Made available in DSpace on 2014-06-11T19:35:16Z (GMT). No. of bitstreams: 0 Previous issue date: 2012-01-19Bitstream added on 2014-06-13T18:46:47Z : No. of bitstreams: 1 rodrigues_gb_dr_ilha.pdf: 434116 bytes, checksum: 2f3a696f931e974dcdb45103ecce5926 (MD5) / Universidade Estadual Paulista (UNESP) / Plantas de cobertura são espécies utilizadas com objetivo de produzir fitomassa, sendo os resíduos mantidos na superfície do solo para formação de cobertura morta, contribuindo para aumentar a eficiência do sistema plantio direto. Este experimento avaliou a capacidade das plantas de cobertura quanto à produção de biomassa e ciclagem de nutrientes ao solo para o sistema plantio direto, também analisou a resposta do cultivar Pérola à aplicação de níveis de nitrogênio em cobertura nos estádios V4-3 e V4-6 do desenvolvimento vegetativo sobre os componentes produtivos, produtividade e qualidade fisiológica das sementes de feijoeiro, sendo conduzido na Fazenda Experimental da Faculdade de Engenharia de Ilha Solteira, UNESP, em Selvíria-MS. No verão de 2008 foram implantadas as plantas de cobertura: milheto, braquiária, braquiária+feijão-de-porco, milho, milheto+feijão-de-porco, braquiária+crotalária, milheto+crotalária, milho+feijão-de-porco, milho+crotalária, sendo o consórcio gramínea/leguminosa com linhas alternadas. Após o manejo das plantas de cobertura foi semeado o feijoeiro no outono/inverno, subdivididas para níveis de N (0, 60, 120 e 180 kg ha-1 de N) em dois estádios do desenvolvimento vegetativo (V4-3 e V4-6), sendo utilizado o delineamento experimental em blocos casualizados, com quatro repetições. Concluiu-se que, (i) As plantas de cobertura cultivadas de forma solteira ou em consórcio se mostraram como opções viáveis para o cultivo do feijoeiro em implantação do sistema plantio direto; (ii) A época mais adequada para a aplicação de N no feijoeiro é V4-3, pois permite maior absorção de nutrientes e maiores produtividades do feijoeiro cv. Pérola; (iii) Devido ao elevado retorno de nutrientes pelas plantas de cobertura não se recomenda a aplicação de N em cobertura; (iv) As sementes... / Covering plants species are used in order to produce biomass, and the straw are kept on the soil surface to form mulching, improving the efficiency of no- tillage system. This research analyzed the ability of cover plants for producing biomass and nutrients return to the soil in no-tillage system, also evaluated the response of the Perola cultivar for application of nitrogen levels in the V4-3 and V4-6 sub phases on the vegetative development under productive components, productivity and physiological quality. The experiments were conducted experimental of the Faculdade de Engenharia de Ilha Solteira, Universidade Estadual Paulista, in Selvíria-MS. In the summer of 2008 were implemented cover plants: millet, Brachiaria brizanta, maize plants, millet+jack bean, sunn hemp+millet, Brachiaria brizanta+jack bean, Brachiaria brizanta+sunn hemp , maize plants+jack bean, maize+sunn hemp , being the consortium grass/legume in alternating rows. After the management of cover crops were sown common beans seeds in the fall / winter, divided to levels of N (0, 60, 120 and 180 kg N ha -1) in two seasons of N application, and used a randomized block design with four repetitions. Concluding that: (i) The cover plants used as a good options of mulching for use in no- tillage with high levels and good potential of nutrients return; (ii) The most appropriate period for application in common bean is V4 -3 , as it allows greater absorption of nutrients and higher productivity of cv. Pérola; (iii) Due to the high return of nutrients by the cover plant is not recommended to apply of nitrogen; (iv) The seed presented high quality regardless of the type of plant, or stadium of N application

Submitted by FRANCISCO CARLOS ALMEIDA DE SOUZA null (carlos.agrofertil@outlook.com) on 2016-09-13T20:42:47Z No. of bitstreams: 1 DISSERTACAO_SOUZA, FCA.pdf: 1449852 bytes, checksum: 9dc68e25d19db297a9c6472c3c73506f (MD5) / Approved for entry into archive by Juliano Benedito Ferreira (julianoferreira@reitoria.unesp.br) on 2016-09-16T21:08:04Z (GMT) No. of bitstreams: 1 souza_fca_me_jabo.pdf: 1449852 bytes, checksum: 9dc68e25d19db297a9c6472c3c73506f (MD5) / Made available in DSpace on 2016-09-16T21:08:04Z (GMT). No. of bitstreams: 1 souza_fca_me_jabo.pdf: 1449852 bytes, checksum: 9dc68e25d19db297a9c6472c3c73506f (MD5) Previous issue date: 2016-09-02 / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / O preparo do solo é uma operação de alto custo na reforma do canavial, portanto medidas para a redução desse custo são desejáveis, desde que propiciem boas condições físicas para o desenvolvimento das plantas. O objetivo deste trabalho foi avaliar os atributos físicos de Latossolo Vermelho e de Argissolo Amarelo após o preparo do solo e