Adoption of no-till (NT) and reduced tillage management is widespread on the Canadian prairies and together form the basic platform of soil management upon which most crop production is based. Elimination of tillage in cropping systems changes the physical and chemical characteristics of the soil profile and can affect crop growth and ultimately yield. As such, understanding how soil biota, as drivers of nutrient turnover, adapt to NT is important for maximizing crop productivity and mitigating environmental damage in agroecosystems. This work aims to achieve a greater understanding of microbial community structure and function in long-term NT versus conventionally tilled (CT) soils. Community phospholipid and DNA fingerprinting did not reveal any consistent tillage-induced shifts in microbial community structure, but demonstrated a clear influence of depth within the soil profile. While tillage did not result in broad changes in the community structure, total, bacterial and fungal biomass was consistently greater near the surface of NT soils. Further examination at one site near Swift Current, SK revealed differences in microbial biomass and community structure in NT and CT in field-formed aggregate size fractions. Measurement of mineralization and nitrification at the same site indicated that differences in the early-season turnover of N may be related to physical rather than microbial differences in NT and CT soils. Potential nitrification was higher prior to seeding than mid-season, was not affected by tillage and was correlated with ammonia oxidizer population size of archaea, but not bacteria. This work indicates that edaphic soil properties and spatial distribution of resources in the soil profile, rather than tillage management, are the primary factors driving microbial community structure in these soils.

Adoption of no-till (NT) and reduced tillage management is widespread on the Canadian prairies and together form the basic platform of soil management upon which most crop production is based. Elimination of tillage in cropping systems changes the physical and chemical characteristics of the soil profile and can affect crop growth and ultimately yield. As such, understanding how soil biota, as drivers of nutrient turnover, adapt to NT is important for maximizing crop productivity and mitigating environmental damage in agroecosystems. This work aims to achieve a greater understanding of microbial community structure and function in long-term NT versus conventionally tilled (CT) soils. Community phospholipid and DNA fingerprinting did not reveal any consistent tillage-induced shifts in microbial community structure, but demonstrated a clear influence of depth within the soil profile. While tillage did not result in broad changes in the community structure, total, bacterial and fungal biomass was consistently greater near the surface of NT soils. Further examination at one site near Swift Current, SK revealed differences in microbial biomass and community structure in NT and CT in field-formed aggregate size fractions. Measurement of mineralization and nitrification at the same site indicated that differences in the early-season turnover of N may be related to physical rather than microbial differences in NT and CT soils. Potential nitrification was higher prior to seeding than mid-season, was not affected by tillage and was correlated with ammonia oxidizer population size of archaea, but not bacteria. This work indicates that edaphic soil properties and spatial distribution of resources in the soil profile, rather than tillage management, are the primary factors driving microbial community structure in these soils.

Made available in DSpace on 2016-12-08T15:50:02Z (GMT). No. of bitstreams: 1 PGMS13DA012.pdf: 1980394 bytes, checksum: 6b37fb6e368ae3bf1a366a8d92ac0afa (MD5) Previous issue date: 2013-02-06 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The use of different management systems alters the chemical, physical and hydric soil, and time a conditioning variable. Long-term experiments incorporate this variable can inform the development of soil properties and their consequences on crop productivity. The objectives of this study were to evaluate the effects on the chemical, physical, and water in a Brown Oxisol and crop yield in long-term experiment under different land use systems and soil management; to evaluate the degree of compaction of Brown Oxisol limiting the growth and development of soybean. Were evaluated two experiments. The first was established in 1978 and consists of the following systems: no-tillage in winter and summer (without lime, with lime applied in surface and incorporated lime); conventional tillage in winter and summer (without lime and incorporated lime), and native