Abstract Three newly selected strains of Cyclopia rhizobia together with an inoculant strain, which has never been tested in the field with adequate experimental design, was assessed under both nursery and field conditions for symbiotic performance. The three new test strains were initially selected for their superior Nz-fixing abilities under glasshouse conditions, and then evaluated in this study for field performance. Cyclopia subternata Vogel and Cyclopia genistoides (L.) R. Br., which have the potential for producing high quality honeybushtea, were used as host plants in both the nursery and field studies.The effect of seedling inoculation at the nursery level was also examined for the four test strains under nursery conditions. The inoculation of cuttings under nursery conditions produced.significant increases in shoot biomass, shoot %N and shoot N content. More specifically, inoculating C. subternata with strains UCT44b and UCT61a significantly increased shoot biomass and N content relative to strain PPRICI3. Strains UCT44b and UCT61a also showed better nodulation with C. subternata cuttings compared to strains UCHOa and PPRICI3. Field inoculation of Cyclopia increased all growth parameters relative to the uninoculated control, except for leaf %N. Cyclopia subternata inoculated with strains UCT44b, UCT40a and UCT61a produced significantly lower b15N values than the uninoculatedC. subternata reference plant. Using the 15N natural abundance method, C. subternata was estimated to be gaining about half of its N from Nz fixation, while C. genistoides obtained less than half of itsN from symbioticnutrition.

Abstract Three newly selected strains of Cyclopia rhizobia together with an inoculant strain, which has never been tested in the field with adequate experimental design, was assessed under both nursery and field conditions for symbiotic performance. The three new test strains were initially selected for their superior Nz-fixing abilities under glasshouse conditions, and then evaluated in this study for field performance. Cyclopia subternata Vogel and Cyclopia genistoides (L.) R. Br., which have the potential for producing high quality honeybushtea, were used as host plants in both the nursery and field studies.The effect of seedling inoculation at the nursery level was also examined for the four test strains under nursery conditions. The inoculation of cuttings under nursery conditions produced.significant increases in shoot biomass, shoot %N and shoot N content. More specifically, inoculating C. subternata with strains UCT44b and UCT61a significantly increased shoot biomass and N content relative to strain PPRICI3. Strains UCT44b and UCT61a also showed better nodulation with C. subternata cuttings compared to strains UCHOa and PPRICI3. Field inoculation of Cyclopia increased all growth parameters relative to the uninoculated control, except for leaf %N. Cyclopia subternata inoculated with strains UCT44b, UCT40a and UCT61a produced significantly lower b15N values than the uninoculatedC. subternata reference plant. Using the 15N natural abundance method, C. subternata was estimated to be gaining about half of its N from Nz fixation, while C. genistoides obtained less than half of itsN from symbioticnutrition.