após o plantio da cana-de-açúcar. O delineamento experimental foi em parcelas grandes e uniformes com dois tratamentos e dez repetições. Os tratamentos consistiram no preparo do solo para plantio da cana-de-açúcar: escarificação na linha de plantio e escarificação em área total. Após o preparo do solo e após o plantio, foram coletadas amostras indeformadas de solo em cada parcela experimental, em quatro camadas: 0,00-0,10; 0,10-0,20; 0,20-0,40 e 0,40-0,60 m em dois locais de amostragem, na linha e na entrelinha de plantio. Foi avaliada a resistência à penetração, a densidade do solo, a porosidade total, a macroporosidade e a microporosidade. Os resultados indicaram que o Latossolo Vermelho foi mais susceptível que o Argissolo Amarelo às alterações nos atributos físicos do solo após as operações de plantio da cana-deaçúcar até a camada de 0,40 m. Para o Latossolo Vermelho, após as operações de plantio da cana-de-açúcar foi verificado redução nos valores dos atributos físicos do solo na camada superficial. Para o Argissolo Amarelo, as operações de plantio da cana-de-açúcar não influenciaram nos valores dos atributos físicos. A escarificação do solo, realizada apenas na linha de plantio, é mais indicada que a escarificação em área total para plantio da cana-de-açúcar em ambos os solos. / The soil tillage demands a high cost operation to repair the canebrake. So, it is necessary some activities to reduce these costs to get good physical conditions for plant development. The aim of this study was to evaluate the physical attributes of Oxisol and Ultisol, after the soil have been prepared and after sugar cane plantation. The experimental approach was in big and uniforms parcels with two treatments and ten repetitions. The treatment was made in the prepare of soil and in the cane plantation: chiselling in the planting line and in total area. After the soil has been prepared, also after planting sugar cane, some undeformed samples of soil was collected in each experimental parcel, in four layers: 0,00-0,10; 0,10-0,20; 0,20-0,40 and 0,40-0,60 m in two different place, in the line and between line of planting area. It was also evaluated the resistance and penetration, soil density, total porosity, macro and micro porosity. The results indicates that Oxisol was more susceptible than Ultisol to alterations in the soil physical attributes after operations in cane plantation until the layer 0,40 m. For the Oxisol, after the plantation of sugar cane, was verified some reduction of values in soil physical attributes in the superficial layer. For Ultisol, the operations in the planted area of sugar cane did not influence in these attributes values. The chiselling of soil was done just in the planting line of sugar cane, it indicates that the chiselling is more recommended in total area for both soils and in plantation of sugar cane. / FAPESP: 2014/14490-2

Resumo: Os diferentes tipos de preparo de solo para a implantação de culturas devem oferecer condições favoráveis para a semeadura, emergência e desenvolvimento das plantas, porém, apresentam diferenças em relação ao consumo de combustível das máquinas e na compactação do solo, além de poderem interferir nas características agronômicas e na produtividade das culturas instaladas. Diferentes sistemas de produção têm diferentes demandas por energia dependendo do tempo de uso de máquinas e implementos, consumo de combustível, herbicidas e inseticidas. As culturas modificadas geneticamente, seja para resistência a pragas ou herbicidas, geralmente, requerem menor quantidade de energia, devido à redução no número de aplicações de agrotóxicos. O presente trabalho teve por objetivo avaliar os efeitos de diferentes preparos de solo quanto a produtividade de grãos e algumas características das plantas da cultura do milho transgênico e de seu isogênico não transgênico, além da demanda energética exigida por diferentes sistemas de produção. O estudo foi conduzido na safra agrícola 2009/2010 na Faculdade de Ciências Agronômicas - UNESP, localizada no município de Botucatu, SP, em área cultivada com plantio direto há 11 anos. O delineamento utilizado foi o fatorial 3x2, constituído por três métodos de preparo de solo e dois híbridos de milho, transgênico e não transgênico, totalizando seis tratamentos cada um com quatro repetições. Os dados obtidos foram submetidos à análise de variância a 5% de probabilidade e as médias estatisticamente diferentes foram comparadas pelo teste de Tukey a 5% de probabilidade. Os resultados obtidos mostram que, quanto ao tipo de preparo de solo, o sistema de plantio direto e o cultivo mínimo foram os que resultaram em maior produtividade... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The different types of soil tillage for crop implementation should offer favorable conditions for sowing, emergence and development of plants, however, differ in relation to fuel consumption of machinery and soil compaction, and may also interfere with the agronomic characteristics and crop productivity installed. Different production systems have different demands for energy depending on time of use of machinery and implements, fuel, herbicides and insecticides. The genetically modified crops, either for resistance to pests or herbicides generally require less energy due to the reduction in the number of agrochemicals applications. This study aimed to evaluate the effects of different soil tillage systems on grain yield and some characteristics of crop plants of transgenic maize and its isogenic non-transgenic, as well energy demands required by different production systems. The study was performed in the 2009/2010 agricultural season in the College of Agronomic Sciences - UNESP, located in Botucatu, SP, in area cultivated with no-tillage for 11 years. The design was 3x2 factorial, consisting of three methods of tillage and two corn hybrids, transgenic and non-transgenic, with six treatments each with four replications. The obtained data were submitted to analysis of variance at 5% probability and statistically different averages were compared by Tukey test at 5% probability. The obtained results show that, the type of tillage, the no-tillage and the minimum tillage were those that resulted in higher productivity differing statistically of the productivity obtained in the conventional system. Regarding hybrids, productivity showed no statistically significant difference. The systems of tillage and the different hybrids did not interfere in most other characteristics analyzed. The greater energy efficiency... (Complete abstract click electronic access below) / Orientador: Sérgio Hugo Benez / Coorientador: Paulo Roberto Arbex Silva / Banca: Silvio José Bicudo / Banca: Marco Antonio Gandolfo / Mestre

A integração Lavoura-Pecuária tem foco na busca pela excelência na produção, sendo reconhecida como ferramenta de otimização de recursos naturais e financeiros, conciliando a interação entre as interfaces solo, planta e animal. O objetivo do presente estudo foi avaliar o efeito da inclusão da ervilhaca como pastagem hibernal, sob pastejo com animais recebendo ou não suplementação, na produção da cultura subsequente (produção de milho para silagem e rendimento de grãos) na dinâmica de decomposição e liberação de nutrientes da biomassa residual pós pastejo e das fezes, em um sistema de integração lavoura-pecuária. O trabalho foi desenvolvido na Universidade Tecnológica federal do Paraná - Campus Dois Vizinhos (UTFPR-DV) e os consórcios foram compostos entre as espécies forrageiras: aveia + azevém + suplementação; aveia + azevém + ervilhaca e aveia + azevém + ervilhaca + suplementação, todos com e sem pastejo. A suplementação utilizada foi milho moído em peneira de 1 mm. Utilizou-se como adubação de base na pastagem 200kg de adubo 5-20-10 e 120 kg de N em cobertura distribuídos em 4 aplicações. Posteriormente para a cultura do milho 185 kg de 5-20-10 como adubação de base e 180 kg de N em cobertura distribuídos em 2 aplicações. Avaliou-se a decomposição da MS e liberação de nutrientes (nitrogênio, fósforo e potássio) oriundos da biomassa do consórcio forrageiro e do esterco, componentes de rendimento do milho, rendimento de grão e produção de silagem de planta inteira. Dentre os nutrientes estudados o nitrogênio foi o que teve maior retorno ao sistema após a decomposição da biomassa pastejada, não pastejada e oriundos do esterco bovino. A taxa de decomposição da biomassa sofreu influência do pastejo, apresentando decomposição mais acelerada, enquanto que para a matéria seca fecal, a taxa de decomposição foi maior para o esterco proveniente de animais que receberam suplementação, não observando-se efeito da ervilhaca no retorno de nutrientes ao solo. A presença do animal influenciou somente a variável de massa de mil grãos do milho, a qual demonstrou ser superior em áreas sem pastejo. / The Integrated Crop-Livestock Systems is focuses on the pursuit of excellence in production, being recognized as an tool of optimization natural and financial resources , combining the interaction between interfaces soil , plant and animal. The objective of this study was to evaluate the effect of inclusion of vetch as winterly herbage, with grazing animals receiving or not supplementation, in the production of subsequent crop (maize production for silage and grain yield ) in the dynamics of decomposition and nutrient release post grazing residual biomass and manure, on a crop-livestock system. The work was developed in Federal Technological University of Paraná - Campus Dois Vizinhos ( UTFPR -DV) and the consortium of forage species, were: oat + ryegrass + supplementation; oat + ryegrass + vetch and oat + ryegrass + vetch + supplementation, all with