Made available in DSpace on 2017-07-10T17:37:11Z (GMT). No. of bitstreams: 1 Tiago_Madalosso.pdf: 2572164 bytes, checksum: 04f38c061e9c675c1dc4b7c079f8fa9f (MD5) Previous issue date: 2015-08-26 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / In Brazil it is possible for two or more per year grain crop cultivation, but there is evidence that the cultivation tillage system with only commercial crops has resulted in soil degradation. The objective of this study was to evaluate the balance and efficiency of use of N, P and K, the effect on the chemical properties of soil and biometric variables of crops in grain production systems in western Parana region, encompassing different fertilization and probate cultures. The experiment was designed in randomized blocks with the treatments arrangement in divided plots with 4 repetitions. In the plots were installed the winter successions (5), wheat, oats, sunn hemp, corn second crop + brachiaria and corn 2nd harvest and the subplots fertilizers (3) organic, organomineral and mineral. The summer crop was planted to soybeans. The test was conducted for three seasons, starting with the planting of soybeans in 2013. Soil samples were collected after the 3rd growing at 0-10 and 10-20 cm. In the first crop, the use of organic fertilizer promoted increase in grain yield, mass of thousand grains, at the height of soybean plants, the bedding, the number of pods per plant, increased the leaf content and export of N by grain soybeans. In the third crop, there were no differences between the fertilizer and succession to black oat and sun hemp provided higher-yielding soybeans. The oat presented the highest dry matter yield, higher concentration of P in the shoot and greater extraction of N, P and K. Corn consortium + brachiaria reduced the yield of maize grain compared to monocrop. The application of poultry litter and the use of oat or crotalária as cover crops in winter, provide increased grain yield for the soybean crop. Using the same dose of P and K there is no difference in the yield of soybeans, corn and wheat between mineral fertilizers and organomineral. A use of poultry litter promotes increase of soil P and K soil, but does not increase the levels organic matter. P and K use efficiency is higher in soy succession - 2 nd harvest corn. The efficiency of use of N, P and K is lower in the fertilizer with organic fertilizer. There is no difference in the use efficiency of P and K between organomineral and mineral fertilizers, as for N, the mineral fertilizer has higher efficiency. ON was the nutrient with the most negative balance in the soil and the use of cover crops (black oats and crotalaria) increases the N balance in the soil. OP showed balance in the soil near zero being lower in succession with wheat and oats. The K balance in the soil was negative and was not different between the tested grain and fertilizer production systems / No Brasil é possível o cultivo de duas ou mais safras de grãos por ano, porém há evidências de que o cultivo em sistema plantio direto apenas com culturas comerciais tem resultado na degradação do solo. O objetivo deste trabalho foi avaliar o balanço e eficiência de utilização de N, P e K, o efeito sobre as propriedades químicas do solo e variáveis biométricas das culturas em sistemas de produção de grãos na região oeste do Paraná, englobando diferentes adubações e sucessões de culturas. O experimento foi delineado em blocos ao acaso com arranjo dos tratamentos em parcelas divididas, com quatro repetições. Nas parcelas foram instaladas as sucessões de inverno (5), trigo, aveia preta, crotalária, milho 2a safra + braquiária e milho 2a safra e nas subparcelas os fertilizantes (3), orgânico, organomineral e mineral. A safra de verão foi cultivada com soja. O ensaio foi conduzido por três safras, iniciando com a semeadura da soja em 2013. As amostras de solo foram coletadas após o 3° cultivo nas profundidades de 0-10 e 10-20 cm. No primeiro cultivo, a utilização de fertilizante orgânico promoveu incremento no rendimento de grãos, na massa de mil grãos, na altura de plantas de soja, no acamamento, no número de vagens por planta, incrementou o teor foliar e exportação de N pelos grãos de soja. No terceiro cultivo, não houve diferenças entre os fertilizantes e as sucessões com aveia preta e crotalária proporcionaram maior rendimento de grãos de soja. A aveia preta apresentou a maior produção de massa seca, maior concentração de P na parte aérea e maior extração de N, P e K. O consórcio de milho + braquiária reduziu o rendimento de grãos de milho quando comparado ao cultivo solteiro. A aplicação de cama de frango e a utilização de aveia preta ou crotalária como planta de cobertura no inverno, proporcionam maior rendimento de grãos para a cultura da soja. Utilizando a mesma dose de P e K não há diferenças no rendimento de grãos de soja, milho e trigo entre