Orientador: Ana Cláudia Ruggieri / Banca: Liziane de Figueiredo Brito / Banca: Paola Pedroso Vantini / Resumo: A ciclagem de nutrientes em pastos no Brasil é responsável pela maior parte dos nutrientes que entram no sistema, uma vez que a exploração tem como características a baixa utilização de insumos. O objetivo desse trabalho foi avalia a decomposição de serapilheira de Cynodon spp. cv Tfiton 85 manejado com índices de área foliar residual pastejados por ovinos. A decomposição da serapilheira foi avaliada através de sacos contendo quantidade conhecida de serapilheira durante os seguintes tempos de incubação, 0, 4, 8, 16, 32, 64, 128 e 256 dias. Foram avaliados o desaparecimento de massa seca, o comportamento do nitrogênio, fósforo, carbono, além da relação C:N. Houve uma maior taxa de desaparecimento nos primeiros 64 dias de incubação, seguido por uma fase lenta até o final dos 256 dias de incubação. Houve aumento na concentração do nitrogênio e do fósforo durante o período avaliado / Abstract: The cycling of nutrients in pastures in Brazil is responsible for most of the nutrients entering the system, since the operating characteristics including low use of inputs. The aim of this study was to evaluate the decomposition of litter Cynodon spp. 85 hp Tfiton plied with residual leaf area indices grazed by sheep. Were evaluated by the decomposition of bags containing a known amount of litter during the following incubation times 0, 4, 8, 16, 32, 64, 128 and 256 days. The disappearance of dry mass were assessed, the behavior of nitrogen, phosphorus , carbon, addition of C:N. There was a higher rate of disappearance in the first 64 days of incubation followed by a slow phase until the end of the 256 days of incubation. There was an increase in the concentration of nitrogen and phosphorus during the study period / Mestre

CAPES / Os objetivos deste trabalho foram avaliar a influencia de períodos de pastejo em trigo duplo propósito sobre a taxa de decomposição das plantas e liberação de nutrientes (N, P, K, Ca e Mg) bem como a produtividade de soja cultivada na sequencia em sistema de semeadura direta. Os tratamentos foram arranjados em delineamento blocos ao acaso com duas repetições. Os tratamentos foram os seis períodos de pastejo (0, 21, 42, 63, 84 e 105 dias) e a taxa de decomposição do material residual destes, foi avaliada pela técnica de litter-bag. A percentagem de biomassa e nutrientes no compartimento mais prontamente decomponível aumentou à medida que aumentou os períodos de pastejo, principalmente devido ao efeito do animal sobre a renovação dos tecidos foliares, o que resultou em uma maior taxa de decomposição da palhada e de liberação de nutrientes para o solo e, consequentemente para a cultura da soja cultivada na sequencia em sistema de integração lavoura pecuária. Entretanto a produtividade de grãos de soja reduziu com o aumento dos períodos de pastejo principalmente devido à diminuição de resíduo de matéria seca sobre o solo. / The aims of this work were to evaluate the influence of dual purpose wheat grazing periods on plant decomposition rates and nutrient release (N, P, K, Ca e Mg) and soybean yielded cultivate in sequence in no-till systems. Treatments were laid out as a random block design with two replications. The treatments were six grazing periods (0, 21, 42, 63, 84 e 105 days), on continuous stocking rate grazing method. From these treatments, dual purpose wheat biomass and nutrients decay constants were evaluated along 7 different field incubation periods (0, 15, 35, 63, 98, 139 e 196 days after soil deposition) by the litter bag technique. The percentage of biomass and nutrients at the easily decomposable compartment increases with the increase of grazing periods, due to the influence of the animal over the plants tissue turnover, which results in highest decomposition rate and nutrients release to the soil and consequently to the soybean cultivated in sequence on crop-livestock system. However the soybean grains yielded reduced with the increase grazing periods mainly due to the diminished of dry matter residue over the soil.