and without grazing. It was used ground maize sieve of 1 mm as supplementation. Were evaluated the decomposition of MS and release of nutrients (nitrogen, phosphorus and potassium) of biomass consortium herbage and manure, corn yield components (number of rows in each ear, number of kernels per row, grains per ear, mass of thousand grain) grain yield (kg ha-1) and production of silage from whole plant. Among the studied nutrients, nitrogen was the more returned to the system after the decomposition of biomass grazed, for not grazed and originating from cattle manure. The biomass decomposition rate was influenced by grazing, with faster decay, whereas for faecal dry matter, the decomposition rate was higher for manure from animals that were supplemented, not observing the effect of vetch return nutrients to the soil. The presence of the animal influenced only mass thousand corn grains, which proved to be superior in ungrazed areas.

A integração Lavoura-Pecuária tem foco na busca pela excelência na produção, sendo reconhecida como ferramenta de otimização de recursos naturais e financeiros, conciliando a interação entre as interfaces solo, planta e animal. O objetivo do presente estudo foi avaliar o efeito da inclusão da ervilhaca como pastagem hibernal, sob pastejo com animais recebendo ou não suplementação, na produção da cultura subsequente (produção de milho para silagem e rendimento de grãos) na dinâmica de decomposição e liberação de nutrientes da biomassa residual pós pastejo e das fezes, em um sistema de integração lavoura-pecuária. O trabalho foi desenvolvido na Universidade Tecnológica federal do Paraná - Campus Dois Vizinhos (UTFPR-DV) e os consórcios foram compostos entre as espécies forrageiras: aveia + azevém + suplementação; aveia + azevém + ervilhaca e aveia + azevém + ervilhaca + suplementação, todos com e sem pastejo. A suplementação utilizada foi milho moído em peneira de 1 mm. Utilizou-se como adubação de base na pastagem 200kg de adubo 5-20-10 e 120 kg de N em cobertura distribuídos em 4 aplicações. Posteriormente para a cultura do milho 185 kg de 5-20-10 como adubação de base e 180 kg de N em cobertura distribuídos em 2 aplicações. Avaliou-se a decomposição da MS e liberação de nutrientes (nitrogênio, fósforo e potássio) oriundos da biomassa do consórcio forrageiro e do esterco, componentes de rendimento do milho, rendimento de grão e produção de silagem de planta inteira. Dentre os nutrientes estudados o nitrogênio foi o que teve maior retorno ao sistema após a decomposição da biomassa pastejada, não pastejada e oriundos do esterco bovino. A taxa de decomposição da biomassa sofreu influência do pastejo, apresentando decomposição mais acelerada, enquanto que para a matéria seca fecal, a taxa de decomposição foi maior para o esterco proveniente de animais que receberam suplementação, não observando-se efeito da ervilhaca no retorno de nutrientes ao solo. A presença do animal influenciou somente a variável de massa de mil grãos do milho, a qual demonstrou ser superior em áreas sem pastejo. / The Integrated Crop-Livestock Systems is focuses on the pursuit of excellence in production, being recognized as an tool of optimization natural and financial resources , combining the interaction between interfaces soil , plant and animal. The objective of this study was to evaluate the effect of inclusion of vetch as winterly herbage, with grazing animals receiving or not supplementation, in the production of subsequent crop (maize production for silage and grain yield ) in the dynamics of decomposition and nutrient release post grazing residual biomass and manure, on a crop-livestock system. The work was developed in Federal Technological University of Paraná - Campus Dois Vizinhos ( UTFPR -DV) and the consortium of forage species, were: oat + ryegrass + supplementation; oat + ryegrass + vetch and oat + ryegrass + vetch + supplementation, all with and without grazing. It was used ground maize sieve of 1 mm as supplementation. Were evaluated the decomposition of MS and release of nutrients (nitrogen, phosphorus and potassium) of biomass consortium herbage and manure, corn yield components (number of rows in each ear, number of kernels per row, grains per ear, mass of thousand grain) grain yield (kg ha-1) and production of silage from whole plant. Among the studied nutrients, nitrogen was the more returned to the system after the decomposition of biomass grazed, for not grazed and originating from cattle manure. The biomass decomposition rate was influenced by grazing, with faster decay, whereas for faecal dry matter, the decomposition rate was higher for manure from animals that were supplemented, not observing the effect of vetch return nutrients to the soil. The presence of the animal influenced only mass thousand corn grains, which proved to be superior in ungrazed areas.