os fertilizantes mineral e organomineral. A utilização de cama de frango promove incremento dos teores de P e K do solo, porém não incrementa os teores de matéria orgânica. A eficiência de uso de P e K é superior na sucessão soja - milho 2ª safra. A eficiência de uso de N, P e K é inferior na adubação com fertilizante orgânico. Não há diferença na eficiência de uso de P e K entre os fertilizantes organomineral e mineral, já para o N, o fertilizante mineral apresenta eficiência superior. O N foi o nutriente com o balanço no solo mais negativo e a utilização de plantas de cobertura (aveia preta e crotalária) incrementa o balanço de N no solo. O P apresentou balanço no solo próximo a zero sendo menor nas sucessões com trigo e aveia preta. O balanço de K no solo foi negativo e não foi diferente entre os sistemas de produção de grãos e fertilizantes testados

Made available in DSpace on 2017-07-10T19:24:45Z (GMT). No. of bitstreams: 1 Marcia Maria Mauli.pdf: 735503 bytes, checksum: 95cbd8669a51013567022eb7120ce6ef (MD5) Previous issue date: 2009-02-02 / The adjustment of a cover crop to the agricultural system, with species whose chemical composition has substances able to control weeds, is a promising alternative to decrease herbicides application in agriculture. So, this trial aimed at analyzing the interference of black oats residues as well as black oat, common vetch and forage turnip consortium on weeds incidence, seeds emergence, seedling emergence, plants development, soybean productivity and its harvested seeds quality. The trial was carried out on field, from 2007 to 2008, with 5 m x 2 m plots and 1 m of border among them, distributed in seven randomized treatments with five replications each. During the crop development, the following parameters were evaluated: emergence speed index, plants development and weeds incidence. After harvest, in the laboratory, harvested seeds were evaluated according to: water content determination, weight of 100 seeds, purity, productivity, percentages of germination and vigor. It was a factorial experimental design with two factors plus one control and the averages were compared by the Tukey test at 5% level of significance. The weeds species did not differ statistically among the treatments. By and large, the treatments did not influence on plants heights, but increased the soybean productivity. However, the seeds showed less vigor when under the accelerated aging test. The seeds purity was inferior when they were under black oats crop. The weight of 100 seeds was changed by the treatments and they were heavier when grown on black oats. The other analyzed parameters did not show any statistic difference. It is, therefore, concluded that these species are good alternatives as winter covers in soybean crop under rotation system, since they improve the agronomic aspects of this culture. / A adequação da cobertura vegetal ao sistema agrícola, com espécies que possuam em sua composição química substâncias capazes de auxiliar no controle das plantas invasoras, é alternativa promissora para diminuir o uso de herbicidas na agricultura. Assim, o objetivo deste trabalho foi analisar a interferência dos resíduos culturais de aveia preta e também do consórcio de aveia preta, ervilhaca comum e nabo forrageiro sobre a incidência de plantas invasoras; emergência de plântulas, crescimento de plantas e produtividade da cultura de soja; além da qualidade da semente da soja colhida. O experimento foi conduzido em campo, nos anos 2007/2008, demarcando-se parcelas de 5 m x 2 m, com 1 m de bordadura entre elas e distribuídas em sete tratamentos, ao acaso, com cinco repetições cada. Durante o desenvolvimento da cultura, avaliaram-se os parâmetros: índice de velocidade de emergência, desenvolvimento de planta e incidência de espécies invasoras. Após a colheita, em laboratório, foram avaliadas as sementes colhidas pela determinação de teor de água, massa de 100 sementes, pureza, produtividade, porcentagem de germinação e vigor. O delineamento experimental foi em esquema fatorial com dois fatores com testemunha e as médias foram comparadas pelo teste de Tukey ao nível de 5% de significância. Observa-se que as espécies invasoras não diferiram estatisticamente entre os tratamentos. De maneira geral, os tratamentos não influenciaram na altura de plantas e aumentaram a produtividade da soja. Entretanto, apresentaram sementes menos vigorosas quando submetidas ao teste de envelhecimento acelerado. A pureza das sementes foi menor quando submetida ao cultivo com aveia preta. A massa de 100 sementes foi alterada pelos tratamentos, sendo maior em cultivo sob aveia preta. Os demais parâmetros analisados não mostraram diferenças estatísticas. Conclui-se, portanto, que tais espécies são indicadas como alternativa para cobertura de inverno, na rotação de culturas com a soja, pois melhoram os aspectos agronômicos da cultura.

