There are apprehensions that genetic modification of maize with Bacillus thuringiensis (Bt) may have negative effects on soil biodiversity, ecosystem processes and functions. This study aimed at determining the effect of Bt maize crop, Bt maize residues and its genetic modification on microbial biomass carbon (MBC), selected enzyme activities, vesicular arbuscular mycorrhizal (VAM) fungi and N and P release patterns. The study was conducted under field, glasshouse and laboratory conditions. In 2010/2011 season, four maize cultivars; DKC 61-25B (Bt), DKC 61-24 (non-Bt), PAN 6Q-321B (Bt) and PAN6777 (non-Bt) were planted. Determination of MBC, enzyme activities and fungal spore count was done at 42, 70, and 105 days after planting (DAP). A loam soil amended with Bt or non-Bt maize leaf residues from a study of 2009/2010 season was incubated to investigate effects of Bt maize residues on MBC and soil enzyme activities. Leaf residues of Bt and non-Bt maize cultivars (DKC 61-25B, DKC 61-24, PAN 6Q-321B and PAN6777) were used and soil without residues was used as a control. Samples were collected at 7, 28 and 56 days of incubation (DOI). An incubation study was also carried out in the laboratory to determine the effect of Bt maize residues (i.e. leaf, stem and root) and its genetic modification on N and P release patterns. Residues of DKC 61-25B, DKC 61-24, PAN 6Q-321B and PAN6777and soil without residues as a control were incubated in the laboratory. After destructive sampling at 0, 7, 14, 28, and 56 DOI, N in the form of NH4-N and NO3-N and P mineralisation were determined. Amendment of soil with residues enhanced MBC (p < 0.05) at all the sampling dates. For example MBC increased from 95 in the control to 146.3 mg/kg in the DKC 61-25B treatment at the end of the glasshouse trial. In the field DKC 61-25B had 9.1 mg/kg greater MBC than DKC 61-24, while PAN 6Q-321B had 23.9 mg/kg more MBC than PAN6777 at the end of the trial. However, no differences (p < 0.05) were observed in enzyme activities under field and glasshouse conditions except for dehydrogenase that had greater activity where DKC 61-25B and PAN 6777 were grown. There were no differences between the type of residues (Bt and non-Bt) on enzyme activities tested. However, differences were observed among the sampling dates. No effects of Bt maize crop on fungal spore count were observed. Similarly no differences were observed in leaf, stem and root tissues composition between Bt and non-Bt maize cultivars. Net N and P mineralisation from Bt maize cultivars did not differ from that of non-Bt maize cultivars. However, differences were observed among the cultivars. The results of this study suggested that Bt maize with Bt MON810 event can be grown in the central region of the Eastern Cape (EC), South Africa without affecting MBC, soil enzyme activities, VAM, and release of N and P nutrients from its residues.

京都大学 / 0048 / 新制・課程博士 / 博士(地球環境学) / 甲第22905号 / 地環博第206号 / 新制||地環||40(附属図書館) / 京都大学大学院地球環境学舎地球環境学専攻 / (主査)教授 舟川 晋也, 准教授 渡邉 哲弘, 准教授 舘野 隆之輔 / 学位規則第4条第1項該当 / Doctor of Global Environmental Studies / Kyoto University / DFAM

Crop management practices, such as soil tillage and crop residue management, are land management activities with potentially large impacts on carbon (C) cycling and climate at the global scale. Improvements in crop management practices, such as conservation tillage or 'no-till' (NT), have been proposed as climate change mitigation measures because such practices may alter C cycles through increased sequestration of soil C in agricultural soils. Despite their potential importance, regional to global scale data are lacking for many crop management practices, and few studies have evaluated the potential impact of the full range of crop management practices on C cycling and climate at the global scale. However, monitoring of crop management practices is crucial for assessing spatial variations in management intensity and informing policy decisions. Inclusion of crop management practices in Earth system models used for assessing global climate is a key requirement for evaluating the overall effects of different crop management practices on C cycling and their potential to mitigate climate change. Studies in this dissertation seek to address these issues by: (1) evaluating the efficacy of remote sensing methods for monitoring differences in soil tillage and crop residue management practices in Iowa; (2) incorporating soil tillage practices into an Earth system model and assessing the potential for soil C sequestration and climate change mitigation through adoption of NT practices; (3) assessing the historical impact of including the full range of crop management practices (residue harvest, grain harvest, soil tillage, irrigation, and fertilization) on changes in C cycling associated with land use and land cover change (LULCC) to crops in an Earth system model. The remote sensing study found that performance of the minimum Normalized Difference Tillage Index (minNDTI) method for assessing differences in tillage and residue management was below average compared to previous studies, even when using imagery from both Landsat 8 and Sentinel-2A sensors. Accurate assessment of these practices using minNDTI was hindered by issues with image quality and inability to obtain sufficient cloud-free, time series imagery during the critical planting window. Remote sensing research aimed at obtaining regional to global scale data on tillage and residue management practices is likely to continue to face these issues in the future, but further research should incorporate additional sensors and assess