A significant increase in nitrogen content of wheat plants growing in plots where wheat and canala were grown in 1998 was observed in the second plant sampling (growth stage 15) and this was attributed to higher nitrogen topdressing. However, on the third sampling date on 14/9/1999 (growth stage 23), the difference was no longer evident. The most important conclusion to make from this study, is that farmers can probably save on fertilizer inputs when including lupins and medics in their wheat production systems, without risking poorer wheat growth. At growth stage 28, a 0.25m2 sub sample of wheat plants was removed at a randomly chosen point in each of the plots described above. Ears and grains were subsequently counted. The wheat remaining on the plots were then harvested at the end of October 1999 using a plot combine. Subsequently the yield, hectolitre mass, thousand grain mass and % crude protein was determined from samples of harvested grain from each plot. The % flour and % bran extraction were then determined whereafter the % flour protein was determined. Micro bread loafs were baked to estimate the loaf volume. Flour and dough properties were also tested using the Falling Number System, mixograph and alveograph. Wheat in cropping systems consisting of legume phases such as lupins and medics, required less nitrogen fertilizer application to achieve statistically the same yield, flour and dough properties. These crop rotations can therefore be considered as more ecologically sustainable and economically viable for the Swartland. This study was aimed at determining the effect of different crop rotations on soil fertility, and because clear soil fertility trends take time to form, this study was probably too short to obtain fully significant differences. / AFRIKAANSE OPSOMMING: Proteïen- en oliesaad produksie in die winter reënval streek van Suid Afrika (hoofsaaklik die Suid- en Weskaap) is ver benede die potensiaal vir die streek. Een moontlike manier om die produksie hiervan te verhoog is om produsente in hierdie streek te oortuig dat die insluiting van proteten en oliesaad gewasse die volhoubaarheid van koring verbouingstelsels sal verhoog. Na aanleiding hiervan, is In projek in 1999 van stapel gestuur om die effek van canola (Brassica napus), lupiene (Lupinus angustifolius) en medies (Medicago spp.) op daaropvolgende koring (Triticum aestivum) produksie, asook die invloed daarvan op grondvrugbaarheid in terme van stikstofinhoud, te ondersoek. Die langtermyn wisselbouproef op Langgewens proefplaas naby Malmesbury, het as infrastruktuur vir die ondersoek gedien. Gedurende die 1999 en 2000 koring groeiseisoene is 50m2 plotte in koringkampe gekies waarop koring, canola, lupiene en medies geproduseer is in onderskeidelik 1998 en 1999. Hierdie plotte is skoon gehou van plantegroei en het ook geen stikstof in kunsmisvorm gekry nie. Met drie tot vier week intervalle is grondmonsters op hierdie plotte versamel in die bogrond (0-15cm diep) en ondergrond (15-30cm diep), waarna die beskikbare nitraat-N en ammonium-N konsentrasie bepaal is. Adissionele grondmonsters van die bogrond is ook geneem op 9/03/2000 na In somer braak periode. Hierdie monsters was geneem op persele wat blootgestel was aan In koringproduksie in 1999, maar voorafgegaan is deur koring, canola, lupiene en medies in 1998. Hierdie monsters is dan vir 60 dae geïnkubeer teen 15°C en 75% van die grond se water houvermoeë. Minerale N inhoud bepalings is gedoen na 0, 3, 7, 15, 30, 45 en 60 dae van inkubasie. Groot variasie in die minerale stikstof inhoud, het die verkryging van herkenbare tendense en konstante statistiese verskille belemmer. Die resultate wat verkry is dui egter dat die insluiting van lupiene en medies in koring produksie stelsels in die Swartland, hoër minerale N vlakke in die grond handhaaf en dit kan boere gevolglik in staat stelom kunsmis insette te besnoei sonder dat grondvrugbaarheid verswak. Op 23/06/99 (groeistadium 5), 5/08/99 (groeistadium 15) en 14/09/99 (groeistadium 23) is plantmonsters versamel van koringpersele. Hierdie persele is gekies om die behandelings van die grondmonsterontledings soos hierbo beskryf, te verteenwoordig. Plante en halms van 'n 0.25m2 area uit die persele is getel en die blaaroppervlaktes is bepaal, waarna die droëmateriaal massa van die area bepaal is. Die persentasie stikstofinhoud van die blare en stingels was daarna bepaal. In terme van vegetatiewe groei was daar nie groot verskille te bespeur nie. Betekenisvolle hoër stikstof inhoud van koringblare in plotte waar daar in die vorige jaar canola en koring verbou was, is in die tweede planttrekking (groeistadium 15) gevind en dit is toegeskryf aan die hoër stikstof kopbemesting wat daardie behandelings ontvang het. Teen die derde monsterneming op 14/09l99 (groeistadium 23), was hierdie verskille nie meer in die ontledingsdata te sien nie. Die afleiding wat van hierdie studie gemaak is, is dat boere moontlik stikstofbemesting kan verminder as hulle lupiene en medies in hulle koring produksiestelsels inbring, sonder om die risiko van swakker groei te verhoog. Op 20/10/99 (groeistadium 28) is 0.25m2 plante van elke koringperseel verwyder waarna die are en die korrels getel is. Die koring wat nog op die persele was is teen die einde van Oktober 1999 met 'n perseelstropertjie geoes. Opbrengs, hektoliter massa, duidendkorrel massa en % ru-proteïene is daarna bepaal. Volgende is die % meel en % semel ekstraksie bepaal waarna die % meelproteïene bepaal is. Mikro broodjies is ook gebak om die broodvolume te bepaal. Meel en deeg eienskappe is ook getoets met die Falling Number System, mixogram en alveogram. Koring in produksiestelsels met peulplant fases (lupien en medies in hierdie geval), het minder N toediening nodig gehad om statisties dieselfde opbrengs, meel- en deeg eienskappe te verkry. Lupien en medic gebaseerde wisselbou praktyke in die Swartland kan gevolglik as meer ekologies volhoubaar en ekonomies haalbaar bestempelword. Hierdie studie het gepoog om die invloed van wisselbou op grondvrugbaarheid te ondersoek. Sodanige veranderings neem egter tyd en daarom is dit waarskynlik nog te gou om werklike grondvrugbaarheids verskille waar te neem.

