Com o grande aumento da população mundial, maior demanda por alimentos e de áreas cultiváveis é necessário uma maior eficiência da agricultura. Dentro deste cenário, um material que libere nutrientes de forma lenta/controlada em níveis necessários para a nutrição da planta garantiria o desenvolvimento da cultura sem carecer de várias aplicações do fertilizante. O aumento da eficiência do fertilizante, a redução da toxicidade no solo pelo uso de biopolímero e a diminuição dos efeitos negativos associados à sobredosagem são algumas das vantagens de materiais de liberação lenta/controlada. O objetivo principal do presente estudo foi a preparação, caracterização e aplicação de estruturas biopolímericas na liberação lenta/controlada de fertilizantes (fertiliberadores) em solo. A motivação principal esteve no preparo de estruturas de quitosana aditada com nutrientes, utilizando a técnica de secagem por atomização (spray drying), e a avaliação da aplicação em solo. O acompanhamento in situ da liberação do nutriente foi feito pela técnica de reflectometria no domínio do tempo (TDR), que monitora a movimentação iônica em sistemas particulados, como é o caso do solo. As estruturas foram preparadas por spray drying, utilizando bico atomizador de duplo fluido ou 2-fluid nozzle (2FN) para o preparo de esferas tipo matricial e, triplo fluido ou 3-fluid nozzle (3FN) para obter cápsulas tipo reservatório (casca-núcleo). As condições e parâmetros de processo em função das características químicas e físicas dos materiais obtidos foram objetos de estudo. As partículas obtidas com sucesso apresentaram diâmetro médio entre 10 e 35 µm, apresentando um retardo na liberação de nutriente em relação ao fertilizante convencional, de 100% para 40 - 60% nas primeiras leituras de teor de potássio durante ensaio de liberação. É importante destacar que o uso da técnica da TDR no monitoramento in situ da liberação do nutriente é inovador na área de materiais aplicados à agricultura e forneceu informações de forma rápida e precisa sobre a eficiência do material no solo. Adicionalmente, foi estudada a relação do tipo de estrutura produzida (cápsula ou esfera) com o mecanismo de liberação em solo e em água. A estrutura casca- núcleo mostrou ser de grande interesse para produzir materiais de liberação controlada de fertilizante. / The large growth in world population and the greater necessity of food and cultivable areas demand an increase on agricultural efficiency. In this scenario, a material which releases nutrientat slowly/controlled levels for plant nutrition would ensure the development of the crop without the multiple fertilizer applications. Some of the advantages of slow/controlled release material are the increase of fertilizer efficiency use, reduce toxicity in soil by use of biopolymer and decrease the negative effects associated with over dosing.The main purpose was the preparation, characterization and application of biopolymers structures in slow/controlled release fertilizer (ferti releasers) in soil. The main motivation of this work was to obtain structures of chitosan and nutrients using the spray drying method. Also, the application and in situ soil monitoring of the nutrient release by time domain reflectometry technique (TDR) was considered. TDR measures the electromagnetic ion movement in particulate systems such as the soil. The structures were prepared by spray drying technique. It was used 2-fluid nozzle (2FN) to prepare sphere or sponge balls structures and 3-fluid nozzle (3FN) to obtain capsule or core-shell structures. Both types of structure were studied. The conditions and process parameters were also studied as a function of chemical and physical characteristics of the materials. The obtained particles had a mean diameter between 10 and 35 µm and it was observed a nutrient release delay in comparison with conventional fertilizer, from 100% to 40 - 60% in the first potassium measurements during the releasing assay. It is noteworthy the use of TDR technique to monitor the in situ nutrient release in the soil is innovative in the area of materials applied to agriculture and it provided information quickly and accurately about material efficiency in the soil, from short to long period. Additionally, it was studied the relationship of the produced structure (capsule or sphere) with the release mechanism in soil and water. The shell-core structure has shown to be of great interest for producing controlled release fertilizer materials.

