Orientador: Renato de Mello Prado / Coorientador: Rogério Falleiros Carvalho / Banca: Arthur Bernardes Cecilio Filho / Banca: Cid Naudi Silva Campos / Banca: Lucas Aparecido Gaion / Banca: Lilian Ellen Pino / Resumo: Uma consequência da toxicidade de amônio (NH4+) é a diminuição do conteúdo de citocininas (CKs). Dessa forma, o fornecimento de CK, na forma de trans-zeatina (tZ), pode aliviar a toxicidade de NH4+, e a CK sintética 6-benziladenina (BA), de menor custo, ainda não foi estudada quanto ao seu efeito sobre a toxicidade de NH4+. Além disso, o silício (Si), que é um elemento benéfico, é capaz de amenizar vários estresses, como a toxicidade de NH4+. Objetivou-se verificar se o alívio da toxicidade de NH4+ com o uso do Si é dependente do aumento do teor de CKs no tomateiro cv Micro-Tom (MT), os efeitos do Si no tomateiro transgênico MT CKX2 (baixo teor de CKs) submetido à toxicidade de NH4+ e se o regulador de crescimento BA alivia a toxicidade de NH4+ no tomateiro MT. Para isso, realizaram-se cinco experimentos em tomateiro, com a aplicação dos tratamentos na solução nutritiva. No experimento com concentrações de NH4+ entre 1,25 e 7,5 mmol L-1, 5,9 mmol L-1 provocou a toxicidade de NH4+, com diminiução de 10% na massa seca da parte aérea. No experimento com concentrações de Si entre 0,2 e 0,8 mmol L-1, na forma de silicato de potássio (SiK) ou ácido silícico estabilizado (ASiE), a toxicidade de NH4+ não foi aliviada. No experimento com concentrações de Si entre 1,0 e 2,5 mmol L-1, na forma de SiK, a concentração de 1,29 mmol L-1 de Si aliviou a toxicidade de NH4+. No experimento com N nas formas de NO3- ou NH4+ (5,9 mmol L-1), na ausência e na presença de Si (1,29 mmol L-1) no tomat... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: A consequence of ammonium (NH4+) toxicity is the decrease in cytokinins (CKs) content. However, the supply of CK in the nutrient solution, in trans-zeatin (tZ) form, can alleviate NH4+ toxicity, and CK synthetic 6-benzyladenine (BA), with lower cost, has not yet been studied on the NH4+ toxicity. Similarly, silicon (Si), which is a beneficial element known to relieve stresses, also alleviates NH4+ toxicity. The objective was to verify if the relief of NH4+ toxicity by Si is dependent on the increase of the CKs content in tomato cv Micro-Tom (MT), the effects of Si on the transgenic tomato MT CKX2 (CKs deficient) submitted to NH4+ toxicity, and if the growth regulator 6-benzyladenine (BA) alleviates NH4+ toxicity in tomato MT. For this, five experiments were carried in tomato, with treatments application in nutrient solution. In experiment with NH4+ concentrations between 1.25 and 7.5 mmol L-1, 5.9 mmol L-1 caused NH4+ toxicity, with shoot dry weight 10% decrease. In experiment with Si concentrations between 0.2 and 0.8 mmol L-1, via potassium silicate (SiK) or stabilized silicic acid (ASiE), NH4+ toxicity was not alleviated. In the experiment with Si concentrations between 1 and 2.5 mmol L-1, via SiK, the concentration of 1.29 mmol L-1 alleviated NH4+ toxicity. In experiment with N in NO3- or NH4+ forms (5.9 mmol L-1), in absence and presence of Si (1.29 mmol L-1) in MT tomato, Si decreased CKs content in root and increase in shoot, independent of the N form. In same experime... (Complete abstract click electronic access below) / Doutor