forest. Chemical characteristics were evaluated in layers of 0-2.5; 2.5-5, 5-10, 10-20 e 20-40 cm, and the physical layers of 0-2.5; 2 0.5 to 5, 5-10, 10-20, 20-40, 40-60, 60-80 and 80-100 cm. The second experiment was conducted in a greenhouse where pots were mounted with 30 cm height, compressing layer of 10-20 cm to obtain the densities of soil: 0.9; 0.96; 1.02; 1.08; 1.14; 1.20 and 1.27 Mg m-3, corresponding to degrees of compaction between 75 and 105%. The use of the soil for long periods with conventional tillage increases the density in subsurface and decreases the aggregate stability (DMG) when compared with no-tillage and forest. However, the no-tillage system increases the stability of aggregates (DMG) to a level equal to the forest, in the layer 0 to 10 cm. It also increases the microporosity, the volumetric water content, water retention and water available to plants, mainly in the upper soil layers, compared to conventional tillage and forest. Generally, liming does not alter the soil physical and hydric properties. The conservation systems improve the soil chemical properties in relation to conventional system, observed by the higher content of exchangeable cations, extractable P, organic carbon and CEC, mainly in the layer 0 to 5 cm. The liming applied in surface in the no-tillage is effective in correcting soil acidity, since soil pH, in the layer 5-40 cm, is the same when lime was surface applied or incorporated. In no-tillage, the recovery in physical properties and the higher nutrient content increases crop yields. The degree of compaction that restricts the soybean crop depends on the attribute being evaluated. When the degree of compaction is over: 75% reduces root growth; 82% plant height is lower; 87% dry mass of shoots is lower; 93% reduces evapotranspiration; and 105% root growth ceases / O uso de diferentes sistemas de manejo altera os atributos químicos, físicos e hídricos do solo, sendo o tempo uma variável condicionante. Experimentos de longa duração incorporam esta variável e podem informar sobre a evolução dos atributos do solo e suas conseqüências na produtividade das culturas. Os objetivos desse trabalho foram: avaliar os efeitos nos atributos químicos, físicos e hídricos num Latossolo Bruno Alumínico típico e na produtividade das culturas agrícolas, em experimento de longa duração sob diferentes sistemas de uso e manejo do solo; avaliar o grau de compactação do Latossolo Bruno Alumínico típico limitante ao crescimento e desenvolvimento da cultura da soja. Foram avaliados dois experimentos. O primeiro foi implantado em 1978 e constitui-se nos seguintes sistemas: plantio direto no inverno e no verão (sem calcário, com calcário aplicado em superfície e com calcário incorporado); preparo convencional no inverno e verão (sem calcário e com calcário incorporado); e mata nativa. Os atributos químicos foram avaliados nas camadas de 0-2,5; 2,5-5; 5-10;10-20 e 20-40 cm e os atributos físicos nas camadas de 0-2,5; 2,5-5; 5-10; 10-20; 20-40; 40-60; 60-80 e 80-100 cm. O segundo experimento foi conduzido em casa de vegetação onde foram montados vasos com 30 cm de altura, compactando a camada de 10-20 cm para obtenção das densidades do solo: 0,9; 0,96; 1,02; 1,08; 1,14; 1,20 e 1,27 Mg m-3, o que corresponde a graus de compactação entre 75 e 105%. O uso do solo por longos períodos com preparo convencional aumenta a densidade em subsuperfície e diminui a estabilidade de agregados (DMG) quando comparado com os sistemas de plantio direto e a mata. Todavia, o sistema de plantio direto aumenta a estabilidade de agregados (DMG) para um patamar igual ao da mata, na camada de 0 a 10 cm. Também aumenta a microporosidade, a umidade volumétrica, a retenção de água e a água disponível às plantas, principalmente nas camadas superficiais do solo, em relação ao preparo convencional e a mata. De maneira geral, a calagem não altera os atributos físicos e hídricos do solo. Os sistemas conservacionistas melhoram os atributos químicos do solo, em relação ao sistema convencional, observado pelo maior teor de cátions trocáveis, P extraível, carbono orgânico e CTC, principalmente na camada de 0 a 5 cm. A calagem superficial realizada no plantio direto é eficiente na correção da acidez, uma vez que não houve diferença no pH do solo, na camada de 5 a 40 cm, quando a calagem foi superficial ou incorporada. No plantio direto, a recuperação nos atributos físicos e o maior teor de nutrientes aumenta o rendimento das culturas. O grau de compactação que restringe a cultura da soja depende do atributo que está sendo avaliado. Quando o grau de compactação é superior a: 75% reduz o crescimento de raízes; 82% a altura das plantas é menor; 87% a massa seca da parte aérea é menor; 93% reduz a evapotranspiração; e 105% cessa o crescimento radicular