A prática da adubação verde tem-se mostrado importante para diferentes cultivos, sejam eles consorciados ou em rotação de culturas. O Objetivo do trabalho foi analisar a dinâmica do nitrogênio em um sistema agroecológico de cultivo protegido com fabáceas intercalares ao minitomateiro em plantio direto sobre palhada de milho durante dois anos de cultivo do minitomateiro. O delineamento experimental foi o de blocos casualizados com oito tratamentos e cinco repetições. Os tratamentos: testemunha com palha de milho, testemunha sem palha de milho, consórcio com as seguintes espécies com o minitomateiro: feijão-de-porco (Canavalia ensiformis DC), crotalária-júncea (Crotalaria juncea L.), mucuna-anã [(Mucuna deeringiana (Bort) Merrill)], feijão-mungo (Vigna radiata (L.) Wilczek), tremoço-branco (Lupinus albus L.), feijão-caupi (Vigna unguiculata (L.) Walp). O tratamento com feijão-caupi teve menor número e massa de frutos comerciais (NFC e MFC) comparados com os tratamentos mucuna-anã e feijão-de-porco, respectivamente. O tratamento com feijão-de-porco apresentou aproximadamente, 25% e 8% maior massa de fruto total (MFT) e massa média de fruto total (MMFT) comparado ao tratamento com feijão-caupi, nesta ordem. O número e massa dos frutos comerciais e totais foram menores no segundo ano. Para o número de frutos totais (NFT), (MFT) e (MMFT), o ano 1 foi superior em 25%, 33% e 13% comparado ao ano 2, respectivamente. Os frutos no primeiro ano apresentaram maior massa média, menor teor de nutriente e menor relação entre solido solúveis totais e acidez titulável total (SST/ATT) do que no segundo ano. O tratamento com feijão-caupi teve maior porcentagem de N transferido na folha do minitomateiro comparado ao tratamento com feijão-mungo. Os adubos verdes não reduziram a produtividade, os parâmetros químicos da qualidade e os teores de macro e micronutrientes do minitomateiro. Não houve interferência entre os adubos verdes e as plantas de minitomate. As leguminosas utilizadas neste trabalho mostram potencial de transferência de N para o minitomateiro. / The practice of green manure has proven important for different crops, whether when on intercropping or on crop rotation. This paper analyzes the dynamics of nitrogen in an agroecological greenhouse intercropped green manure with cherry tomato under no-tillage system. The experimental design is a randomized block with eight treatments and five replications, which are: control treatment with corn straw, control treatment without corn straw; intercropping of the following species with the cherry tomato: jack bean (Canavalia ensiformis), crotalaria juncea (Crotalaria juncea DC), velvet bean [(Mucuna deeringiana (Bort) Merrill)], mung bean (Vigna radiata (L.) Wilczek), white lupine (Lupinus albus L.), cowpea bean (Vigna unguiculata (L.) Walp). The treatment with cowpea had lower number and weight of commercial fruits (NCF and WCF) compared to the treatments velvet bean and jack bean, respectively. Treatment with jack bean showed approximately 25% and 8% higher total fruit weight (TFW) and total average fruit weight (TAFW), compared to treatment with cowpea bean, in this order. The number and weight of commercial and total were lower in the second year. For the total number of fruits (TNF), (TFW) and (TAFW), year 1 was higher in 25%, 33% and 13% compared to year 2, respectively. The fruits in the first year showed higher average weight, lower nutrient content, and lower relation between total soluble solids and total titratable acidity (TSS/TTA) than in the second year. plants. Treatment with cowpea beans had a higher % of N transferred in the leaf of cherry tomato compared to the treatment with mung bean. Green manures did not reduce productivity, chemical quality parameters, and macro and micronutrient contents of the cherry tomato. There was no interference between green manures and cherry tomato. The legumes used in this work show the potential of transfer of N to the cherry tomato.

