No description available.

The replacement of the native vegetation by pastures and silviculture can result in clear changes on the carbon and nitrogen pools, stocks and dynamics. We aimed to assess the impact of the woodland cerrado (cerradão) conversion into pastures and Eucalyptus plantations on the soil organic carbon (SOC) labile pools and dynamics, on the concentrations of N variables and on the potential for nitrogen mineralization (PMN) in the first 200 cm of the soil profile. We also assessed the seasonal variation on the overall variability in soil C and N pools and dynamics. Finally, we investigated the C and N stocks belowground (up to 50 cm depth) and C stocks aboveground. We had three sampling sites in a region originally covered by cerradão physiognomy. Each sampling included a control area (Cerrado) and two land uses (Pasture, Eucalyptus). Soil samples were taken at 0-10, 10-30, 30-50, 50-100 and 100-200 cm depths during the dry and wet climate seasons, from which we used the first three depths for stocks calculation. We also collected litter and herbs+shrubs biomass, and measured the tree biomass for C stocks calculation. Our results showed ~50% reduction of the microbial biomass (MBC) and MBC:SOC for pastures and Eucalyptus plantations, indicating lower SOC stability. Reduction in the dissolved organic carbon (DOC) and DOC:SOC, and increment on the metabolic quotient were also registered for both land uses along the soil profile up to 30 or 50 cm depth. Higher SBR and qCO2 rates are associated to a microbial community under stress. Land use effect on SOC labile pools and dynamics was more marked in the dry season. The inorganic forms of nitrogen (NH4-N and NO3-N) and PMN were significantly affected by land use conversion, with decreases in both land uses compared to native Cerrado, with lower values found in Eucalyptus. Urease activity also decreased with land conversion. The N variables all decreased with depth from 10 to 50 cm depth. Land conversion also resulted in C and N stock losses, and in redistribution among the system compartments. Pastures showed 53% less overall C stock, and Eucalyptus plantations had 20% more. Carbon was mostly stored belowground in pastures, and aboveground in Eucalyptus, as the native Cerrado showed a balanced distribution. Aboveground, C was 94% reduced in pastures compared to Cerrado, and 80% increased in Eucalyptus plantations; belowground, pastures had 19% and 25% reductions in the overall C and N stocks respectively, with significant decreases for the stocks of arboreal C, MBC, coarse root C and N, NO3-N and PMN. Eucalyptus plantations had 23% decrease in C and 19% in N stocks, with significant reductions in the stocks of herbs+shrubs C, MBC, fine and coarse root C, fine root N, NH4-N and PMN. Both land uses had similar overall losses of C and N belowground, which were evident until 50 cm depth, but higher at the 10-30 cm layer. Our results show negative impacts on carbon and nitrogen pools, cycling processes and stocks due to Cerrado conversion to pastures and Eucalyptus plantations / A substituição da vegetação nativa por pastagem e silvicultura pode resultar em mudanças nas concentrações, estoques e dinâmica do carbono e nitrogênio. O objetivo do trabalho foi analisar o impacto da conversão de cerradão em pastagens de braquiária e plantações de eucalipto na dinâmica e na concentração de variáveis da fração lábil do carbono orgânico do solo (SOC), nas concentrações das variáveis de nitrogênio e no seu potencial de mineralização (PMN), para os primeiros 200 cm de profundidade do solo. Foi ainda avaliada a variação sazonal na variabilidade das concentrações e dinâmicas de C e N no solo. Além disso, investigamos os estoques de C e N abaixo do solo (até 50 cm de profundidade) e os estoques de C acima do solo. Nossas amostragens foram realizadas em três áreas de pesquisa, numa região originalmente coberta por cerradão. Cada área de pesquisa era constituída por um sítio controle (Cerrado) e dois usos das terras (pastagem, eucalipto). Amostras de solo foram coletadas nas profundidades de 0-10, 10-30, 30-50, 50-100 e 100-200 cm durante as estações seca e chuvosa, para as análises das frações de C e N; para o cálculo dos estoques de C e N, foram utilizadas somente as três primeiras profundidades. Também