Sistemas com semeadura direta sobre palhada são cada vez mais utilizados na agricultura, e a ramulose do algodoeiro, causada pelo fungo Coletotrichum gossypii var. cephalosporioides Costa, é uma das doenças mais importantes na cultura. Foram realizados durante os anos de 2004/05, 2005/06 e 2006/07 na Escola Superior de Agricultura "Luiz de Queiroz", USP/ESALQ, em Piracicaba, SP, experimentos com a cultura do algodoeiro (Gossypium hirsutum L. var. latifolium Hutch), conduzidos sob preparo do solo convencional com semeadura convencional do algodoeiro, e ausência de preparo do solo com semeadura do algodoeiro sobre palhada de milheto, com o objetivo de avaliar se as modificações microclimáticas causadas pela utilização da palhada de milheto em relação às variáveis temperatura e duração de período de molhamento foliar (DPM) poderiam interferir no desenvolvimento e evolução da ramulose do algodoeiro. Foi utilizado também o Índice de Favorabilidade temperatura-molhamento para a ramulose do algodoeiro, que utiliza os parâmetros temperatura e DPM no seu cálculo para explicar o desenvolvimento da doença entre os dois sistemas de semeadura. Os dados microclimáticos foram medidos por uma plataforma de aquisição de dados na região central da área experimental. Em blocos alternados entre os dois sistemas de semeadura, o patógeno foi inoculado artificialmente nas subparcelas dos blocos, e a doença foi avaliada por escala de notas (1 a 5). As médias de notas de sintomas de ramulose foram submetidas à análise estatística, através de testes não paramétricos. A fim de avaliar se a ausência de preparo poderia interferir no desenvolvimento das plantas, este também foi avaliado. Os resultados permitiram concluir que sob semeadura convencional, houve nos dois primeiros anos maiores médias de massa seca, altura de plantas, IAF, e que no terceiro ano foram constatados maior número de raízes laterais e maior número de plantas com encurvamento da raiz pivotante sob semeadura direta. O aumento da severidade da ramulose foi decorrente de interações muito particulares para cada período, onde muitas variáveis estão envolvidas, ou seja, características intrínsecas ao patógeno, à fase de desenvolvimento da planta e às condições macro e microclimáticas; O IF-tm teve uma boa relação com o aumento da severidade e diferenças na severidade da ramulose entre os dois sistemas de semeadura; Pode ocorrer maior severidade da ramulose para sistemas de produção convencionais em maior proporção do que em sistemas com utilização de palhada em períodos onde os valores de IF-tm são altos, associados à ocorrência de chuvas; Com Índices de Favorabilidade temperatura-molhamento menores que 0,500 não se observau aumento efetivo da severidade da ramulose em quaisquer sistema de semeadura, mesmo havendo outras condições favoráveis; O sistema de semeadura utilizado não influenciou na produtividade da cultura. / Systems with direct seeding over mulching are more often used in agriculture, and the Ramulosis from the cotton plant caused by the fungus Coletotrichum gossypii var. cephalosporioides Costa, one of the most important diseases in cotton crop. During the years of 2004/05, 2005/06; and 2006/07at the University of Agriculture "Luiz De Quieroz", USP/ ESALQ, in Piracicaba, SP, experiments were made with the cotton crop (Gossypium hirsutum L. var latifolium Hutch), under the preparation of conventional tillage with conventional seeding of the cotton crop and the absence of the preparation of the tillage with the seeding of the cotton crop over the mulching of millet (Pennisetum glaucum L.) with the objective to evaluate if the modifications microclimates caused by the use of the mulching of millet in relation to the variables temperatures and the leaf wetness duration, (LWD) could interfere on the development of the ramulosis of the cotton crop. It was also used the Favorability Index for the ramulosis of the cotton crop which uses the temperature parameter and DPM in its calculation to explain the development of the disease between the two systems of seeding. The Weather variables data were measured by a platform of acquisition of data in the central zone of the experimental area. In alternated blocks between both systems of seeding, the pathogen was inoculated artificially and the disease was measured by scales from 1 to 5. The average of