A prática da adubação verde tem-se mostrado importante para diferentes cultivos, sejam eles consorciados ou em rotação de culturas. O Objetivo do trabalho foi analisar a dinâmica do nitrogênio em um sistema agroecológico de cultivo protegido com fabáceas intercalares ao minitomateiro em plantio direto sobre palhada de milho durante dois anos de cultivo do minitomateiro. O delineamento experimental foi o de blocos casualizados com oito tratamentos e cinco repetições. Os tratamentos: testemunha com palha de milho, testemunha sem palha de milho, consórcio com as seguintes espécies com o minitomateiro: feijão-de-porco (Canavalia ensiformis DC), crotalária-júncea (Crotalaria juncea L.), mucuna-anã [(Mucuna deeringiana (Bort) Merrill)], feijão-mungo (Vigna radiata (L.) Wilczek), tremoço-branco (Lupinus albus L.), feijão-caupi (Vigna unguiculata (L.) Walp). O tratamento com feijão-caupi teve menor número e massa de frutos comerciais (NFC e MFC) comparados com os tratamentos mucuna-anã e feijão-de-porco, respectivamente. O tratamento com feijão-de-porco apresentou aproximadamente, 25% e 8% maior massa de fruto total (MFT) e massa média de fruto total (MMFT) comparado ao tratamento com feijão-caupi, nesta ordem. O número e massa dos frutos comerciais e totais foram menores no segundo ano. Para o número de frutos totais (NFT), (MFT) e (MMFT), o ano 1 foi superior em 25%, 33% e 13% comparado ao ano 2, respectivamente. Os frutos no primeiro ano apresentaram maior massa média, menor teor de nutriente e menor relação entre solido solúveis totais e acidez titulável total (SST/ATT) do que no segundo ano. O tratamento com feijão-caupi teve maior porcentagem de N transferido na folha do minitomateiro comparado ao tratamento com feijão-mungo. Os adubos verdes não reduziram a produtividade, os parâmetros químicos da qualidade e os teores de macro e micronutrientes do minitomateiro. Não houve interferência entre os adubos verdes e as plantas de minitomate. As leguminosas utilizadas neste trabalho mostram potencial de transferência de N para o minitomateiro. / The practice of green manure has proven important for different crops, whether when on intercropping or on crop rotation. This paper analyzes the dynamics of nitrogen in an agroecological greenhouse intercropped green manure with cherry tomato under no-tillage system. The experimental design is a randomized block with eight treatments and five replications, which are: control treatment with corn straw, control treatment without corn straw; intercropping of the following species with the cherry tomato: jack bean (Canavalia ensiformis), crotalaria juncea (Crotalaria juncea DC), velvet bean [(Mucuna deeringiana (Bort) Merrill)], mung bean (Vigna radiata (L.) Wilczek), white lupine (Lupinus albus L.), cowpea bean (Vigna unguiculata (L.) Walp). The treatment with cowpea had lower number and weight of commercial fruits (NCF and WCF) compared to the treatments velvet bean and jack bean, respectively. Treatment with jack bean showed approximately 25% and 8% higher total fruit weight (TFW) and total average fruit weight (TAFW), compared to treatment with cowpea bean, in this order. The number and weight of commercial and total were lower in the second year. For the total number of fruits (TNF), (TFW) and (TAFW), year 1 was higher in 25%, 33% and 13% compared to year 2, respectively. The fruits in the first year showed higher average weight, lower nutrient content, and lower relation between total soluble solids and total titratable acidity (TSS/TTA) than in the second year. plants. Treatment with cowpea beans had a higher % of N transferred in the leaf of cherry tomato compared to the treatment with mung bean. Green manures did not reduce productivity, chemical quality parameters, and macro and micronutrient contents of the cherry tomato. There was no interference between green manures and cherry tomato. The legumes used in this work show the potential of transfer of N to the cherry tomato.

Whole farm nutrient budgets (WFNB) enable producers to link dairy herd management with traditional field nutrient management plans. The objective of this study was to calculate WFNBs of nitrogen, phosphorus, and potassium (N, P, and K) at a commercial farm in New Brunswick and in Prince Edward Island. Reliable estimates of N fixation from alfalfa and red clover on the farms were obtained with adjustments to the Høgh-Jensen et al. (2004) dry matter conversion models. The farms had surpluses of N, P, and K. Both farms imported feed as well as nutrient inputs for crop production. Surpluses of all nutrients were typical in comparison to WFNBs of similar dairy farms; however, the nutrient use efficiencies were low. The imported manure and fertilizer used in the crop production components contributed to surpluses of N and P which could likely be reduced to improve overall farm nutrient use efficiency.