Made available in DSpace on 2017-07-10T19:25:21Z (GMT). No. of bitstreams: 1 Gislaine.pdf: 1925118 bytes, checksum: dda812a967e8b5085aecc8b34c8c0f3b (MD5) Previous issue date: 2012-02-14 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The tillage efficiency is directly related to the management and choice of vegetation species prior to sowing the crop. In this context, this study examined the effect of brachiaria sowing densities (Brachiaria ruziziensis) (10; 15 and 20 kg ha-1), stylosanthes (Stylosanthes macrocephala and Stylosanthes capitata) (3; 4.5 e 6 kg ha-1) and consortium of these species (10 + 3; 15 + 4.5; 20 + 6 kg ha-1) as vegetation cover for soybean crop and seed quality. Under field conditions in the agricultural years 2009/2010 and 2010/2011 were demarcated 3.5 m x 4.5 m plots with 1 m border between them for seeding cover crops. The cover crops were sown in August 2009 and 2010, period in which the incidence of invasive plants, biomass productivity, coverage persistence and soil coverage percentage promoted by plants were evaluated. At 90 days after sowing, before fruiting, covers were mowed and arranged on each respective plot. The soybean sowing was performed in early December 2009 and 2010, 20 days after mowing the cover, with 0.45 m spacing, seven sowing lines and 14 seeds per meter. In the soybean crop was determined the emergence speed index, emergence speed, emergence percentage and plant height; incidence of invasive plants, productivity; in addition to the physiological and nutritional quality of seed. The experimental design cover plants cycle and soybean was completely randomized with 10 treatments and five repetitions; means were submitted to regression analysis. The experimental design for seed quality data was completely randomized in 3 x 4 factorial arrangement, five repetitions; means compared by the by Scott and Knott test at 5% probability. The incidence of invasive plants and the fresh weight of narrow-leaf weeds in the cover crops had proportional reduction to the increase of planting density, in addition, cover crops with higher seeding rate showed higher percentage of ground cover. It was observed higher nutritional quality of seeds when grown under intercropping at intermediate sowing density (15 + 4.5 kg ha-1). In general, the results indicate the possibility of using the species Brachiaria ruziziensis in single condition or consortium, as cover crop prior to soybean; however, more detailed studies should be performed considering the species with the possibility of being used via crop rotation in the tillage system, as well as under regional climate and soil conditions / A eficiência do sistema plantio direto está diretamente relacionada ao manejo e à escolha das espécies de cobertura vegetal que antecedem a semeadura da cultura agrícola. Analisou-se neste contexto, o efeito das densidades de semeadura de braquiária (Brachiaria ruziziensis), estilosantes (Stylosanthes macrocephala e Stylosanthes capitata) e consórcio dessas espécies no ciclo das coberturas vegetais e da cultura da soja, e na qualidade das sementes da soja. Em condições de campo, nos anos agrícolas 2009/2010 e 2010/2011 foram demarcadas parcelas de 3,5 m x 4,5 m, com 1 m de bordadura entre elas, para a semeadura das coberturas vegetais. As coberturas vegetais foram semeadas em agosto dos anos 2009 e 2010, período em que foram avaliadas a incidência de plantas invasoras, a produtividade de biomassa, a persistência de cobertura e a porcentagem de cobertura do solo promovida pelas plantas. Aos 90 dias após a semeadura, antes da frutificação, as coberturas foram roçadas e dispostas sobre cada parcela respectiva. A semeadura da soja foi realizada no início de dezembro de 2009 e 2010, 20 dias após a roçada da cobertura, com espaçamento entre linhas de 0,45 m, sete linhas de semeadura e 14 sementes por metro. Na cultura da soja, foi determinado índice de velocidade de emergência, velocidade de emergência, porcentagem de emergência e altura de planta, incidência de plantas invasoras, produtividade, além da qualidade fisiológica e nutricional da semente. O delineamento experimental, referente aos dados do ciclo das plantas de cobertura e da cultura da soja, foi inteiramente casualizado, com dez tratamentos e cinco repetições. Os dados foram submetidos à análise de variância e as médias foram submetidas à análise de regressão. O delineamento experimental referente aos dados da qualidade de sementes foi inteiramente casualizado, em esquema fatorial 3 x 4, com cinco repetições. Os dados foram submetidos à análise de variância e as médias foram comparadas pelo teste de Scott e Knott a 5% de probabilidade. A incidência de plantas invasoras e a massa fresca das plantas invasoras de folha estreita nas coberturas