Made available in DSpace on 2014-08-20T14:36:55Z (GMT). No. of bitstreams: 1 Dissertacao_Adilson_Luis Bamberg.PDF: 1957992 bytes, checksum: 8dd6dcb7feee17d92477c82ec0703e45 (MD5) Previous issue date: 2007-02-15 / The agricultural sustainability of the rice (Oryza sativa L.) cultivation in lowland soils is based on the use of different cultivation systems and cultures, needed for a more efficient red and black rice control. The effects of these systems on the soil attributes, mainly in the long run, deserve deeper studies, particularly compaction. The present work had the objective of evaluating the bulk density of an Albaqualf submitted to different cultivation systems, in 19 years of a long-term experiment, through the use of the Volumetric Ring and the Computerized Tomography Methods, and compared the results obtained with that obtained from Pedrotti (1996) at 10 years of the experiment conduction. The experiment has been conducted since 1985, in the Lowland Experimental Field of the Embrapa Clima Temperado, in a random box plot with 8 treatments and 4 replications. It was concluded that the Computerized Tomography Method allowed the identification of a soil surface sealing (0,005 a 0,02m), mainly in the T1 (one year rice with conventional tillage followed by two years of fallow), T4 (rice x soybeans (Glicine Max L.) rotation under conventional tillage), T5 (soybeans x corn (Zea maiz L.) x rice rotation under conventional tillage), and T7 (soybeans under conventional tillage x rice under no-tillage rotation), and other in the 0,08 to 0,14m layer (plow pan), in the T1, T2 (continuous rice under conventional tillage), T4 and T5 treatments, in comparison to the control treatment (T8), that was not detected by the Volumetric Ring Method. In the 0,04 to 0,08m layer, in the other hand, all treatments presented bulk density values significantly lower or similar to the control treatment, with the opposite situation in the 0,12 to 0,18m layer, except to the T6 treatment (rye-grass (Lolium multiflorum L.) and rice under no-tillage succession). The T5 treatment showed higher bulk density values along the entire studied layer (0- 0,20m), while the T6 treatment showed values closer to the control treatment. The bulk density values obtained after 19 years of the experiment conduction where systematically lower than those obtained by Pedrotti (1996) at 10 years of conduction in the same experiment. / A sustentabilidade dos solos de várzea cultivados com arroz (Oryza sativa L.) irrigado está alicerçada na utilização de diferentes sistemas de cultivo e de culturas, fundamentais para um adequado controle do arroz vermelho e preto. Os reflexos desses sistemas nos atributos do solo, principalmente ao longo do tempo merecem maiores estudos, especialmente relacionados à compactação do solo. O presente trabalho teve como objetivo avaliar a densidade de um Planossolo Háplico Eutrófico solódico submetido a diferentes sistemas de cultivo, obtida aos 19 anos de condução do experimento, através dos Métodos do Anel Volumétrico e da Tomografia Computadorizada, e comparar com os dados obtidos por Pedrotti (1996) aos 10 anos de condução. O experimento vem sendo conduzido desde 1985, na Estação Experimental Terras Baixas da Embrapa Clima Temperado, num experimento de blocos ao acaso com 8 tratamentos e 4 repetições. Concluiu-se que o Método da Tomografia Computadorizada permitiu identificar a presença de uma camada superficial compactada (0,005 a 0,02m) nos tratamentos T1 (um ano com arroz em preparo convencional do solo seguido de dois anos de pousio), T4 (rotação de arroz x soja (Glicine Max L.) com preparo convencional do solo), T5 (rotação de arroz x soja x milho (Zea maiz L.) em preparo convencional do solo) e T7 (rotação de arroz sob plantio direto x soja sob preparo convencional do solo), e outra na camada de 0,08 a 0,14m, nos tratamentos T1, T2 (cultivo contínuo de arroz com preparo convencional do solo), T4 e T5, em relação à testemunha, o que não pôde ser detectado pelo Método do Anel Volumétrico. Na camada de 0,04 a 0,08m, por outro lado, todos os tratamentos apresentaram valores de densidade significativamente menores ou iguais em relação à testemunha, invertendo-se a situação na camada de 0,12 a 0,18m, com exceção do T6 (sucessão de azevém (Lolium multiflorum L.) x arroz sob plantio direto). O T5 apresentou os maiores valores de densidade ao longo de praticamente todo o perfil estudado (0-0,20m), enquanto que o T6 apresentou os valores mais próximos aos da testemunha. Os valores de densidade obtidos aos 19 anos de condução do experimento foram sistematicamente inferiores aos obtidos por Pedrotti (1996) aos 10 anos de condução neste mesmo experimento.

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.