Switchgrass (Panicum virgatum), a perennial C4 grass species, has the capacity to not only improve the quality of the soil in which it grows but also promote soil carbon storage to offset rising atmospheric CO2. This research investigated soil organic carbon (SOC) dynamics beneath switchgrass using natural abundance 13C and soil carbon fractionation following the establishment of this crop in a native and predominantly C3 plant region in southeastern Ontario. I investigated SOC dynamics by sampling adjacent commercial switchgrass fields and appropriate paired control fields at sites where the time since switchgrass establishment varied from 4-11 years. SOC and natural 13C abundance were measured in paired fields to assess management-induced changes in the quantity, source, and turnover time of soil carbon. To better elucidate carbon cycling dynamics over a relatively short time since switchgrass establishment, multiple soil fractionation techniques were applied to better understand carbon dynamics of soil organic matter with various mean residence times. Establishment of switchgrass results in marginal increases in SOC, primarily at sites where intensive soil management (i.e. tillage) practices preceded switchgrass establishment. Changes were observed in some of the more labile SOC pools, as well as in the δ13C values of the bulk soil and soil carbon fractions, indicating that growing switchgrass was causing the incorporation of switchgrass-derived carbon into the soil. Even resistant SOC pools, with turnover times of over 100 years, incorporated significant quantities of switchgrass carbon in 11 years. Annual increases in SOC, however, were less than values reported elsewhere. The potential for soil carbon storage exists, likely due to longer mean residence times of the carbon in soils beneath switchgrass compared with other cultivation systems. Changes in SOC following switchgrass establishment related strongly to the amount of root biomass, time since establishment and prior soil management practices. The decomposition rates derived in this research should be integrated into soil carbon modeling applications intended to support the emergence of switchgrass in southeastern Ontario. The results of my research can advance soil carbon models and be used to make regional assessment of the potential impact of growing switchgrass for bioenergy in southeastern Ontario. / Thesis (Master, Geography) -- Queen's University, 2012-01-30 13:56:06.269

Soil organic matter (SOM) is a dynamic soil property, sensitive and responsive to many factors. The possibility of increasing soil carbon (C) sequestration by changing land use and management practices has been of great interest recently due to concerns with global changes in the atmospheric carbon dioxide (CO2) balance. Nonetheless, as a result of the complex dynamics of SOM, there is still the need for SOM characterization procedures capable of monitoring SOM stabilization, taking into account all the factors involved. This study characterized SOM stabilization as affected by management practices in three long-term field experiments, considering physical, chemical and biological components. The field experiments are located near Lexington, Kentucky, on a Maury silt loam (fine, mixed, mesic Typic Paleudalfs). The first experiment evaluates tillage and nitrogen (N) rate effects. The second experiment studies manure and N rate effects. The third experiment evaluates the five corn components of three crop rotations [continuous (monoculture) corn, corn-wheat/double crop soybean, and hay-hay-corn-corn-corn]. Soil organic matter content, stability, and composition, for physically separated fractions, were assessed using δ13C natural abundance and diffuse reflectance Fourier transformed infrared (DRIFT) spectroscopy. In addition, management effects on microbial biomass and microbial function as indicated by phenol oxidase enzyme activity were evaluated. The results indicate that management practices affect SOM content, stability, and composition, and these effects differ by the soil aggregate fraction. No-tillage (NT), N fertilization, manure application and increased corn in crop rotations enhanced SOM levels. However, the effect of NT was observed mainly at the soil surface. Soil organic matter storage was determined by the aggregate size distribution. The proportion of recently deposited C was generally positively related to aggregate size, especially for the first and third experiments. Most of the recently deposited C was stabilized in microaggregates within macroaggregates, across the management treatments and field experiments. In addition, this fraction consistently exhibited low to medium SOM reactivity. These results suggest that SOM stabilization, as influenced by management practices, required achieving a specific composition and location within the soil matrix. This implies that soil C forms and aggregate size and stability are closely interrelated.

No description available.

No description available.