vegetais apresentaram redução proporcional ao aumento da densidade de semeadura, além disso, as plantas de cobertura com maior densidade de semeadura proporcionaram maior porcentagem de cobertura do solo. Foi observada maior qualidade nutricional das sementes, quando cultivadas sob consórcio na densidade de semeadura intermediária (15 + 4,5 kg ha-1). Em geral, os resultados obtidos indicam a possibilidade da utilização da espécie Brachiaria ruziziensis, em condição solteira ou em consórcio, como planta de cobertura antecedendo à cultura da soja. Entretanto, estudos mais detalhados devem ser realizados considerando a diversidade de culturas com possibilidade de serem empregadas no sistema plantio direto, bem como as condições climáticas regionais

Made available in DSpace on 2017-05-12T14:48:08Z (GMT). No. of bitstreams: 1 Marcia Maria Mauli.pdf: 735503 bytes, checksum: 95cbd8669a51013567022eb7120ce6ef (MD5) Previous issue date: 2009-02-02 / The adjustment of a cover crop to the agricultural system, with species whose chemical composition has substances able to control weeds, is a promising alternative to decrease herbicides application in agriculture. So, this trial aimed at analyzing the interference of black oats residues as well as black oat, common vetch and forage turnip consortium on weeds incidence, seeds emergence, seedling emergence, plants development, soybean productivity and its harvested seeds quality. The trial was carried out on field, from 2007 to 2008, with 5 m x 2 m plots and 1 m of border among them, distributed in seven randomized treatments with five replications each. During the crop development, the following parameters were evaluated: emergence speed index, plants development and weeds incidence. After harvest, in the laboratory, harvested seeds were evaluated according to: water content determination, weight of 100 seeds, purity, productivity, percentages of germination and vigor. It was a factorial experimental design with two factors plus one control and the averages were compared by the Tukey test at 5% level of significance. The weeds species did not differ statistically among the treatments. By and large, the treatments did not influence on plants heights, but increased the soybean productivity. However, the seeds showed less vigor when under the accelerated aging test. The seeds purity was inferior when they were under black oats crop. The weight of 100 seeds was changed by the treatments and they were heavier when grown on black oats. The other analyzed parameters did not show any statistic difference. It is, therefore, concluded that these species are good alternatives as winter covers in soybean crop under rotation system, since they improve the agronomic aspects of this culture. / A adequação da cobertura vegetal ao sistema agrícola, com espécies que possuam em sua composição química substâncias capazes de auxiliar no controle das plantas invasoras, é alternativa promissora para diminuir o uso de herbicidas na agricultura. Assim, o objetivo deste trabalho foi analisar a interferência dos resíduos culturais de aveia preta e também do consórcio de aveia preta, ervilhaca comum e nabo forrageiro sobre a incidência de plantas invasoras; emergência de plântulas, crescimento de plantas e produtividade da cultura de soja; além da qualidade da semente da soja colhida. O experimento foi conduzido em campo, nos anos 2007/2008, demarcando-se parcelas de 5 m x 2 m, com 1 m de bordadura entre elas e distribuídas em sete tratamentos, ao acaso, com cinco repetições cada. Durante o desenvolvimento da cultura, avaliaram-se os parâmetros: índice de velocidade de emergência, desenvolvimento de planta e incidência de espécies invasoras. Após a colheita, em laboratório, foram avaliadas as sementes colhidas pela determinação de teor de água, massa de 100 sementes, pureza, produtividade, porcentagem de germinação e vigor. O delineamento experimental foi em esquema fatorial com dois fatores com testemunha e as médias foram comparadas pelo teste de Tukey ao nível de 5% de significância. Observa-se que as espécies invasoras não diferiram estatisticamente entre os tratamentos. De maneira geral, os tratamentos não influenciaram na altura de plantas e aumentaram a produtividade da soja. Entretanto, apresentaram sementes menos vigorosas quando submetidas ao teste de envelhecimento acelerado. A pureza das sementes foi menor quando submetida ao cultivo com aveia preta. A massa de 100 sementes foi alterada pelos tratamentos, sendo maior em cultivo sob aveia preta. Os demais parâmetros analisados não mostraram diferenças estatísticas. Conclui-se, portanto, que tais espécies são indicadas como alternativa para cobertura de inverno, na rotação de culturas com a soja, pois melhoram os aspectos agronômicos da cultura.