Com o grande aumento da população mundial, maior demanda por alimentos e de áreas cultiváveis é necessário uma maior eficiência da agricultura. Dentro deste cenário, um material que libere nutrientes de forma lenta/controlada em níveis necessários para a nutrição da planta garantiria o desenvolvimento da cultura sem carecer de várias aplicações do fertilizante. O aumento da eficiência do fertilizante, a redução da toxicidade no solo pelo uso de biopolímero e a diminuição dos efeitos negativos associados à sobredosagem são algumas das vantagens de materiais de liberação lenta/controlada. O objetivo principal do presente estudo foi a preparação, caracterização e aplicação de estruturas biopolímericas na liberação lenta/controlada de fertilizantes (fertiliberadores) em solo. A motivação principal esteve no preparo de estruturas de quitosana aditada com nutrientes, utilizando a técnica de secagem por atomização (spray drying), e a avaliação da aplicação em solo. O acompanhamento in situ da liberação do nutriente foi feito pela técnica de reflectometria no domínio do tempo (TDR), que monitora a movimentação iônica em sistemas particulados, como é o caso do solo. As estruturas foram preparadas por spray drying, utilizando bico atomizador de duplo fluido ou 2-fluid nozzle (2FN) para o preparo de esferas tipo matricial e, triplo fluido ou 3-fluid nozzle (3FN) para obter cápsulas tipo reservatório (casca-núcleo). As condições e parâmetros de processo em função das características químicas e físicas dos materiais obtidos foram objetos de estudo. As partículas obtidas com sucesso apresentaram diâmetro médio entre 10 e 35 µm, apresentando um retardo na liberação de nutriente em relação ao fertilizante convencional, de 100% para 40 - 60% nas primeiras leituras de teor de potássio durante ensaio de liberação. É importante destacar que o uso da técnica da TDR no monitoramento in situ da liberação do nutriente é inovador na área de materiais aplicados à agricultura e forneceu informações de forma rápida e precisa sobre a eficiência do material no solo. Adicionalmente, foi estudada a relação do tipo de estrutura produzida (cápsula ou esfera) com o mecanismo de liberação em solo e em água. A estrutura casca- núcleo mostrou ser de grande interesse para produzir materiais de liberação controlada de fertilizante. / The large growth in world population and the greater necessity of food and cultivable areas demand an increase on agricultural efficiency. In this scenario, a material which releases nutrientat slowly/controlled levels for plant nutrition would ensure the development of the crop without the multiple fertilizer applications. Some of the advantages of slow/controlled release material are the increase of fertilizer efficiency use, reduce toxicity in soil by use of biopolymer and decrease the negative effects associated with over dosing.The main purpose was the preparation, characterization and application of biopolymers structures in slow/controlled release fertilizer (ferti releasers) in soil. The main motivation of this work was to obtain structures of chitosan and nutrients using the spray drying method. Also, the application and in situ soil monitoring of the nutrient release by time domain reflectometry technique (TDR) was considered. TDR measures the electromagnetic ion movement in particulate systems such as the soil. The structures were prepared by spray drying technique. It was used 2-fluid nozzle (2FN) to prepare sphere or sponge balls structures and 3-fluid nozzle (3FN) to obtain capsule or core-shell structures. Both types of structure were studied. The conditions and process parameters were also studied as a function of chemical and physical characteristics of the materials. The obtained particles had a mean diameter between 10 and 35 µm and it was observed a nutrient release delay in comparison with conventional fertilizer, from 100% to 40 - 60% in the first potassium measurements during the releasing assay. It is noteworthy the use of TDR technique to monitor the in situ nutrient release in the soil is innovative in the area of materials applied to agriculture and it provided information quickly and accurately about material efficiency in the soil, from short to long period. Additionally, it was studied the relationship of the produced structure (capsule or sphere) with the release mechanism in soil and water. The shell-core structure has shown to be of great interest for producing controlled release fertilizer materials.