A recuperação de funções e processos ecossistêmicos, entre outros atributos, é um dos indicadores mais importantes no processo de retorno de um ecossistema à sua trajetória histórica. A ciclagem de nutrientes é um atributo fundamental do ecossistema, e relaciona-se diretamente à regulação do funcionamento e do desenvolvimento dos ecossistemas e inclui, em um modelo geral, as entradas de nutrientes, as transferências internas entre plantas e solo e as saídas do sistema. A compreensão das mudanças nos processos biogeoquímicos durante a sucessão secundária em áreas em restauração ecológica ainda é incipiente, principalmente em áreas de florestas tropicais. Esse estudo tem por objetivo elucidar a dinâmica do nitrogênio ao longo do processo de restauração ecológica em áreas reflorestadas com espécies nativas da Mata Atlântica. A questão norteadora deste estudo é a seguinte: A restauração florestal com alta diversidade de espécies e predominância de espécies arbóreas nativas regionais restaura a dinâmica original do nitrogênio? Esse estudo visa investigar o funcionamento da ciclagem de nutrientes, com foco no nitrogênio, que é um elemento limitante à sucessão secundária, especialmente em florestas tropicais. Para tal, alguns indicadores da ciclagem do nitrogênio foram mensurados em uma cronosequência florestal formada por uma floresta natural preservada e florestas restauradas de diferentes idades (21 e 52 anos) reflorestadas com alta diversidade de espécies e predominância de nativas regionais. Os indicadores utilizados foram: 15N e teor de N da vegetação, serrapilheira e solo; razão N:P da vegetação e da serrapilheira; taxas líquidas de mineralização e nitrificação; teor de amônio, nitrato, N mineral e razão nitrato:amônio. As florestas foram amostradas entre agosto de 2008 e abril de 2009, nas seguintes estações: seca, transição entre seca e chuvosa, chuvosa, e transição entre chuvosa e seca. Foram encontrados padrões claros de mudanças na ciclagem do N ao longo da cronosequência estudada, incluindo diferenças nos valores de 15N foliar, teor de N, razão N:P, N mineral e taxas líquidas de mineralização e nitrificação, caracterizadas por um aumento de valores médios dessas variáveis ao longo da cronosequência. Os resultados encontrados sugerem que as florestas em processo de restauração, mesmo a de 52 anos, ainda não possuem uma ciclagem de N característica de uma floresta madura e, portanto, a recuperação da ciclagem de N ainda não foi completamente atingida. Entretanto, é possível afirmar que as florestas em processo de restauração estudadas estão seguindo uma trajetória de desenvolvimento caracterizada por uma ciclagem de N cada vez mais parecida com a de uma floresta natural madura, como a da floresta natural madura utilizada como referência. Através dos modelos de restauração utilizados para as florestas da cronosequência estudada, os processos da ciclagem do N são recuperados à medida que a floresta desenvolve-se, com uma clara tendência de mudança na economia de N para economia de P típica de florestas tropicais maduras. / The recuperation of ecosystem processes and functions, among other attributes, is one of the most important indicators in the process of return of an ecosystem to its historic trajectory. Nutrient cycling is a fundamental ecosystem attribute, and relates directly to regulation of functioning and development of ecosystems and includes, in a general model, nutrients entering, being transferred internally between plants and soil, end leaving the system. The comprehension of changes in biogeochemical processes during secondary succession in areas in ecological restoration is still incipient, mainly in tropical forests. This study aims to elucidate nitrogen dynamics along the process of ecological restoration in areas reforested with Atlantic Forest native species. The question driving this study is: Does ecological restoration with high diversity of species and predominance of regional native tree species restore nitrogen original dynamics? This research investigated nutrients cycling functioning, focusing on nitrogen, which is a limiting nutrient in secondary succession, particularly in tropical forests. In order to do so, some indicators of nutrient cycling were assessed in a forest chronosequence formed by a preserved natural forest and restored forests of different ages (21 and 52 years) reforested using high species diversity and predominance of regional native species. The indicators used were: 15N and N content in green foliage, litter and soil; N:P ratio of green foliage and litter; net mineralization and net nitrification rates; content of ammonium, nitrate, inorganic N, and nitrate:ammonium ratio. The forests were sampled between August 2008 and April 2009, in the following seasons: dry, dry-rainy transition, rainy, rainy-dry transition. Clear patterns of change in the N cycling along the studied chronosequence were found, including differences in green foliage 15N values, N content, N:P ratio, inorganic N and net mineralization and nitrification rates, characterized by an increase in the mean values of these variables along the chronosequence. The results found suggest that the forests in restoration process, even the 52 years old one, still do not present a N cycling characteristic of a mature forest and, therefore, the recuperation of the N cycling was not completely reached yet. However, it is possible to state that the forests in restoration process studied here are following a development trajectory characterized by a N cycling progressively more similar to what is common to a mature native forest, as the one used as the reference ecosystem in this study. Through the restoration models used for the forests studied, the N cycle processes are recovered as the forests develop, as they present a clear tendency of changing from N economy to P economy, typical to mature tropical forests.