Made available in DSpace on 2017-05-12T14:48:43Z (GMT). No. of bitstreams: 1 Gislaine.pdf: 1925118 bytes, checksum: dda812a967e8b5085aecc8b34c8c0f3b (MD5) Previous issue date: 2012-02-14 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The tillage efficiency is directly related to the management and choice of vegetation species prior to sowing the crop. In this context, this study examined the effect of brachiaria sowing densities (Brachiaria ruziziensis) (10; 15 and 20 kg ha-1), stylosanthes (Stylosanthes macrocephala and Stylosanthes capitata) (3; 4.5 e 6 kg ha-1) and consortium of these species (10 + 3; 15 + 4.5; 20 + 6 kg ha-1) as vegetation cover for soybean crop and seed quality. Under field conditions in the agricultural years 2009/2010 and 2010/2011 were demarcated 3.5 m x 4.5 m plots with 1 m border between them for seeding cover crops. The cover crops were sown in August 2009 and 2010, period in which the incidence of invasive plants, biomass productivity, coverage persistence and soil coverage percentage promoted by plants were evaluated. At 90 days after sowing, before fruiting, covers were mowed and arranged on each respective plot. The soybean sowing was performed in early December 2009 and 2010, 20 days after mowing the cover, with 0.45 m spacing, seven sowing lines and 14 seeds per meter. In the soybean crop was determined the emergence speed index, emergence speed, emergence percentage and plant height; incidence of invasive plants, productivity; in addition to the physiological and nutritional quality of seed. The experimental design cover plants cycle and soybean was completely randomized with 10 treatments and five repetitions; means were submitted to regression analysis. The experimental design for seed quality data was completely randomized in 3 x 4 factorial arrangement, five repetitions; means compared by the by Scott and Knott test at 5% probability. The incidence of invasive plants and the fresh weight of narrow-leaf weeds in the cover crops had proportional reduction to the increase of planting density, in addition, cover crops with higher seeding rate showed higher percentage of ground cover. It was observed higher nutritional quality of seeds when grown under intercropping at intermediate sowing density (15 + 4.5 kg ha-1). In general, the results indicate the possibility of using the species Brachiaria ruziziensis in single condition or consortium, as cover crop prior to soybean; however, more detailed studies should be performed considering the species with the possibility of being used via crop rotation in the tillage system, as well as under regional climate and soil conditions / A eficiência do sistema plantio direto está diretamente relacionada ao manejo e à escolha das espécies de cobertura vegetal que antecedem a semeadura da cultura agrícola. Analisou-se neste contexto, o efeito das densidades de semeadura de braquiária (Brachiaria ruziziensis), estilosantes (Stylosanthes macrocephala e Stylosanthes capitata) e consórcio dessas espécies no ciclo das coberturas vegetais e da cultura da soja, e na qualidade das sementes da soja. Em condições de campo, nos anos agrícolas 2009/2010 e 2010/2011 foram demarcadas parcelas de 3,5 m x 4,5 m, com 1 m de bordadura entre elas, para a semeadura das coberturas vegetais. As coberturas vegetais foram semeadas em agosto dos anos 2009 e 2010, período em que foram avaliadas a incidência de plantas invasoras, a produtividade de biomassa, a persistência de cobertura e a porcentagem de