Crabgrass is a warm-season annual species that has the potential to provide high-quality summer forage for ruminants in the transition zone between subtropical and temperate regions of the United States. Growing annual lespedeza in association with crabgrass may be beneficial due to nitrogen transfer from the legume to the grass. The objectives of the research reported in this thesis were to (1) determine the effects of pH on establishment and growth of crabgrass; and (2) evaluate the effects of lespedeza seeding rate and N fertilization treatment on the yield, botanical composition, and nutritive value of crabgrass-lespedeza mixtures. A greenhouse study was conducted using three soil pH levels of 4.8, 5.5, and 6.3. Crabgrass germination and root and shoot yields were not affected by soil pH values. A field study was conducted to evaluate the influence of six lespedeza seeding rates (0-28 kg ha-1) and two N fertilization treatments (140 kg total N ha-1 or zero N) on crabgrass-annual lespedeza mixtures. In most cases, increasing lespedeza seeding rate increased lespedeza in the sward. However, lespedeza rate had limited effect on yield and nutritive value of the mixture. Nitrogen fertilization increased crabgrass in the sward and total yield by as much as 46%. Responses of nutritive value parameters to N fertilization were variable and appeared linked to weather factors. In vitro true digestibilities ranged from 750 to 875 g kg-1, and were largely unaffected by N fertilization and seeding rate The results of these studies indicate that crabgrass could provide moderate amounts of highly digestible forage while growing on acidic soils commonly found in the southeastern United States. Annual lespedeza may be grown in association with crabgrass, but limited improvement in yield and nutritive value were found for this practice. / Master of Science

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / This work was carried out with the objective of evaluating the dynamics of forage accumulation and structural characteristics of the Digitaria eriantha submitted to different defoliation frequencies from January 2015 to February 2016. Four frequencies of defoliation were evaluated: very (25 cm), high (35 cm), medium (45 cm) and low (55 cm), in two seasons of the year: higher sunshine (September to March) and lower sunshine (April to August). A randomized complete block design with four replicates was used. In general, the reduction in frequency of defoliation increased the interval between cuts, leaf area index, rates of total forage accumulation, stem and dead forage, and percentages of stalks and dead forage, accumulations of total deforest, Stems and dead fodder. In turn, this reduction in leaf defoliation frequency decreased leaf blade accumulation rate, leaf blade percentage and leaf blade accumulation and blade / stem ratio. The reduction in the frequency of defoliation increased dry matter, total carbohydrate and lignin content, as well as decreased crude protein content and estimated digestibility of Digitaria eriantha. In general, Digitaria eriantha presented higher rates of total forage accumulation, leaf blade and stalks, percentage of stalks and dead forage, shoot volume density and population density of tillers in the period of greatest sunshine. On the other hand, the Digitaria eriantha showed lower rate of accumulation of dead fodder and percentage of dead fodder in the period of lower insolation. Less frequent defoliation increases and increases the forage accumulation rates of Digitaria eriantha, but with less desirable morphological composition, contributing to a lower quality. / Este trabalho foi realizado com o objetivo de avaliar a dinâmica do acúmulo de forragem e as características estruturais do capim faixa-branca submetido a diferentes frequências de desfolhação, no período de janeiro de 2015 a fevereiro de 2016. Foram avaliadas quatro frequências de desfolhação: muito alta (25 cm), alta (35 cm), média (45 cm) e baixa (55 cm), em duas épocas do ano: maior insolação (setembro a março) e menor insolação (abril a agosto). Utilizou-se o delineamento experimental em blocos casualizados com quatro repetições. De maneira geral, a redução na frequência de desfolhação aumentou o intervalo entre cortes, o índice de área foliar, as taxas de acúmulo de forragem total, de colmos e forragem morta e as porcentagens de colmos e forragem morta, os acúmulos de forragem total, de colmos e de forragem morta. Por sua vez, esta redução na frequência de desfolhação diminuiu a taxa de acúmulo de lâmina foliar, a porcentagem de lâmina foliar e o acúmulo de lâminas foliares e a relação lâmina/colmo. A