Winter wheat is commonly grown in dryland cropping systems in the Pacific Northwest region of semi-arid eastern Oregon. For agronomic, economic, and environmental reasons, it is important to understand the long-term sustainability of such dryland systems. The objective of this study was to evaluate the long-term effects of tillage, nitrogen (N), soil depth, and the influence of precipitation on wheat yields in dry land cropping systems of eastern Oregon. Data were taken from the Tillage/Fertility or "Balenger" experiment, which was established in 1940 by a Soil Conservation employee, and is one of the oldest replicated research experiments in the western United States. The experiment consisted of a winter wheat-summer fallow rotation arranged in a randomized block design with three replications. The main plot consisted of three primary tillage treatments (moldboard plow, offset disk, and subsurface sweep) and subplots consisted of six nitrogen treatments that changed over time and most recently ranged from 0 to 180 kg ha�����. Soil depth of individual plots ranged from 1.2- to 3.0-m. The study was divided into four main time periods (1940-1951, 1952-1961, 1962-1987, and 1988-1997) within which experimental treatments were consistently maintained. The moldboard plow tillage treatment significantly increased yields by more than 300 kg ha����� over the subsurface sweep tillage treatment in all four time periods. Yields with the moldboard plow system were significantly higher than with the offset disk system in time periods 3 and 4. The same trend was evident for mean yield in time periods 1 and 2, but differences were not statistically significant. In time periods 1, 2, and 3, mean yields were higher with the offset disk tillage treatment than the subsurface sweep tillage system, although the differences were not statistically significant. In time period 4, mean yield was higher for the subsurface sweep system than the offset disk treatment, but differences were not statistically significantly. The optimum amount of N for winter wheat differed from year to year, within, and between experiment periods. This was apparently in response to rainfall patterns and improved management factors, specifically more N responsive semi-dwarf varieties. For time period 1, the maximum fertilizer rate was 11.2 kg N ha�����, which tended to produce higher mean grain yields than an application rate of than 0 kg N ha�����, regardless of the quantity or distribution of precipitation. For time period 2, the maximum fertilizer rate was 33.7 kg N ha�����, which produced significantly higher grain yields than an application rate of than 0 kg N ha�����, regardless of the quantity or distribution of precipitation. For time period 3 (1962-1987), which had below-normal annual and growing season precipitation, yield increased with the addition of 45 kg N ha�����. For time period 4 (1988- 1997), which had above-normal annual and growing season precipitation, yield increased with the addition of 90 kg N ha�����. Yield increases at greater rates of N were insignificant. For time periods 3 and 4, maximum mean yield was obtained at an application rate of 135 kg N ha�����. The response of wheat yield to N during dry years was greater for deep (> 2.8 m) soils than for shallow soils. In addition to amount, rainfall distribution during the winter (October to March) and growing (April to June) season significantly affected yield. Results demonstrate the importance of rainfall and nitrogen to winter wheat production in eastern Oregon, and that the most environmentally sound tillage systems are not necessarily the most profitable from farmers' point of view. / Graduation date: 2000

Breadmaking quality is an important criterion in breeding and development of hard wheat (Triticum aestivum L.) cultivars. Improvements in N management are needed to produce superior quality grain and satisfy market demands for protein content. Field experiments with three hard red and two hard white spring wheat cultivars were conducted in 1998 and 1999 at Corvallis and Pendleton, Oregon. Nitrogen rates were varied from 0 to 250 kg N ha�����, applied all at planting, or split between planting and stem elongation. Resulting grain was evaluated for protein content, protein quality, dough handling, and bread-making quality. Grain protein content of the five cultivars increased with increasing levels of applied nitrogen. There was a concurrent improvement in bread-making quality, as indicated by increasing protein quality, loaf volume, loaf crumb score. Use of split nitrogen applications contributed to increased grain protein content at both the intermediate and high N rates. At the higher N rates, a split application had no apparent influence on protein quality. However, at intermediate N rates, a split application contributed to improvements in protein quality and loaf volume. Nitrogen use efficiency and wheat end-use quality can be improved by using split applications of nitrogen during the crop cycle. / Graduation date: 2001