Les exploitations mixtes d'agriculture-élevage sont le pilier des systèmes agricoles des pays en développement. Dans les hauts plateaux de Madagascar, les exploitations familiales d'agriculture-élevage sont basées sur l'association riz et élevage bovin. Les bovins ont un rôle central dans l'économie et la reconnaissance sociale de ces exploitations malgaches. Cependant ces exploitations sont souvent confrontées à des problèmes de faibles productivités liés à la dégradation de la fertilité des sols et à un accès limité aux intrants. Dans ce contexte, les exploitants doivent gérer les ressources végétales pour trouver un compromis entre alimentation humaine, alimentation animale et retours aux sols. Certaines pratiques de gestion des biomasses peuvent aggraver les phénomènes de dégradation de la fertilité des sols et remettre alors en cause la durabilité des exploitations. L'objectif de cette thèse est de montrer que la diversité des pratiques de gestion des biomasses au sein des exploitations familiales d'agriculture-élevage des hauts plateaux de Madagascar conditionne la durabilité des systèmes en termes de fertilité des sols, de recyclage des éléments nutritifs, de revenus et de sécurité alimentaire. Pour cela, il a été nécessaire de : i) caractériser au préalable la diversité des exploitations familiales d'agriculture-élevage du Vakinankaratra et de comprendre le fonctionnement de ces exploitations mixtes ; ii) étudier les effets des pratiques de gestion des parcelles sur la variabilité de la fertilité des sols des exploitations ; iii) évaluer la durabilité des exploitations d'agriculture-élevage et tester l'impact d'améliorations des pratiques d'alimentation animale, de gestion des effluents et de fertilisation sur la durabilité des exploitation. Quatre exploitations d'agriculture-élevage du Vakinankaratra, sélectionnées à dires d'experts, ont été enquêtées par immersion. Une étude typologique des exploitations d'agriculture-élevage du Vakinankaratra a été effectuée. Des prélèvements de sol ont été effectués pour l'ensemble des parcelles des quatre exploitations d'agriculture-élevage étudiées. Un outil de calcul des flux d'azote au sein des exploitations a été élaboré, puis a été associé aux matrices du Network Analysis afin de générer des indicateurs environnementaux, sociaux et économiques. Cet outil a été utilisé pour simuler les options d'améliorations des pratiques d'alimentation animale, de gestion des effluents et de fertilisation.L'étude typologique a identifié six types d'exploitations d'agriculture-élevage au Vakinankaratra. L'étude du fonctionnement des exploitations sélectionnées a mis en évidence d'une grande diversité des pratiques d'alimentation des animaux, de gestion des effluents d'élevage et de fertilisation. Une hétérogénéité de la fertilité des sols induite par les pratiques de gestion des parcelles a été révélée. Pour les quatre exploitations étudiées, l'amélioration des pratiques d'alimentation du troupeau bovin laitier associée à l'amélioration des pratiques de gestion des effluents d'élevage a permis d'améliorer la durabilité environnementale (efficience azotée globale, recyclage de l'azote, bilan azoté du sol), économique (marge brute agricole) et sociale (autosuffisance alimentaire).Ce travail a permis de caractériser la diversité des exploitations d'agriculture-élevage du Vakinankaratra, la diversité des pratiques et leurs effets sur la fertilité du/des sol. Cette étude s'est avérée être une approche intéressante pour évaluer des options d'amélioration de la durabilité des exploitations d'agriculture-élevage dans un contexte peu documenté. / Mixed crop-livestock systems constitute the backbone of agriculture in developing countries. In highlands of Madagascar, crop–livestock systems are based on rice and cattle. Cattle play a major role in the economy and the social recognition of these smallholder farms. Smallholder farms used to face with low crop productivity related to soil fertility degradation and to low access to inputs. In this context, smallholders have to manage plant resources in order to find a trade-off between food, feed and soil returns. Some biomass management may increase soil fertility degradation and then compromise farms sustainability.The objective of this thesis is to show that the diversity of biomass management on smallholder crop–livestock systems of highlands of Madagascar determines the sustainability of farming systems in terms of soil fertility, nutrients recycling, incomes and food security. For this, it was necessary to: i) characterize the diversity of crop-livestock systems in the region of Vakinankaratra and understand how smallholder farms are managed; ii) study the effects of soil management on the soil variability; iii) assess the farms sustainability and explore improvements of feeding, manure management and fertilization.Four crop-livestock farms of the Vakinankaratra (selected with local experts) were surveyed using participant observation methodology. A typology of crop-livestock farms was performed. Topsoil samples were collected in all plots of the four cases studies. A nitrogen flows calculating tool was developed and has been associated with Network Analysis matrices to generate environmental, social and economic indicators. This tool was used to simulate improvements in feeding, manure management and fertilization.The typology identified six farm types of crop-livestock systems in the Vakinankaratra. The farms study revealed a great diversity of animal feeding practices, manure management and fertilization. Heterogeneity of soil fertility induced by farmer management was shown. For the four case studies, improved feeding practices on dairy combined with improved manure management have increased environmental (farm nitrogen efficiency, nitrogen recycling, soil nitrogen balance), economic (agricultural gross margin) and social (food self-sufficiency) sustainability.This study characterized the diversity of crop-livestock farms of the Vakinankaratra, the diversity of practices and their effects on soil fertility. It proved to be an interesting approach to explore options for improving sustainability of crop-livestock farms in context of data scarcity.