the efficacy of the minNDTI method for multiple locations and years. Adoption of NT practices in the Community Land Model, which is the land component of the Community Earth System Model, resulted in a cumulative soil C sequestration of 6.6 – 14.4 Pg C from 2015 – 2100 under a future climate change scenario (Representative Concentration Pathway 8.5), and cumulative soil C sequestration was equal to approximately one year of present-day fossil fuel emissions. Adjusting for areas where NT is already practiced had minor impacts on cumulative soil C storage, reducing gains in soil C from NT adoption by 0.4 – 0.9 Pg C globally. These results indicate that soil C sequestration and potential for climate change mitigation through NT may be more limited than has been anticipated elsewhere. Soil C sequestration via NT adoption was highest in temperate regions of developed countries with high initial soil C contents, indicating these areas should be targeted for NT adoption. Simulating the full range of crop management practices in the Community Land Model resulted in an increase in C emissions due to LULCC of 29 – 38 Pg C compared to scenarios with generic crops and model defaults. Individual crop management practices with the largest impact on LULCC emissions were crop residue harvest (18 Pg C), followed by grain harvest (9 Pg C) and soil tillage (5 Pg C). Although implementation of crop residue harvest and soil tillage was extreme in this study, these results imply that Earth system models may underestimate emissions from LULCC by excluding the full range of crop management practices. Studies in this dissertation corroborate the importance of crop management practices for C cycling and climate, but further research on these management practices is needed in terms of data collection, improving process-level understanding, and inclusion of these practices in Earth system models. / Doctor of Philosophy

Six combinations of grazing, tillage, and herbicides were studied during 2 yr in a randomized block design to determine alfalfa (Medicago sativa) survival, corn (Zea mays) plant populations and corn growth in an alfalfa-corn rotation. Alfalfa was overseeded with rye (Secale cereale) in autumn prior to planting corn in spring of each year. Treatments were 1) non-grazed control with standard chemical treatments for no-till establishment of corn, 2) grazing alfalfa, then grazing rye until corn planting followed by dicamba application, 3) alfalfa grazing plus glyphosate prior to corn planting, 4) treatment 3 plus grazing prior to rye jointing, and 5) alfalfa grazing plus autumn application of glyphosate, 6) alfalfa grazing plus autumn disking (no herbicides). Grazing until corn planting decreased (P<0.05) alfalfa stands and rye biomass, but increased (P<0.05) corn plant populations and soil bulk density compared to shorter grazing periods. Grazing prior to rye jointing increased (P <0.05) soil bulk density and corn plant populations, and decreased (P<0.05) rye biomass compared to no spring grazing. Autumn disking decreased (P<0.05) bulk density, but generally provided less (P<0.05) control of alfalfa compared to autumn application of glyphosate. Autumn disking and glyphosate application (Trts. 5 and 6) increased (P<0.05) rye biomass compared to no autumn treatment (Trts. 3 and 4). Applying glyphosate prior to corn planting (Trts. 3 and 4) improved (P<0.05) corn populations and growth compared to autumn glyphosate or disking (Trts. 5 and 6) and was similar to conventional no-till establishment (Trt. 1). Herbicides were necessary to completely kill alfalfa, but grazing reduced TNC in alfalfa roots and alfalfa plant persistence. / Master of Science

Master of Science / Department of Entomology / Brian P. McCornack / Robert J. Whitworth / No-till management of soybean benefits producers by lowering input costs and retaining soil moisture, but may also provide optimal conditions for increasing populations of soil-inhabiting pests. For Kansas soybean, damaging populations of soil-inhabiting isopods (Malacostraca: Isopoda) have been observed in fields under no-tillage management. To control damage to soybean stands from feeding isopods, current management strategies need to be evaluated. The objectives of my research were to evaluate the effects of chemical and cultural control combinations (seed treatment and planting date, planting date and seed size, seed treatment and natural crop residue removal, and seeding rate and seed treatment) on soybean stand densities exposed to natural isopod populations, and to evaluate the effects of burning crop residue on isopod populations and emergence rates in soybean under no-tillage management. Field studies were conducted in consecutive years (2009 and 2010) in two separate soybean fields within each year. All fields were under no-till management and had a history of damaging isopod populations. In the second chapter, we demonstrated that seed treatment with an insecticide is not a reliable strategy. Doubling normal seeding rates can potentially reduce the number of trips a grower makes across a field (single, high-density versus multiple, low-density plantings). In doing so, growers may save time and money (e.g., fuel). A high seeding rate (563,380/ha), along with a low rate (50 g a.i. / 100 kg seed) of neonicotinoid seed treatment, appears to improve soybean stands (P < 0.05). No other combinations of control methods appeared to affect stand density. In the third chapter, we show burning to be an effective strategy to directly influence isopod populations but its overall effect on soybean stands needs further investigation.

