The use of urea fertiliser has been associated with relatively poor nitrogen (N) use efficiency (NUE) due to heavy N losses such as gaseous emissions of ammonia (NH₃) and nitrous oxide (N₂O) and nitrate (NO₃⁻) leaching into surface and ground waters. Improving N use-efficiency of applied urea is therefore critical to maximise its uptake and to minimise its footprint on the environment. The study was conducted under laboratory-glasshouse conditions (Chapter 2-4)and lysimiter-field plot studies (Chapter 5). In chapter 2, Two glasshouse-based experimentswere conducted to investigate the potential of incorporating urea fertiliser with ureaseinhibitor, (N-(n-butyl) thiophosphoric triamide (nBTPT) or ‘Agrotain’) to enhance fertiliser N uptake efficiency. Urea, with or without Agrotain, was applied to Ryegrass (Lolium perenne L.) grown in standard plant trays maintained at soil moisture contents of 75–80% field capacity, at rates equivalent to 25 or 50 kg Nha⁻¹. These treatments were compared with other common forms of N fertilisers (ammonium nitrate, ammonium sulphate and sodium nitrate). In a separate pot experiment, granular ¹⁵N urea (10 atom %) with or without Agrotain, was applied at 25 kg Nh⁻¹ to track N use-efficiency and the fate of ¹⁵N-labelled fertiliser. In both experiments, Agrotain-treated urea improved bioavailability (defined as the fraction of total soil N that can interact with a biological target in the plant or that can be taken up by plant) of added N and resulted in significantly higher herbage DM yield and N uptake than urea alone or other forms of N fertilisers. Results from the ¹⁵N experiment support the suggestion that a delay in urea hydrolysis by Agrotain provided an opportunity for direct plant uptake of an increased proportion of the applied urea-N than in the case of urea alone. In chapter 3, two more glasshouse-based experiments were conducted to investigate if urea applied in fine particle application (FPA), with or without Agrotain, had any effect on fertiliser-N uptake efficiency (defined as the difference in N uptake between the fertiliser treatment and the control as a percentage of the amount of N applied) under optimum soil moisture (75-80% field capacity) and temperature (25 °C) conditions, in comparison with other common forms of N fertilisers applied, either in FPA or in granular form. In a separate pot experiment, ¹⁵N urea (10 atom %), with or without Agrotain, was applied to either shoots or leaves only or to the soil surface (avoiding the shoots and leaves) to determine urea hydrolysis, herbage DM and ¹⁵N uptake. In both experiments, herbage DM yield and N uptake were significantly greater in the FPA treatments than in those receiving granular application. Agrotain-treated urea FPA resulted in significantly higher N response efficiency (difference between the dry matter produced by the various fertiliser treatments and the control, divided by the amount of N applied) than urea FPA alone or other forms of N fertilisers. Results from the ¹⁵N experiment support the idea that Agrotain treatment improves the N response of urea applied in FPA form due to a delay in hydrolysis of urea, thus providing herbage an extended opportunity to absorb added urea directly through leaves, cuticles and roots. A further glasshouse-based study was conducted to investigate the effect of Agrotain and irrigation on urea hydrolysis and its movement in a Typic Haplustepts silt loam soil (Chapter 4). A total of 72 repacked soil cores (140 mm inner diameter and 100 mm deep) were used - half (36) of these cores were adjusted to soil moisture contents of 80% field capacity (FC) and the remaining 36 cores to 50% FC. Granular urea, with or without Agrotain, was applied at a rate equivalent to 100 kg N ha⁻¹. Twelve pots were destructively sampled at each day after 1, 2, 3, 4, 7, and 10 days of treatment application to determine urea hydrolysis and its lateral and vertical movement in different soil layers. Agrotain-treated urea delayed urea hydrolysis compared with urea alone during the first 7 days of its application. This delay in urea hydrolysis by Agrotain enabled added urea to disperse and move away from the surface soil layer to the sub-surface soil layer both vertically and laterally. In contrast, most urea in the absence of Agrotain hydrolysed within 2 days of its application. Irrigation after 1 day resulted in further urea movement from the surface soil layer (0-10 mm) to the sub-soil layer (30-50 mm) in Agrotain-treated urea. These results suggest that Agrotain delayed urea hydrolysis and allowed more time for rainfall or