Des données synchroniques de sols observées pendant 20 à 40 ans dans différentes zones agro-écologiques du Togo ont été utilisées pour analyser l’évolution de la fertilité du sol sous différentes pratiques culturales. Trois modèles de complexité croissante d’évolution du stock de C du sol ont été testés et le plus performant a été couplé au modèle QUEFTS pour apprécier l’effet des pratiques culturales sur l’évolution de cette fertilité. Bien que la fertilisation NPK ait été continuellement appliquée à la dose recommandée par la recherche (RR) ou à cette dose augmentée de 50% (1.5RR), les rendements initiaux de 1,5 à 2 t ha-1 pour le coton et 2 à 3 t ha-1 pour les céréales ont baissé pour ne représenter qu’environ 1 t ha-1 après 20 années de culture. L’alternance de 2 ou 3 années consécutives de jachère à la rotation culturale n’a pas amélioré le rendement des cultures, mais tend à stabiliser la production dans le long terme. Les stocks initiaux de C de 15 à 39 t ha-1 ont fortement baissé durant les premières années et ont atteint un équilibre après seulement 10 à 15 ans de culture. La baisse du stock de C a été peu dépendante de la quantité de C retournant au sol et a été mieux décrite avec le modèle à deux compartiments de C. Le taux de minéralisation de la fraction labile de C varie entre 0,15 et 0,24 et le stock de C stable représente 33-67% du stock initial ; pour une quantité de C ayant résisté à l’hydrolyse acide de 30% du stock initial. Les stocks de N du sol ont fortement baissé et cette baisse a été peu dépendante de la dose de fertilisation minérale. L’apport NPK à 1.5RR pendant 20 ans a contribué significativement à la baisse du pH du sol, puis a accentué de 20 et 40% les baisses respectives des concentrations de Ca et Mg. Nous avons conclu que l’apport de Ca/Mg couplé à celui de NPK à la dose RR serait (plus que le surdosage de P et K) une meilleure option pour gérer la fertilité minérale de ces sols. Le labour minimum, associé aux apports externes de C, devrait permettre de mieux gérer leur fertilité organique. / Using data observed during 20 to 40 years in different agro-ecosystems of Togo, we analyzed soil fertility dynamic under different agricultural management practices. Tree soil C models of varying complexity were tested, and the most accurate in terms of soil C dynamics description in these tropical soils was associated with the QUEFTS model and with nutrient partial balance to analyze the effect of each agricultural management practice. Results indicated that, although fertilizers N, P and K were continuously applied at a recommended rate by the research (RR) or at this rate increased in 50% (1.5RR), initial cotton and cereals yields of 1.5 to 2 t ha˗1 and 2 to 3 t ha˗1, respectively, decreased to around 1 t ha-1 after 20 years of soil cultivation. Alternation of 2 or 3 consecutive years of fallow plot with 3 years cropping did not improved crops yields as compared with continuous cropping system, but tends to stabilize crops production in the long-term. In the upper soil 20 cm, soil C stock of 15 to 39 t ha˗1 after vegetation clearance dropped faster during the first years to reached equilibrium after only 10 to 15 years of soil cultivation. Such a decrease was less depended on soil C input and was accurately descried with a two-pool C model, running on an annual time step basis. Calibrated decomposition rate of labile soil C ranged between 0.15 and 0.24, and stable soil C pool represented 33 to 67% of initial total C; while soil C that was resistant for hydrolyze acid was about 30% of initial total C. Soil N stock was also decreased faster and less associated with a rate of N input to soil. Application of NPK at 1.5RR during 20 years contributed significantly to soil pH decrease and pronounced soil Ca and Mg decreases, which respectively were 20 and 40% more than in plots that were not fertilized. We concluded that, association of Ca/Mg and NPK at a recommended rate would be (more than over-dosage of P and K) a promising option to achieving a sustainable management of mineral fertility of these soils. Minimum tillage, associated with external C input, would be an asset to a sustainable management of organic fertility of these soils.

