'Newhall' navel oranges on 'Carrizo' rootstock were planted in Mar. 1997 at the Citrus Agricultural Center. The objectives of this experiment were: i) to determine the effects of N rate and fertigation frequency for microsprinkler-irrigated navel oranges on tree N status, and crop yield and quality; and ii) to develop Best Management Practices which promote optimum tree growth and production while minimizing nitrate leaching. The trees are equipped with a microsprinkler irrigation system. The experiment is a randomized complete block factorial with N rates of 0, 0.15, 0.30, and 0.45 lb N/tree/year, and fertigation frequencies of weekly, monthly, and three times per year. Unfertilized control trees are also included in the experimental design. Each of the ten treatments is replicated five times. The trees were harvested for the first time in Feb. 2001. Fruit were processed through an automatic fruit sizer, and fruit from each plot were further evaluated for fruit quality. Although unfertilized control trees had lower leaf N content than fertilized trees, fruit yield and quality of controls was no lower than fertilized trees. Similarly, there were few statistically significant differences in fruit yield and quality between trees receiving different N rates and fertigation frequencies.

This experiment was established in January 2000 in a block of 'Washington' navel orange trees at Verde Growers, Stanfield, AZ. Treatments included: normal grower practice, winter low biuret (LB) urea application, summer LB urea application, winter LB urea application plus winter and spring potassium phosphite, winter LB urea application plus summer potassium phosphite, and normal grower practice plus spring potassium phosphite. Each treatment was applied to approximately four acres of trees. For 2000-01, yields ranged from 40 to 45 lbs. per tree, and there was no effect of treatments upon total yield. There was a slight effect upon fruit size and grade. Trees subject to summer LB urea application had significantly more fruit of size 56, compared to trees subject to winter LB urea, and untreated, and untreated trees had significantly more fruit of size 88 than did treated trees. Also, treated trees had slightly more fruit in the fancy grade than did untreated trees.

Master of Science / Department of Agronomy / Dorivar Ruiz Diaz / Corn (Zea mays) response to fertilization and placement methods has been studied extensively; however studies on soybean [Glycine max (L.) Merr.] response to placement have been limited. Three studies were completed to evaluate different aspects of crop response. The objective of the first study was to evaluate the effect of starter and broadcast fertilizer application on corn and soybean, in a typical corn-soybean rotation in Kansas. Treatments were unfertilized control, starter (N, P and K), broadcast P and K using mono ammonium phosphate (MAP) and potassium chloride (KCl) and the combination of starter and broadcast. Corn and soybean yield generally was not affected by starter and broadcast treatments. Thus fertilization may be recommended only under specific conditions. The objectives of the second study were (i) to evaluate the effect of residual and direct fertilization on soybeans after corn under a corn-soybean rotation system, and (ii) study the effect of fertilizer P and K application on soil test P (STP) and soil test K (STK) changes over time. Direct fertilization increased soybean yield while residual fertilizer did not. Therefore maintenance rates may be effective to improve soybean yield and likely maintain STP and STK levels. Application of P and K fertilizer generated significant increases in STP and STK after one year of application. The rate of P and K fertilizer required to increase 1 mg kg-1 yr-1 was between 2.8 - 5.1 kg ha-1 for P and between 1.0- 2.5 kg ha-1 for K, respectively. The objective of the third study evaluate both corn and soybean response to direct P fertilization including starter and broadcast. The treatments were a control, two starter fertilizers (with N-P and N only), five P rates (9.8, 19.6, 29.3, 39.1, 48.9 kg P ha-1) and one treatment with starter fertilizer in addition to the broadcast fertilizer application. Corn grain yield was not significantly affected by any broadcast or starter treatments. Broadcast application rates significantly increased soybean yield on low STP levels. Results of this study show that large corn or soybean yield response to starter and broadcast P application are likely with low STP levels.