CAPES / Os objetivos deste trabalho foram avaliar a influencia de períodos de pastejo em trigo duplo propósito sobre a taxa de decomposição das plantas e liberação de nutrientes (N, P, K, Ca e Mg) bem como a produtividade de soja cultivada na sequencia em sistema de semeadura direta. Os tratamentos foram arranjados em delineamento blocos ao acaso com duas repetições. Os tratamentos foram os seis períodos de pastejo (0, 21, 42, 63, 84 e 105 dias) e a taxa de decomposição do material residual destes, foi avaliada pela técnica de litter-bag. A percentagem de biomassa e nutrientes no compartimento mais prontamente decomponível aumentou à medida que aumentou os períodos de pastejo, principalmente devido ao efeito do animal sobre a renovação dos tecidos foliares, o que resultou em uma maior taxa de decomposição da palhada e de liberação de nutrientes para o solo e, consequentemente para a cultura da soja cultivada na sequencia em sistema de integração lavoura pecuária. Entretanto a produtividade de grãos de soja reduziu com o aumento dos períodos de pastejo principalmente devido à diminuição de resíduo de matéria seca sobre o solo. / The aims of this work were to evaluate the influence of dual purpose wheat grazing periods on plant decomposition rates and nutrient release (N, P, K, Ca e Mg) and soybean yielded cultivate in sequence in no-till systems. Treatments were laid out as a random block design with two replications. The treatments were six grazing periods (0, 21, 42, 63, 84 e 105 days), on continuous stocking rate grazing method. From these treatments, dual purpose wheat biomass and nutrients decay constants were evaluated along 7 different field incubation periods (0, 15, 35, 63, 98, 139 e 196 days after soil deposition) by the litter bag technique. The percentage of biomass and nutrients at the easily decomposable compartment increases with the increase of grazing periods, due to the influence of the animal over the plants tissue turnover, which results in highest decomposition rate and nutrients release to the soil and consequently to the soybean cultivated in sequence on crop-livestock system. However the soybean grains yielded reduced with the increase grazing periods mainly due to the diminished of dry matter residue over the soil.

Brachiaria brizantha (Hochst ex. A. Rich) Stapf apresenta boa adaptação às condições edafoclimáticas brasileiras e é muito utilizada como planta forrageira em pastagem na produção de bovinos. Apesar de seu potencial na produção de ovinos, ainda são necessárias novas investigações para aperfeiçoar o seu manejo. Objetivou-se com esta pesquisa avaliar as características produtivas, fisiológicas e bromatológicas de um pasto formado por Brachiaria brizantha cv. Marandu, fertilizada com doses de nitrogênio (N) e sob pastejo ovino. O delineamento experimental foi em blocos completos casualizados com 04 repetições e 05 tratamentos experimentais: 0; 90; 180; 270; 360 kg de N.ha-1, totalizando 20 parcelas experimentais. O método de pastejo foi o rotativo, com ciclo de pastejo de 30 dias, sendo 25 dias de descanso e 5 dias de ocupação, como forma de rebaixar o pasto à altura de resíduo de 6 cm. As medições no pasto foram feitas a cada 3 dias em 3 ciclos de pastejo, quando se avaliou: o fluxo de tecidos, a dinâmica de perfilhamento, a produção e a composição bromatológica da planta forrageira. Para massa seca de forragem verificou-se comportamento quadrático nas doses crescentes de N, atingindo o platô em 246 kg.ha-1. As variáveis taxas de senescência foliar, peso médio e densidade populacional de perfilhos não foram influenciados (P>0,05) pela adubação nitrogenada enquanto que a taxa de alongamento e de aparecimento de folhas, a taxa de alongamento de colmo, o número de folhas vivas, o comprimento final de folhas foram influenciados pela adubação nitrogenada (P<0,05). O filocrono e a duração de vida da folha foram mais curtos na presença do N. Em relação às características bromatológicas, o N afetou positivamente nos teores de FDA, FDN, e PB. Pelo manejo imposto aos pastos, a utilização do N teve efeito positivo nas características fisiológicas, produtivas e nutritivas do capim-marandu. / Brachiaria Brizantha (Hochst ex. A. Rich) Stapf is well adapted to Brazilian climatic conditions, and is widely used as a forage grass on pasture production in cattle. Despite its potential for use in the present sheep production, further research studies are still needed to optimize their management. The objective of this research was evaluate yield, physiological and chemical characteristics of a pasture of Brachiaria brizantha cv. Marandu, fertilized with nitrogen and grazing sheep. The experimental design was a randomized complete block with 04 replications and 05 experimental treatments: 0, 90, 180, 270 and 360 kg N.ha-1 totaling 20 experimental plots. The grazing method was rotating with cicle of grazing of 30 days, 25 days of rest and 5 days of occupancy to reach height of pasture residue of 6 cm. Measurements were made in the pasture every 3 days, at,three grazing cycle evaluated. Thus analyzing the flow of plant tissue, the dynamics of tillering, yield and composition chemical of forage. For dry herbage mass there was a quadratic behavior in increasing doses. The increase of N, there was a quadratic behavior, reaching a plateau where the best dose was 270 kg.ha-1. The variables leaf senescence rate, average weight and tiller density were not affected (P>0.05) by use of N, while the variables leaf elongation rate and appearance, stem elongation rate, number of living leaves, final length of leaves were influenced by nitrogen fertilization (P<0.05), Phyllochron and lifetime leaves were shorter in the presence of N. Regarding the chemical caracteristics, the presence of N affected positively the levels of the ADF, NDF and CP, The grazing management imposed, the use of N had a positive effect on the physiological, productive and chemical characteristics of Marandugrass.