Nas últimas décadas as mudanças climáticas foram evidenciadas pelo aumento da temperatura global, diminuição dos estoques de carbono terrestres, associados ao aumento nas emissões de gases de efeito estufa (GEE). A floresta Amazônica é o maior bioma tropical do mundo e desenvolve serviços ambientais estratégicos no planeta. Entretanto, há mais de duas décadas que o desmatamento na Amazônia impulsiona as emissões globais de GEE, diminuindo o armazenamento de carbono do solo com alterações na dinâmica nas populações microbianas e nos ciclos biogeoquimicos pela mudança de uso da terra. O objetivo desse estudo foi avaliar as alterações temporais dos atributos químicos do solo, quantificar as emissões de CO2, CH4 e N2O e verificar as alterações na estrutura bacteriana do solo após o corte e queima de vegetação nativa na Amazônia. O estudo foi desenvolvido em área de vegetação nativa no norte do estado de Rondônia, região sul da Amazônia no Brasil. A área de estudo consistiu-se de quatro hectares, onde foi realizado o corte e queima em 2,25 hectares. Foram realizadas amostragens para avaliação da fertilidade do solo e estoques de carbono (C) e nitrogenio (N) nas profundidades de 0-5, 5-10, 10-15, 15-20, 20-30, 30-40, 40-50, 50-60, 60-80 e 80-100 cm. As coletas foram realizadas em vegetação nativa e aos 2, 30, 60, 90, 120, 240 e 365 dias após corte e queima. Foram determinados os atributos pH, Al, H+Al, Ca, Mg, K, P, C, N e calculados os valores de soma de bases, CTC, V % e m %. As coletas para quantificar as emissões dos GEE foram realizadas simultaneamente na área de vegetação nativa e no hectare central da área de corte e queima aos 19, 31, 48, 61 e 81 dias após corte e 2 , 4, 6, 8, 15, 31, 45, 61, 88, 122, 153, 180, 240 e 350 dias após queima, com amostragens aos 0, 20, 40 e 60 minutos. Os atributos microbiológicos do solo foram avaliados pela técnica de T-RFLP com amostragens realizadas simultaneas nas duas áreas, aos 32 e 62 dias após o corte e aos 2, 15, 30, 45, 60, 90, 120, e 360 dias após queima da biomassa vegetal. Foi verificado rápido aumento da fertilidade do solo e diminuição da acidez e teores de Al+3 após a queima, entretanto esse efeito foi pouco persistente, retornando ao status inicial do solo após um ano. Houve redução de 30 % nos estoques de C e N do solo no final do estudo, evidenciando os efeitos deletérios da mudança do uso da terra nos atributos químicos do solo. Foi registrado redução de 50 % das emissões de CO2 equivalente após o corte, comparada à vegetação nativa e reduções nas emissões de GEE de 35 % após um ano de estudo. Verificou-se na camada superficial, alterações significativas na estrutura da comunidade bacateriana do solo em decorrência do impacto do fogo e das alterações nos atributos químicos em função da deposição superficial de cinzas no solo, entretanto não foi verificada alterações significativa nas camadas abaixo de 5 cm. Este estudo forneceu importantes informações para o entendimento dos impactos e as alterações causadas pelo processo de conversão florestal tropical pelo corte e queima de vegetação nativa na Amazônia. / In recent decades, climate change has been evidenced by the increase in global temperature and the decrease in terrestrial carbon stocks, associated with an increase in greenhouse gas (GHG) emissions. The Amazon rainforest is the largest tropical biome in the world and develops strategic environmental services on the planet. However, for more than two decades, deforestation in Amazon has driven global GHG emissions, reducing soil carbon storage with changes in microbial populations dynamics and in biogeochemical cycles due to land use change. The objective of this study was to evaluate the temporal alterations of soil chemical attributes, quantify CO2, CH4 and N2O emissions and verify changes in soil bacterial structure, due to the slash and burn of the native vegetation in Amazon. The study was developed in an area of native vegetation in the north of Rondônia state, southern region of Amazon in Brazil. The study area consisted of 4 hectares, where it was cut and burned in 2.25 hectares. Samples were collected to evaluate soil fertility and carbon (C) and nitrogen (N) stocks at the depths of 0-5, 5-10, 10-15, 15-20, 20-30, 30-40, 40- 50, 50-60, 60-80 and 80-100 cm. These samples were collected in native vegetation at 2, 30, 60, 90, 120, 240 and 365 days after cutting and burning. The attributes pH, Al, H + Al, Ca, Mg, K, P, C, N were determined and the values of base sum, CEC, base saturation and aluminum saturation were calculated. The samples to quantify GHG emissions were carried out simultaneously in the native vegetation area and in the central hectare of the cutting and burning area at 19, 31, 48, 61 and 81 days after cutting and 2, 4, 6, 8, 15, 31, 45, 61, 88, 122, 153, 180, 240 and 350 days after burning, with samples at 0, 20, 40 and 60 minutes. The microbiological attributes of the soil were evaluated by T-RFLP technique with simultaneous samplings in the two areas, at 32 and 62 days after cutting and at 2, 15, 30, 45, 60, 90, 120, and 360 days after plant biomass burning. A rapid increase in soil fertility and a decrease in acidity and Al+3 contents after burning were verified, however this effect was not persistent, returning to the initial soil status after one year. There was a 30 % reduction in soil C and N stocks at the end of the study, evidencing the deleterious effects of land use change on soil chemical attributes. Also, a 50 % reduction in CO2 emissions after cutting, compared to native vegetation and, a 35 % reduction in GHG emissions after one year of study, were observed. We verified in the surface layer, significant alterations in the soil bacteria structure due to the fire impact and the changes in the chemical attributes, such as surface deposition of ashes. However, we did not verified significant changes in the layers lower than 5 cm. Our study provided important information for understanding the impacts and changes of the tropical forest conversion process by slash and burning native vegetation in Amazon.