redução na frequência de desfolhação aumentou o teor de matéria seca, carboidratos totais e lignina, assim como diminuiu o teor de proteína bruta e a digestibilidade estimada do capim faixa-branca. De maneira geral, o capim faixa-branca apresentou maiores taxas de acúmulo de forragem total, de lâmina foliar e colmos, porcentagens de colmos e forragem morta, densidade volumétrica de colmo e a densidade populacional de perfilhos no período de maior insolação. Por sua vez, o capim faixa-branca apresentou no período de menor insolação menor taxa de acúmulo de forragem morta e porcentagem de forragem morta. Desfolhações menos frequentes incrementem e aumentam as taxas de acúmulo de forragem do capim faixa-branca, porém com composição morfológica menos desejável contribuindo para uma menor qualidade. / São Cristóvão, SE

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / This study was conducted to evaluate the tillering dynamics, forage production, and use potential of digitgrass subjected to four defoliation intensities: Very High (25 cm), High (35 cm), Medium (45 cm), and Low (55 cm), evaluated in two periods of the year (higher and lower insolation) from January 2015 to January 2016. A randomized-block design with four replicates was adopted and measures repeated over time. Increasing defoliation frequencies increased the number of tiller generations, tiller appearance and mortality rates, aerial tiller density, and forage use potential and reduced tiller survival rate, daily stem production, daily leaf senescence, total daily production, and net daily accumulation of forage. Daily leaf production was lower at the Very High frequency as compared with the other frequencies. In the period of lower insolation, daily leaf senescence and tiller appearance and mortality rates were higher, while survival rate, balance, aerial tiller density, daily stem production, net daily accumulation of forage, and forage use potential were lower. Basal tiller density increased as the defoliation densities were elevated, with higher values observed during the period of greater insolation at the Very High and High frequencies. The Very High defoliation frequency did not provide good plant development, whereas the Low frequency led to increased stem production. The defoliation frequencies and times of the year evaluated here do not change the population stability of digitgrass plants when irrigated, thus ensuring its persistence. Higher defoliation frequencies result in greater tiller renewal in digitgrass. The High and Medium defoliation frequencies are more suitable for the defoliation of digitgrass, promoting a larger proportion of leaves in relation to stems. / O objetivo com este trabalho foi avaliar a dinâmica do perfilhamento, produção de forragem e potencial de utilização do capim faixa-branca submetido a quatro frequências de desfolhação: Muito Alta (25 cm), Alta (35 cm), Média (45 cm) e Baixa (55 cm), avaliadas em duas épocas do ano (maior e menor insolação) no período de janeiro de 2015 a janeiro de 2016. Utilizou-se o delineamento em blocos casualizados, com quatro repetições e medidas repetidas no tempo. A elevação na frequência de desfolhação aumentou o número de gerações de perfilhos, taxas de aparecimento e mortalidade de perfilhos, densidade populacional de perfilhos aéreos e o potencial de utilização da forragem e reduziu a taxa de sobrevivência de perfilhos, produção diária de colmo, senescência diária de folhas, produção total diária e o acúmulo líquido diário líquido de forragem. A produção diária de folhas foi menor na frequência muito alta em relação às outras frequências. Na época de menor insolação a senescência diária de folhas, as taxas de aparecimento e mortalidade de perfilhos foram maiores, em contrapartida, a taxa de sobrevivência, balanço, densidade populacional de perfilhos aéreos, produção diária de colmos, acúmulo líquido diário de forragem e o potencial de utilização de forragem foram menores. A densidade populacional de perfilhos basais aumentou com elevação das frequências de desfolhação e foi maior na época de maior insolação nas frequências muito alta e alta. A frequência de desfolhação muito alta não proporcionou um bom desenvolvimento da planta, enquanto que a frequência baixa apresentou elevada produção de colmos. As frequências de desfolhação e épocas do ano avaliadas não alteram a estabilidade da população de plantas do capim faixa-branca, quando irrigado, garantindo assim sua persistência. Maiores frequências de desfolhação resultam em maior renovação de perfilhos do capim faixa-branca. As frequências de desfolhação alta e média são mais indicadas para a desfolhação do capim faixa-branca, promovendo uma melhor proporção de folhas em relação a colmos. / São Cristóvão, SE