Doctor of Philosophy / Department of Horticulture and Natural Resources / Dale J. Bremer / Turfgrasses sequester and emit carbon dioxide, and emit nitrous oxide (N₂O) when fertilized with nitrogen and irrigated. Future water availability is a serious issue and drought restrictions may be imposed on turf managers while turf areas are subjected to traffic stress. My objectives in Chapter 2 were to: 1) quantify the magnitude and patterns of N₂O emissions and carbon (C) sequestration in zoysiagrass (Zoysia japonica Steud.); and 2) determine how irrigation (66% and 33% reference evapotranspiration [ET₀] replacement) and fertilization (polymer-coated urea, urea, and unfertilized) management may reduce N₂O emissions and enhance carbon sequestration. My objectives in Chapters 3 and 4 were to evaluate above- and below-ground responses of cool-season (C3) [Kentucky bluegrass (Poa pratensis L.) and perennial ryegrass (Lolium perenne L.)] and warm-season (C4) grasses {buffalograss [Buchloe dactyloides (Nutt.) Engelm] and zoysiagrass] at golf course-related mowing heights [1.6-cm (fairway) and 6.4-cm (rough)], with and without traffic during a simulated drought and subsequent recovery period (without traffic). In Chapter 2, N₂O emissions increased by 6.3% with more irrigation during summers and increased from 4.06 kg ha⁻¹ in unfertilized turf to 4.50, and 5.62 kg ha⁻¹ in polymer-coated urea and urea treated turf, respectively, during the 2-year study. There was no difference in C sequestration rates between a high vs. low input management schedule. The C sequestration rate was 0.952 Mg C ha⁻¹ yr⁻¹ for zoysiagrass when averaged across management schedules and depths. The use of a controlled-release fertilizer such as PCU compared to the use of a quick-release fertilizer and/or lower irrigation will reduce N₂O emissions in turfgrass. In Chapters 3 and 4, the better drought tolerance of C4 grasses led to more differences between traffic treatments within C4 than C3 grasses, but C4 grasses maintained the highest quality and green cover. Quality at rough- compared to fairway-height was more impacted by traffic. Decreasing soil moisture due to drought led to a minimal impact from traffic on soil bulk density, soil penetration resistance (SPR), and root measurements. During drought, SPR at deeper soil depths and fairway plots increased and exceeded the critical value of 2.0 MPa. Both C4 grasses and perennial ryegrass had larger root diameters, which may have led to better soil compaction resistance. Traffic during drought will have a negative and accelerated impacts above-ground, but minimal impact below-ground, which will vary with turf species and mowing height.

No description available.

No description available.

Sustainable landscaping includes utilization of plants requiring few inputs. We chose four species showing potential for use in arid landscapes: Purshia mexicana, Shepherdia argentea, Shepherdia rotundifolia, and Alnus maritima. We sowed seeds of S. rotundifolia, S. argentea and P. mexicana in three substrates with various water-holding properties due to differing amounts of organic matter (OM). S. rotundifolia germination was maximized in a calcined clay (66.2%) containing no OM and had low germination (12.7 - 21.8%) in the other substrates. S. argentea germination (42.3 to 53.7%) was similar in all substrates. Poor seed quality of P. mexicana resulted in inconclusive results. Our results suggest that germination of some species is enhanced by substrates with excellent drainage properties. We also investigated effects of different rates of controlled-release fertilizer (CRF) on symbiotic nodule formation in seaside alder. We found that lower than prescribed rates of CRF enhanced nodulation without compromising nitrogen status.