coletamos serapilheira e biomassa de herbáceas + arbustos, assim como tiramos medidas das árvores para o cálculo do estoque de C acima do solo. Nossos resultados mostraram uma redução de aproximadamente 50% da biomassa microbiana (MBC) e da taxa MBC:SOC para pastagens e plantios de eucalipto, indicando menor estabilidade do carbono orgânico do solo. Também foram registrados decréscimos para o carbono orgânico dissolvido (DOC) e para as taxas DOC:SOC, além de aumentos para o quociente metabólico em ambos os usos, ao longo do perfil do solo até 30 ou 50 cm de profundidade. Taxas mais altas de respiração edáfica e do quociente metabólico estão associadas a uma comunidade microbiana sob estresse. O efeito do uso das terras nas concentrações e na dinâmica das variáveis lábeis do C orgânico do solo foi mais acentuado na estação seca. As formas inorgânicas de nitrogênio (NH4-N e NO3-N) e PMN foram significativamente afetados pela conversão do uso da terra, com decréscimos em ambos os usos em comparação ao Cerrado nativo, sendo menores os valores encontrados no Eucalipto. A atividade da urese também decresceu com a mudança de uso. Todas as variáveis de N diminuíram com a profundidade de 10 a 50 cm. A conversão de uso também resultou em perdas nos estoques de C e N e em sua redistribuição entre os compartimentos acima e abaixo do solo. O estoque total de C em pastagens reduziu em 53% e nas plantações de eucalipto ocorreu aumento de 20%. O carbono foi armazenado principalmente abaixo do solo em pastagens e acima do solo nos plantios de eucaliptos, enquanto que o Cerrado nativo apresentou uma distribuição equilibrada entre esses dois grandes compartimentos. Na pastagem, foi registrada uma redução de 94% no estoque da biomassa aérea, em comparação com o Cerrado, enquanto que as plantações de eucalipto apresentaram um aumento de 80%; abaixo do solo, as pastagens tiveram reduções de 19% e 25% nos estoques totais de C e N, respectivamente, com decréscimos significativos para o estoque C de árvores, de MBC, de C e N de raizes grossas, de NO3-N e de PMN. As plantações de eucalipto tiveram redução de 23% para o estoque total de C abaixo do solo e de 19% para o estoque de N (abaixo do solo), com reduções significativas para estoque C da biomassa de ervas + arbustos, de MBC, de C de raízes finas e grossas, bem como para os estoque de N de raízes finas, de NH4-N e de PMN. Ambos os usos da terra tiveram perdas totais semelhantes para os estoques de C e N abaixo do solo, que ficaram evidentes até 50 cm de profundidade, porém, mais significativos na camada de 10-30 cm. Nossos resultados demonstraram impactos negativos da conversão do cerrado em pastagens e plantações de eucalipto para as concentrações de carbono e nitrogênio, assim como em seus processos de ciclagem e estoques

O nitrogênio (N) é o nutriente exigido em maior quantidade pelo cafeeiro e o segundo mais exportado pelos grãos. O uso do consórcio entre o cafeeiro e a braquiária é cada vez mais usado pelos cafeicultores. Nesse sistema de produção a fertilização é feita, em geral, nas duas espécies, sem conhecimento suficiente que respalde esse manejo. O N do resíduo vegetal pode ser absorvido pela planta após a mineralização, ser perdido por vários processos, ou ainda, ser imobilizado pela microbiota. O uso de fertilizantes enriquecidos isotopicamente é uma ferramenta que permite avaliar o N do fertilizante nos componentes do sistema, como no resíduo da forrageira, no solo e na planta. Essa pesquisa foi realizada com o objetivo de avaliar o crescimento e a produtividade do cafeeiro; elaborar o balanço de N; e avaliar a decomposição da biomassa da braquiária sob a copa do café, como fonte desse nutriente. A biomassa da braquiária sob a copa do cafeeiro reduziu em 49% a perda de água nos meses secos, com aumento do crescimento da planta entre março e setembro de 2011. A granação dos frutos e a produtividade do cafeeiro foram superiores quando aplicou-se 50% da dose do N na planta e os outros 50% na braquiária, cujo resíduo foi depositado sob a copa da planta, para a decomposição. A forrageira recuperou mais N (84,28% do aplicado ou 126,42 kg ha-1) do que o cafeeiro (38,63% ou 57,94 kg ha-1 de N), com a aplicação da mesma dose de N em ambas as plantas. O cafeeiro recuperou 38,63% do N do fertilizante, quando