Please read the section 05chapter5 (General summary and conclusions, especially p168-170) of this document / Thesis (DSc (Agriculture))--University of Pretoria, 2007. / Agricultural Economics, Extension and Rural Development / unrestricted

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Brazil has a vast area consisting of forage plants, therefore, a large number is at some stage of degradation mainly due to inappropriate choice of the species in relation to the cultivation environment, and as a result, this work took place in order to evaluate the Morphogenesis of White-Band Grass Submitted to Nitrogen Fertilization. The experiment was conducted to evaluate the morphogenetic, structural and productive characteristics of White-Band grass (Digitaria umfolozii) subjected to nitrogen fertilization from January to May 2014. Five doses of nitrogen were evaluated: 0, 100, 200, 300 and 500 kg/ha. The experimental outline was randomized blocks, with four repetitions. Nitrogen fertilization did not affect (P> 0.05) the final length of the leaves, leaf senescence rate, the number of green leaves per tiller, plant height and the ratio of leaf to stem of grass-Range White, presenting, respectively average amounts of 26.9 cm; 0.77 cm / tiller day; 4.2 leaves / tiller; 43.4 cm and 1.04. The appearance and leaf elongation rates, the tiller population density and accumulation of forage, leaves, stems and dead materials of White-Band grass were influenced by nitrogen doses adjusted to a positive quadratic equation (P <0.05) by nitrogen doses. In general, the increase in the amount of nitrogen applied increased the amounts of these rates, reaching maximum points at doses between 300 and 400 kg/ha according to the respective adjusted models. Phyllochron and the lifespan of the leaves were affected in a negative quadratic way (P <0.05) by nitrogen doses. Similarly, the increase in the amount of nitrogen applied declined the values of these rates, reaching minimum points at doses between 300 and 400 kg /ha, according to the respective equations set. The stem elongation rate increased linearly with the nitrogen dose. The White-Band grass has a higher renewal of tissues and productivity when fertilized. The improvement in productive characteristics of White-Band grass reaches maximum amount with nitrogen doses around 300 kg/ha. / O Brasil possui uma vasta área composta por plantas forrageiras, no entanto, grande parte encontra-se em algum estagio de degradação devido principalmente a escolha inadequada da espécie em relação ao ambiente de cultivo, diante disso realizouse esse trabalho a fim de avaliar a Morfogênese do Capim Faixa-Branca Submetido a Adubação Nitrogenada. O experimento foi desenvolvido objetivando avaliar as características morfogênicas, estruturais e produtivas do capim Faixa-Branca (Digitaria umfolozii) submetido a adubação nitrogenada, no período de janeiro a maio de 2014. Foram avaliadas cinco doses de nitrogênio: 0, 100, 200, 300 e 500 kg/ha. O delineamento experimental utilizado foi o de blocos casualizados, com quatro repetições. A adubação nitrogenada não influenciou (P>0,05) o comprimento final das folhas, a taxa de senescência foliar, o número de folhas vivas por perfilho, a altura das plantas e a relação folha:colmo do capim Faixa-Branca, apresentando, respectivamente, valores médios de 26,9 cm; 0,77 cm/perfilho dia; 4,2 folhas/perfilho; 43,4 cm e 1,04. As taxas de aparecimento e de alongamento de folhas, a densidade populacional de perfilhos e os acúmulos de forragem, de folhas, de colmos e de material morto do capim Faixa-Branca foram influenciadas pelas doses de nitrogênio ajustando-se a uma equação quadrática positiva (P<0,05) pelas doses de nitrogênio. De maneira geral, a elevação na quantidade de nitrogênio aplicada aumentou os valores destas taxas, atingindo pontos de máximo com doses entre 300 e 400 kg/ha, segundo os respectivos modelos ajustados. O filocrono e a duração de vida das folhas foram afetados de maneira quadrática negativa (P<0,05) pelas doses de nitrogênio. De maneira semelhante, a elevação na quantidade de nitrogênio aplicada diminuiu os valores destas taxas, atingindo pontos de mínimo com doses entre 300 e 400 kg/ha, segundo as respectivas equações ajustadas. A taxa de alongamento de colmo aumentou linearmente com a dose de nitrogênio. O capim Faixa- Branca apresenta maior renovação de tecidos e produtividade quando adubado. A melhoria nas características produtivas do capim Faixa-Branca atingem valores máximos com doses de nitrogênio em torno de 300 kg/ha.