Master of Science / Department of Animal Sciences and Industry / Karol E. Fike / This thesis involves two separate studies that evaluate the effects of different beef cattle management practices on reproduction. The objective of the first study was to determine if feedlot heifers administered melengestrol acetate (MGA) and growth promoting implants could serve as viable oocyte donors for in vitro embryo production. Ovaries from heifers administered MGA and growth promotants (MGA-Implant) and ovaries from heifers not administered either substance (Control) were collected from heifers post-slaughter. Oocytes were harvested and in vitro maturation, in vitro fertilization (IVF), and in vitro culture were completed. Treatment and time interacted to affect the number of oocytes aspirated per ovary (P = 0.07) and the number of zygotes per ovary (P = 0.07). Fertilization (P = 0.90) and cleavage rates (P = 0.80) did not differ between treatments. Blastocyst rates (P = 0.30) and the number of embryos per ovary (P = 0.50) did not differ between treatments. We concluded that beef feedlot heifers fed MGA and implanted with growth promotants seem to be a viable source of oocytes for in vitro embryo production. In the second study, we hypothesized that continuous fenceline exposure of prepubertal beef bulls to cycling beef females would hasten the onset of puberty as well as increase the percentage of bulls passing their initial breeding soundness examination (BSE). Bulls were either exposed to estrous females (exposed) or were not exposed (control). Monthly scrotal circumference (SC) measurements, blood samples, semen evaluations, and bull behavior assessments were conducted. Age at puberty (P = 0.40), SC at puberty (P = 0.50), and weight at puberty (P = 0.30) did not differ between treatments. A similar (P = 0.50) percentage of bulls passed their initial BSE at 363 ± 21.5 d of age (exposed: 87.8%; control: 74.2%). Treatment, month, and stage of the estrous cycle of cows interacted to affect the number of mount attempts (P = 0.05) and the number of flehmen responses (P < 0.001). In conclusion, bulls given continuous fenceline exposure to cycling beef females were neither younger at puberty nor did a greater percentage pass their initial BSE.

Orientador: Antonio Ismael Inácio Cardoso / Banca: Dirceu Maximino Fernandes / Banca: Luis Felipe Villani Purqueiro / Resumo: Embora existam recomendações de adubação para o cultivo comercial de abobrinha-de-moita, são escassos os trabalhos de pesquisa que relacionam o efeito da adubação potássica em cobertura sobre a produtividade e qualidade desta cultura. Assim, faz-se a necessidade de determinar doses deste nutriente em cobertura que auxiliem estas recomendações. Dessa forma, foram conduzidos ensaios no outono e na primavera na Fazenda Experimental São Manuel, da FCA-UNESP, em São Manuel-SP, Brasil. O delineamento experimental utilizado foi o de blocos ao acaso com cinco tratamentos e quatro repetições. Os tratamentos utilizados foram cinco doses de potássio em cobertura (0, 50, 100, 200 e 400 kg K2O ha-1). Nos dois experimentos foram avaliadas as características químicas do solo ao final do cultivo, características vegetativas das plantas ao final do cultivo (altura, número de folhas, massa fresca e seca da parte vegetativa), características químicas da parte aérea (teor de macronutrientes na fase de diagnose foliar, teor de macronutrientes na parte vegetativa e no fruto ao fim do cultivo e a extração de macronutrientes na parte aérea ao fim do cultivo), características de produção de frutos (número de frutos totais e comerciais, produção total e comercial). No experimento de primavera, além destas características, também foram avaliadas o teor de macronutrientes nos frutos das colheitas semanais e as características de qualidade de frutos (pH, acidez total titulável, sólidos solúveis, relação sólidos solúveis e acidez total titulável, açúcares redutores e textura). Para a comparação das características comuns das duas épocas de experimentação foi realizada a análise estatística conjunta. Ocorreu aumento linear para as características teor de potássio no solo no outono e primavera, nas folhas diagnose... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Although there are fertilizer recommendations for commercial cultivation of summer squash, there are few research papers that relate the effect of potassium fertilizer in topdressing on productivity and quality of the crop. Thus, is necessary to determine doses of this nutrient to assist in covering these recommendations. Thus, experiments were conducted in the fall and spring on the Experimental Farm Manuel, the FCA-UNESP, São Manuel-SP, Brazil. The experimental design was randomized blocks with five treatments and four replications. The treatments were five levels of potassium fertilization (0, 50, 100, 200 and 400 kg K2O ha-1). In both experiments were evaluated soil chemical characteristics at the end of the cycle, vegetative characteristics of plants at the end of the cycle (plant height, leaf number, fresh and dry mass of shoots) at the end of the cycle, the chemical characteristics of the plant ( macronutrients in the phase of leaf analysis, macronutrients in the vegetative plant parts and fruit at the end of the cycle and the extraction of nutrients in the plant at the end of the cycle), characteristics of fruit yield (fruit number and total trade, total output and commercial). In the spring experiment, and these characteristics were also assessed the macronutrient composition of the fruits of the weekly harvest and fruit quality characteristics (pH, total acidity, soluble solids, soluble solids and total acidity, reducing sugars and texture). For comparison of common features of two seasons of experimentation was performed statistical joint analysis. There was a linear increase of the characteristics of the potassium content in soil in autumn and spring, diagnosis leaves in autumn, the vegetative plant parts in spring and fruit in late season in the fall to the extent that increased doses... (Complete abstract click electronic access below) / Mestre

A dissertation submitted in fulfilment of the requirements for the degree of Master of Science in Medicine Faculty of Health Sciences University of the Witwatersrand Johannesburg 2015 / Treatment of hormone-dependent breast tumours is typically conducted using hormone-therapy, with NK cell immunotherapy a novel modality. In this study, the effects of hormone-therapy and combined hormone-therapy with immunotherapy in MCF-7 breast cancer cells was investigated. A hormone pre-treatment of 17β-oestradiol and progesterone was performed to simulate the in vivo microenvironment. Subsequently cells were treated with the hormone-therapy drugs Anastrozole or RU486 alone, or with continued hormone simulation. Combined therapy was conducted with in vitro activated NK cells co-cultured with MCF-7 cells undergoing hormone-therapy. Biomarkers ERα, PR and MUC1 were immunolocalised and expression analysed qualitatively, and quantitatively using image analysis software. Hormone pre-treatment reduced biomarker expression, stressing the importance of hormone environment simulation for in vitro experimentation. Hormone-therapy increased cytoplasmic ERα and decreased PR expression. Anastrozole increased MUC1 and RU486 decreased nuclear MUC1. With continued hormone simulation, Anastrozole further decreased all biomarkers whereas RU486 decreased ERα, increased PR expression with variable effects on MUC1 expression. RU486 induced MUC1/PR and MUC1/ERα correlation, which, under continued hormone simulation, was maintained in the nucleus only. Anastrozole induced MUC1/PR correlation in the cytoplasm which was maintained under continued hormone simulation. Hormone-therapy also induced a decrease in apoptosis, with continued hormone simulation abrogating Anastrozole induced apoptosis. While hormone-therapy did not increase proliferation, the associated changes observed in biomarker expression are linked with tumour progression indicating that short-term treatment may be detrimental for overall survival. Combined NK cell immunotherapy resulted in decreased PR, while ERα and MUC1 expression increased in a hormone-dependent manner. Biomarker correlation was evident, albeit reduced with continued hormone simulation. Independently of hormone-therapy and hormone stimulation, immunotherapy reduced apoptosis, contrary to expectation. Proliferation was marginally reduced by immunotherapy. The results indicate that immune cell function is inhibited by interaction with tumour cells, an effect that hormone-therapy cannot abrogate. Furthermore, that this study shows treatment alters both nuclear and cytoplasmic expression of biomarkers, indicates that diagnostic procedures should consider both cellular compartments in tumour progression. It is further shown that qualitative analysis of biomarker expression is not always validated by quantitative analysis, with the latter proposed as a more objective and precise method to be used diagnostically.