irrigation to move the added urea from the surface layer to sub-soil layers where it is likely to make good contact with plant roots. This distribution of urea in the rooting zone (0-200 mm) has the potential to enhance N use efficiency and minimise N losses via ammonia (NH₃) volatilisation from surface-applied urea. Finally, a field study using lysimeters (300 mm inner diameter and 400 mm deep), and small field plots (1 m² in area) was established using a silt loam Typic Haplustepts soil (Soil Survey Staff 1998) to investigate the effect of FPA and granular applications of urea, with or without Agrotain, on N losses and N use efficiency (Chapter 5). The five treatments were: control (no N) and ¹⁵N-labelled urea (10 atom %), with or without Agrotain, applied to lysimeters or mini plots (un-labelled urea), either in granular form to the soil surface or in FPA form (through a spray) at a rate equivalent to 100 kg N ha⁻¹. Gaseous emissions of NH₃ and N₂O, NO₃⁻ leaching, herbage production, N response efficiency, total N uptake and total recovery of applied ¹⁵N in the plant and soil were determined up to 63 days. Urea-alone and urea with Agrotain, applied in FPA form, was more effective than its granular form and reduced N2O emissions by 5-12% and NO3- leaching losses by 31-55%. Urea-alone applied in FPA form had no significant effect in reducing NH₃ losses compared with granular form. However, urea with Agrotain applied in FPA form reduced NH₃ emissions by 69% compared with the equivalent granular treatment. Urea-alone and with Agrotain applied in FPA form increased herbage dry matter production by 27% and 38%, and N response efficiency compared with the equivalent granular urea application, respectively. Urea applied in FPA form resulted in significantly higher ¹⁵N recovery in the shoots compared with granular treatments – this was improved further when urea in FPA form was applied with Agrotain. Thus, treating urea with Agrotain in FPA under field conditions has the potential to delay its hydrolysis, minimise N losses and improve N use efficiency and herbage production. The lower dry matter production and N-response efficiency to urea applied in FPA form in Chapter 3 are probably because of additional factors such as lower application rates (25 kg N ha⁻¹ ) or lack of interception of urea by the leaves. Applying urea in FPA form is a good management strategy and I conclude that combining FPA urea with Agrotain has the potential to increase N use efficiency and herbage production further.

Thesis (Ph. D.)--University of Tennessee, Knoxville, 2009. / Title from title page screen (viewed on Nov. 2, 2009). Thesis advisor: Thomas C. Mueller. Vita. Includes bibliographical references.

Thesis (M.S.)--University of Missouri-Columbia, 2005. / The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file viewed on (July 14, 2006) Includes bibliographical references.

At present, and more so in the future, irrigated agriculture will take place under water scarcity. Owing to the global expansion of irrigated areas and the limited availability of irrigation water, there is a need to optimize water production and use efficiency (WUE). In South Africa, annual ryegrass (Lolium multiflorum) is one of the most widely grown cool season pasture species under irrigation. It is mainly used in dairy farming enterprises. Shortages of water and nitrogen can, however, be limiting factors for the production of this pasture. By using appropriate irrigation and nitrogen management tools, water and nitrogen productivity of the pasture can be improved. The objective of this study was, therefore, to determine the effects of different water levels in combination with different N fertiliser applications on the growth rate and dry matter production, quality, water use and water use efficiency of annual ryegrass. For two seasons, the trial was conducted under a rain shelter on the Hatfield Experimental Farm of the University of Pretoria. Higher frequency of irrigation coupled with high nitrogen application significantly improved the dry matter yield. Canopy size influenced the LAI and FI which in turn affects the yield. The study showed that the treatments that were irrigated twice weekly and top-dressed with 60 kg N ha-1 after each cut consumed the most water, and this resulted in the production of higher yield, maintenance of the largest leaf area index and higher interception of the incoming solar radiation. The increase in these parameters may be due to the sufficient water and nitrogen fertiliser that induces rapid cell elongation as a result of higher water potential, higher