The distribution and potential sources of 15 polycyclic aromatic hydrocarbons (PAHs) in soils and Digitaria eriantha in the vicinity of three South African coal-fired power plants, Matla, Lethabo and Rooiwal were determined by gas chromatography–mass spectrometry. An ultrasonic assisted dispersive liquid-liquid microextraction (UA-DLLME) method was developed for the extraction of polycyclic aromatic hydrocarbon in soil, followed by determination using gas chromatography mass spectrometry. The study showed that an extraction protocol based on acetonitrile as dispersive solvent and C2H2Cl2 as extracting solvent, gave extraction efficiencies comparable to conventional soxhlet extraction for soil samples. The extraction time using ultrasonication and the volume of the extraction solvent was also investigated. Using a certified reference material soil (CRM), the extraction efficiency of UA-DLLME ranged from 64 to 86% in comparison with the Soxhlet result of 73 to 95%. In comparison with the real sample, the CRM result did not show a significant difference at 95% C.I. The UA-DLLME proved to be a convenient, rapid, cost-effective and greener sample preparation approach for the determination of PAHs in soil samples. PAH compound ratios such as phenanthrene/phenanthrene + anthracene (Phen/ Phen + Anth) were used to provide a reliable estimation of emission sources. The total PAH concentration in the soils around three power plants ranged from 9.73 to 61.24 μg g−1, a range above the Agency for Toxic Substances and Disease Registry levels of 1.0 μg g−1 for a significantly contaminated site. Calculated values of the Phen/Phen + Anth ratio were 0.48±0.08, 0.44±0.05, and 0.38+0.04 for Matla, Lethabo and Rooiwal, respectively. The flouranthene/fluoranthene + pyrene (Flan/ Flan + Pyr) levels were found to be 0.49±0.03 for Matla, 0.44±0.05 for Lethabo, and 0.53±0.08 for Rooiwal. Such values indicate a xx pyrolytic source of PAHs. Higher molecular weight PAHs (five to six rings) were predominant, suggesting coal combustion sources. The carcinogenic potency B[a]P equivalent concentration (B[a] Peq) at the three power plants ranged from 3.61 to 25.25, indicating a high carcinogenic burden. The highest (B[a] Peq) was found in samples collected around Matla power station. It can, therefore, be concluded that the soils were contaminated with PAHs originating from coal-fired power stations. Nine metals (Fe, Cu, Mn, Ni, Cd, Pb, Hg, Cr and Zn) were analysed in soil and the Digitaria eriantha plant around three coal power plants (Matla, Lethabo and Rooiwal), using ICP-OES and GFAAS. The total metal concentration in soil ranged from 0.05 ± 0.02 to 1835.70 ± 70 μg g-1, 0.08 ± 0.05 to 1743.90 ± 29 μg g-1 and 0.07 ± 0.04 to 1735.20 ± 91 μg g-1 at Matla, Lethabo and Rooiwal respectively. The total metal concentration in the plant (Digitaria eriantha) ranged from 0.005 ± 0.003 to 534.87 ± 43 μg g-1 at Matla, 0.002 ± 0.001 to 400.49 ± 269 μg g-1 at Lethabo and 0.002 ± 0.001 to 426.91 ± 201 μg g-1 at Rooiwal. The accumulation factor (A) of less than 1 (i.e. 0.003 to 0.37) at power plants indicates a low transfer of metal from soil to plant (excluder). The enrichment factor values obtained (2.4 – 5) indicate that the soils are moderately enriched, with the exception of Pb that had significant enrichment of 20. The Geo-accumulation Index values of metals indicate that the soils are moderately polluted (0.005 – 0.65), except for Pb that showed moderate to strong pollution (1.74 – 2.53). / Chemistry / D. Phil. (Chemistry)