A sexagem espermática tem um grande impacto na produção animal, pois permite a escolha do sexo dos descendentes, tendo o seu uso aumentado consideravelmente nos últimos anos. Atualmente, as taxas de blastocistos produzidos in vitro com sêmen sexado são semelhantes às com sêmen não sexado. Entretanto, quando utilizado na inseminação artificial (IA) e/ou transferência de embriões (TE) as taxas de gestação ou produção de embriões ainda são inferiores às obtidas com sêmen convencional. Esses resultados indicam que são necessários mais esclarecimentos sobre o efeito da sexagem nas células espermáticas. Este estudo teve o objetivo de avaliar possíveis alterações moleculares e funcionais dos espermatozoides causadas pelo processo de sexagem, além de tentar identificar diferenças entre espermatozoides contendo o cromossomo X ou Y. Para isto, um ejaculado de cada touro Nelore (n=4) foi colhido e separado em três frações: não sexado (NS), sexado X (SX) e sexado Y (SY), sendo utilizado em 3 experimentos. Nos experimentos 2 e 3, um quarto grupo foi formado pelo pool de espermatozoides sexados X e Y (XY). No primeiro experimento, utilizando a técnica de bisulfito de sódio, foi realizada a avaliação do padrão de metilação dos genes imprinted IGF2 e IGF2R em espermatozoides sexados e não sexados. No segundo experimento, foi avaliado o efeito da sexagem no tamanho e na forma da cabeça do espermatozoide e as possíveis diferença entre espermatozoides contendo cromossomo X ou Y. No último experimento, verificou-se o efeito da sexagem espermática na longevidade dos espermatozoides mantidos em meio de cultivo por 12 horas e na sua capacidade de se ligar às células da tuba uterina (CTU). No experimento relacionado à epigenética, não foi encontrada diferença no padrão de metilação dos genes IGF2 e IGF2R. Entretanto, identificou-se um polimorfismo no gene IGF2, e um padrão de metilação específico do gene IGF2R, provavelmente devido a uma característica epigenética especifica de animais Bos indicus. No experimento 2, não foi encontrada diferença em nenhuma das 23 variáveis estudadas entre os grupo X e Y. Entretanto, usando simultaneamente diversos parâmetros por meio de análise discriminante, na tentativa de diferenciar os grupos, o modelo mais discriminante atingiu 100% de precisão na identificação de espermatozoides de cada grupo NS, SX, SY e SXY. No experimento 3 foi identificado que o processo de sexagem afeta características estruturais da célula espermática, induzindo umacapacitação e reação acrossômica. Porém, ao longo de 12 horas de cultivo, a cinética dos espermatozoides sexados foi semelhante a do sêmen convencional. Além disto, foi identificado que o processo de sexagem comprometeu a capacidade dos espermatozoides de se manterem ligados às CTU. Em relação aos espermatozoides X e Y, foi observada uma menor capacidade do grupo X de se ligar às CTU, assim como uma diferença em características relacionadas à motilidade e acrossoma. Esses resultados podem contribuir no estabelecimento de procedimentos mais adequados para melhorar o aproveitamento e os resultados quando da utilização do sêmen sexado e em melhorias no processo de sexagem, ou mesmo no desenvolvimento de novas tecnologias para a separação de espermatozoides X ou Y. / Sperm sorting can have a great impact on breeding programs because it allows sex selection of the offspring, being its use increased considerably in last few years. Currently the rate of in vitro produced blastocyst using sexed sperm is similar to that obtained with no sexed sperm. However, lower rates of pregnancy and blastocyst are observed when sexed sperm are used for artificial insemination or embryo transfer compared to the conventional sperm. These results suggest that further studies are needed to clarify the effects of sexing process on sperm cells. This study aimed to evaluate molecular and functional changes caused by the sorting process, as well as to identify possible differences between sperm containing the X or Y chromosome. Each ejaculate of Nelore bulls (n=4) was collected and separated into three fractions: non-sexed (NS), sexed for X-sperm (SX), and sexed for Y-sperm (SY), being used in 3 experiments. For the experiment 2 and 3 a fourth group was formed by pooling SX and SY samples (SXY). On the first experiment, methylation pattern of the IGF2 and IGF2R imprinted gene in sexed and non sexed sperm was assessed using sodium bisulfite method. On the experiment 2, we evaluated whether sexing by flow cytometry changes the shape and size of the sperm head, and if these measurements differ between cells that bearing the X or Y chromosome. In the last experiment, the effect of sorting process on sperm longevity during 12 h incubation and their ability to bind to oviduct cells were evaluated. In the experiment related to methylation patterns, sex-sorting procedures have not affected DNA methylation patterns of the IGF2 and IGF2R genes. However, a polymorphism was found in IGF2 gene, and a very specific methylation patterns was observed in the IGF2R gene, probably due to an epigenetic characteristic in Bos indicus cattle. On experiment 2, no differences between X and Y sperm group were observed for any of the studied characteristics. However, using different parameters simultaneously in discriminator analysis, in an attempt to differentiate groups, the greatest discriminator model had 100% accuracy to identify the sperm from NS, SX, SY and SXY group. On experiment 3, it was identified that sorting process affected structural sperm characteristics, inducing a pre capacitation status and acrosome reaction. However, after 12 hours of incubation the kinetics of the sexed sperm was similar to the non sexed sperm. Furthermore, sexing process affected the ability of sperm to maintained bound to the oviduct cells. Regarding X and Y sperm, it was observed that X group had a lower ability to bind to the CTU, being the X sperm more susceptible to sorting process than the Y sperm. These results can contribute to improve the use and results of the sexed sperm, as well as to induce enhancements in the sexing process, or even to develop new technologies for separation of X or Y sperm cell.