cobertura do solo promovida pelas plantas. Aos 90 dias após a semeadura, antes da frutificação, as coberturas foram roçadas e dispostas sobre cada parcela respectiva. A semeadura da soja foi realizada no início de dezembro de 2009 e 2010, 20 dias após a roçada da cobertura, com espaçamento entre linhas de 0,45 m, sete linhas de semeadura e 14 sementes por metro. Na cultura da soja, foi determinado índice de velocidade de emergência, velocidade de emergência, porcentagem de emergência e altura de planta, incidência de plantas invasoras, produtividade, além da qualidade fisiológica e nutricional da semente. O delineamento experimental, referente aos dados do ciclo das plantas de cobertura e da cultura da soja, foi inteiramente casualizado, com dez tratamentos e cinco repetições. Os dados foram submetidos à análise de variância e as médias foram submetidas à análise de regressão. O delineamento experimental referente aos dados da qualidade de sementes foi inteiramente casualizado, em esquema fatorial 3 x 4, com cinco repetições. Os dados foram submetidos à análise de variância e as médias foram comparadas pelo teste de Scott e Knott a 5% de probabilidade. A incidência de plantas invasoras e a massa fresca das plantas invasoras de folha estreita nas coberturas vegetais apresentaram redução proporcional ao aumento da densidade de semeadura, além disso, as plantas de cobertura com maior densidade de semeadura proporcionaram maior porcentagem de cobertura do solo. Foi observada maior qualidade nutricional das sementes, quando cultivadas sob consórcio na densidade de semeadura intermediária (15 + 4,5 kg ha-1). Em geral, os resultados obtidos indicam a possibilidade da utilização da espécie Brachiaria ruziziensis, em condição solteira ou em consórcio, como planta de cobertura antecedendo à cultura da soja. Entretanto, estudos mais detalhados devem ser realizados considerando a diversidade de culturas com possibilidade de serem empregadas no sistema plantio direto, bem como as condições climáticas regionais

Agricultural intensification reliant on monocrops could change soil health in a way that does not support maximum crop productivity. Twenty-nine-year-old no-till field plots at the University of Kentucky Spindletop research farm showed a significant reduction in corn yields from continuous corn plots compared to those from plots in various types of rotation. The objective of this study was to determine what role soil microbes might play in yield reduction and how management and time effects microbial community structure. Samples were collected from the following treatments: continuous corn (CC), continuous soybean (SS), a 2-year corn/soybean rotation (CCSS), Corn in rotation with soybean with winter wheat cover (C/W/S), and sod controls (SOD). Soil health-related parameters were determined along with microbial community structure using phospholipid fatty acid analysis (PLFA). Results show that there is a strong seasonal dynamic in microbial communities with May, July and September showing the greatest differentiation between treatments. Nonparametric multidimensional analysis (NMDS) shows that microbial communities under SS, CC treatments were significantly different from the CS and CWS treatments across all four years of the study. My findings will prove useful for assessing the contribution of biological indicators to agroecosystem function and will aid in making recommendations of when and how to manage these parameters to improve soil health and maximize yield.