Submitted by Gabriela Lopes (gmachadolopesufpel@gmail.com) on 2017-03-09T15:58:23Z No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Dissertação _Thaís Antolini Veçozzi (para impressão).pdf: 2198036 bytes, checksum: 0b6a9f3bfafdc322a425a6d9fd27a705 (MD5) / Approved for entry into archive by Aline Batista (alinehb.ufpel@gmail.com) on 2017-03-10T19:34:35Z (GMT) No. of bitstreams: 2 Dissertação _Thaís Antolini Veçozzi (para impressão).pdf: 2198036 bytes, checksum: 0b6a9f3bfafdc322a425a6d9fd27a705 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Made available in DSpace on 2017-03-10T19:34:35Z (GMT). No. of bitstreams: 2 Dissertação _Thaís Antolini Veçozzi (para impressão).pdf: 2198036 bytes, checksum: 0b6a9f3bfafdc322a425a6d9fd27a705 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Previous issue date: 2015-05-13 / Fundação de Amparo à Pesquisa do Estado do Rio Grande do Sul - FAPERGS / A eficiência dos fertilizantes nitrogenados utilizados no cultivo de arroz é baixa, reflexo da susceptibilidade do N a perdas no sistema solo-planta, destacando aquelas originadas da produção de óxido nitroso (N2O). O N2O, juntamente com o metano (CH4) e o dióxido de carbono (CO2), são os principais gases de efeito estufa e suas emissões para a atmosfera são apontadas como a principal causa das mudanças climáticas globais. No Brasil, grande parte da emissão desses gases advém da agricultura e do desmatamento, caracterizando estas atividades como potenciais para reduzir suas emissões. Os fertilizantes nitrogenados de liberação controlada (FLC) são utilizados visando aumentar o aproveitamento de N, em função de sua propriedade de liberar gradativamente o nutriente ao solo. Este trabalho buscou avaliar a eficiência agronômica de fertilizante de liberação controlada e seus efeitos nas emissões de CH4 e N2O no arroz irrigado. O Estudo 1 foi realizado através de um experimento delineado em blocos casualizados, com quatro repetições, em casa de vegetação e composto pelos tratamentos: T1: testemunha sem aplicação de N; T2: ureia aplicada de acordo com a recomendação para a cultura; T3: ureia incorporada; T4: FLC 1; T5: FLC 2. Foram analisadas as concentrações de NH4+e NO3- na solução do solo ao longo do alagamento do solo e o N mineral das plantas. O Estudo 2 foi realizado em condições de campo, com três repetições e os tratamentos: T0: testemunha sem a aplicação de N; T1: ureia aplicada de acordo com a recomendação; T2: FLC em cobertura na semeadura; T3: FLC no sulco de plantio. Foram avaliadas as emissões de CH4 e N2O, o Potencial de Aquecimento Global parcial (PAGp), as concentrações de compostos minerais na solução do solo ao longo do período de alagamento, a eficiência dos fertilizantes e o rendimento de grãos. De acordo com os resultados, a solubilização dos fertilizantes de liberação controlada ocorreu mais rapidamente do que o esperado, não ultrapassando 23 dias de alagamento. A eficiência agronômica no uso de N foi de 17,20 kg kg-1 para o tratamento com uréia, 13,55 kg kg-1 no tratamento com FLC em superfície e 11,51 kg kg-1 para o FLC aplicado incorporado ao solo, resultados que não mostraram diferença estatística. A emissão de CH4 não foi influenciada pelas fontes e formas de aplicação de N. A emissão total de N2O foi de 0,44 kg/ha no tratamento sem N, de 1,09 kg/ha no tratamento com ureia, 2,09 kg/ha no tratamento com FLC em superfície e de 2,94 kg/ha no tratamento com FLC incorporado ao solo. O potencial de aquecimento global parcial não foi afetado pelo manejo da adubação nitrogenada. A aplicação de FLC não tem potencial para reduzir as emissões de CH4 e N2O do solo cultivado com arroz irrigado. O uso de FLC no arroz irrigado não eleva o rendimento de grãos. As contradições e variações observadas nos estudos com fertilizantes de liberação controlada demostram a necessidade de pesquisas amplas que avaliem seu comportamento no solo e a rentabilidade econômica. / Nitrogen use efficiency of the fertilizers used is low, as a result of its loss susceptibility in plant-soil system, highlighting among these those originated of the production of N2O. N2O, along with methane (CH4) and carbon dioxide (CO2) are the main greenhouse gases and these gases emissions to the atmosphere are seen as the main cause of possible climate change. In Brazil, much of the greenhouse gas emissions comes from agriculture and deforestation, featuring such activities as potential to reduce air pollution. Controlled-release nitrogen fertilizers (CRF) are used to increase the use of N by plants, due to its property to gradually release nutrients to the soil. This study aimed to evaluate the controlled release fertilizer agronomic efficiency and its effects on CH4 and N2O emissions in irrigated rice cultivation. Study 1 was conducted through an experiment in randomized block