No Brasil, está ocorrendo a expansão da área florestal plantada com espécies do gênero Eucalyptus, sendo que a elevada produtividade pode ser atribuída às pesquisas e melhorias operacionais introduzidas nas ultimas décadas. Nos experimentos realizados em diferentes regiões do Brasil, tem se observado maior incremento dos eucaliptos com o aumento das doses de fertilizantes. Mas o excesso ou a aplicação inadequada de fertilizantes gera freqüentemente o desperdício dos insumos e a lixiviação dos elementos, que podem contaminar o solo e o lençol freático. Portanto, foi objetivo deste trabalho analisar o efeito de doses, bem como do parcelamento da aplicação de fertilizantes na produtividade e na ciclagem de nutrientes em plantios de eucaliptos, além de avaliar a lixiviação de nitrogênio e potássio no solo, após a fertilização de cobertura parcelada em comparação à aplicação em dose única, três meses após o plantio. O experimento foi implantado no município de Anhembi-SP, sendo constituído por cinco tratamentos com a aplicação de doses crescentes e eqüidistantes de N, P e K com a aplicação da fertilização de cobertura (N e K) em 4 parcelas e por um tratamento com fertilização de cobertura aplicada em dose única, três meses após o plantio. Foram avaliados o incremento volumétrico e a produção da biomassa aérea e radicular das árvores, as concentrações e os estoques de nutrientes nos eucaliptos (mineralomassas), a eficiência do uso dos nutrientes, a transferência de nutrientes das árvores para o solo através da produção de folhedo (ciclo biogeoquímico), a ciclagem interna dos nutrientes (ciclo bioquímico), bem como o fluxo de água e a lixiviação do N e K no solo nas profundidades de 20 e 90 cm. Os eucaliptos responderam positivamente ao aumento das doses de fertilizantes, principalmente na fase inicial, apresentando maior produtividade (altura, volume e biomassa). O tratamento com a maior dose obteve, aos 24 meses de idade, 105 t ha-1 de biomassa total, sendo 48% superior ao tratamento sem fertilização, com apenas 71 t ha-1. Entretanto o efeito das maiores doses de fertilizantes foi mais acentuado na fase inicial do crescimento, até os 12 meses de idade. Ocorreu a atenuação do incremento ao longo do tempo, sendo que aos 24 meses não foram observadas diferenças significativas entre os tratamentos com a aplicação de doses de fertilizantes. A fertilização também propiciou maior acúmulo de nutrientes (mineralomassa) nos componentes das árvores (folhas, galhos, lenho, casca e raízes) e maior transferência de nutrientes para o solo, através do folhedo. Assim, os eucaliptos com a adição das doses mais elevadas de fertilizantes devolveram ao solo, via folhedo, aproximadamente 50 kg ha-1 ano-1 de N, 20 kg ha-1 ano-1 de K e 80 kg ha-1 ano-1 de Ca, enquanto o tratamento sem fertilização transferiu para o solo apenas 25 kg ha-1 ano-1 de N, 6,5 kg ha-1 ano-1 de K e 47 kg ha-1 ano-1 de Ca, no período entre 12 a 24 meses de idade. Foi observado que os eucaliptos com menor disponibilidade de nutrientes foram mais eficientes no uso do N e K. Não foram observadas diferenças significativas na produção de biomassa lenhosa entre os tratamentos com aplicação da fertilização de cobertura de forma parcelada ou em dose única, sendo observado maior lixiviação do N e do K, aos 90 cm de profundidade, com a aplicação em dose única. / It is occurring, in Brazil, the expansion of planted forest area with species that belong to the Eucalyptus genus, one of the reasons is the high biomass productivity resulting from the research and the operational improvements that have been implemented during the last decades. In several field experiments, has been observed an increase of eucalypts growth by using a higher amount of fertilizers. But excessive or inappropriate application of fertilizers may generate the fertilizer waste and nutrients leaching that may contaminate soil and watertable. The objective of this study was to evaluate the effect of fertilization doses in the biomass production and nutrient cycling from the eucalypt plantation, as well as evaluating the N and K leaching in the soil after the application of split and single dose of N and K fertilization. The experiment was set up in the Anhembi city (State of São Paulo), and