5 p. / an easy to use framework to help develop a contingency plan for drought

The seasonal distribution of herbage growth has particular importance for the management of grazing animals since the major objective of most pasture utilization plans is to provide sufficient feed for continuous grazing for as great a portion of the year as possible. Providing a more even distribution of herbage production has obvious practical advantages. The main objective of this study was to examine the annual growth pattern of herbage in the South Coastal region of British Columbia as affected by cultivars, cutting management and fertilizer management, with the aim of extending herbage production in the fall and increasing herbage availability during the summer months. These investigations were conducted in plot trials at three different sites. Forage quality was also examined at two of these sites. In addition to these plot cutting trials an investigation into the accuracy of a height/density meter (disc meter) was conducted. The disc meter, and other similar non-destructive devices, have great potential as both research and farm management aids. The first plot cutting trial was conducted at Agassiz, B.C. and examined the productivity of two orchardgrass (Dactylis glomerata L.) cultivars, Prairial and Sumas and two perennial ryegrass (Lolium perenne L.) cultivars, Barlano and Norlea under two cutting regimes (low-infrequent and high-frequent). Annual yields averaged over the three years for low-infrequent (LI) cutting showed significant (P<0.05) differences between cultivars with the following ranking: Prairial (10,644) > Sumas (9,537) > Barlano (8,448) > Norlea (6,666 kg DM/ha). Annual yields averaged over two years for high-frequent (HF) cutting also showed significant (P<0.05) differences between the cultivars with the same ranking: Prairial (9,390) > Suinas (8,625) > Barlano (7,686) > Norlea (5,953 kg DM/ha). The same ranking of cultivars in terms of annual yield was obtained in each harvest year for both LI and HF cutting treatments. Annual herbage yields over the three years of the trial showed considerable variation in response to climatic factors. Average annual yields in 1984 (10,116) and 1986 (10,237 kg DM/ha) were not significantly different (P>0.05). However, yields in 1985 (5,916 kg DM/ha) were significantly (P<0.01) lower than 1984 and 1986 due to a wet, cool spring and exceptionally dry summer. Cutting regime did not have a significant effect on annual yields. There were no significant (P>0.05) differences between average annual yields under HF (7,914) and LI (8,824 kg DM/ha) cutting, nor were there any significant (P>0.05) differences in annual yields between cultivars due to cutting treatments. There was a tendency for LI cutting to produce higher yields than HF cutting for Prairial, Sumas and Barlano with the reverse being true for Norlea. Examination of productivity on a seasonal basis indicated differences in yield due to cutting regime, depending on the season. During the spring LI cutting produced greater yields than HF cutting due to the greater yields obtained from the longer regrowth period and lower cutting height (Reid and MacLusky, 1960; Bland, 1967; Anslow, 1967). However, during the dry summer months the reverse situation was observed with HF cutting producing higher yields than LI cutting. Sucli a reversal in yield is attributable to the dry conditions under which high cutting has been shown to produce more herbage than low culling (Janti and Kramer, 1956; Appadurai and Holmes, 1964). Under LI cutting orchard grass produced 34 and 46% of annual yield in the spring for 1984 and 1985 respectively and 52 and 40% of annual yield in the summer for the same two years. This distribution was changed under HF cutting with 21 and 36% of annual yield produced in the spring for 1984 and 1985 respectively and 65 and 50% of annual yield produced in the summer for the same two years. The situation was similar for perennial ryegrass. Under Ll cutting perennial ryegrass produced 53 and 58% of annual yield in the spring for 1984 and 1985 respectively and 25 and 30% in the summer for the same two years. Distribution of annual yield was more even under HF cutting with 28 and 35% of yield produced in the spring of 1984 and 1985 respectively and 63 and 50% produced in the summer of the same two years. Variation in the distribution of annual production was also evident between orchardgrass and perennial ryegrass. Both orchardgrass cultivars produced a greater portion of their yield during the summer, whereas both perennial ryegrasses produced a greater portion of yield during the spring and early summer. Growth curves were developed for each cultivar for both cutting treatments over all harvest years which indicate the variability in the seasonal distribution of annual yield attributable to climatic factors and which can be varied by cutting management and choice of cultivars. Another trial conducted at the U.B.C. Research Farm #2, Oyster River, examined the effect of split nitrogen (N) applications on annual and seasonal yields. Under regime I a total of 100 kg N/ha was applied in April. Regimes II, III and IV involved application of a total of 300 kg N/ha at varying times over the growing season. Application of 300 kg N/ha produced significantly (P<0.05) higher annual yields (mean, 10,228) than application of 100 kg N/ha (7,706 kg DM/ha). Annual yields produced under regimes II, III and IV were not significantly (P>0.05) different (10,248, 10,245 and 10,192 kg DM/ha respectively). The seasonal distribution of yield was affected by N application regime. Regime III produced a greater portion of annual yield during August (20.1%) compared to the other three regimes (mean, 13.4%) and application of 100 kg N/ha in August produced significantly (P<0.05) higher yields for regime IV (1,104) compared to the other three regimes (mean, 426 kg DM/ha). The August N application also produced significantly (p<0.05) higher yields in the following spring for regime IV (2,774) than yields obtained for regimes II and III (mean, 1,810) and regime I (1,341 kg DM/ha). Such yield improvements in the spring could have been due to improved root reserves and/or root mass produced from the August N application. Two other trials conducted at Abbotsford also examined cutting treatments and N application regimes. The cutting trial examined the yields produced by four cutting regimes examining: high-frequent (HF), high-infrequent (HI), low-frequent (LF) and low-infrequent (LI) cutting combinations. Annual yields were significantly (P<0.()5) lower for LF (6,721), HI (6,066) and HF (5,674) cutting regimes than the LI (8,207 kg DM/ha) regime. Low cutting (7,464) produced significantly (P<0.05) greater yields than high cutting (5,870 kg DM/ha) while there were no significant (P>0.05) differences between frequent (6,197) and infrequent cutting (7,137 kg DM/ha). Unlike the Agassiz trial, high cutting produced no yield advantage during the dry summer months due to the exceptionally dry period where growth stopped under all cutting regimes. The Abbotsford fertilizer trial examined split N application in a similar manner to the Oyster River trial. However, due to the dry summer there was little response to applied N throughout most of the summer and thus little variation in distribution of annual yield. Regimes II, III and IV involved application of a total of 300 kg N/ha and produced significantly (P<0.05) more herbage (mean, 5,584) than the application of 0 N under regime I (3,758 kg DM/ha). Annual yields did not differ significantly (P>0.05) between regimes II, III and IV. Results from the four cutting trials indicate that the annual and seasonal distribution of yield can be affected by management factors such as variety and cultivar selection, fertilization management and defoliation management. Forage quality was examined at both the Agassiz and Oyster River sites. Differences in forage quality were noted as a result of year, seasonal, cultivar, fertilization and cutting treatment effects. Investigations were also conducted to examine the use of a height/density disc meter to measure herbage yield. A significant relationship (P < 0.001) was found between herbage yield and disc height for vegetative growth but more mature growth, with stems and seed heads, yielded a poor relationship. The use and accuracy of the instrument is discussed. / Land and Food Systems, Faculty of / Graduate