design with four replications, conducted in a greenhouse and composed for the treatments: T1: control without N fertilization; T2: application of urea according to Southern Brazil recommendation; T3: all dose of urea incorporated; T4: CRF 1; T5: CRF 2. NH4 + and NO3 - concentration were analyzed in the soil solution along the soil flooding and mineral N in plant aerial part. Study 2 was conducted by experiment under field conditions, with three replications and the treatments: T0: control without N application; T1: urea applied in according with the recommendation; T2: CRF in coverage at sowing; T3: CRF in the furrow. Were evaluated CH4 and N2O emissions along the cultivation, Global Warming Potential partial (GWPp), concentrations of mineral compounds in the soil solution along the soil flooding, efficiency of fertilizers and grain yield. According to the results, the solubilization of the controlled release fertilizer is occurs more faster than expected, not exceeding 23 days flooding. The agronomic N use efficiency was 17,20 kg kg -1 for treatment with urea, 13,55 kg kg-1 in the treatment with CRF in coverage at sowing and 11,51 kg kg-1 for CRF in the furrow, results statistically not difference. The CH4 emission was not influenced by sources and N forms of application. The N2O emission total was 0,44 kg/ha treatment without N, 1,09 kg/ha of treatment with urea, 2,09 kg/ha of treatment with CRF in coverage at sowing and 2,94 kg/ha on treatment with CRF in the furrow. Global Warming Potential partial was not affected by nitrogen fertilization management. The application of CRF has no potential to reduce CH4 and N2O emissions in soil cultivated with rice. The use of CRF in the rice does not increase the yield. Contraventions and variations observed in studies with controlled-release fertilizers demonstrate the need for extensive research to assess the behavior in soil and the economic profitability of these products.

Plants require N to complete their life cycle. Without adequate concentration of N, crops will not produce their potential yields. For turfgrass systems, N fertilizer application allows for the maintenance of functional, aesthetic, and recreational properties. However, fertilizer mismanagement is common and leads to N pollution in the environment. Controlled-release and slow-release fertilizers can enhance nitrogen (N)-use efficiency, reduce N pollution, minimize the need for repeated fertilizer applications, and reduce turfgrass shoot growth and associated costs. In order to evaluate the effectiveness of these fertilizers in the Intermountain West, research is needed. The timing of N release was evaluated for seven urea fertilizers: uncoated, sulfur coated (SCU), polymer-sulfur coated (PSCU), and four polymer-coated (PCU) with release timings of 45, 75, 120, and 180 d estimated release. These products were placed on bare soil, a Kentucky bluegrass (Poa pratensis L.) thatch layer, and incorporated into soil. These three placement treatments were replicated to allow for enough samples to be placed in two locations. The first was outside in a field to represent field conditions with diurnal fluctuating temperatures and the second was placed in a storage facility to replicate laboratory conditions with static diurnal temperatures. The PCU prills incorporated into soil under field conditions generally released N over the estimated release period. However, when applied to bare soil or thatch, N from PCU had 80% or greater N release by 35 d after application regardless of expected release time. Fertilizers under laboratory conditions had minimal N release despite having similar average daily temperatures, suggesting that fluctuating temperatures impact N release. The PSCU and SCU treatments were no different from uncoated urea, showing no slow release properties for this particular product. Spring-applied N fertilizer trials were conducted over two years to determine the optimal N rate for Kentucky bluegrass. Similar PCU120 products were applied at 50, 75, and 100% of the recommended full rate, while also being compared to an unfertilized control and urea applied either all at once or split monthly. Spring-applied PCU showed minimal initial N response while urea applied all at once resulted in an initial spike of N uptake. Once PCU began to release N, there was minimal difference for all rates compared to urea split monthly for biomass growth, verdure, and shoot tissue N. Although at the 50% rate, there were a few sampling dates with slower growth and lower verdure. The decrease in verdure at this low rate was slight, and it is recommended that PCU could be applied effectively at a reduced rate between 50 and 75%. Although for better results, additional quick release N is required to compensate for early season lag in N release.