it was constituted by five treatments with doses of fertilizers and N and K in split application (4 times) and also a treatment with a single dose of N and K application, 3 months after planting. It was evaluated the wood volume, root and shoot biomass, concentrations and stocks of nutrients in eucalypts biomass (mineralomass), the efficiency of nutrient use, the nutrient transference from the canopy to the soil through litter production (leaf-fall), internal nutrients cycling (biochemical cycle), the water flow and leaching of N and K in the soil at the depths of 20 and 90 cm. The eucalypts responded positively to the increased fertilization doses, especially in the first year, with higher productivity (height, DBH and biomass). Treatment with the highest dose for 24 months produced 105 tons ha-1 of biomass, 48% higher than the treatment without fertilization, with only 71 tons ha-1. However the effect of higher doses was more evident at an early stage of tree growth, up to 12 months of age. However, the difference decrease over time, and at 24 months there were not significant differences among the treatments with fertilization application. Fertilization also resulted in higher nutrients accumulation (mineralomass) in all tree components (leaves, branches, wood, bark and roots) and increased nutrient transfer to the soil through deposition of leaf litter. Thus, the eucalypts applied the highest addition of fertilization dose returned to the soil through litter, about 50 kg ha-1 yr-1 of N, 20 kg ha-1 yr-1 of K and 80 kg ha-1 yr-1 of Ca, while the treatment without fertilization transferred to the soil only 25 kg ha-1 yr-1 of N, 6.5 kg ha-1 yr-1 of K and 47 kg ha-1 yr-1 of Ca during 12 months (between 12 to 24 months after planting). It was observed more efficient use of nutrients from the eucalypts with lower nutrients availability. Also, there were no significant differences in the growth of eucalypts from the treatments with split N and K application and single N and K application. However, there was a higher leaching of K and N, 90 cm deep, in the single application treatment.

O objetivo deste trabalho foi verificar qual o sistema mais eficiente de aplicação e fornecimento de fósforo como nutriente para produção de cana, enfatizando formas de aplicação (fosfatagem) determinando a dose a ser utilizada e a fonte mais eficiente na disponibilização do fósforo ao longo dos anos. O experimento foi instalado na Usina Rio Vermelho, localizada ao oeste do Estado de São Paulo, na cidade de Junqueirópolis. As médias anuais de temperatura e precipitação pluviométrica são de 23,4oC, 1.263 mm, respectivamente. A variedade utilizada foi a SP 89-1115. O delineamento utilizado foi em blocos ao acaso, com parcelas subdivididas (split-plot), com quatro repetições. As parcelas eram compostas por duas doses (100 e 200 kg ha-1), três formas de aplicação (sulco de plantio, área total e dividido 50% no sulco e 50% em área total) e mais a testemunha como tratamento adicional. As sub-parcelas foram compostas por cinco fontes de fósforo (Salmec, rocha fosfática nacional (Araxá), rocha fosfática importada (Arad), fosfato solúvel (Super triplo), e uma combinação Salmec + ST. Realizou-se a avaliação da produção nos três anos de experimento, e no terceiro corte da cana foram avaliadas as características tecnológicas do colmo. As aplicações de fósforo no plantio produziram efeitos positivos no primeiro corte independente da fonte e forma de aplicação, e não foram suficientes para causar efeitos nas produtividades dos cortes subsequentes. Como não houve diferença entre formas de aplicação, a aplicação no sulco de plantio tem maior retorno econômico. O uso da fonte alternativa Salmec é viável e foi mais vantajoso economicamente que outras fontes de P. Não há necessidade de aplicação de doses elevadas (200 kg P2O5 ha-1) sem controle de fatores limitantes. Para as características tecnológicas, os tratamentos não foram suficientes para causar diferenças significativas. / The objective of this work was to get the most efficient system to supply phosphorus as a nutrient for sugarcane production, prioritizing the application and use of phosphate as well as determine the rate to be used and which source is more efficient in the