turgor pressure and higher photosynthetic processes. As hypothesized, the decrease in the frequency of water application resulted in an increase in the DMC, digestibility, ME and CP values. Nitrogen application had an effect on the WU, as less water was used in the treatments that received no nitrogen. Highest KC value recorded was in the optimal range and this indicates that the treatments were not over-irrigated. As the irrigation interval increased, more water was depleted from the soil profile. Depletion rates increased as the season progressed but generally it was minimal in the frequently irrigated treatments. Increase in WUE was achieved by reducing the frequency of irrigation from twice a week to once a week without causing significant yield loss. A possible reason for the increase in the WUE by reducing the irrigation frequency could be ascribed in part to reduced evaporation from the soil resulting from the lower wetting frequency of the deficit irrigation treatments. Within the same irrigation frequency, higher WUE was achieved by alleviating a limiting factor, N fertiliser, in this case, through increases in dry matter production. The highest WUE was achieved by irrigating once every two weeks. However, in some treatments, the WUE was not improved with the reduction in the frequency of irrigation as the water saved was overshadowed by yield loss. In summary, it can be said that the hypotheses that pasture production will be positively associated with soil moisture content, water stress can improve the quality of the pasture, N fertiliser will increase the DM response to soil moisture content and WUE will increase by alleviating a limiting factor, N fertiliser in this case were accepted. A logical extension of this work would be to do the trial in an open field to analyze the effect of irrigation and nitrogen fertilization on the growth, yield and quality of the pasture and then extrapolate the results to other sites and soil types using models. / Dissertation (MSc(Agric))--University of Pretoria, 2011. / Plant Production and Soil Science / unrestricted

Glyphosate-resistant (GR) Italian ryegrass has been documented in many different countries around the world and has now become a major problem in row crop production areas of Mississippi. Field experiments were conducted from 2006 to 2008 in the Mississippi Delta to evaluate various herbicide and tillage treatment programs for its control. style='mso-spacerun:yes'> Highest level of control and reduction of GR Italian ryegrass biomass was observed with mechanically incorporated as well as surface applied residual herbicides in the fall of the year. style='mso-spacerun:yes'> Control of GR Italian ryegrass was 86-95% with surface applications of clomazone at 0.56, 0.84, and 1.12 kg ai/ha, s-metolachlor at 1.79 kg class=SpellE>ai/ha and KIH-485 at 0.16 kg ai/ha 171 days after emergence. Using a systems approach, preplant incorporated (PPI) class=SpellE>clomazone and/or s- class=SpellE>metolachlor followed by preemergence (PRE) application of paraquat + linuron+ non-ionic surfactant was also found to control and reduce biomass of GR Italian ryegrass.

White clover (Trifolium repens) is a common and difficult weed to control in turfgrass as it is a highly visible and unsightly weed that disrupts the uniformity of the turfgrass surface. This weed is a serious problem in the turfgrass industry in California and there is a need for better methods of control. With more regulations on pesticides and less information about efficient application techniques, controlling white clover with available herbicides can be difficult. Compatibility trials were conducted during the summer of 2005 to determine the compatibility of the herbicides and adjuvants planned for use in subsequent greenhouse and field trials. A greenhouse trial was conducted in the spring of 2006, followed by field trials in fall of 2006 and spring of 2007 to determine the efficacy of two herbicides on white clover when combined with each of three adjuvants and two nozzles. Results showed the nozzles to have no significant effect on phytotoxicity to white clover in the greenhouse trial, while some of the herbicides and adjuvants significantly increased phytotoxicity to white clover. In the field trials, adjuvants had no effect on phytotoxicity, while some herbicides and nozzles significantly increased phytotoxicity to white clover, perennial ryegrass and common bermudagrass. Information about the combination of herbicides, adjuvants and nozzles will help turfgrass managers to improve their management of white clover in turfgrass.