A planta daninha vassourinha-de-botão (Borreria densiflora DC.) está apresentando aumento na sua infestação em áreas cultivadas com cana-de-açúcar e soja, respectivamente nos estados do Maranhão, Goiás e Tocantins. Observações de campo têm relatado a deficiência de controle químico sobre esta espécie, quando ocorre em estádio de crescimento avançado. Sendo assim, este trabalho objetivou classificar botanicamente B. densiflora DC., analisar a influência da luz e da temperatura na germinação desta espécie, seu crescimento, desenvolvimento e estruturas reprodutivas, sua susceptibilidade a herbicidas em condições de pré e pósemergência, e a influência da interação entre a profundidade de enterrio e a presença de palha em diferentes quantidades sobre a superfície do solo sobre a emergência desta planta daninha. A classificação botânica foi realizada na Facultad de Ciencias Exactas y Naturales y Agrimensura - UNNE / IBONE, Argentina; o experimento que analisou a germinação sob diferentes condições foi realizado no Laboratório de Análise de Sementes, do Departamento de Produção Vegetal da USP / ESALQ, e todos os demais experimentos foram conduzidos em casa-de-vegetação, do mesmo departamento. Todos os trabalhos foram conduzidos entre 2006 e 2007. Constatou-se que a planta daninha vassourinha-de-botão se trata da espécie Borreria densiflora DC., pertencente à família Rubiaceae. Com relação à germinação, constatou-se que a vassourinha-de-botão é fotoblástica positiva preferencial, uma vez que sua germinação é favorecida na presença de luz, respondendo diferentemente às condições de luz e temperatura estudadas. As maiores taxas de germinação e índices de velocidade de germinação foram alcançados em condição de fotoperíodo (12h) sob as temperaturas constantes de 30ºC e 35ºC e alternada de 20-30ºC. Praticamente, não houve germinação no escuro constante. Sobre o crescimento e desenvolvimento, observou-se que a planta daninha Borreria densiflora DC. é uma espécie com desenvolvimento inicial lento, de ciclo de vida perene simples, apresentado grande incremento nas variáveis massa seca total, taxa de crescimento relativo e de assimilação líquida entre os 26 e 36 dias após transplante (DAT). Ao final do experimento, os ramos se mostram como os compartimentos mais participativos na partição de fotoassimilados pela vassourinha-de-botão. Esta espécie é capaz de produzir, em média, 93.090 sementes por planta. Com relação ao manejo químico de Borreria densiflora DC., a maioria dos herbicidas promoveram controles considerados adequados, com exceção ao clomazone e MSMA, em condições de pré e pós-emergência, respectivamente. Sendo assim, várias opções de herbicidas e de misturas destes podem ser recomendadas para o manejo da planta daninha B. densiflora DC., tanto em condições de pré-semeadura quanto pré e pós-emergência. O estudo sobre a influência da interação entre profundidade da semente no solo e presença de palha de cana-de-açúcar na superfície do solo sobre a emergência desta espécie demonstrou haver interação entre os dois fatores testados, sendo que quanto maior a profundidade da semente no solo e a quantidade de palha sobre a superfície, menor é a porcentagem de emergência e biomassa fresca de B. densiflora DC. Tais resultados são importante na medida em que favorecem o entendimento da dinâmica populacional da B. densiflora DC., auxiliando o manejo integrado desta espécie. / The weed vassourinha-de-botao (Borreria densiflora DC.) has been presenting increase in its infestation in areas cultivated with sugarcane and soybean, respectively in Maranhao and Goias states and north of Tocantins state, Brazil. Field observations have reported the control deficiency of this species, when it occurs in advanced growth stage. Thus, this research was conducted with the objective of classify botanically the weed, analyze the light and temperature influence on the germination of this species, its growth, development and reproductive structures, its susceptibility to herbicides in pre and post conditions, as well as the influence of the interaction between seed burial and the presence of crop residue in different amounts in the soil surface on the emergence of this weed. The botanical classification of vassourinha-de-botao was done in the Exact and Natural Sciences College - UNNE / IBONE, Argentina; the experiment that evaluated germination under different conditions was conducted in the Seeds Analyzes Laboratory, of the Crop Science Department of USP / ESALQ, and all the other experiments were carried out in the same department, between 2006 and 2007. It was concluded that the weed vassourinha-de-botao is the species Borreria densiflora DC. and it belongs to Rubiaceae family. Related to germination, it was observed that B. densiflora DC. is preferencial