ramulosis was submitted to a statistic analysis through not parametric tests with the intent to find out if the absence of the preparation could interfere on the development of the plants, which was also evaluated. The results enable the conclusion that through conventional seeding, on the first two years there was an average of higher dry mass higher height of the plants, IAF, and in the third year it was found a higher number of lateral roots and a higher number of plants with bending on the primary roots over direct seeding. The increase of the severity of the ramulosis happened due to specific interactions for each period where many variables were involved, which means, intrinsic characteristic to the at the stage of the development of the plant and the conditions macro and microclimates. The Favorability Index had a good relation with the increase and the differences within the severity of the ramulosis between both systems of seeding. Higher severity of the ramulosis can occur for conventional systems of production in bigger proportions than in systems that uses the mulching in periods where the value of the IF-tm are high, associated to rain. With indications of Favorability Index lower than 0,500 there is no evidence of the effective increase of the severity of the ramulosis in any system of the seeding. The system of seeding used does not affect in the productivity of the cotton crop.

A major challenge facing agriculture today is to sustain the productivity of agricultural systems with the reduction of weed invasion. The Swartland region in the Western Cape (South Africa) is intensively cropped, producing wheat (Triticum aestivum) as the major crop. As a result of the weedy ryegrass invasion the wheat yield is reduced. In addition, ryegrass has developed resistance to grass herbicides (graminicides). This situation has increased the need to use alternative practices for controlling the invasion of ryegrass in wheat fields. In this regard, crop rotation and tillage systems were proposed as techniques to suppress the ryegrass invasion. This could thus maintain a sustainable long-term wheat production system with less application of herbicides, decreased input costs and increased total grain yield. Against this background, the effects of crop rotation and tillage were determined on ryegrass seedling emergence in a field and shade netting experiment, while seed dormancy was determined in the laboratory. The objectives were to compare the wheat production of two crop rotations with mono-cropped wheat and assess the impact on the ryegrass population in no-till and minimum tillage systems. Analyses of variance on data sets of ryegrass seeds from 2009, 2010 and 2011 were used to determine germination and dormancy percentages in laboratory experiments. The performance of laboratory treatments was evaluated on the basis of germination percentage of seeds. In the field and shade netting experiments, analyses of variance for data from 2007, 2011 and 2012 were used to determine crop rotation x tillage system response. Field and shade netting performance were evaluated on the basis of ryegrass population inhibition and stimulation respectively. Ryegrass seeds from 2009 and 2010 showed higher germination percentages (80 per cent and 73 per cent) than 2011 (42 per cent). Primary dormancy prevented high germination of newly harvested seeds as dormancy release increase with age of the seed. Results of field and shade netting experiments showed stimulation of the ryegrass weed population in wheat monoculture under minimum tillage. However, when wheat was rotated with leguminous crops under both tillage systems (minimum-till and no-till) ryegrass was significantly inhibited. It was concluded that the critical period for weed competition is the first six weeks after planting. Results from this study provide a basis for producers of cereals to make good decisions with regards to timing weed control measures. It is essential to use competitive crop sequences which will inhibit weeds. The challenge is getting this practice adopted and implemented by producers as it will promote conservation agriculture within the region. This study promotes long-term sustainable wheat production systems with an efficient weed management programme that is environmentally friendly using less herbicides within the Swartland region.