A pesquisa teve como objetivo contribuir para a sustentabilidade das formas de uso dos solos na Amazônia central, avaliando a influência da cobertura vegetal nos teores de nutrientes na solução do solo, ou seja, nos teores de cátions, ânions e carbono orgânico dissolvido (COD). Tomou-se como referência uma floresta primária, para comparação com áreas degradada, de reflorestamento, e de floresta secundária. O estudo foi realizado nos municípios de Manaus e Presidente Figueiredo, AM. Em cada área foram instalados extratores de tensão, nas profundidades de 10, 20, 50, 100 e 150 cm, para as coletas de solução de solo para análise da fase inorgânica, e nas profundidades 20 e 100 cm, para a fase orgânica. A coleta de solo para análise química foi realizada nas mesmas profundidades utilizadas para as coletas de solução do solo da fase inorgânica. As coletas de solução do solo e a quantificação da água da chuva foram realizadas ao longo de um ano hidrológico, seguindo a sazonalidade do clima regional, durante os anos de 2002 e 2003. Após a coleta, filtragem e preservação, as amostras foram encaminhadas ao laboratório para a determinação das concentrações de cátions e ânions por cromatografia líquida (Equipamento Dionex, modelo DX500). As concentrações de COD foram determinadas por combustão, com detecção do CO2 gerado nesta por infra vermelho não-dispersivo (Equipamento Shimadzu, modelo TOC 5000A). A maioria dos solos foi classificada como latossolos, muito ácidos, intemperizados e com baixa disponibilidade de nutrientes. Dos cátions presentes na solução do solo observou-se a predominância sódica-potássica, com grande influência dos aportes atmosféricos. Em relação aos ânions, a predominância foi de bicarbonato e cloreto, com grande contribuição da atividade biológica nas concentrações de bicarbonato em áreas cobertas por vegetação, e do aporte atmosférico nas concentrações de cloreto nas áreas sem cobertura vegetal. A vegetação apresentou forte influência na dinâmica dos íons, principalmente para nitrogênio, fósforo, potássio e magnésio, que apresentam como principal fontes a reciclagem da matéria orgânica e a transprecipitação. Na área degradada ocorreu predominância de cloreto e sódio, elementos que apresentam como principal fonte de entrada a precipitação. Na floresta secundária e no reflorestamento observou-se sinais de recuperação, com níveis mais elevados de nutrientes do que observado na área degradada, com destaque para aumentos significativos de COD e nitrato. Não somente a vegetação afetou a dinâmica dos íons avaliados, mas também a textura do solo, acidez, profundidade e precipitação. Para o carbono orgânico dissolvido observou-se enriquecimento à 100 cm de profundidade, provavelmente em função dos menores teores de ferro e alumínio em profundidade no solo. Este aumento em profundidade pode estar indicando uma ligação entre os sistemas terrestre e aquático, na qual o primeiro funciona como possível exportador de carbono para o segundo. / The main objective of this study was to contribute for the sustainability of land use in the central Amazon, evaluating the influence of vegetation cover on nutrient concentrations in soil solution that is, on the amounts of cations, anions and dissolved organic carbon (DOC). Using a primary forest as reference, we compared these concentrations with those in a degraded area, in a reforestation and also in a secondary forest. The study was conducted in the counties of Manaus and Presidente Figueiredo. In each site we collected soil solution using tension lysimeters installed at the depths of 10, 20, 50, 100 and 150 cm for the inorganic phase and at 20 and 100 cm for the analysis of the organic phase. The soil itself was also collected at the same depths used for the study of the inorganic phase of soil solution, to determine its structure and chemical composition. Soil solution and precipitation were collected during a hydrological year, following the regional climate seasonality in the years of 2002 and 2003. After sampling, filtering and preserving in the field, soil solution samples were sent to the laboratory for the determination of cation and anion concentrations by liquid chromatography (Dionex, DX500) and DOC concentrations in a total organic carbon analyzer (Shimadzu, TOC5000A). Most of the soils were classified as Oxisols, very acid, highly weathered and with low nutrient availability. Sodium and potassium were the most predominant cations in soil solution, due to the influence of the atmospheric inputs. For anions, bicarbonate and chloride were showed the highest concentrations. At the sites covered with vegetation, biological activity played an important role in bicarbonate concentrations, as opposed to the site without vegetation, in which chloride was predominant, due to atmospheric inputs. There was a good correlation between vegetation cover and the dynamics of nitrogen, phosphorus, potassium and magnesium, all of which have as the main source recycling of organic matter recycling and throughfall. At the degraded area, chloride and sodium predominated, due to their main source, which is the precipitation. At the secondary forest and the reforestation there are indicators of the recovery of pristine conditions, whit higher levels of nutrients than those of the degraded area, specially significant increases in DOC and nitrate concentrations. Not only the vegetation influenced the dynamics of these nutrients in soil solution, but also soil texture, acidity, soil depth and precipitation. DOC, for example, showed significant increases in concentrations at 1m depths, probably due to the lowest iron and aluminum concentrations at these soil depths. This increase of DOC with depth may indicate an important connection between terrestrial and aquatic ecosystem, with the acting as an exporter of C to the rivers of the region.