positive photoblastic, since its germination is favored by presence of light, responding differently to the studied light and temperature conditions. The highest germination rates and speeds of germination were reached in presence of photoperiod condition (12h), under the constant temperatures 30ºC and 35ºC and the alternated 20-30ºC. Basically, there was not germination in the constant dark condition. About the growth and development, it was observed that the weed Borreria densiflora DC. is a species with slow initial growth, with a simple perennial life cycle, presenting a big increment in the variables total dry biomass, relative growth and liquid assimilation rates between 26 and 36 days after transplanting (DAT). At the end of the experiment, the stems appear as the most participative compartments in the photosynthate partition by Borreria densiflora DC. This species is able to produce, in average, 93,090 seeds per plant. Related to the chemical management of Borreria densiflora DC., the majority of the herbicides provided controls considered adequate, except clomazone and MSMA, in pre and post-emergence conditions, respectively. Therefore, many herbicide options and mix of herbicides can be recommended to the management of the weed Borreria densiflora DC., since in pre-plant to pre and post-emergence. The study about the influence of the interaction between seed burial and presence of dry sugarcane residue in the soil surface on the emergence of this species demonstrated to exist interaction between those two tested factors, being that the bigger depth in the soil and amount of dry sugarcane residue in the soil surface, the lower is the percentage of emergence and fresh biomass of B. densiflora DC. Those results are important since they favor the understanding of the population dynamics of Borreria densiflora DC., aiding the integrated management of this weed species.

O esforço global em diversificar a matriz mundial de combustíveis líquidos, busca substituir as fontes fósseis por renováveis. A produção de bioenergia derivada da biomassa assume importante papel neste cenário. A biomassa gerada após a colheita da cana-de-açúcar ganha destaque como matéria prima pela grande quantidade de material que pode ser usado para geração direta (queima) e indireta (biocombustíveis) de bioenergia. No entanto, ainda pouco se sabe sobre os efeitos da remoção de quantidades de palha de cana-de-açúcar voltado à produção de bioenergia sobre os atributos biológicos do solo. Assim, o objetivo deste estudo foi avaliar o efeito da remoção da palha de cana-de-açúcar no carbono e nitrogênio microbiano e na comunidade microbiana do solo. O estudo foi conduzido em duas áreas cultivadas com cana-de-açúcar (Saccharum spp. L.) nos municípios de Capivari, SP (Usina Bom Retiro) e Valparaíso, SP (Usina Univalem). Em Bom Retiro o experimento foi instalado em um Latossolo Vermelho distrófico típico de textura franco-argilo-arenosa e, em Univalem foi um Argissolo Vermelho-Amarelo distrófico de textura arenosa. Em ambos locais, o delineamento experimental utilizado foi blocos casualizados, com cinco tratamentos e quatro repetições. Os tratamentos testados corresponderam a diferentes intensidades de remoção de palha de cana-de-açúcar (i.e., 100%; 75%; 50%; 0 de remoção; e aleiramento da quantidade remanescente na área após colheita), sendo 0; 3,4; 7,8; 16,6; 15,6 Mg ha-1 de palha em massa de matéria seca na Usina Bom Retiro e 0; 4,2; 8,7; 18,9; 23,3 Mg ha-1 na Usina Univalem. Um ano após a instalação do experimento, foram coletadas amostras de palha e de solo na camada 0-10 cm e, passados quatro meses após o segundo manejo de remoção da palha nos tratamentos foram coletadas amostras de palha e de solo nas camadas 0-5 e 5-10 cm. Os atributos avaliados foram: carbono e nitrogênio total da palha e do solo, fração mais oxidável do carbono do solo, carbono e nitrogênio da biomassa microbiana da palha e do solo e, quantificação de genes microbianos no solo. Os resultados mostraram que as quantidades de C e N totais no solo não apresentaram resposta em função das quantidades de palha, no entanto, a fração de C mais facilmente oxidável e o C e N microbiano apresentaram tendência de redução em função de maiores níveis de remoções de palha, sendo a resposta da biomassa microbiana mais expressiva no solo de textura arenosa (i.e., Univalem). Da mesma forma, as comunidades microbianas foram mais sensíveis às diferentes remoções de palha, apresentando maior abundância com menor remoção de palha. Desta forma, a remoção de elevadas quantidades da palha de cana-de-açúcar do campo, ao alterar a microbiologia do solo, pode ter consequências nas específicas funções exercidas por este compartimento, que garantem o bom funcionamento do solo e podem prevenir contra a