This research assessed the seasonal effects of contrasting tillage and crop rotation systems on soil ammonia oxidizing bacteria (AOB) and archaea (AOA). Four different cropping systems under till and no-till were analyzed in a 30 year-old agricultural field trial. Samples were collected during the 2010 growing season at times corresponding with agronomic events. Nucleic acids were preserved in the field and subsequently analyzed by quantitative real-time polymerase chain reactions (qPCR). Tillage decreased AOB activity and abundance in the plow layer (0-15 cm) immediately after fall moldboard plow events, but observed AOB dynamics at other times suggest tillage had a long-term distribution effect across depth (0-30 cm). AOA abundance was significantly greater in no-till plots at all times indicating tillage had longer-term effects on these communities. Crop rotation had minimal effect on AOB and AOA, but there was a noted yield advantage for corn following wheat, regardless of tillage treatment. / OMAFRA Highly Qualified Personnel Program, NSERC

The purpose of this study was to investigate the economic feasibility of alternative crop rotations and to determine the economic implications of including forages and livestock during the transition to organic agriculture in Nova Scotia. The rotation systems were distinguished by: (i) frequency of forage in the rotation, (ii) source of nutrient supply, and (iii) type of farming operation. The economic analysis was divided in two parts. The first part analysed data from a four-year crop rotation experiment, using enterprise budgeting and statistical methods to compare differences among rotations under different treatments. The second part involved the development of a multi-period linear programming (LP) model to simulate a commercial operation. / The results from the statistical analysis suggest that crop enterprise net returns tended to be higher in forage-based rotations and in the livestock systems compared to cash crop rotations and the stockless system. Results from the LP model suggest that including forages and beef cattle during the transition to organic agriculture can provide considerable economic benefits, especially when crops were grown under ruminant compost.

Cabbage is one of the most important and widely grown crops in KwaZulu-Natal (KZN). In cabbage production, no clear cropping methods exist (other than succession cropping) to allow the soil to recover its fertility status naturally after the harvested has crop absorbed nutrients from the soil. Succession cropping system is extensively practiced by cabbage farmers. Succession cropping is when a succeeding vegetable crop is planted immediately after harvesting the preceding crop. This does not allow soil fertility status to be balanced by soil microbes in an environmentally friendly approach. Instead, synthetic fertilizers are heavily used to rectify soil fertility status and these have negative impacts on the soil in the long term, followed by yield decline. However, the economic downturns and green environment awareness have caused researchers and some farmers to focus more on developing environmentally healthy crop production technologies. A priority in this study was to elucidate effects of cover crops-green manure as rotational crops in cabbage production. The experimental site is located at Cedara Research Station. In 2009, soil samples were taken from the top 30 cm of the soil profile, in a zigzag pattern in 5 m x 5 m grids for fertility analysis. Results were used to determine nutrient deficiencies, and blanket application of phosphorus and potassium followed according to each grid’s deficiency. The study was divided into two cycles, with each cycle consisting of season one and season two. The study was conducted over a two year period. Cycle one, season one, 2009/2010 (Dec-Mar): four treatments (sunn hemp: planted at 50 kg/ha seeding rate; forage sorghum: planted at 50 kg/ha seeding rate; mixture of sunn hemp-forage sorghum: each planted at 25 kg/ha seeding rate and control: cabbage planted at 30 cm within rows x 60 cm between rows) were used. The statistical design of the study was a 4x4 Latin Square experiment repeated twice in adjacent fields (347 m2 each) 6 m apart, with a total of 32 plots. Each experimental plot was 8.5 m x 9 m. Genstat Package, 9th Edition was used for data analysis. Standard cabbage production recommendations were followed in control treatments. Cabbage yield was determined in all control plots. Weed coverage percentages were determined in all four treatments. Cycle one, season two, 2010, (Apr-Aug): all 32 plots from season one were each split into four, in a Split Plot design, resulting in a total of 128 plots in both fields. Nitrogen was applied at four different levels: 0, 80, 160 and 240 kg N/ha. Standard cabbage production methods were followed again as in the control treatment in season one. Cover crops were replaced by planting cabbage. Cabbage was repeated in the control plots. Cabbage yield, cabbage leaf nutrients, soil nitrate and ammonium nitrate and soil carbon to nitrogen (C:N) ratio were measured. Cycle two, season one, 2010 (Sep-Dec): The same method in cycle one, season one was repeated. Cycle two, season two, 2010/2011, (Dec-Apr): The same method in cycle one, season two was repeated. Although in this study there was visibly a large amount of residues left over after the trial was harvested, the use of a tractor-drawn slasher was not very effective. The slashed material was not chopped into smaller pieces, as it would if a roll-chopper had been used. A tractor-drawn slasher was used because it is a tool available to many farmers. As a result, it was not a simple process