The importance of resource supply and herbivory in driving competitive interactions among species has been an important but contentious issue within ecology. These variables exhibit different effects on species competition when manipulated in isolation but interact when manipulated together. I tested the direct and interactive effects of nutrient addition and simulated grazing (clipping) on the competitive performance of primary producers and community structure of a seagrass bed in South Florida. One square meter experimental plots were established in a mixed seagrass meadow from August 2007 to July 2009. The experiment was a 3 x 3 factorial experiment: 3 fertility treatments: control, medium (2.4 mg N d-1 and 80 µg P day-1) and high (4.8 mg N d-1 and 160 µg P day-1) x 3 clipping intensities (0, 25% and 50 % biomass removal (G)) x 5 replicates for each treatment = 45 plots). Nutrient additions and simulated grazing were done every two months. Fertilization and simulated grazing decreased sexual reproduction in S. filiforme. Fertilization increased competitive dominance within the primary producers while simulated grazing counteracted this effect by removal of the dominant species. Fertilization ameliorated the negative impacts of simulated grazing while simulated grazing prevented competitive exclusion in the fertilized plots. Nutrient addition and simulated grazing both exerted strong control on plant performance and community structure. Neither bottom up nor top down influences was eliminated in treatments where both factors where present. The effects of fertilization on plant performance were marked under all clipping intensities indicating that the system is regulated by nutrient availability both in the presence or absence of grazers. Clipping effects were strong under both fertilized and unfertilized conditions indicating that the seagrass bed can be simultaneously under top-down control by grazers.