degradação. Estes resultados podem servir de base para avaliações mais amplas que buscam uma estratégia sustentável de manejo da palha de cana-de-açúcar que garanta o bom funcionamento do solo / The global effort to diversify the global matrix of liquid fuels seeks to replace fossil sources by renewable ones. Bioenergy production derived from biomass plays an important role in this scenario. The biomass generated after the harvest of sugarcane stands out by the large amounts of straw that can be used for direct generation (burning) and indirect (biofuels) of bioenergy. However, little is know about the effects of sugarcane straw removal to bioenergy production on biological soil properties. The objective of this study was to evaluate the effect of the straw removal on soil microbial carbon and nitrogen as well as on soil microbial community. The experiments were conducted in two areas cultivated with sugarcane (Saccharum spp. L.) in Capivari, SP (Bom Retiro) and Valparaíso, SP (Univalem). The soils studied were an Oxisoil with clay texture in Bom Retiro and an Ultisoil with sandy texture in Univalem. In both sites, the experimental designer was a randomized blocks with five treatments and four replications. The treatments tested were decreasing intensities of sugarcane straw harvest (i.e., 100%; 75%; 50%; 0 removing of the original straw deposition) : i) Bom Retiro: 0; 3,4; 7,8; 16,6; 15,6 Mg ha-1 of dry matter of straw kept on soil surface; ii) Univalem: 0; 4,2; 8,7; 18,9; 23,3 Mg ha-1 of dry matter of straw kept on the soil surface. One year after experiment installation, straw and soil (0-10 cm layer) samples were collected. A new sugarcane straw and soil (0-5 and 5-10 cm) sampling was performed four months from the second deposition of sugarcane straw on the field. The attributes evaluated were: total and microbial C and N of straw and soil, soil easily-oxidizable C, straw and soil microbial genes quantification using qPCR method. Our results showed that soil C and N contents were not impacted by sugarcane straw removal. However, the fraction of easily-oxidizable C and microbial C and N tended to decrease due to increased straw removal, with a more significant microbial biomass response for the sandy soil site (Univalem). Likewise, microbial communities were also sensitive to straw management, resulting in a significant decrease in the number of gene copies with increasing intensities of sugarcane straw harvest. Therefore, we can concluded that the large amounts of sugarcane straw removal from field as affects soil microbiology, may have consequences in specific functions performed by microorganisms, which ensure the soil functioning and can prevent soil degradation. These results can serve as a basis for more comprehensive assessments that seek a sustainable crop residue management strategy for sugarcane, to ensure the proper functioning of the soil

A planta daninha vassourinha-de-botão (Borreria densiflora DC.) está apresentando aumento na sua infestação em áreas cultivadas com cana-de-açúcar e soja, respectivamente nos estados do Maranhão, Goiás e Tocantins. Observações de campo têm relatado a deficiência de controle químico sobre esta espécie, quando ocorre em estádio de crescimento avançado. Sendo assim, este trabalho objetivou classificar botanicamente B. densiflora DC., analisar a influência da luz e da temperatura na germinação desta espécie, seu crescimento, desenvolvimento e estruturas reprodutivas, sua susceptibilidade a herbicidas em condições de pré e pósemergência, e a influência da interação entre a profundidade de enterrio e a presença de palha em diferentes quantidades sobre a superfície do solo sobre a emergência desta planta daninha. A classificação botânica foi realizada na Facultad de Ciencias Exactas y Naturales y Agrimensura - UNNE / IBONE, Argentina; o experimento que analisou a germinação sob diferentes condições foi realizado no Laboratório de Análise de Sementes, do Departamento de Produção Vegetal da USP / ESALQ, e todos os demais experimentos foram conduzidos em casa-de-vegetação, do mesmo departamento. Todos os trabalhos foram conduzidos entre 2006 e 2007. Constatou-se que a planta daninha vassourinha-de-botão se trata da espécie Borreria densiflora DC., pertencente à família Rubiaceae. Com relação à germinação, constatou-se que a vassourinha-de-botão é fotoblástica positiva preferencial, uma vez que sua germinação é favorecida na presença de luz, respondendo diferentemente às condições de luz e temperatura estudadas. As maiores taxas de germinação e índices de velocidade de germinação foram alcançados em condição de fotoperíodo (12h) sob as temperaturas constantes de 30ºC e 35ºC e alternada de 20-30ºC. Praticamente, não houve germinação no escuro constante. Sobre o crescimento e