O consumo e o mercado de cafés especiais, como orgânicos, gourmets e socialmente justos, cresce no mundo todo oferecendo preços atraentes para o produtor, enquanto o mercado de cafés commodity encontra grande oferta e preços muito baixos. A produção orgânica revela-se como alternativa ambiental, social e econômica, pois não contamina o meio ambiente e nem as pessoas direta e indiretamente envolvidas, além de agregar mais valor ao produto final. Apesar de o Brasil ser o maior produtor mundial de café, com aproximadamente 45 milhões de sacas em 2002, a produção de café orgânico foi aproximadamente de 70 mil sacas, de acordo com a ACOB (Associação de Cafeicultura Orgânica do Brasil). O México é o maior produtor mundial de café orgânico, com aproximadamente 500 mil sacas em 2002, sendo a maioria proveniente de sistemas sombreados de café. A cafeicultura nacional caracteriza-se por extensas áreas de monocultivo a pleno sol, desconsiderando o fato do café ser uma espécie originária de florestas caducifólias da Etiópia. A produção de café orgânico brasileira também é, em sua maioria, a pleno sol, com pouca biodiversidade e grande input ao sistema. Países produtores de café orgânico em sistemas sombreados e consumidores criticam a ausência de biodiversidade do sistema brasileiro. Portanto, a pesquisa nacional deve avaliar cientificamente diferentes manejos de café orgânico, obtendo informações quantitativas e qualitativas, visando a sustentabilidade sócio-ambiental e ganho de competitividade internacional do produto brasileiro neste nicho de mercado. Na busca de parâmetros que permitam a caracterização do sistema sombreado e do sistema a pleno sol de café orgânico, a composição química elementar avaliada em elevado nível metrológico é uma ferramenta potencial. Esta alta confiabilidade metrológica pode ser obtida através da análise por ativação neutrônica instrumental (INAA). Para a caracterização destes sistemas de produção de café orgânico, vários elementos químicos foram quantificados por INAA em grãos e folhas de café Coffea arabica, variedade Mundo Novo, e nos solos de ambos os sistemas - café sombreado por árvore leguminosa Platycyamus regnellii e café a pleno sol, na fazenda Jacarandá, Machado, Minas Gerais. Foram também avaliados os parâmetros de produtividade, fertilidade do solo, nutrição vegetal e qualidade do café. Os resultados indicam uma perspectiva positiva para a discriminação dos dois sistemas de produção utilizando-se da composição química elementar determinada por INAA. As avaliações demonstram uma tendência à superioridade do sistema sombreado, principalmen te quanto às maiores concentrações de potássio encontrados em grãos, folhas e solo, que podem ter propiciado uma melhor qualidade do café deste sistema. / The consumption of special coffee, mainly organic coffee, is increasing worldwide following the tendency of consuming products socially fair and ecologically sustainable, providing new market opportunities for coffee farmers in developing countries. The organic coffee is considered to have a better quality, once no agrochemicals are used and therefore, only the essential elements of the coffee will be present in the final product. Brazil is the largest world coffee producer, with 2,700,000 tons of green coffee in the 2002 harvest. However, only 4,200 tons are certified organic coffee, according to the Organic Coffee Brazilian Association (ACOB). The cultivation of organic coffee and shaded coffee are common in Central America, while in Brazil both conventional and organic coffee are mainly cultivated in the full sun system. Mexico, the largest world organic coffee producer, harvested 24,000 tons of certified organic coffee in the 2001-2002 season, most of it from shaded organic coffee system. In Brazil, such system is not well trusted and is also known as less productive. The full sun organic system is very criticized because of the lack of biodiversity and the high demand for external organic fertilizers. The shaded coffee system recycles more nutrients and has biodiversity, consequently, less dependent on external organic fertilizers, insecticides and fungicides. To characterize these two distinct organic coffee production systems, several inorganic chemical elements were quantified by instrumental neutron activation analysis (INAA) in coffee beans and leaves from Coffea arabica, variety Mundo Novo, leguminous shade tree (Platycyamus regnellii) leaves and soil from both systems at the Jacarandá farm, Machado, Minas Gerais State, Brazil. Other parameters such as productivity, soil fertility, plant nutrition and coffee quality were also evaluated. Results show a positive perspective for discrimination of the two production systems, through the chemical composition by INAA. The evaluations show a tendency of superiority for the shaded treatment, mainly according to the higher mass fractions of K in grains, leaves and soil, which may have caused better coffee quality.

