This study evaluated the effects of tillage system, rotational tillage sequences, and winter seed burial depth on weed seedling recruitment in irrigated cropping systems. Notill (NT) planting of vegetable crops reduced emergence of hairy nightshade by 77 to 99% and Powell amaranth emergence from 50 to 87% compared to conventional tillage (CT) and planting of crops. Cover crops suppressed weed emergence if soils were undisturbed but not if soils were tilled in the spring. Four years of NT vegetable crops reduced summer annual weed density by 48 to 79% at two sites. Rotational tillage sequences that alternated between NT and CT only reduced summer annual weed density if the shorter season crop of snap beans was paired with CT and sweet corn was paired with NT. Hairy nightshade density decreased by 83 to 90% if NT was paired with the longer season crop of sweet corn. Hairy nightshade seedling recruitment at 30.7 C was more than 15 times greater for seeds buried at 6, 13 and 25 cm than when buried at 1 cm in simulated NT. Recruitment potential was low in March and April but increased to a maximum in May and June. Germination rates for seeds buried at 1 cm were lower and mortality and dormancy greater than for seeds buried from 6 to 25 cm during the winter. Protecting the seeds buried at 1 cm from rainfall during the winter increased seedling recruitment from 0 to 2 of 10 buried seeds, but had a negligible effect on seed mortality and dormancy. Treatment of seeds buried at 25 cm with 1 cm soil temperature reduced recruitment from 4.8 to 2.3 of 10 buried seeds at 33.3 C, but did not significantly increase seed mortality or dormancy. Estimates of seed drift using electronic transponders found that 16% of the seeds at 5 cm moved to within the emergence zone for hairy nightshade. Seed drift coupled with the faster germination rate and lower mortality of seeds buried at 12 cm or below predicts that hairy nightshade recruitment will be optimized when soil is tilled in the spring. / Graduation date: 2005

The use of no-tillage (NT) system has increased in the past few years in South Africa, but its effects on soil physical conditions have not been adequately documented. This study was undertaken to ascertain these effects, as compared to Conventional tillage (CT) system. Several sites were selected in the Bergville and Winterton areas of the midlands of KwaZulu-Natal, and at the Cedara Agricultural Research Station. NT generally increased bulk density in the topsoil and this altered total porosity and poresize distribution. Water retention, organic C and aggregate stability were increased under NT, partly due to the maintenance of the mulch cover on the surface soil. Organic C and aggregate stability were positively correlated with each other. Differences in bulk density between tillage systems with soil depth did not clearly indicate where soil compaction had occurred. Significant differences in soil compaction between treatments were, however, illustrated by changes in soil penetration resistance (SPR), especially at the. 150 mm depth. In addition, depending on the soil type, SPR was greater in the topsoil under NT than CT. It was suggested that conversion from CT to NT was carried out when the topsoil of the CT-fields was structurally poor, due to a previous history of continuous CT. Tractor traffic under CT and repeated tillage when the soil was wet had, in some cases, resulted in the formation of a compacted layer at the depth of cultivation. In clay soils, this has resulted in subsoil compaction. The formation of compacted layers caused major changes to pore size distribution and continuity and this resulted in substantially reduced hydraulic conductivity, infiltration rate,air-filled porosity and air permeability. It was concluded that compacted subsoil layers need to be broken up prior to conversion from CT to NT, and that compaction in the surface soil under NT has occurred and, in some cases, this will be a limitation to crop production. The use of minimum tillage systems should be considered and researched in these cases. / Thesis (M.Sc.)-University of Natal, Pietermaritzurg, 2003.

A field tillage tool carrier was constructed using a tractor trailer, hydraulic cylinder and steel construction material. Tillage tool blades of varying lengths, widths and angles of attack were fabricated from steel and were used in the study of the effect of tool rake angle, tool width and depth of operation on soil strength properties, draft, draft efficiency, volume of soil manipulated, degree of soil loosening and penetration resistance. / The results showed that the draft increased with tool rake angle and width. Operating at a depth of 150 mm and 100 mm depth did not make any significant difference on the draft requirement. Low angles of attack were observed to have a greater potential to loosen the soil, and the loosening increased to a depth of 150 mm then decreased. The draft efficiency was affected by the angle of attack as well as the depth of operation. The cross sectional area of the furrow and hence the volume of soil manipulated was seen to depend on the width of the tool and the operating depth. / Slender tools and high rake angles were found to loosen the soil better than wide ones. No distinct trend existed between depth to width aspect ratio and draft requirement. No variation was observed between draft efficiency and d/w ratio. Penetration resistance increased with depth of operation as well as distance from the furrow centre after tillage. Some areas of residual high strength were sometimes left within the sphere of influence of the tools. Some tools dealt with these omissions better than others.