Intensive tillage and monoculture cropping practices reduce soil C accumulation hence increasing soil vulnerability to chemical, physical and biological degradation. This study focussed on enhancing biomass production of wheat and oat winter cover crops as a means of increasing C sequestration in the low organic C soils of the central part of Eastern Cape Province. The specific objectives were (i) to evaluate the short-term effects of no till and cereal-fallow based crop rotations on; soil organic matter related parameters, pH and electrical conductivity, (ii) soil bulk density, water retention and aggregate stability, (iii) soil microbial biomass C and N, mineralizable N, soil respiration, and dehydrogenase enzyme activity, (iv) grain yield, soil nutrient concentration (N, P and K) and their uptake by maize, and (v) to identify soil parameters with high sensitivity to tillage under maize-fallow-maize, maize-wheat-maize and maize-oat-maize rotational cover cropping practices. The experiment was laid out as a split-plot arrangement in a randomized complete block design with 4 replicates. Tillage treatments (CT and NT) were applied on the main plots which measured 8 × 18 m while crop rotation treatments were applied in the subplots which measured 8 × 6 m. The rotation treatments were maize-fallow-maize (MFM), maize-wheat-maize (MWM) and maize-oat-maize (MOM). Weed control in NT plots involved preplant application of glyphosate to control mainly the grass weeds while post emergence weed management was done using Atrazine (485 atrazine and 15 g l-1 triazines). Initial weed control in CT plots was achieved through ploughing to a depth of 20 cm followed by disking while post emergence weed iii management was done by hand hoeing. Soil parameters measured were; (i) particulate organic matter (POM), soil organic carbon (SOC), total nitrogen (TN), pH and electrical conductivity (EC), (ii) soil bulk density (b), moisture at field capacity (FC), aggregate mean weight diameter (MWD) determined by fast wetting (FW), slow wetting (SW), mechanical breakdown by shaking (MB) and the stability index (SI), (iii) soil microbial biomass C (MBC) and N (MBN), mineralizable N (MN), soil respiration (SR), and dehydrogenase enzyme activity (DHEA). No-till increased POM and TN compared to CT in Lenye and Burnshill, respectively. The MWM and the MOM rotations increased TN relative to the MFM rotation in Lenye. The MWM and MOM rotations enhanced SOC relative to MFM in all sampled soil depths at Burnshill and similar observations were made under MOM rotation in the 5-20 cm depth in Lenye. The MWM and MOM rotations tended to depress soil pH relative to the MFM rotation in both sampled soil depths in Lenye while NT reduced soil pH relative to CT on the surface soil layer in Burnshill. Soil EC and pH varied with depth across tillage practices but both parameters remained within the ideal range for successful crop production over the study period. Soil stability index (SI) and aggregate MWD determined by FW, SW and MB were higher in Lenye compared to Burnshill. The MOM rotation enhanced the SI relative to MFM and MWM rotations at both sites. Scanning electron microscope (SEM) showed that more organic C was incorporated into the soil under NT and MOM rotation compared to CT and MFM rotation which had few organic coatings on the soil particles. Microbial properties varied with plant biomass input as influenced by tillage and type of rotational cover crop at both sites. Like in other past studies, NT showed higher levels of MBC, MBN, NM and SR at the soil surface layer compared to CT in Burnshill. No till increased MN iv relative to CT in both sampled soil depths in Lenye and resulted in higher DHEA compared to CT in Burnshill. The MOM rotation increased MBC, MBN, MN relative to MFM rotation especially within surface soil layer. Similar observations were made with respect to MN and SR in both sampled soil layers at Lenye. By contrast, the DHEA was higher under the MFM relative to the MWM and MOM rotations in Lenye but similar under the MFM and MOM rotations in Burnshill. Maize grain yield was not affected by both tillage and crop rotations but varied with cropping season. Comparable grain yields observed under the two tillage practices with similar fertilizer application rates indicated the advantage of NT over CT in saving on labour costs in maize production without compromising yields. High plant biomass retention under NT relative to CT contributed to high soil N and P levels under the former compared to the latter tillage practice especially on soil surface layer at both study sites. Principal component analysis (PCA) revealed that soil chemical and biological parameters closely linked to organic matter, namely SOC, MN, MBC and MBN showed the highest sensitivity to tillage and crop rotation treatments. Soil aggregate MWD determined by SW and b were the physical parameters which were highly altered by agronomic management practice. The MWM and MOM rotations were clustered together and clearly separated from the MFM rotation and this observed trend only applied to the 0-5 and 5-20 cm depths in Lenye site only. No till, MWM and MOM rotations enhanced POM, SOC and TN relative to CT and MFM rotation suggesting these practices have greater potential to improve soil chemical properties compared to intensive tillage and maize monoculture based production practices. Reduced soil b under MOM rotation and improved SI under NT compared to MFM and CT, respectively v indicate that these practices have the potential to improve degraded soils. Although not significantly different, NT values for MBC, MBN, MN, SR and DHEA were higher compared to CT indicating the potential of the practice to improve soil biotic activity relative to conventional tillage practices. No till enhanced surface soil nitrate N and extractable P compared to CT at both sites revealing the long-term potential of NT in improving the supply of these essential plant nutrients compared to CT. Principal component analysis showed that SOC, MN, K, P, MBC, MBN, soil aggregate MWD determined by SW and b were the most sensitive parameters to tillage and crop rotations. Therefore, these parameters could constitute the minimum data set for assessments of the impact of selected CA practices on soil quality attributes.