Submitted by Cátia Araújo (catia.araujo@unipampa.edu.br) on 2017-01-25T12:07:05Z No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Análise da secagem de Azevém (Lolium multiflorum) em leito fixo com escoamento de ar.pdf: 1759730 bytes, checksum: c7b966ec881ab3aa3f2074dfd2e095f2 (MD5) / Approved for entry into archive by Cátia Araújo (catia.araujo@unipampa.edu.br) on 2017-01-25T12:07:33Z (GMT) No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Análise da secagem de Azevém (Lolium multiflorum) em leito fixo com escoamento de ar.pdf: 1759730 bytes, checksum: c7b966ec881ab3aa3f2074dfd2e095f2 (MD5) / Made available in DSpace on 2017-01-25T12:07:33Z (GMT). No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Análise da secagem de Azevém (Lolium multiflorum) em leito fixo com escoamento de ar.pdf: 1759730 bytes, checksum: c7b966ec881ab3aa3f2074dfd2e095f2 (MD5) Previous issue date: 2013-05-09 / No Rio Grande de Sul a pecuária é uma das principais e tradicionais atividades econômicas com a produção alicerçada no campo nativo. Porém, nas estações frias ocorre a necessidade da implementação de pastagens para suprir o vazio forrageiro, pois o campo nativo é composto predominantemente de gramíneas de verão. O azevém (Lolium multiforum) é a gramínea mais utilizada no sul do Brasil, devido à facilidade e ao baixo custo de implementação. Entretanto, esta forrageira possui problemas quanto à qualidade das sementes no que se refere à baixa taxa de germinação e ao vigor. Isso ocorre em função de apresentar um processo natural de debulha, resultando em uma colheita de sementes com alto grau de umidade. Uma forma de minimizar os problemas encontrados na qualidade destas sementes é a aplicação de tecnologias adequadas no seu beneficiamento. Dentre as etapas envolvidas no beneficiamento das sementes a secagem é tida como processo fundamental. A secagem é caracterizada pela transferência de calor e de massa, permitindo a redução do teor de água em níveis adequados, possibilitando assim, a preservação da qualidade fisiológica do produto. Neste contexto, foram estudadas as condições de secagem do azevém em secador de leito fixo com escoamento de ar paralelo visando obter melhor qualidade nas sementes. O estudo foi dividido em quatro etapas. A primeira etapa consistiu na caracterização física e fisiológica das sementes, onde foram obtidos os valores de densidade real, densidade bulk, diâmetro médio das partículas, esfericidade, porosidade do leito estático e índices de germinação. Na segunda etapa foi o estudo da reumidificação das sementes visando colocar sementes adquiridas no mercado local em condições de umidade semelhantes as encontradas em sementes recém colhidas e limpas. A terceira etapa baseou-se no estudo das isotermas de dessorção das sementes reumidificadas para a determinação da umidade de equilíbrio. Este estudo foi feito para a temperatura de 40 °C utilizando-se o método estático para o qual foram utilizadas soluções ácidas em diversas concentrações. Por fim, na quarta e última etapa, foi desenvolvido o estudo da secagem das sementes reumidificadas em um secador de leito fixo com escoamento de ar paralelo operando na temperatura de 40 °C e sob condições de altura da bandeja de 0,50, 0,75 e 1,0 cm, de velocidade do ar de 1,0, 1,5 e 2,0 m/s e de tempo de secagem de 2,0, 2,5 e 3 h. Os dados obtidos nas secagens foram analisados através de um planejamento experimental fatorial completo 23 com duplicata no ponto central, tendo como respostas o índice de umidade final e o índice de germinação. Também determinaram-se os valores da difusividade efetiva de cada ensaio de secagem. Os resultados obtidos mostraram que as condições de secagem aplicadas nas sementes podem influenciar significativamente sua umidade final, sua qualidade fisiológica e os valores da difusividade efetiva do processo. / The livestock is one of the major and traditional economic activities with production rooted in native pasture in Rio Grande do Sul. But in the cold seasons is the need to implement the empty pastures to supply fodder, because the field is composed predominantly of native summer grasses. Ryegrass (Lolium multiflorum) is the most widely used grass in the southern of Brazil, due to the ease and low cost of implementation. However it has problems as forage seed quality regarding low rate of germination and vigor. This is due to present a natural process of threshing, resulting in a harvest of seeds with high moisture content. One way to minimize the problems encountered in the quality of these seeds is the application of appropriate technologies in processing. Among the steps involved in the processing of seed drying process is considered