Thesis (PhD)--University of South Australia, 1998

Thesis (PhD)--University of South Australia, 1998

Resumo: O trabalho teve como objetivos avaliar os efeitos de sistemas de cultivo e métodos de implantação no sistema radicular da cebola e nas propriedades fisicas do solo (Experimentos I e 11), bem como na produtividade de cultivares no verão, visando à colheita de bulbos na entressafra (Experimentos 111 e IV). Os experimentos foram conduzidos em um Latossolo Vermelho, em São José do Rio Pardo-SP, entre dezembro de 2004 e setembro de 2005. No Experimento I, instalado em dezembro, foram avaliados os sistemas de cultivo na palha e convencional (aração/gradagem) e pontos de coleta de amostras do solo: linha e entrelinha. No Experimento 11, instalado em fevereiro, foram avaliados os sistemas de cultivo na palha e convencional, implantados por semeadura direta, transplantio de mudas de bandejas e de raizes nuas. No Experimento 11I, instalado em dezembro, foi avaliada a produtividade de Alfa Tropical, Alfa São Francisco e Mercedes, implantadas por transplantio de mudas de bandejas e de raizes nuas, no cultivo na palha e convencional. No Experimento IV, instalado em fevereiro, foram avaliados os mesmos tratamentos do Experimento 111 e foi adicionado o método da semeadura direta. O sistema radicular concentrou-se entre O e 20 cm de profundidade. A densidade de raizes foi maior no sistema de cultivo na palha do que no convencional, entre O e 10 cm. Os atributos físicos do solo não alteraram o desenvolvimento radicular. A semeadura direta propiciou maior densidade de raizes que mudas de bandejas e de raizes nuas. Altas produtividades foram obtidas com Alfa Tropical e Alfa São Francisco em dezembro, e em fevereiro com Mercedes. O transplantio de mudas de bandejas e a semeadura direta proporcionaram produtividades de até 50 t ha-1, quase o dobro da constatada no método de mudas de raizes nuas. Maiores produtividades ou precocidade de colheita foram obtidas no cultivo na palha em relação ao sistema convencional. / Abstract: The aim of the study was to determine the effects of til/age system and method of crop implementation on the root system of onions and on the physical properties of the soil (Experiment I and 11), as well as on the productivity of the cultivars in the summer, for the purpose of collecting bulbs in the period of low onion yield (Experiments 111 and IV). The experiments were conducted in red latosol soil, in São José do Rio Pardo-SP, between Oecember, 2004 and September, 2005. Experiment I, started in Oecember, compared tillage systems, conventional (plowing/harrowing) versus no-tillage, and collection areas of soil samples, row versus interrow. Experiment 11, started in February, examined the two tillage systems, where crops were implemented by direct seeding (DS) and transplanting seedlings produced in trays (TST) or in raised beds (TSR). Experiment 11I, started in Oecember, studied the productivity of Alfa Tropical, Alfa São Francisco and Mercedes, implemented by TST and TSR, cultivated with no tillage and with conventional soil preparation. Experiment IV, started in February, examined the same treatments as in Oecember but also the OS method. The root system was concentrated at a depth of O to 20 cm. The density of the roots was greater between O and 10 cm with no tillage compared to conventional soi! preparation. The physical attributes of the soil had no influence on root development. OS favored a greater root density compared to TST and TSR. High productivity was obtained with Alfa Tropical and Alfa São Francisco in Oecember, and in February with Mercedes. TST and OS resulted in productivities of up to 50 t ha-1, almost double that with TSR. Greater yield was obtained with no tillage versus the conventional system. / Orientador: Leila Trevizan Braz / Coorientador: Itamar Andrioli / Coorientadora: Teresinha de Jesus Deléo Rodrigues / Banca: Arthur Bernardes Cecílio Filho / Banca: Marcos David Ferreira / Mestre