Fertilizantes de liberação controlada como a ureia revestida com polímeros podem propiciar melhor sincronia entre a disponibilidade de nitrogênio (N) no solo e as exigências do nutriente pela cultura de milho (Zea mays L.). Para avaliar o efeito de diferentes estratégias de uso da ureia revestida com polímeros na disponibilização de nitrogênio inorgânico, nitrato (NO3-) e amônio (NH4+) no solo durante o ciclo da cultura de milho, e na produtividade final de grãos, foram conduzidos experimentos na safra 2012/2013, em duas condições edafoclimáticas no município de Piracicaba, Estado de São Paulo. Os solos dos experimentos foram: Latossolo Vermelho Distrófico (LVd) e Latossolo Vermelho Amarelo Distrófico (LVAd). O delineamento experimental foi de blocos completos ao acaso com quatro repetições e os tratamentos constaram da aplicação da dose de 180 kg ha-1 de N, utilizando-se duas fontes de N, ureia revestida com polímeros e ureia convencional, aplicadas, respectivamente, nas proporções de 100:0, 90:10, 80:20, 70:30, 60:40, 50:50 e 0:100%, além de um tratamento com ureia em manejo convencional com aplicação parcelada (20% na semeadura e 80% em cobertura entre os estádios V4-V6), e o controle sem aplicação de N. Foi semeado híbrido de milho com elevado potencial de produtividade. Os fertilizantes aplicados na semeadura foram incorporados a 5 cm de profundidade e 10 cm ao lado da linha de milho. Para determinar o teor de nitrogênio inorgânico no solo, nas camadas de 0-0,1, 0,1-0,2, 0,2-0,4 e 0,4-0,6 m, foram realizadas amostragens na semeadura e em V4, V12 e R3 no LVd e na semeadura e em V6, V14 e R4 no LVAd. Produtividade de grãos, massa seca da parte aérea, acúmulo de N na parte aérea, exportação de N nos grãos, e a eficiência de utilização interna de nitrogênio foram avaliados na maturidade fisiológica da cultura. Os resultados foram submetidos à análise de variância e quando observado efeito significativo de tratamentos, foram realizadas análises de contraste de médias (p<=0,1). A produtividade máxima nos dois experimentos foi da ordem de 10 Mg ha-1 de grãos de milho. Nos dois experimentos a ureia revestida com polímeros disponibilizou nitrogênio mineral no solo ao longo de todo o ciclo da cultura de milho, o que resultou no LVAd em produtividade de grãos mais elevada em relação à utilização de ureia convencional, diferentemente do ocorrido no LVd, onde não foram observados efeitos de tratamentos. A utilização de misturas de URP e U na adubação da cultura do milho, com proporções variando de 100% a 50% da fonte de liberação controlada, mostrou-se eficiente e pode ser considerada uma estratégia que fornece N conforme a exigência da cultura, o que resulta em maior produtividade de grãos em condições edafoclimáticas favoráveis. / Controlled release fertilizers such polymer coated urea can provide better synchrony between nitrogen (N) availability in the soil and its requirements by maize (Zea mays L.). To evaluate the effect of different use strategies of polymer coated urea on the availability of inorganic nitrogen, nitrate (NO3-) and ammonium (NH4+) throughout the crop cycle, and the grain yield, field experiments were carried out in the 2012-2013 growing season, in two soil-climatic conditions, in Piracicaba, São Paulo State. The soils were a clayey and a sandy Oxisol. The experimental design was randomized blocks with four replications, and the treatments consisted of 180 kg N ha-1, using two sources of N, polymer coated urea and conventional urea, respectively, in proportions of 100:0, 90:10, 80:20, 70:30, 60:40, 50:50% and 0:100%, besides a treatment with urea in conventional