Orientador: Luiz Roberto Cottas / Banca: Marilia Locatelli / Banca: Evaristo Castro Junior / Banca: Juércio Tavares de Mattos / Banca: Jairo Roberto Jiménez Rueda / Resumo: O histórico das modificações do uso da terra em Rondônia, e mais especificamente no município de Porto Velho, mostra transformações de grandes áreas de florestas em pastagens com rápida degradação de seus solos. A criação extensiva de gado de corte é a principal causa da ocupação e uso das terras no Estado. O objetivo deste trabalho foi avaliar a degradação ambiental associada à compactação dos solos por pisoteio animal. Foram considerados solos em pastagens degradadas, com vinte anos de pastejo, e florestas naturais em manchas contínuas de um Latossolo Amarelo Distrófico (LAd) e um Argissolo Vermelho Amarelo Distrófico plíntico (PVAd). A avaliação da densidade máxima e umidade ideal, obtida pelo Ensaio de Proctor, bem como observações referentes às diferenças da densidade aparente e a umidade dos solos, em seus limites inferior e superior de água disponível, registraram valores de compactação acima de 2,5 MPa indicando um nível prejudicial ao desenvolvimento radicular de algumas espécies. A resistência mecânica à penetração nas duas classes de solos ocorreu entre 0 - 10 cm com aumento entre 11 - 20 cm de profundidade, sendo que o Latossolo mostrou-se mais compactado em ambiente de pastagem que o Argissolo. As taxas de infiltração básica nas áreas de pastagens e de florestas evidenciaram diferenças entre os ambientes e seus solos, com reduções da infiltração básica nas áreas de pastagens do Latossolo. Influências antrópicas próximas das áreas de pastagens apresentaram-se como fatores associados na distribuição dos altos índices de compactação detectados. Os resultados obtidos evidenciaram de forma satisfatória os índices mais e menos significativos de caráter físico e químico da fertilidade para as áreas de pastagens e comparativamente as de floresta, permitindo detectar as áreas mais compactadas e suas relações aos... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The history of land use changes in Rondônia, and more specifically the city of Porto Velho, shows transformations of large forest areas into pastures with rapid soils degradation. The extensive beef cattle creation is the main cause of the occupation and land use in the state. The objective of this study was to evaluate the environmental degradation associated with soil compaction by cattle trampling. It was considered soils in degraded pastures, with twenty years of grazing, and natural forest patches in a continuous Oxisol Distrophic (LAd) and a Ultisol (Red Yellow Distrophic Plinthic - PVAd). The maximum density and optimum moisture content evaluation obtained by the Proctor test and observations relating to differences in bulk density and soil moisture on its lower and upper limits of available water, recorded values of compaction above 2.5 MPa indicating a detrimental level to root development for some species. The mechanical resistance to penetration in the two soil classes occurred between 0 to 10 cm with an increase between 11 to 20 cm deep, and the Oxisol was more compressed in a pasture environment than in the Ultisol. The basic infiltration rates in pasture areas and forests showed differences between environments and soils, with reductions of basic infiltration in Oxisol pasture areas. Anthropogenic influences near pasture areas were factors associated in the distribution of high compaction indexes detected. The obtained results showed as satisfactory manner the most and least significant indexes for physical and chemical nature of fertility in pasture areas compared to forest, allowing to detect the most compressed areas and their relationship to physical and chemical parameters considered in this study. / Doutor

Orientador: Morel de Passos e Carvalho / Banca: Marcelo Andreotti / Banca: Célia Regina Lopes Zimback / Resumo: O arroz é uma das fontes básicas de alimentação da humanidade. No processo de modernização e racionalização da agricultura brasileira, o uso de adubação adequada constitui um fator importante para o aumento da produtividade das culturas, redução dos custos de produção, maior retorno econômico para os produtores e redução do risco de degradação do meio ambiente. Assim, durante o ano agrícola 2009/2010, no município de Selvíria (MS), no Cerrado Brasileiro, foram estudados os atributos do arroz de terras e os atributos químicos de um LATOSSOLO VERMELHO Distroférrico sob sistema plantio direto, irrigado por pivô central. O objetivo foi selecionar entre os atributos pesquisados, aquele com a melhor correlação, linear e espacial, para explicar a variabilidade da produtividade do arroz de terras altas. Foi instalada a malha geoestatística, para a coleta de dados do solo e da planta, com 120 pontos amostrais, numa área de 3,0 ha e declive homogêneo de 0,055 m m-1. Do ponto de vista linear, o número de espiguetas viáveis por panícula apresentou correlação potencial direta com a produtividade de grãos de arroz. Entretanto, do ponto de vista espacial, o teor da matéria orgânica do solo, quando avaliada na camada 0,10 - 0,20 m, apresentou-se como indicador da produtividade de grãos de arroz. Dessa forma, visando-se auxiliar futuros trabalhos voltados à agricultura de precisão, os quais venham a utilizar os mesmos atributos que os do presente, os valores dos alcances da dependência espacial a serem empregados deverão estar compreendidos entre 40,2 e 181,2 metros / Abstract: The rice is one of the basic sources of the humanity's feeding. In the modernization process and rationalization of the Brazilian agriculture, the use of appropriate fertilization constitutes an important factor for the increase of the yield crop, reduction of the production costs, larger economical return for the producers and reduction of the risk of degradation of the environment. Like this, during the agricultural year 2009/2010, in Selvíria County, Mato Grosso do Sul State, in the Brazilian Savannah, they were studied the attributes of the rice uplands and the chemical attributes in a Dystropherric Red Latosol (Typic Acrustox) under no-tillage, irrigated by central pivot. The objective was to select among the researched attributes, that with the best correlation, spatial and linear, to explain upland rice yield variability. The geostatistical grid was installed, to collect the soil and plant data, with 120 sampling points, in an area of 3.0 ha and and homogeneous slope of 0.055 m m-1. Of the linear point of view, the number of viable spikelets per panicle showed direct potential correlation with the yield of grains of rice. However, of the spatial point of view, the organic matter soil, when appraised in the layer 0.10-0.20 m, showed up came as indicator of the yield of grains of rice. Thus, in order to support future researches concern precision agriculture, which uses the same attributes of this research, the values of the range of the spatial dependence to be utilized should be among 40.2 and 181.2 meters / Mestre