Made available in DSpace on 2014-06-11T19:28:32Z (GMT). No. of bitstreams: 0 Previous issue date: 2006-12-18Bitstream added on 2014-06-13T20:18:19Z : No. of bitstreams: 1 vandervinne_j_me_jabo.pdf: 347258 bytes, checksum: b5423484849f6fdd515cedd6cecc561c (MD5) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / O trabalho teve como objetivos avaliar os efeitos de sistemas de cultivo e métodos de implantação no sistema radicular da cebola e nas propriedades fisicas do solo (Experimentos I e 11), bem como na produtividade de cultivares no verão, visando à colheita de bulbos na entressafra (Experimentos 111 e IV). Os experimentos foram conduzidos em um Latossolo Vermelho, em São José do Rio Pardo-SP, entre dezembro de 2004 e setembro de 2005. No Experimento I, instalado em dezembro, foram avaliados os sistemas de cultivo na palha e convencional (aração/gradagem) e pontos de coleta de amostras do solo: linha e entrelinha. No Experimento 11, instalado em fevereiro, foram avaliados os sistemas de cultivo na palha e convencional, implantados por semeadura direta, transplantio de mudas de bandejas e de raizes nuas. No Experimento 11I, instalado em dezembro, foi avaliada a produtividade de Alfa Tropical, Alfa São Francisco e Mercedes, implantadas por transplantio de mudas de bandejas e de raizes nuas, no cultivo na palha e convencional. No Experimento IV, instalado em fevereiro, foram avaliados os mesmos tratamentos do Experimento 111 e foi adicionado o método da semeadura direta. O sistema radicular concentrou-se entre O e 20 cm de profundidade. A densidade de raizes foi maior no sistema de cultivo na palha do que no convencional, entre O e 10 cm. Os atributos físicos do solo não alteraram o desenvolvimento radicular. A semeadura direta propiciou maior densidade de raizes que mudas de bandejas e de raizes nuas. Altas produtividades foram obtidas com Alfa Tropical e Alfa São Francisco em dezembro, e em fevereiro com Mercedes. O transplantio de mudas de bandejas e a semeadura direta proporcionaram produtividades de até 50 t ha-1, quase o dobro da constatada no método de mudas de raizes nuas. Maiores produtividades ou precocidade de colheita foram obtidas no cultivo na palha em relação ao sistema convencional. / The aim of the study was to determine the effects of til/age system and method of crop implementation on the root system of onions and on the physical properties of the soil (Experiment I and 11), as well as on the productivity of the cultivars in the summer, for the purpose of collecting bulbs in the period of low onion yield (Experiments 111 and IV). The experiments were conducted in red latosol soil, in São José do Rio Pardo-SP, between Oecember, 2004 and September, 2005. Experiment I, started in Oecember, compared tillage systems, conventional (plowing/harrowing) versus no-tillage, and collection areas of soil samples, row versus interrow. Experiment 11, started in February, examined the two tillage systems, where crops were implemented by direct seeding (DS) and transplanting seedlings produced in trays (TST) or in raised beds (TSR). Experiment 11I, started in Oecember, studied the productivity of Alfa Tropical, Alfa São Francisco and Mercedes, implemented by TST and TSR, cultivated with no tillage and with conventional soil preparation. Experiment IV, started in February, examined the same treatments as in Oecember but also the OS method. The root system was concentrated at a depth of O to 20 cm. The density of the roots was greater between O and 10 cm with no tillage compared to conventional soi! preparation. The physical attributes of the soil had no influence on root development. OS favored a greater root density compared to TST and TSR. High productivity was obtained with Alfa Tropical and Alfa São Francisco in Oecember, and in February with Mercedes. TST and OS resulted in productivities of up to 50 t ha-1, almost double that with TSR. Greater yield was obtained with no tillage versus the conventional system.

Please read the abstract in the dissertation. / Dissertation (MSc)--University of Pretoria, 2000. / Plant Science / unrestricted

No description available.

Call number: LD2668 .T4 1956 P41 / Master of Science