to transplant seedlings mechanically, due to the amount of organic matter that was in the soil after it had been incorporated. The mechanical planter pulled off, removed and became blocked by the residues, and as a result it was not able to operate as it would in normal soils. The residues removed soil from the furrows and that caused seedlings to fall over as all the soil for the root system support had been moved by the planter and stuck residues. The planter had to be assisted by hand planting seedlings that were not properly planted mechanically. Hence, from the operational perspective, the choice of tools for chopping were not effective in this study and this is something to be considered in future studies, where it will be necessary to compare different tools for planting and cover crop incorporation into the soil. During the present study, soil N content in different plots had significant differences (P=0.05). The control showed high levels of total N content, but this was not related to the low yields exhibited by cabbage after cabbage at all levels of N. Since, where there were cover crops, the N content was low, this could mean that N was immobilized, compared to the cabbage treatments where plenty of N was available. Immobilized N is thus not available for leaching, polluting the environment. The yield of cabbage was significantly lowest in controls. The study showed that cover crop-green manure use has a positive effect in terms of yield improvement. The cabbage yields from the sunn hemp plots at a 0 kgN/ha were significantly different from the yield of cabbage planted following cabbage at 240 kgN/ha N. The study also showed that N is not the only yield determinant in cabbage production. Too much N has a tendency to suppress cabbage yields. The cover crop-green manures selected for this study were shown to be ineffective in suppressing weeds. This was true even though the weed coverage percentage in each of the cover crop-green manure plots was above 65%, except for the cabbage crop. This study did not separate different weeds, but the most dominant weeds were Amaranthus hybridus (pigweed), Galinsoga parviflora (gallant soldier), Bidens pilosa (common blackjack) and Cyperus esculentus (yellow nutsedge). These weeds were effectively controlled in the cabbage sole crop by the use of herbicides and mechanical weeding. The result of cover crop-green manures not suppressing weeds was significantly associated with the cover crop-green manure seeding rate. This study has been a starting point in the development of cover crops-green manure as rotational crops in cabbage production. It is concluded that cover crop-green manure (sunn hemp and forage sorghum) used in this study for vegetable (cabbage) production has proven to be successful in improving yields. Yields obtained from cover crop-green manure treatments were better than yields obtained from - conventional tillage methods for cabbage production (control). However, in cabbage, weed suppression and soil N content, failed to improve significantly in response to the cover crop green manures used. The high plant population density under a cover crop, combined with weed population, may lead to high uptake of soil N for plant growth, leaving less N in the soil and in the plant. In the sole cabbage crop, because of low competition, there was adequate uptake of N for plant growth and yet the crop was not exhaustive of soil N. Further research is required in the following areas: comparison of cabbage with other vegetable crops in response to the effect of the selected cover crops; comparison of mechanical weeding and herbicide use as means of controlling weeds during cover crop-green manure growth; identification of dominant weeds in the presence and absence of cover crops, and monitoring of soil water relations and other fertiliser effects. / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2012.

Mechanical weed control, chisel plow tillage and organic fertilization are important components of sustainable agriculture that can contribute to the preservation and improvement of soil and water resources. These practices can each affect weed communities, crop weed interactions and crop yields. Little is known about their combined effects on weed populations and weed community dynamics in common cropping systems. The main objective of this project was to determine the effects of crop rotation, weed control, tillage and nutrient source and their interactions on weed communities and weed emergence. The field experiment was conducted on a Sainte-Rosalie clay and a Duravin loam in Saint-Hyacinthe, Quebec, Canada, in 1996 and 1997. Mechanical control was not as effective as chemical control in controlling weed populations. Weed density increased after the second pass of the rotary hoe in soybean. Cultivation in corn triggered flushes of weed emergence, but corn yield was not affected by the increase in weed density. Chisel plow tillage reduced the efficacy of mechanical weed control in both crops. Reduced soybean yields were partly attributed to the large quantities of corn residues under chisel plow tillage. Nutrient source had no effect on weed densities. However, environmental stress conditions experienced in spring 1997 resulted in reduced crop growth and increased weed biomass under organic fertilization. Seed production of dominant residual weed species was greater under mechanical compared with chemical weed control, but was unaffected by tillage and nutrient source. Particular attention to weed management will be required when including both chisel plow tillage and organic nutrient source in a corn-soybean rotation, especially when resorting to mechanical weed control only.