todo o N foi fornecido à planta; recuperou 14,31% do N (21,46 kg ha-1) na aplicação feita somente na forrageira, em que o resíduo foi depositado sob a copa da planta; e recuperou 53,3% do N (39,98 kg ha-1) do adubo e outros 15,28% (11,46 kg ha-1) proveniente da decomposição da biomassa, na aplicação da mesma dose de N na cultura e na forrageira. A taxa de crescimento do cafeeiro (altura e ramos produtivos) no período seco, de março a setembro de 2011, foi superior quando a planta e a forrageira receberam a mesma dose de N. A competição líquida por N entre a braquiária e o café foi pequena e variou de 1,22% (0,91 kg ha-1) a 0,24% (0,34 kg ha-1 de N), sem prejuízo ao crescimento e à produtividade do cafeeiro. A perda de N por lixiviação foi maior quando forneceu todo o N somente no cafeeiro (6,05% do N aplicado ou 9,07 kg ha-1), em relação à adubação feita apenas na braquiária (1,02% ou 1,53 kg ha-1 de N); e, na aplicação de doses iguais no café e na braquiária, a lixiviação variou de 3,4% do N aplicado (2,55 kg ha-1) sob a copa da planta a 1,15% (0,86 kg ha-1) na área da forrageira, cultivada na entre linha da cultura. A biomassa da braquiária fertilizada com N possuia menores relações lignina/N e C/N; e a mineralização do N foi mais rápida do que a decomposição da biomassa. A ciclagem do N depende da época de corte, com maior intensidade quando a ceifa ocorreu entre 30 e 55 dias na braquiária fertilizada e até 30 dias após rebrota, quando não recebeu N. / Nitrogen (N) is the nutrient required in larger quantities by coffee and the second most exported by the grains. The use of intercropping coffee and the Brachiaria is increasing within coffee farmers. In this production the fertilization is done generally in both species, without enough knowledge support for this. The N of the plant residue can be absorbed by the plant after mineralization, can be lost by various processes or even immobilized by micro biota. The use of isotopic enriched fertilizer is a tool that allows the evaluation of N of the fertilizer in component of the system, such as in the residue of forage, in soil and in the plant. This research was conducted to evaluate the growth and productivity of coffee plant, elaborate the N balance and evaluate the decomposition of biomass of Brachiaria under the canopy the crop as a source of this nutrient. The Brachiaria biomass under the coffee plant canopy reduced by 49% the water loss in dry months, with an increase in plant growth within the dry season that went throw March to September 2011. The gain in fruit development and the plant productivity were higher when applied an N doses of 50% within the coffee plant and 50% on the Brachiaria, which the wastes were deposited under the canopy of the crop for decomposition. The forage Bracharia recovered more N (84.28% of the applied or 126.42 kg ha-1) than coffee plant (38.63% or 57.94 kg N ha-1) with the application of the same dose of N in both plants. The N of the fertilizer recovered by the coffee plant was: 38.63% when all N was supplied to the plant, 14.31% (21.46 kg ha-1) when the application was made only in forage residue which was deposited under canopy of the plant, 53.3% (39.98 kg ha-1) from the fertilizer and other 15.28% (11.46 kg ha-1) from the decomposition of biomass in the application of the same dose of N in culture and forage. The growth rate of coffee plant (height and productive branches) in the dry season was superior when the culture and the forage received the same doses of N. The total net competition on N between the culture and Brachiaria was low, about 0.91 kg ha-1 to 0.34 kg N ha-1 (1.22 to 0.24%), not prejudicing the culture growth and productivity. The N loss due to leaching was higher when provided only to the coffee plant (6.05% of N applied or 9.07 kg ha-1) comparing to applying N exclusively to the brachiaria (1.02% or 1, 53 kg N ha-1). When applying equal doses in coffee plant and brachiaria the leaching varied from 3.4% of applied N (2.55 kg ha-1) under the canopy of the plant to 1, 15% (0.86 kg ha-1) in the forage area, grown between the crop rows. The rate of decomposition of the residue of Brachiaria was inversely proportional to the relations C / N and lignin / N. The cycling of N was faster when the reaping occurred up to 55 days of forage development.