The distribution and potential sources of 15 polycyclic aromatic hydrocarbons (PAHs) in soils and Digitaria eriantha in the vicinity of three South African coal-fired power plants, Matla, Lethabo and Rooiwal were determined by gas chromatography–mass spectrometry. An ultrasonic assisted dispersive liquid-liquid microextraction (UA-DLLME) method was developed for the extraction of polycyclic aromatic hydrocarbon in soil, followed by determination using gas chromatography mass spectrometry. The study showed that an extraction protocol based on acetonitrile as dispersive solvent and C2H2Cl2 as extracting solvent, gave extraction efficiencies comparable to conventional soxhlet extraction for soil samples. The extraction time using ultrasonication and the volume of the extraction solvent was also investigated. Using a certified reference material soil (CRM), the extraction efficiency of UA-DLLME ranged from 64 to 86% in comparison with the Soxhlet result of 73 to 95%. In comparison with the real sample, the CRM result did not show a significant difference at 95% C.I. The UA-DLLME proved to be a convenient, rapid, cost-effective and greener sample preparation approach for the determination of PAHs in soil samples. PAH compound ratios such as phenanthrene/phenanthrene + anthracene (Phen/ Phen + Anth) were used to provide a reliable estimation of emission sources. The total PAH concentration in the soils around three power plants ranged from 9.73 to 61.24 μg g−1, a range above the Agency for Toxic Substances and Disease Registry levels of 1.0 μg g−1 for a significantly contaminated site. Calculated values of the Phen/Phen + Anth ratio were 0.48±0.08, 0.44±0.05, and 0.38+0.04 for Matla, Lethabo and Rooiwal, respectively. The flouranthene/fluoranthene + pyrene (Flan/ Flan + Pyr) levels were found to be 0.49±0.03 for Matla, 0.44±0.05 for Lethabo, and 0.53±0.08 for Rooiwal. Such values indicate a xx pyrolytic source of PAHs. Higher molecular weight PAHs (five to six rings) were predominant, suggesting coal combustion sources. The carcinogenic potency B[a]P equivalent concentration (B[a] Peq) at the three power plants ranged from 3.61 to 25.25, indicating a high carcinogenic burden. The highest (B[a] Peq) was found in samples collected around Matla power station. It can, therefore, be concluded that the soils were contaminated with PAHs originating from coal-fired power stations. Nine metals (Fe, Cu, Mn, Ni, Cd, Pb, Hg, Cr and Zn) were analysed in soil and the Digitaria eriantha plant around three coal power plants (Matla, Lethabo and Rooiwal), using ICP-OES and GFAAS. The total metal concentration in soil ranged from 0.05 ± 0.02 to 1835.70 ± 70 μg g-1, 0.08 ± 0.05 to 1743.90 ± 29 μg g-1 and 0.07 ± 0.04 to 1735.20 ± 91 μg g-1 at Matla, Lethabo and Rooiwal respectively. The total metal concentration in the plant (Digitaria eriantha) ranged from 0.005 ± 0.003 to 534.87 ± 43 μg g-1 at Matla, 0.002 ± 0.001 to 400.49 ± 269 μg g-1 at Lethabo and 0.002 ± 0.001 to 426.91 ± 201 μg g-1 at Rooiwal. The accumulation factor (A) of less than 1 (i.e. 0.003 to 0.37) at power plants indicates a low transfer of metal from soil to plant (excluder). The enrichment factor values obtained (2.4 – 5) indicate that the soils are moderately enriched, with the exception of Pb that had significant enrichment of 20. The Geo-accumulation Index values of metals indicate that the soils are moderately polluted (0.005 – 0.65), except for Pb that showed moderate to strong pollution (1.74 – 2.53). / Chemistry / D. Phil. (Chemistry)