The effect of planting density and nitrogen (N) fertilization on growth, yield, and N partitioning in young and mature 'Bluecrop' blueberry plants was studied over a two year period. Depleted 15N-ammonium sulfate was applied at different rates and on different dates in a mature planting, and at different rates in a young, newly established planting during the first year of study (2002). Non-labeled fertilizer was applied the second year (2003). Three rates of N fertilizer (0, 100, and 200 kgha1 of N) in combination with two in-row spacing treatments (0.45 m and 1.2 m) were studied in the mature planting. In addition, three different dates of application of labeled fertilizer at the same rate was also tested. In a young planting, four N fertilizer rates (0, 50, 100 and 150 kgha^-1 of N) were applied in the establishment year. In all studies, the N fertilizer was divided into three equal portions and applied from April through June. Plants were destructively harvested from the field and divided into parts on 6 to 11 dates from Feb. 2002 to Jan. 2004, depending on experiment. Plant parts were analyzed for dry weight (DW), N, and '5N concentration (%) and nitrogen derived from the fertilizer (NDFF) calculated. Shoots on mature plants were divided into small (S), medium (M), large (L) and extra large (XL) categories, based on length, and the effect of N and plant spacing on the number, DW, and flushes of growth characterized. The number of shoots per plant ranged from 249 to 298 with plants spaced at 1.2 m having more shoots than those at 0.45 m. Fifty percent of the shoots in the plant were S, whereas only 8% were XL. Nitrogen rate did not affect shoot number, but higher rates of N did increase shoot biomass and the proportion of XL and S shoots. One to four flushes of growth per shoot were recorded, with the number of flushes dependent upon shoot size; 60 to 80% of S shoots had only one flush of growth compared to 8 to 12% of XL shoots. Eighty percent of total shoot biomass was in the first flush of growth and 20% in the second or later flushes with no effect of in-row spacing or N rate. Yield per plant was 30 to 80% greater at 1.2 m than at 0.45 m. However, yield per hectare was 30 to 140% higher in plants at 0.45 m than those at 1.2 m. The roots and crown were the heaviest organs, whereas roots and leaves contained the most nitrogen. Percent biomass partitioning was affected by sampling date for all plant parts, and by in-row spacing only for the crown and three-year-old wood. In the mature planting, total plant DW was affected by sampling date, in-row spacing, and N fertilization rate. Plants at the 1.2 m in-row spacing had 32% more DW over time than those at 0.45 m, but less DW per hectare. Nitrogen fertilization increased plant DW in the second year of study, affecting mainly the younger plant parts. Plants fertilized with 200 kgha^-1 of N had the greatest total N. Nitrogen concentration (%N) varied greatly with plant part and was affected by sampling date and N fertilization rate. Younger tissues had the highest %N in spring (3.5%) and flower buds in winter (2.4%). Total plant NDFF increased from Apr. 2002 to May 2003. The lowest NDFF per plant and per hectare was found in Apr. 2002, when almost 60% of the NDFF was in the new shoots. Nitrogen fertilization rate and in-row plant spacing had an impact on total NDFF accumulated per plant and per hectare. More total NDFF was found in plants fertilized with 200 kgha^-1 of N than with 100 kgha^-1 of N, independent of spacing. Fertilizer recovery was 17% for plants at 1.2 m and 23% for plants at 0.45 m, independent of N fertilization rate. Partitioning of 15N (mg per plant part) and percent of total 15N per part changed with sampling date. Nitrogen fertilization rate and spacing did affect the total amount of fertilizer-15N present in each part, but percent partitioning of 15N was only affected by plant part. Plants at 1.2 m had a higher percentage of 15N partitioned to the crown and three-year and older wood, but reduced partitioning to large roots than plants at 0.45 m. Application date had a large effect on the total amount of NIDFF recovered in the plant at the end of the first season. Application of N fertilizer in either April or May resulted in five times more NDFF in the plant than fertilizer application in July. Percent partitioning of NDFF was also affected by application date. Late fertilization resulted in labeled N allocated mainly to small roots, leaves and shoots, whereas spring-applied fertilizer was allocated mainly to leaves and fruits. In the new planting, established using two-year-old plants, N fertilization rate affected plant dry weight, total N content, percent NDFF, and fertilizer recovery. By October, plants fertilized with 50 kgha1 of N had the largest dry weight and N accumulation. Ammonium toxicity was observed in plants fertilized with 100 and 150 kgha1 of N. Percent NDFF was 60% and 67% for the 50 and 100 kgha^-1 of N, respectively. Fertilizer recovery reached a maximum of 10 to 17% in October, depending on N fertilization rate. / Graduation date: 2006

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Plant growth regulators and nitrogen fertilization have been associated with the increased incidence of fusarium head blight, a destructive disease of wheat (Triticum aestivum L.). In Canada, the major causal organism of this disease is Fusarium graminearum Schwabe, the conidial state of Gibberella zeae (Schw.) Petch. Most studies concerning the effect of plant growth regulators on fusarium head blight were conducted in fields with natural infection. The objective of this research was to evaluate the effect of growth regulators and nitrogen fertilizer on the incidence of fusarium head blight of wheat with artificial inoculations. / A survey conducted in a field trial testing the effect of the plant growth regulator Cerone on the yield components of several cultivars of spring wheat showed that Cerone treatments increased Fusarium infection only in cultivar Columbus. Further research was conducted using cultivar Max, a cultivar susceptible to fusarium head blight, which is widely grown in Quebec. In controlled-condition greenhouse trials, the growth regulators Cycocel and Cerone, as well as nitrogen fertilization did not influence the disease progress. In the 1991 field experiment, the highest incidence of seed infection was observed in Cycocel treatments when the macroconidia of F. graminearum were directly applied to the heads, but not significantly different from the non-treated control. None of the nitrogen levels affect the incidence of seed infection. In the 1992 field trial, the plots were treated with macroconidia of F. graminearum applied to the heads or with Fusarium-colonized corn applied to the rows. Both Cycocel and Cerone significantly increased the incidence of spikelet only in the colonized corn treatments. Cycocel also increased the incidence of seed infection, but only in colonized corn treatments. Cycocel also increased the incidence of seed infection in the non-inoculated treatments. Growth regulators had no effect on the disease when heads were inoculated directly with macroconidia.