fundamental. It is characterized by heat transfer and mass, allowing the reduction of the water content at appropriate levels, thus enabling the preservation of physiological quality of the product. In this context the work studied the drying conditions of ryegrass in fixed bed dryer with air flowing parallel to obtain better quality seeds. The study was divided in to four stages. The first step was to determine the physical and physiological characteristics of the seed which were obtained the values of true density real and bulk density, average, particle, diameter, sphericity, porosity of the static bad end germination rates. In the second phase of the study aimed at putting rewetting seeds seeds purchased at local markets in damp conditions similar to those found in fresh seeds and clean. The third stage was based on the study of sorption isotherms of seeds reumidificadas for the determination of moisture content. This study was done to a temperature of 40 ° C, using the static method with solutions at various concentrations. Finally, the fourth and final step of the study was conducted reumidificadas seed drying in a fixed bed dryer with air flowing parallel operating at a temperature of 40 ° C and under conditions tray height 0.5, 0.75 and 1.0 cm air speed of 1.0, 1.5 and 2.0 m / s and drying time of 2.0, 2.5 and 3.0 hours. The data obtained were analyzed by drying in an experimental design with 23 duplicate at the midpoint having answers as the final moisture content and germination. We also determined the effective diffusivity values for each studied drying process. The results showed that the drying conditions applied in the seed can significantly influence their final moisture, physiological quality and effective diffusivity values of the process.

2 pp. / Describes the proper timing of overseeding, selecting winter grasses, and procedures to prepare for overseeding with the amount of seed to use followed by irrigating, fertilizing, and mowing.

In traditional forage breeding programmes, breeders have spent decades improving the agronomic characteristics of grasses, such as herbage yield, persistence and resistance to diseases, without considering the nutrient requirements of the grazing animal. In an attempt to improve the nutritive value of Italian ryegrass, which is widely utilised for intensive dairy, lamb and beef production in South Africa, Enhancer ryegrass was developed from predominantly Italian types of Lolium multiflorum, with a minor Westerwolds component, by selecting for a higher concentration of total nonstructural carbohydrate (TNC) and lower moisture content than that currently available in commercial cultivars. The nutritional value of Enhancer was compared with Midmar ryegrass in a controlled environment study and in a grazing trial with weaned lambs; and with Dargle ryegrass in a grazing trial with Holstein dairy cows. Neutral detergent fibre, acid detergent fibre, lignin, nitrogenous compounds, mineral content and in vitro digestibility were also investigated as parameters of nutritive value. The anatomical features of Enhancer and Midmar were studied to determine possible structural differences. Weaned lambs grazed Enhancer and Midmar in an eight-paddock rotational grazing system, with 3.5 days spent in each paddock, allowing a 24.5 day regrowth period for the pastures. Holstein dairy cows grazed Enhancer and Dargle which were established on 16 and 19 hectare pastures, respectively. The n-alkane technique was used to estimate dry matter intake (DMI) in both grazing trials. Results from the controlled environment study suggest that the differences in the dry matter and TNC concentration of Enhancer are not positively linked to anti-quality factors associated with forage species, but can be attributed to genetic differences between the two grasses. Despite the significantly higher (P < 0.01) DMI of weaned lambs grazing Midmar compared with Enhancer, the lambs on Enhancer outperformed those on Midmar in terms of liveweight gain and carcass quality. The superior animal performance on Enhancer is likely due to an improvement in the readily digestible energy to protein ratio as a result of its significantly higher (P < 0.001) concentration of TNC compared with Midmar. Milk yield for cows grazing Enhancer in period 1 of the cross-over study was significantly higher (P < 0.05) than for cows grazing Dargle, despite the significantly lower (P < 0.05) DMI of animals on Enhancer. The higher TNC concentration relative to the true protein content of Enhancer would suggest that the protein metabolism in the rumen can be enhanced. / Thesis (Ph.D.)-University of Natal, Pietermaritzburg, 2003.