desenvolvimento, observou-se que a planta daninha Borreria densiflora DC. é uma espécie com desenvolvimento inicial lento, de ciclo de vida perene simples, apresentado grande incremento nas variáveis massa seca total, taxa de crescimento relativo e de assimilação líquida entre os 26 e 36 dias após transplante (DAT). Ao final do experimento, os ramos se mostram como os compartimentos mais participativos na partição de fotoassimilados pela vassourinha-de-botão. Esta espécie é capaz de produzir, em média, 93.090 sementes por planta. Com relação ao manejo químico de Borreria densiflora DC., a maioria dos herbicidas promoveram controles considerados adequados, com exceção ao clomazone e MSMA, em condições de pré e pós-emergência, respectivamente. Sendo assim, várias opções de herbicidas e de misturas destes podem ser recomendadas para o manejo da planta daninha B. densiflora DC., tanto em condições de pré-semeadura quanto pré e pós-emergência. O estudo sobre a influência da interação entre profundidade da semente no solo e presença de palha de cana-de-açúcar na superfície do solo sobre a emergência desta espécie demonstrou haver interação entre os dois fatores testados, sendo que quanto maior a profundidade da semente no solo e a quantidade de palha sobre a superfície, menor é a porcentagem de emergência e biomassa fresca de B. densiflora DC. Tais resultados são importante na medida em que favorecem o entendimento da dinâmica populacional da B. densiflora DC., auxiliando o manejo integrado desta espécie. / The weed vassourinha-de-botao (Borreria densiflora DC.) has been presenting increase in its infestation in areas cultivated with sugarcane and soybean, respectively in Maranhao and Goias states and north of Tocantins state, Brazil. Field observations have reported the control deficiency of this species, when it occurs in advanced growth stage. Thus, this research was conducted with the objective of classify botanically the weed, analyze the light and temperature influence on the germination of this species, its growth, development and reproductive structures, its susceptibility to herbicides in pre and post conditions, as well as the influence of the interaction between seed burial and the presence of crop residue in different amounts in the soil surface on the emergence of this weed. The botanical classification of vassourinha-de-botao was done in the Exact and Natural Sciences College - UNNE / IBONE, Argentina; the experiment that evaluated germination under different conditions was conducted in the Seeds Analyzes Laboratory, of the Crop Science Department of USP / ESALQ, and all the other experiments were carried out in the same department, between 2006 and 2007. It was concluded that the weed vassourinha-de-botao is the species Borreria densiflora DC. and it belongs to Rubiaceae family. Related to germination, it was observed that B. densiflora DC. is preferencial positive photoblastic, since its germination is favored by presence of light, responding differently to the studied light and temperature conditions. The highest germination rates and speeds of germination were reached in presence of photoperiod condition (12h), under the constant temperatures 30ºC and 35ºC and the alternated 20-30ºC. Basically, there was not germination in the constant dark condition. About the growth and development, it was observed that the weed Borreria densiflora DC. is a species with slow initial growth, with a simple perennial life cycle, presenting a big increment in the variables total dry biomass, relative growth and liquid assimilation rates between 26 and 36 days after transplanting (DAT). At the end of the experiment, the stems appear as the most participative compartments in the photosynthate partition by Borreria densiflora DC. This species is able to produce, in average, 93,090 seeds per plant. Related to the chemical management of Borreria densiflora DC., the majority of the herbicides provided controls considered adequate, except clomazone and MSMA, in pre and post-emergence conditions, respectively. Therefore, many herbicide options and mix of herbicides can be recommended to the management of the weed Borreria densiflora DC., since in pre-plant to pre and post-emergence. The study about the influence of the interaction between seed burial and presence of dry sugarcane residue in the soil surface on the emergence of this species demonstrated to exist interaction between those two tested factors, being that the bigger depth in the soil and amount of dry sugarcane residue in the soil surface, the lower is the percentage of emergence and fresh biomass of B. densiflora DC. Those results are important since they favor the understanding of the population dynamics of Borreria densiflora DC., aiding the integrated management of this weed species.