Nas últimas décadas as mudanças climáticas foram evidenciadas pelo aumento da temperatura global, diminuição dos estoques de carbono terrestres, associados ao aumento nas emissões de gases de efeito estufa (GEE). A floresta Amazônica é o maior bioma tropical do mundo e desenvolve serviços ambientais estratégicos no planeta. Entretanto, há mais de duas décadas que o desmatamento na Amazônia impulsiona as emissões globais de GEE, diminuindo o armazenamento de carbono do solo com alterações na dinâmica nas populações microbianas e nos ciclos biogeoquimicos pela mudança de uso da terra. O objetivo desse estudo foi avaliar as alterações temporais dos atributos químicos do solo, quantificar as emissões de CO2, CH4 e N2O e verificar as alterações na estrutura bacteriana do solo após o corte e queima de vegetação nativa na Amazônia. O estudo foi desenvolvido em área de vegetação nativa no norte do estado de Rondônia, região sul da Amazônia no Brasil. A área de estudo consistiu-se de quatro hectares, onde foi realizado o corte e queima em 2,25 hectares. Foram realizadas amostragens para avaliação da fertilidade do solo e estoques de carbono (C) e nitrogenio (N) nas profundidades de 0-5, 5-10, 10-15, 15-20, 20-30, 30-40, 40-50, 50-60, 60-80 e 80-100 cm. As coletas foram realizadas em vegetação nativa e aos 2, 30, 60, 90, 120, 240 e 365 dias após corte e queima. Foram determinados os atributos pH, Al, H+Al, Ca, Mg, K, P, C, N e calculados os valores de soma de bases, CTC, V % e m %. As coletas para quantificar as emissões dos GEE foram realizadas simultaneamente na área de vegetação nativa e no hectare central da área de corte e queima aos 19, 31, 48, 61 e 81 dias após corte e 2 , 4, 6, 8, 15, 31, 45, 61, 88, 122, 153, 180, 240 e 350 dias após queima, com amostragens aos 0, 20, 40 e 60 minutos. Os atributos microbiológicos do solo foram avaliados pela técnica de T-RFLP com amostragens realizadas simultaneas nas duas áreas, aos 32 e 62 dias após o corte e aos 2, 15, 30, 45, 60, 90, 120, e 360 dias após queima da biomassa vegetal. Foi verificado rápido aumento da fertilidade do solo e diminuição da acidez e teores de Al+3 após a queima, entretanto esse efeito foi pouco persistente, retornando ao status inicial do solo após um ano. Houve redução de 30 % nos estoques de C e N do solo no final do estudo, evidenciando os efeitos deletérios da mudança do uso da terra nos atributos químicos do solo. Foi registrado redução de 50 % das emissões de CO2 equivalente após o corte, comparada à vegetação nativa e reduções nas emissões de GEE de 35 % após um ano de estudo. Verificou-se na camada superficial, alterações significativas na estrutura da comunidade bacateriana do solo em decorrência do impacto do fogo e das alterações nos atributos químicos em função da deposição superficial de cinzas no solo, entretanto não foi verificada alterações significativa nas camadas abaixo de 5 cm. Este estudo forneceu importantes informações para o entendimento dos impactos e as alterações causadas pelo processo de conversão florestal tropical pelo corte e queima de vegetação nativa na Amazônia. / In recent decades, climate change has been evidenced by the increase in global temperature and the decrease in terrestrial carbon stocks, associated with an increase in greenhouse gas (GHG) emissions. The Amazon rainforest is the largest tropical biome in the world and develops strategic environmental services on the planet. However, for more than two decades, deforestation in Amazon has driven global GHG emissions, reducing soil carbon storage with changes in microbial populations dynamics and in biogeochemical cycles due to land use change. The objective of this study was to evaluate the temporal alterations of soil chemical attributes, quantify CO2, CH4 and N2O emissions and verify changes in soil bacterial structure, due to the slash and burn of the native vegetation in Amazon. The study was developed in an area of native vegetation in the north of Rondônia state, southern region of Amazon in Brazil. The study area consisted of 4 hectares, where it was cut and burned in 2.25 hectares. Samples were collected to evaluate soil fertility and carbon (C) and nitrogen (N) stocks at the depths of 0-5, 5-10, 10-15, 15-20, 20-30, 30-40, 40- 50, 50-60, 60-80 and 80-100 cm. These samples were collected in native vegetation at 2, 30, 60, 90, 120, 240 and 365 days after cutting and burning. The attributes pH, Al, H + Al, Ca, Mg, K, P, C, N were determined and the values of base sum, CEC, base saturation and aluminum saturation were calculated. The samples to quantify GHG emissions were carried out simultaneously in the native vegetation area and in the central hectare of the cutting and burning area at 19, 31, 48, 61 and 81 days after cutting and 2, 4, 6, 8, 15, 31, 45, 61, 88, 122, 153, 180, 240 and 350 days after burning, with samples at 0, 20, 40 and 60 minutes. The microbiological attributes of the soil were evaluated by T-RFLP technique with simultaneous samplings in the two areas, at 32 and 62 days after cutting and at 2, 15, 30, 45, 60, 90, 120, and 360 days after plant biomass burning. A rapid increase in soil fertility and a decrease in acidity and Al+3 contents after burning were verified, however this effect was not persistent, returning to the initial soil status after one year. There was a 30 % reduction in soil C and N stocks at the end of the study, evidencing the deleterious effects of land use change on soil chemical attributes. Also, a 50 % reduction in CO2 emissions after cutting, compared to native vegetation and, a 35 % reduction in GHG emissions after one year of study, were observed. We verified in the surface layer, significant alterations in the soil bacteria structure due to the fire impact and the changes in the chemical attributes, such as surface deposition of ashes. However, we did not verified significant changes in the layers lower than 5 cm. Our study provided important information for understanding the impacts and changes of the tropical forest conversion process by slash and burning native vegetation in Amazon.