management, split-applied (20% at seeding and 80% side-dressed in V4-V6 corn growth stage) and a control (without N). Maize hybrid with high productivity potential was used. The fertilizers applied at seeding were placed in bands 5 cm depth and 10 cm aside the corn row. To determine the inorganic nitrogen content in the soil at 0-0.1, 0.1-0.2, 0.2-0.4 and 0.4-0.6 m soil layers, samples were collected at seeding, V4, V12 and R3 corn growth stage in the clayey Oxisol, and at sedding, V6, V14 and R4 in the sandy Oxisol. Grain yield, aerial biomass, nitrogen uptake by the aerial biomass, grain nitrogen uptake and internal utilization efficiency of nitrogen were evaluated. Data were analyzed using analysis of variance and when differences were detected, means where separated using contrast test (p<=0.1). The maximum maize grain yield in the experiments was approximately 10 Mg ha-1. In the two experiments, polymer coated urea led to a greater inorganic nitrogen availability throughout the maize cycle, which resulted in higher yield comparing to the use of conventional urea in the sandy Oxisol, not thus in the clayey Oxisol, where no effects of treatments in grain yield were observed. The use of blends of polymer coated urea and conventional urea in maize fertilization, with ratios ranging from 100 to 50% of the controlled release source, was efficient and can be considered a strategy that supplies N as the crop demands it, and thus lead to a greater maize grain yield under agro-climatic favorable conditions.

Misturas de ureia (U) e ureia revestida com enxofre e polímero (URP) podem ser uma alternativa para melhorar a eficiência de utilização de nitrogênio (EUN) e reduzir custos quando aplicadas de uma única vez em cultivos agrícolas. Em experimentos de campo foram investigados diferentes índices de EUN (eficiência de recuperação aparente (ERA), eficiêncica fisiológica (EF), eficiência de utilização interna (EUI), eficiência agronômica (EA) e fator parcial (FPP) do N aplicado) e o acúmulo e particionamento de macronutrientes no milho (Zea mays L.) com misturas de U e URP na dose de 180 kg ha-1 aplicados totalmente na semeadura em Latossolo Vermelho Amarelo distrófico (LVAd) e Latossolo Vermelho distrófico (LVd). Foi incluído tratamento com ureia em manejo convencional (UMC). As misturas de URP+U foram incorporadas em faixa, 5 cm abaixo e 10 cm ao lado da linha de semeadura. As plantas foram amostradas em quatro estádios e divididas em quatro frações da planta (partes da planta) para a determinação de nutrientes. No LVAd, tratamentos com 100%URP, 70%URP+30%U e 60%URP+40%U apresentaram maior produtividade que o tratamento controle; 100%U e UMC tiveram menor EF e EUI que o 100%URP; todos os tratamentos com N apresentaram maior acúmulo total de N e massa seca que o controle em R6; a proporção de 70%URP+30%U apresentou maior acúmulo de S total do que o controle e UMC em R6. Não foram verificadas diferenças entre os tratamentos para produtividade, índices de EUN e acúmulo total de nutrientes no LVd. Em experimentos em casa de vegetação foram avaliados a condutividade elétrica (CE) e o pH do solo, altura, diâmetro, massa seca e acúmulo de N no desenvolvimento inicial de plantas de milho usando a mistura de 70%URP+30%U aplicada em faixa na semeadura do milho, das seguintes maneiras: 1) aplicando-se uma dose equivalente a 180 kg ha-1 de N em diferentes posições (5, 10 e 15 cm abaixo e 0, 5 e 10 cm ao lado da linha de semeadura) em um Latossolo Vermelho eutrófico (LVe) e comparando com 100%U; 2) variando as doses de N (equivalente a 0, 90, 180, 360 e 540 kg ha-1 de N) em uma posição considerada adequada (15 cm