O esforço global em diversificar a matriz mundial de combustíveis líquidos, busca substituir as fontes fósseis por renováveis. A produção de bioenergia derivada da biomassa assume importante papel neste cenário. A biomassa gerada após a colheita da cana-de-açúcar ganha destaque como matéria prima pela grande quantidade de material que pode ser usado para geração direta (queima) e indireta (biocombustíveis) de bioenergia. No entanto, ainda pouco se sabe sobre os efeitos da remoção de quantidades de palha de cana-de-açúcar voltado à produção de bioenergia sobre os atributos biológicos do solo. Assim, o objetivo deste estudo foi avaliar o efeito da remoção da palha de cana-de-açúcar no carbono e nitrogênio microbiano e na comunidade microbiana do solo. O estudo foi conduzido em duas áreas cultivadas com cana-de-açúcar (Saccharum spp. L.) nos municípios de Capivari, SP (Usina Bom Retiro) e Valparaíso, SP (Usina Univalem). Em Bom Retiro o experimento foi instalado em um Latossolo Vermelho distrófico típico de textura franco-argilo-arenosa e, em Univalem foi um Argissolo Vermelho-Amarelo distrófico de textura arenosa. Em ambos locais, o delineamento experimental utilizado foi blocos casualizados, com cinco tratamentos e quatro repetições. Os tratamentos testados corresponderam a diferentes intensidades de remoção de palha de cana-de-açúcar (i.e., 100%; 75%; 50%; 0 de remoção; e aleiramento da quantidade remanescente na área após colheita), sendo 0; 3,4; 7,8; 16,6; 15,6 Mg ha-1 de palha em massa de matéria seca na Usina Bom Retiro e 0; 4,2; 8,7; 18,9; 23,3 Mg ha-1 na Usina Univalem. Um ano após a instalação do experimento, foram coletadas amostras de palha e de solo na camada 0-10 cm e, passados quatro meses após o segundo manejo de remoção da palha nos tratamentos foram coletadas amostras de palha e de solo nas camadas 0-5 e 5-10 cm. Os atributos avaliados foram: carbono e nitrogênio total da palha e do solo, fração mais oxidável do carbono do solo, carbono e nitrogênio da biomassa microbiana da palha e do solo e, quantificação de genes microbianos no solo. Os resultados mostraram que as quantidades de C e N totais no solo não apresentaram resposta em função das quantidades de palha, no entanto, a fração de C mais facilmente oxidável e o C e N microbiano apresentaram tendência de redução em função de maiores níveis de remoções de palha, sendo a resposta da biomassa microbiana mais expressiva no solo de textura arenosa (i.e., Univalem). Da mesma forma, as comunidades microbianas foram mais sensíveis às diferentes remoções de palha, apresentando maior abundância com menor remoção de palha. Desta forma, a remoção de elevadas quantidades da palha de cana-de-açúcar do campo, ao alterar a microbiologia do solo, pode ter consequências nas específicas funções exercidas por este compartimento, que garantem o bom funcionamento do solo e podem prevenir contra a degradação. Estes resultados podem servir de base para avaliações mais amplas que buscam uma estratégia sustentável de manejo da palha de cana-de-açúcar que garanta o bom funcionamento do solo / The global effort to diversify the global matrix of liquid fuels seeks to replace fossil sources by renewable ones. Bioenergy production derived from biomass plays an important role in this scenario. The biomass generated after the harvest of sugarcane stands out by the large amounts of straw that can be used for direct generation (burning) and indirect (biofuels) of bioenergy. However, little is know about the effects of sugarcane straw removal to bioenergy production on biological soil properties. The objective of this study was to evaluate the effect of the straw removal on soil microbial carbon and nitrogen as well as on soil microbial community. The experiments were conducted in two areas cultivated with sugarcane (Saccharum spp. L.) in Capivari, SP (Bom Retiro) and Valparaíso, SP (Univalem). The soils studied were an Oxisoil with clay texture in Bom Retiro and an Ultisoil with sandy texture in Univalem. In both sites, the experimental