The purpose of this research was to investigate how sustainable agriculture is being conceptualized and implemented in Saskatchewan. Zero tillage, organic farming, and the discourses surrounding them were examined as theoretical and practical responses to sustainable agriculture. Characteristics of 33 organic and 33 zero tillage farming systems located throughout the soil climatic zones of southern Saskatchewan were compared, as well as farmers' perceptions of sustainable agriculture and factors influencing their management decisions. The analysis was extended beyond the local level by examining the links between major socio-political forces shaping agriculture and farmers' perceptions and choices. Central to this analysis is an examination of the role of informal and formal knowledge systems in the development of sustainable agriculture, and how relations of power affect the knowledge that is being produced and ultimately the direction of change in agriculture. Interdisciplinary and exploratory approaches were used to identify and examine a range of emergent issues. The data gathered was analyzed both quantitatively and qualitatively. This study revealed commonalities between zero tillage and organic farmers' basic views on sustainable agriculture, and important differences in the ways these two groups of farmers translated these ideas into practice. Most farmers defined sustainability at the farm-level, focusing on land stewardship and the preservation of the family farm. Farmers adopted zero tillage because of specific environmental, economic and labour advantages, whereas organic farming was adopted for a combination of environmental, health, economic, philosophical/spiritual and labour factors. In general, zero tillage and organic farming systems differed in size, in production and management operations, in land tenure, and in the use of purchased inputs and labour. Zero tillage farms tended to be large, capital-intensive, specialized cropping operations, with a significant proportion of rented land and non-family hired labour. Organic farms were moderate-sized, diversified crop and livestock operations that substituted biological and cultural practices for purchased (agrochemical) inputs, had a high degree of ownership, and relied more upon labour exchange. These characteristics create distinct environmental, economic and social advantages and disadvantages. Zero tillage, compatible with the dominant agricultural paradigm and the industrial model, continues to be promoted by agricultural institutions and agribusiness as the best solution to farm-level sustainability. Interest in organic agriculture and the alternative agricultural paradigm is increasing, however, due to the current crisis in the farm economy and changes in consumers' perceptions and choices.

Fundação de Amparo a Pesquisa do Estado de Minas Gerais / The growing demand on renewable fuel, despite oil higher prices and pollutant power has promoted an increase on sugarcane s area in Brazil. Its expansion has been occurring preference at savannah s area occupying pasture and crop. In this context, the project was conducted with the purpose of studying different sugarcane environment production under six different soil tillage, and their effects on, soil physical attributes, root system development and sugarcane yield. The experiment was conducted at Brazilian savannah, from April 2009 through May 2010, in a pasture area and in a sugarcane renew field. There were assessed six different soil tillage in each production environment: 1 -drying + moldboard plough + harrow disk (DAVG); 2 - moldboard plough + harrow disk (AVG); 3 - intermediate harrow disk + moldboard plough + leveler harrow disk (PC); 4 - Zero Tillage (PD); 5- subsoiler (SU) 6 - intermediate harrow disk + disk plough + leveler harrow disk (PCAd) for the expansion environment, being the same ones at the other area but on the treatment 5 and 6 it was used ratton destroyer. The treatments were set prior to sugarcane planting, which was done after mechanical opening the groove for seedpiece deployment. The experimental design was a completely randomized with four replications. Each plot had 13 rows spaced of 1,5 m and 50 meters long. The soil physical attributes evaluated were: macro, micro and total porosity and soil bulk density at three depths: 0 0,20m ; 0,20 0,40m; 0,40 0,60m, on May 2010. Root evaluation was done after the sugarcane harvest using the profile wall and root counting, and by the use of Racine 2 software it was calculated the root length density. In each plot it was opened a trench with 1,5 m length by 0,90m depth. The results were compared between treatments, depth and horizontal distance from the plant. There were evaluated number of stems per meter, 5 middle rows and 30 meters, plant height and diameter, 10 plants, and yield of burned and manually harvested sugarcane, 5 middle rows and 50 meters. On both environment productions soil physical proprieties at zero tillage were similar to all treatments. At the renew area the depth of 0 0,20m presented highest values of RLD. The highest yield was found at moldboard plough areas, on both production environments. / A cultura da cana-de-açúcar têm-se expandido para a região do Cerrado, promovendo a ocupação de áreas exploradas por pastagens e lavouras. Neste contexto, objetivou-se com este trabalho estudar os efeitos dos preparos de solo nos atributos físicos do solo, no desenvolvimento do sistema de raízes e na produtividade da cana-de-açúcar, em área de expansão e de renovação, no Cerrado brasileiro. O experimento foi conduzido em área de cana planta, entre o período de abril de 2009 e maio de 2010. Foram avaliados seis diferentes preparos de solo em cada área de estudo. Área de expansão: 1- arado aiveca + grade leve com dessecação (DAV); 2 - arado aiveca + grade leve sem dessecação (AVG); 3 - grade média + arado de aiveca + grade leve (PC); 4 - plantio direto (PD); 5 - subsolador (SU); 6 - grade média + arado de discos + grade leve (PCAd). Área de renovação: 1 - dessecação + arado aiveca + grade leve - (AVG), 2 - dessecação + plantio direto (PD); 3 - dessecação + subsolador - (SU); 4 - subsolador + grade leve - (SUG); 5 - destruidor de soqueira + subsolador (DsSU); 6 - destruidor de soqueira + grade média + arado de aiveca + grade leve (DsPC). Os tratamentos foram implantados no momento da instalação do canavial, sendo que, em todas as parcelas, o plantio foi realizado de forma manual, após sulcação e adubação de plantio. O delineamento foi em blocos casualizados com quatro repetições. Cada parcela foi composta por 13 linhas de cana, espaçadas de 1,5 metros com 50 metros de comprimento. As avaliações dos atributos físicos do solo (macroporosidade, microporosidade, densidade) foram realizadas em três profundidades: 0 0,20m ; 0,20 0,40m; 0,40 0,60m após a colheita da cana, em maio de 2010. Neste período realizou-se também a avaliação das raízes utilizando o método da parede do perfil e contagem de intersecção de raízes e posterior cálculo da densidade de comprimento de raiz (DCR), através do programa Racine. Para as características agronômicas foram avaliados o número de colmo por metro, a altura e o diâmetro médio de colmos e a produtividade da cana. Tanto na área de expansão quanto na área de renovação os atributos físicos do solo, o desenvolvimento de raízes e a produtividade de cana, o plantio direto mostrou-se viável de ser adotado para cana de primeiro ano. Em camadas de solos mais férteis, como na área de renovação há um maior desenvolvimento do sistema radicular, neste caso na camada superficial até 0,20 m. O arado de aiveca em área de renovação de cana proporcionou a maior produtividade para cana planta em ambas as áreas estudadas. / Doutor em Agronomia