O nitrogênio (N) é o nutriente exigido em maior quantidade pelo cafeeiro e o segundo mais exportado pelos grãos. O uso do consórcio entre o cafeeiro e a braquiária é cada vez mais usado pelos cafeicultores. Nesse sistema de produção a fertilização é feita, em geral, nas duas espécies, sem conhecimento suficiente que respalde esse manejo. O N do resíduo vegetal pode ser absorvido pela planta após a mineralização, ser perdido por vários processos, ou ainda, ser imobilizado pela microbiota. O uso de fertilizantes enriquecidos isotopicamente é uma ferramenta que permite avaliar o N do fertilizante nos componentes do sistema, como no resíduo da forrageira, no solo e na planta. Essa pesquisa foi realizada com o objetivo de avaliar o crescimento e a produtividade do cafeeiro; elaborar o balanço de N; e avaliar a decomposição da biomassa da braquiária sob a copa do café, como fonte desse nutriente. A biomassa da braquiária sob a copa do cafeeiro reduziu em 49% a perda de água nos meses secos, com aumento do crescimento da planta entre março e setembro de 2011. A granação dos frutos e a produtividade do cafeeiro foram superiores quando aplicou-se 50% da dose do N na planta e os outros 50% na braquiária, cujo resíduo foi depositado sob a copa da planta, para a decomposição. A forrageira recuperou mais N (84,28% do aplicado ou 126,42 kg ha-1) do que o cafeeiro (38,63% ou 57,94 kg ha-1 de N), com a aplicação da mesma dose de N em ambas as plantas. O cafeeiro recuperou 38,63% do N do fertilizante, quando todo o N foi fornecido à planta; recuperou 14,31% do N (21,46 kg ha-1) na aplicação feita somente na forrageira, em que o resíduo foi depositado sob a copa da planta; e recuperou 53,3% do N (39,98 kg ha-1) do adubo e outros 15,28% (11,46 kg ha-1) proveniente da decomposição da biomassa, na aplicação da mesma dose de N na cultura e na forrageira. A taxa de crescimento do cafeeiro (altura e ramos produtivos) no período seco, de março a setembro de 2011, foi superior quando a planta e a forrageira receberam a mesma dose de N. A competição líquida por N entre a braquiária e o café foi pequena e variou de 1,22% (0,91 kg ha-1) a 0,24% (0,34 kg ha-1 de N), sem prejuízo ao crescimento e à produtividade do cafeeiro. A perda de N por lixiviação foi maior quando forneceu todo o N somente no cafeeiro (6,05% do N aplicado ou 9,07 kg ha-1), em relação à adubação feita apenas na braquiária (1,02% ou 1,53 kg ha-1 de N); e, na aplicação de doses iguais no café e na braquiária, a lixiviação variou de 3,4% do N aplicado (2,55 kg ha-1) sob a copa da planta a 1,15% (0,86 kg ha-1) na área da forrageira, cultivada na entre linha da cultura. A biomassa da braquiária fertilizada com N possuia menores relações lignina/N e C/N; e a mineralização do N foi mais rápida do que a decomposição da biomassa. A ciclagem do N depende da época de corte, com maior intensidade quando a ceifa ocorreu entre 30 e 55 dias na braquiária fertilizada e até 30 dias após rebrota, quando não recebeu N. / Nitrogen (N) is the nutrient required in larger quantities by coffee and the second most exported by the grains. The use of intercropping coffee and the Brachiaria is increasing within coffee farmers. In this production the fertilization is done generally in both species, without enough knowledge support for this. The N of the plant residue can be absorbed by the plant after mineralization, can be lost by various processes or even immobilized by micro biota. The use of isotopic enriched fertilizer is a tool that allows the evaluation of N of the fertilizer in component of the system, such as in the residue of forage, in soil and in the plant. This research was conducted to evaluate the growth and productivity of coffee plant, elaborate the N balance and evaluate the decomposition of biomass of Brachiaria under the canopy the crop as a source of this nutrient. The Brachiaria biomass under the coffee plant canopy reduced by 49% the water loss in dry months, with an increase in plant growth within the dry season that went throw March to September 2011. The gain in fruit development and the plant productivity were higher when applied an N doses of 50% within the coffee plant and 50% on the Brachiaria, which the wastes were deposited under the canopy of the crop for decomposition. The