designer was a randomized blocks with five treatments and four replications. The treatments tested were decreasing intensities of sugarcane straw harvest (i.e., 100%; 75%; 50%; 0 removing of the original straw deposition) : i) Bom Retiro: 0; 3,4; 7,8; 16,6; 15,6 Mg ha-1 of dry matter of straw kept on soil surface; ii) Univalem: 0; 4,2; 8,7; 18,9; 23,3 Mg ha-1 of dry matter of straw kept on the soil surface. One year after experiment installation, straw and soil (0-10 cm layer) samples were collected. A new sugarcane straw and soil (0-5 and 5-10 cm) sampling was performed four months from the second deposition of sugarcane straw on the field. The attributes evaluated were: total and microbial C and N of straw and soil, soil easily-oxidizable C, straw and soil microbial genes quantification using qPCR method. Our results showed that soil C and N contents were not impacted by sugarcane straw removal. However, the fraction of easily-oxidizable C and microbial C and N tended to decrease due to increased straw removal, with a more significant microbial biomass response for the sandy soil site (Univalem). Likewise, microbial communities were also sensitive to straw management, resulting in a significant decrease in the number of gene copies with increasing intensities of sugarcane straw harvest. Therefore, we can concluded that the large amounts of sugarcane straw removal from field as affects soil microbiology, may have consequences in specific functions performed by microorganisms, which ensure the soil functioning and can prevent soil degradation. These results can serve as a basis for more comprehensive assessments that seek a sustainable crop residue management strategy for sugarcane, to ensure the proper functioning of the soil

Intercropping, defined as two or more crops grown on the same land area at the same time, is a sustainable alternative to sole crops. Intercropping has been associated with multiple benefits, such as increased nutrient and soil organic carbon (SOC) cycling, decreased soil erosion and increased carbon (C) sequestration. A common intercropping practice is to integrate cereal and legume crops such as maize (Zea mays L.), and soybean (Glycine max (L.) Merr.). Most studies on intercropping have focused on yield, weed control, and land use efficiency in the tropics. Few studies have researched C and nitrogen (N) dynamics in temperate intercrops, with respect to soybean and maize residue stabilization. Soil from Balcarce, Argentina, was incubated for 140 days with soybean, maize, or no residue. Throughout the incubation, results illustrated the effect of residue application upon the soil, specifically through significantly higher amounts of light fraction (LF) C and LFN concentrations, soil microbial biomass (SMB) C and SMBN concentrations, higher microbial diversity, lower N2O production rates, in addition to distinct isotopic values in soil fractions and CO2 (p<0.05). Furthermore, it was observed from δ15N-TN and δ15N-LF that treatments with soybean residues included had higher N cycling (p<0.05), emphasizing the importance of including N-fixing legumes in complex agroecosystems. Significant changes over time in SMB and SMCS characteristics, and isotope values (p<0.05) indicated the preferential utilization of relatively young and easily accessible litter. Furthermore, the loss of labile material over the incubation resulted in more recalcitrant forms (such as older C and lignin) to be utilized. Slightly higher SOC, TN, LFC and LFN concentrations, as well as lower CO2 production rates suggested 2:3 (rows of maize:rows of soybean) as a more desirable intercrop design for C sequestration. The 1:2 intercrop design was observed to be more beneficial for microbial community structure, furthering the idea that intercropping is a beneficial alternative to sole cropping. This study improves knowledge in residue stabilization and C sequestration in complex agroecosystems, providing encouragement for the implementation of more sustainable management practices.