phosphorus supply over the years. The experiment was installed in the Rio Vermelho sugar cane plant, located west of the State of Sao Paulo at Junqueirópolis. The average annual temperature and precipitation were 23.4ºC and 1263 mm, respectively. The variety used was SP 89-1115. The experimental design was randomized blocks with split-plots and four replications. The plots were composed by two rates (100 and 200 kg ha-1), and three application methods (furrow, total area and half furrow and half total area) and additional treatment without aplication. The internal plots were consisted by five sources of phosphorus (Salmec, Araxá phosphate rock, Arad phosphate rock, triple superphosphate (TSP), and the combination of Salmec + TSP. In the three years of the experiment was made the evaluation of production, and the third year were evaluated the technological characteristics. The phosphorus applications at planting had positive effect on yields on first harvest, without effect the source or application methods, and were not sufficient to cause effects on the subsequent yields. There was no difference between those forms of application and to provide the phosphate in the furrow has greater economic return. The use of Salmec as an alternative source is viable, and more economically advantageous than other phosphorus sources. There is no need to provide rates above 200 kg P2O5 ha-1, without the control of limiting factors. For the technological characteristics, the treatments were not sufficient to show significant differences.

O aprimoramento das práticas agronômicas e a utilização de alta tecnologia nas lavouras contribuiu para os aumentos significativos na produtividade das culturas e, pode ter alterado a dinâmica de absorção e partição dos nutrientes pelas plantas. As recomendações oficiais de adubação para a cultura de milho no Brasil estão baseadas no teor crítico do nutriente no solo e são provenientes de literaturas mais antigas. Por serem dinâmicos, os fatores que interagem em um sistema de produção agrícola podem ser melhor estudados através de modelos matemáticos. A técnica de modelagem em agricultura pode expandir a compreensão das interações que ocorrem no sistema solo-planta-atmosfera. Sendo assim, o objetivo deste estudo é propor um modelo para o cálculo de recomendação de adubação da cultura de milho, a partir da modelagem da marcha de absorção de nutrientes, da evapotranspiração potencial da cultura e, da partição dos nutrientes nas plantas, levando em consideração a taxa de absorção de cada nutriente para cada genótipo em um determinado sistema de produção. O modelo proposto considera que a recomendação de adubação deve ser realizada com base na variação temporal da taxa de absorção de nutrientes, a qual define melhor a demanda da cultura, em comparação com o teor crítico dos nutrientes no solo. Para a validação do modelo, sugere-se um ensaio de campo comparando as metodologias. / The improvement of agronomic practices and the use of high technology in field crops contributed for their significant increases in productivity, and could also have altered the dynamics of nutrient uptake and partition by the plant. Official recommendations for fertilizer applications to the maize crop in Brazil are based on the critical soil nutrient content and are relatively outdated. Since the factors that interact in an agricultural production system are dynamic, mathematical modeling turns out to be an appropriate tool for these studies. Agricultural modeling can expand our knowledge about the interactions prevailing in the soilplant- atmosphere system. In this way, the objective of this study is to propose a model for fertilizer recommendation of the maize crop, based on modelling nutrient uptake, potential evapotranspiration of the crop, and the partition of nutrients in the plant, taking into account the nutrient uptake rate of each genotype in a given production system. The proposed model considers that the fertilizer recommendation should be made based on the temporal variation of the uptake rate, which should better define crop needs in relation to the classic recommendation based on the critical soil nutrient content. To validate the model an experiment is suggested to compare methodologies.