Four experiments were conducted to evaluate different technologies and supplementation strategies that may impact beef cattle production in the Northern Great Plains. Our overarching hypothesis was that we can enhance beef cattle performance and production through strategic supplementation of energy and minerals. In experiment 1, steers were fitted with transmission beacons on collars to determine effects of preweaning creep feeder attendance influences on post-weaning performance, feeding behavior, and carcass characteristics. Calves that visited creep feeders more frequently spent more time eating and ate more meals during the first 28 d of the finishing period. In experiment 2, we utilized electronic feeders to monitor mineral intake of cow-calf pairs and found that HIGH (>90 g/d; average 125.4 g/d) intake cows and calves spent more time at the mineral feeder than their LOW (<90 g/d; average 33.5 g/d) intake counterparts. Furthermore, we noted greater concentrations of Se, Cu, and Co in livers of HIGH intake cows compared to LOW intake cows. In experiment 3, we evaluated a slow-release vitamin and mineral bolus in feedlot heifers which failed to influence heifer performance, liver mineral concentrations or carcass characteristics. Overall, heifers performed as expected while on a finishing diet from feeds sourced in the Northern Great Plains. In experiment 4, we further utilized the SmartFeed system to control intake of individual heifers assigned to different treatments in a group pasture scenario. Our results clearly show that the feed controlling portion can be used for precision feeding of individuals in extensive group managed scenarios. Though heifers had similar BW and ADG among treatment groups, treatments that provided supplemental mineral enhanced liver concentrations of Se, Fe, Cu, and Co. Furthermore, the CowManager system was able to detect divergence in highly active behavior among treatment groups, but also reported many false health and estrus-related alerts. Overall, we were able to successfully monitor individual mineral intakes in cow-calf pairs and report differences in energy and mineral supplement intakes in heifers grazing native range. We were also able to corroborate differences in supplement intakes with changes in concentrations of mineral in the liver of animals. / North Dakota Agricultural Experiment Station (NDAES) Precision Agriculture Fund; North Dakota State Board of Agricultural Research and Education Graduate Research Assistantship

Vegetation in semi-arid regions is subject to change when heavily utilised by herbivores. Changes in species richness, species and growth form composition, total cover and plant palatability in response to rest (fenced) and grazing (open) treatments was investigated in Sanbona Wildlife Reserve over five years (2004-2008). This reserve is over 55 000 ha and has four dominant vegetation types: Little Karoo Quartz Vygieveld, Western Little Karoo, Montagu Shale Renosterveld and previously transformed Renosterveld classified here as Old Lands. There was no significant change in vegetation dynamics between the fenced or open plots. There were significant differences between years in some vegetation types. All vegetation types showed both treatments having similar shifts in floristic composition. Floristic composition deviated the greatest in 2008 in all vegetation types. This was attributed to an increase in summer and winter rainfall in 2008, as all plots were similarly affected. There was no observed impact of herbivores although disturbance from small rodents and baboons was observed in a few plots. The lack of detectable difference between the fenced and open sites was attributed to low stocking rates, good rainfall and insufficient time.

The vegetation of the Kosi Bay Coastal Forest Reserve was classified by means of Braun-Blanquet and TWINSPAN procedures. Twelve major plant communities were identified, occurring along a gradient from the inland fresh water habitats, to the beach with influences from strong winds and salt spray. Some of these communities were further divided into plant communities and sub-communities giving a total of 27 plant communities and three sub-communities. A vegetation map was compiled for the study area using Geographical Information System procedures. Veld condition was good and the grazing capacity high ranging between 2.9 and 5.6 ha/LSU (cattle). A checklist of 1 164 vascular plant species collected in the study area was compiled. The distribution of 71 plant species endemic to the Maputaland Centre of Endemism was related to plant communities. The coastal grassland communities were prioritized for conservation, as a large number of Maputaland Centre endemics are restricted to these communities. / Dissertation (MSc)--University of Pretoria, 1996. / Plant Science / MSc / Unrestricted