Limited water supplies are available to satisfy the increasing demands of crop production. It is therefore very important to conserve the water, which comes as rainfall, and water, which is used in irrigation. A proper irrigation water management system requires accurate, simple, automated, non-destructive method to schedule irrigations. Utilization of infrared thermometry to assess plant water stress provides a rapid, nondestructive, reliable estimate of plant water status which would be amenable to larger scale applications and would over-reach some of the sampling problems associated with point measurements. Several indices have been developed to time irrigation. The most useful is the crop water stress index (CWSI), which normalizes canopy to aIr temperature differential measurements, to atmospheric water vapour pressure deficit. A field experiment was conducted at Cedara, KwaZulu-Natal, South Africa, to determine the non-water-stressed baselines, and CWSI of cereal rye (Secale cereale L.) from 22 July to 26 September 2002, and aImual (Italian) ryegrass (Lolium multiflorum Lam.) from October 8 to December 4, 2002, when the crops completely covered the soil. An accurate measurement of canopy to air temperature differential is crucial for the determination of CWSI using the empirical (Idso et al., 1981) and theoretical (Jackson et al., 1981) methods. Calibrations of infrared thermometers, a Vaisala CS500 air temperature and relative humidity sensor and thermocouples were performed, and the reliability of the measured weather data were analysed. The Everest and Apogee infrared thermometers require correction for temperatures less than 15 QC and greater than 35 QC. Although the calibration relationships were highly linearly significant the slopes and intercepts should be corrected for greater accuracy. Since the slopes of the thermocouples and Vaisala CS500 air temperature sensor were statistically different from 1, multipliers were used to correct the readings. The relative humidity sensor needs to be calibrated for RH values less than 25 % and greater than 75 %. The integrity of weather data showed that solar irradiance, net irradiance, wind speed and vapour pressure deficit were measured accurately. Calculated soil heat flux was underestimated and the calculated surface temperature was underestimated for most of the experimental period compared to measured canopy temperature. The CWSI was determined using the empirical and theoretical methods. An investigation was made to determine if the CWSI could be used to schedule irrigation in cereal rye and annual rye grass to prevent water stress. Both the empirical and theoretical methods require an estimate or measurement of the canopy to air temperature differential, the non-waterstressed baseline, and the non-transpiring canopy to air temperature differential. The upper (stressed) and lower (non- stressed) baselines were calculated to quantify and monitor crop water stress for cereal rye and annual ryegrass. The non-water-stressed baselines were described by the linear equations Te - Ta = 2.0404 - 2.0424 * VPD for cereal rye and Te - Ta = 2.7377 - 1.2524 * VP D for annual ryegrass. The theoretical CWSI was greater than the empirical CWSI for most of the experimental days for both cereal rye and annual ryegrass. Variability of empirical (CWSI)E and theoretical (CWSI)T values followed soil water content as would be expected. The CWSI values responded predictably to rainfall and irrigation. CWSI values of 0.24 for cereal rye and 0.29 for annual ryegrass were found from this study, which can be used for timing irrigations to alleviate water stress and avoid excess irrigation water. The non-water-stressed baseline can also be used alone if the aim of the irrigator is to obtain maximum yields. However the non-water-stressed baseline determined using the empirical method cannot be applied to another location and is only valid for clear sky conditions. And the non-water-stressed baseline determined using theoretical method requires computation of aerodynamic resistance and canopy resistances, as the knowledge of canopy resistance, however the values it can assume throughout the day is still scarce. The baseline was then determined using a new method by Alves and Pereira (2000), which overcomes these problems. This method evaluated the infrared surface temperature as a wet bulb temperature for cereal rye and annual ryegrass. From this study, it is concluded that the infrared surface temperature of fully irrigated cereal rye and annual ryegrass can be regarded as a surface wet bulb temperature. The value of infrared surface temperature can be computed from measured or estimated values of net irradiance, aerodynamic resistance and air temperature. The non-water-stressed baseline is a useful concept that can effectively guide the irrigator to obtain maximum yields and to schedule irrigation. Surface temperature can be used to monitor the crop water status at any time of the day even on cloudy days, which may greatly ease the task of the irrigator. / Thesis (M.Sc.)-University of Natal, Pietermaritzburg, 2003