forage Bracharia recovered more N (84.28% of the applied or 126.42 kg ha-1) than coffee plant (38.63% or 57.94 kg N ha-1) with the application of the same dose of N in both plants. The N of the fertilizer recovered by the coffee plant was: 38.63% when all N was supplied to the plant, 14.31% (21.46 kg ha-1) when the application was made only in forage residue which was deposited under canopy of the plant, 53.3% (39.98 kg ha-1) from the fertilizer and other 15.28% (11.46 kg ha-1) from the decomposition of biomass in the application of the same dose of N in culture and forage. The growth rate of coffee plant (height and productive branches) in the dry season was superior when the culture and the forage received the same doses of N. The total net competition on N between the culture and Brachiaria was low, about 0.91 kg ha-1 to 0.34 kg N ha-1 (1.22 to 0.24%), not prejudicing the culture growth and productivity. The N loss due to leaching was higher when provided only to the coffee plant (6.05% of N applied or 9.07 kg ha-1) comparing to applying N exclusively to the brachiaria (1.02% or 1, 53 kg N ha-1). When applying equal doses in coffee plant and brachiaria the leaching varied from 3.4% of applied N (2.55 kg ha-1) under the canopy of the plant to 1, 15% (0.86 kg ha-1) in the forage area, grown between the crop rows. The rate of decomposition of the residue of Brachiaria was inversely proportional to the relations C / N and lignin / N. The cycling of N was faster when the reaping occurred up to 55 days of forage development.

<p>Cereal rye (<i>Secale cereale</i>, L., CR) is the most commonly utilized cover crop species within the United States. Yet, the total land area planted to CR on an annual basis remains relatively low despite its numerous proven environmental benefits. The relatively low rates of CR adoption could be due to a dearth of knowledge surrounding certain agronomic and economic components of CR adoption. Currently, there exists knowledge gaps within the scientific literature regarding CR performance, N cycling, and associated economic risk. <a>Thus, to address the above-mentioned knowledge gaps, three individual studies were developed to: i) investigate the fate of scavenged CR nitrogen (N) amongst soil N pools, ii) assess the suitability of visible-spectrum vegetation indices (VIs) to predict CR biomass and nutrient accumulation (BiNA), and iii) characterize the economic risk of CR adoption at a regional scale over time.</a></p> <p>In the first study, ¹⁵N, a stable isotope of N, was used in an aerobic incubation to track the fate of CR root and shoot N among the soil microbial biomass, inorganic, and organic N pools, as well as explore CR N bioavailability over a simulated corn growing season. In this study, the C:N ratio of the shoot residues was 16:1 and the roots was 31:1 and differences in residue quality affected the dynamics of CR N release from each residue type. On average, 14% of whole plant CR N was recovered in the soil inorganic N pool at the final sample date. Correspondingly, at the final sampling date 53%, 33%, and less than 1% of whole plant CR N was recovered as soil organic N, undecomposed residue, and as microbial biomass N, respectively. Most CR N remained unavailable to plants during the first cash crop growing season subsequent to termination. This knowledge could support the advancement of N fertilizer management strategies for cropping systems containing cereal rye.</p> <p>In the second study, a commercially available unmanned aerial vehicle (UAV) outfitted with a standard RGB sensor was used to collect aerial imagery of growing CR from which visible-spectrum VIs were computed. Computed VIs were then coupled with weather and geographic data using linear multiple regression to produce prediction models for CR biomass, carbon (C), N, phosphorus (P), potassium (K), and sulfur (S). Five visible-spectrum VIs (Visible Atmospherically Resistant Index (VARI), Green Leaf Index (GLI), Modified Green Red Vegetation Index (MGRVI), Red Green Blue Vegetation Index (RGBVI), and Excess of Green (ExG)) were evaluated and the results determined that MGRVI was the best predictor for CR biomass, C, K, and S and that RGBVI was the best predictor for CR N and P. Furthermore, the final prediction models for