Potato requires high levels of nitrogen fertilizer. Up to now in Quebec, no nitrogen fertilizer recommendation has been based on nitrogen availability in the soil, even those soil nitrogen testing is available. The objectives of this study were: (1) to determine the relation between soil nitrate-N content, nitrogen fertilization and potato yield; and (2) to determine the time and the sampling depth of soil most appropriate to predict potato yields and response to nitrogen fertilizer under Quebec conditions. Soil samples were taken at two depths at planting and at hilling time in 28 sites fertilized at four levels of nitrogen. Laboratory measures of nitrate-N were carried out on those samples. A combination of nitrate-N and nitrogen fertilisation gave the best explanation of the variation potato yields. A maximum of 46% of yield variation was attributed to the combination of those two factors in general. Best coefficients of determination were obtained when the sampling of nitrate-N was done at planting time compared to time. Regression models predicted nitrogen fertilizer needs of 89 to 200 kg ha$ sp{-1}.$ The same conclusions were found in the case of the variety Superior alone. The variation of yield explained was up to 62%. Regression models predicted nitrogen fertilizer needs of 77 to 224 kg ha$ sp{-1}$ for Superior. It was concluded that the analysis of soil nitrate-N can improve the prediction of nitrogen fertilizer needs for an optimum potato production.

The use of high N fertilizer in sweet corn (Zea mays L.) and wheat (Triticum aestivium L.) production often results in leaching losses and contamination of ground water. Cover crops planted after harvest of sweet corn and wheat may reduce residual soil NO$ sp- sb3$-N levels by crop N uptake and subsequently minimize NO$ sp- sb3$-N content in gravitational water. Field experiments were conducted on a Ste. Rosalie heavy clay (Humic Gleysol) and a St. Bernard sandy clay loam (Melanic Brunisol) to determine the contribution of the six cover crops to nutrient uptake, subsequent N release, leaching losses, denitrification rates and soil properties such as aggregate stability, organic matter. The cover crops were red clover (Trifolium pratense L.), crimson clover (Trifolium incarnatum L.), forage radish (Raphanus sativus L.), canola (Brassica rapa L.), barley (Hordeum vulgare L.), annual rye grass (Lolium multiflorum L.). Three replicates were used in a split plot arrangement of a randomized complete block experiment. Sweet corn and wheat were grown at three fertilizer N rates, 0-75-150 kg N ha$ sp{-1}$ for sweet corn and 0-45-90 kg N ha$ sp{-1}$ for wheat. Cover crop of forage radish, canola and barley were more effective at absorption or soil N than rye grass and clover species at all sample times. Levels of soluble N in the soil were reduced with cover crop in the off-season. Cover crop plots had higher NO$ sp- sb3$-N levels than control plots in the spring, indicating net mineralization and nitrification. Gravitational water NO$ sp- sb3$-N contents were higher in the control plots relative to cover crop plots at both sites. Therefore growing cover crops after harvest of sweet corn and wheat can reduce residual NO$ sb3$-N level in the soil and thus restrict ground water contamination with fertilizer N.

An experiment was conducted to investigate the effects of N formulation, application rate, and application time on corn yield and quality under Eastern Canadian conditions, to evaluate the hypothesis that application of N will increase corn grain yield and protein concentration without decreasing the total energy content. Three N formulations, each with the rates of 90, or 180 kg ha$ sp{-1}$ were applied at different times. The results indicated that the grain yield increased with increasing N fertilizer rate and with increasing numbers of N application times. N application significantly increased grain protein concentration, on both a per kernel and a dry matter basis, and protein yield. Such as, N application increased the averaged protein concentration, on a dry matter basis, of corn grain by about 8.40% as compared to the control. The protein concentration was not affected by the number of N application times before the plants were 90 cm high. Neither lipid nor non-structural carbohydrate concentration, on both a per kernel and a dry matter basis, were significantly affected by N application in most of the location-years. In addition Near infrared reflectance (NIR) was used to determine the lipid concentration in the aerial corn tissue at different growth stages. The correlation coefficients between the standard analytical method and the NIR method of lipid concentration were all above 0.95, and were significant at 0.01 level.