abaixo e 10 cm ao lado da linha de semeadura) no LVe e no LVAd. As aplicações feitas 15 cm abaixo da linha de semeadura apresentaram maior CE na linha do fertilizante na camada 9-18cm, pH na linha do fertilizante, massa seca total e N total que 5 e 10 cm. 70%URP+30%U apresentou maior altura, massa seca total e N total que 100%U quando aplicados abaixo da linha de semeadura. Nas aplicações 10 cm ao lado da linha de semeadura observou-se menor CE na linha do fertilizante comparado com as de 0 cm. No LVAd, massa seca total e N total apresentaram comportamento quadrático em resposta ao aumento da dose de N. Misturas de U e URP são eficientes quando aplicadas na semeadura do milho e elevadas doses interferem no desenvolvimento inicial de plantas de milho mesmo em uma posição considerada adequada no LVAd. / Blends of urea (U) and polymer sulfur coated urea (PSCU) can be an alternative to improve nitrogen (N) use efficiency (NUE) and reduce costs when applied in a single application in agricultural crops. Different indices of NUE (apparent crop recovery applied N (RE), physiological efficiency of applied N (PE), internal utilization efficiency of N (IE), agronomic efficiency of applied N (AE), partial factor productivity of applied N (PFP)) were investigated in field experiments, as well as nutrient uptake and partitioning in corn (Zea mays L.) with blends of U and PSCU applied in a single application of 180 kg N ha-1 at sowing in a Typic Haplustox and Rhodic Haplustox. It was included a treatment with urea in conventional management (UCM). The blends of U and PSCU were incorporated in a band 5 cm below and 10 cm to the side of the seed row. Plants were sampled at four growth stages and divided into four fractions for nutrient determination. In the Typic Haplustox, treatments with 100%PSCU, 70%PSCU+30%U and 60%PSCU+40%U had higher grain yield than control treatment (without N application); treatments with 100%U and UCM had lesser PE and IE than 100%PSCU; all the N treatments had higher total biomass and total N uptake than control at physiological maturity (R6); treatment with 70%PSCU+30%U had higher total S uptake than control and UCM at R6. There weren\'t differences between treatments for grain yield, indices of NUE, and total nutrient uptake at R6 in the Rhodic Haplustox. In greenhouse experiments, electrical conductivity (EC) and pH of soil, height, diameter, dry weight and nitrogen uptake in early plant growth were evaluated using a blend of 70%PSCU+30%U applied in a band at sowing maize in the following ways: 1) applying a rate equivalent to 180 kg N ha-1 in different positions (5 , 10 and 15 cm below and 0, 5 and 10 cm to the side of the seed) in a Rhodic Eutrustox and comparing with 100%U; 2) varying rates (equivalent to 0, 90, 180, 360, 540 kg N ha-1) in a position considered adequate (15 cm below and 10 cm to the side of the seed) in a Rhodic Eutrustox and Typic Haplustox. The N fertilizer application 15 cm below of the seed had higher EC in fertilizer row at 9-18cm, pH in fertilizer row, total dry weight and total N uptake than 5 and 10 cm below of the seed. The treatment with 70%PSCU+30%U had higher height, total dry weight and total N uptake than 100%U in the application 0 cm to the side of the seed. The N fertilizer application 10 cm to the side of seed had lesser EC in the fertilizer row than 0 cm. In the Typic Haplustox, total dry weight and total N uptake had quadratic behavior in response to increase N rates. Blends of U and PSCU are efficient when applied at corn sowing and can affect early plant growth at high rates even in a position considered adequate in Typic Haplustox.