the VIs selected as the best predictors developed in this study performed satisfactorily in the prediction of CR biomass, C, N, P, K, and S producing adjusted R² values of 0.79, 0.79, 0.75, 0.81, 0.81, and 0.78, respectively. The results of this study have the potential to aid producers in making informed decisions regarding CR and fertility management. </p> <p>In the final study, agronomic data for corn and soybean cropping systems with and without CR was collected from six states (Illinois, Indiana, Iowa, Minnesota, Missouri, and Wisconsin) and used within a Monte-Carlo stochastic simulation to characterize the economic risk of adopting CR at a regional scale over time. The results of this study indicate that average net returns to CR are always negative regardless of CR tenure primarily due to added costs and increased variability in cash crop grain yields associated with CR adoption. Further, the results demonstrate that the additional risk assumed by adopting CR is not adequately compensated for with current CR adoption incentive programs and that the risk premium necessary can be 1.7 to 15 times greater than existing incentive payments. Knowledge gained from this study could be used to reimagine current incentive programs to further promote adoption of CR.</p>

[Truncated abstract] Recovery of soil nutrients, microbial populations and carbon (C) and nitrogen (N) cycling processes are critical to the success of rehabilitation following major ecosystem disturbance. Bauxite mining represents a major ecosystem disturbance to the jarrah (Eucalyptus marginata) forest in the south-west of Western Australia. Mining has created a mosaic of mined areas in various stages of succession surrounded by non-mined forest areas. Initial site preparations within rehabilitation areas such as contour ripping alter soil structure (creation of mound and furrows) and over time also influence the distribution of vegetation and litter. Current performance criteria developed by industry, government and other stakeholders have determined that before post-bauxite mined areas of jarrah forest can be integrated back into normal forest management practises they should be functional and demonstrate resilience to normal forest disturbances such as fire. Furthermore, resilience should be of a manner comparable to non-mined analogue forest sites. Currently little is known of the resilience of microbial communities and C and N cycling in rehabilitation sites to normal forest disturbances such as prescription burning. As such, before rehabilitated jarrah forests can be successfully integrated into broad scale forest management regimes, a more thorough knowledge of the potential impacts of burning practises on the soil microbial community and C and N cycling processes in these systems is required. ... While there are similar rates of C and N cycling the underlying microbial community structure was distinctly different; implying a high degree of functional redundancy with respect to C and N cycling. Differences in the C and N cycling and structure of the microbial communities were likely to be due to differences in soil environmental conditions (i.e. soil alkalinity/acidity, soil moisture) and C substrate availability which influence the physiological status of the microbial community and in turn are related to successional age of the forests. Results also suggest that the measurement of CLPP can be a useful approach for assessment of changes in the functional ability of microbial communities. However, the interpretation of how well these rehabilitation forests have recovered heterotrophic abilities was greatly affected by the methodological approach used (e.g. MicroRespTM or Degens and Harris, 1997). Importantly, results from Chapter 4 and 5 suggested that the effects of a moderate prescription fire on C and N processes, CLPP and microbial community structure of 18 year old rehabilitation forests are likely to be short-lived (< 2 years). Furthermore, the effects of the moderate spring prescription fire were not large enough to decouple C and N cycling processes over the short-term (< 1 years) which suggests that by 18 years of age rehabilitation forests demonstrate comparable functional resilience to a moderate prescription burn.

No description available.