In the Northern Great Plains (NGP), weed management within organic systems remains a challenge. Experiments were conducted at two distinct sites in North Dakota to investigate effects of deep mulch no-till (NT) on soil quality indices, weed densities, and weed seedbank densities. We hypothesized that alfalfa mulch no-till and arbuscular mycorrhizal fungi (AMF) inoculant would be associated with reductions in weed densities and improvements to soil quality and vegetable yield. NT treatments were associated with reductions in weed densities and time required for weeding, with improvements in soil quality, such as increased AMF biomass, and yield for snap pea, onion, beet, and butternut squash compared to tilled treatments. Our findings suggest deep mulch no-till using alfalfa residue may be a viable option for small-scale organic vegetable producers in the NGP. Additional research is required to determine costs associated with sowing, harvesting, baling, and applying alfalfa mulch compared to tilling.

Detection of unexpectedly high concentrations of agricultural pollutants in ground water have inspired investigations of the role of preferential movement of chemicals through agricultural soils. This research focuses on preferential flow and solute transport processes and the effects of agricultural management practices on these processes. Experimental methods for monitoring preferential flow and solute transport in the field as well as a stochastic, physically-based model for predicting water flow and transport of non-reactive chemicals in heterogeneous soils with naturally occurring macropores were developed and evaluated. Field experiments, aimed at monitoring the occurrence of preferential flow and solute transport, were conducted in a conventionally-tilled and a no-till soybean field in the Coastal Plain of Virginia. A rainfall simulator was used to apply a one-hour storm at rates of 5.0, 6.5 and 7.5 cm/hr to six 1.83 by 1.83 m plots. Chloride was added to the water to serve as a non-reactive tracer. Electrical conductivity equipment provided a useful method for monitoring solute transport. The moisture and solute conditions, observed during a 28-hour period after the start of the rainfall event, clearly indicated the occurrence of preferential flow and solute movement in the field plots. The variability of the solute concentrations in the field plots was generally higher in the no-till plots than in the conventionally-tilled plots. The plots that received rain at 6.5 and 7.5 cm/hr showed more variability than the plots that received rain at 5 cm/hr. The observed solute concentrations indicated that if the solute transport would have taken place by advection only, 61% of the solute transport in the conventionally-tilled plots and 50% of the solute transport in the no-till plots could be attributed to preferential flow. A physically-based, finite element model for simulating flow and solute transport in variably-saturated soils with macropores (MICMAC) was developed. Flow and solute transport are described by the Richards' equation and the convection-dispersion equation. Flow in the macropores is described by the Hagen-Poiseuille equation. An axisymmetric coordinate system is used to simulate the flow and solute transport from the macropore into the surrounding soil matrix, assuming a vertically oriented, surface-vented, cylindrical macropore. Flow and solute transport between the macropore and the soil matrix are driven by the pressure head at the macropore-matrix boundary. To assess the natural heterogeneity of the soil properties a stochastic component was added to the model. Flow and solute transport at the field scale were simulated by regarding the field as a collection of statistically independent, non-interacting vertical soil columns, using Monte Carlo simulation. The sensitivity analysis of the model indicated that, for a soil with macropores, the model is most sensitive to the saturated water content of the soil matrix, the initial moisture content, and the rainfall rate. The model is not very sensitive to the macropore dimensions. Examination of the stochastic approach indicated that the representation of a heterogeneous field as a collection of non-interacting stream columns may substantially underestimate water and solute leaching. A change of 5% in the soil properties of the neighboring soil columns may underpredict the solute leaching, 24 hours after a rainstorm, by 157% for a soil column with a macropore, and by 58% for a soil column without a macropore. These differences decreased to 47% and 8%, respectively, 168 hours after the rainfall. Field application of the model suggested that the model underestimates the leaching of water and solutes from the root zone. However, the computed results were substantially better than the results obtained when no preferential flow component was included in the model. The model performed best under conditions that favored preferential flow, i.e., a high rainfall rate and high initial moisture conditions. The simulated and observed solute concentrations in the root zone agreed reasonably well, although the maxima of the observed data were generally higher than those of the simulated data. / Ph. D.