No description available.

No description available.

Dry matter production must be predicted to utilize nitrogen recommendation models for winter wheat at growth stage 30. Four methods of dry matter estimation were evaluated for their ability to predict dry matter production. The pasture probe, height, and rising plate methods did not have adequate prediction ability. The drop plate method predicted dry matter with an r² of prediction of 0.82 for all sites combined. The predictive ability for an individual site was lower. The combined model on an individual site caused a wide range of errors. Consequently, the four methods are not recommended for estimating dry matter. The changes in percent nitrogen and dry matter near growth stage 30 were measured. Dry matter increased significantly, but percent nitrogen did not vary significantly. The number of clipped samples necessary to estimate the dry matter for the five ha field studied was four samples. The number of samples needed for larger fields will depend on the variability of the dry matter in the field and on the variation inherent to the sampling technique. Adequate potassium nutrition is required for high yields of winter wheat. Current soil test levels were evaluated and found to adequately describe the crop’s need for potassium. The influence of preplant and growth stage 25 applied potassium on yield and lodging was evaluated. On the medium to high potassium test soils used, the timing of the application did not affect yields or lodging. Ethephon reduced lodging better than potassium. / Master of Science

The enhancing effect of K on alfalfa (Medicago sativa L.) yield has frequently been reported, but the nature of this influence has not been clearly shown. It was assumed that K contributed either to increased leaf expansion, thereby resulting in a larger photosynthetic surface, or to higher CO₂ assimilation rates per unit leaf area. Sand culture technique for growing plants was used in two greenhouse experiments, while field plants were grown in plots with soil differing in available K. Yield increases were consistently obtained with high K. Added K increased plant height and leaves per plant and per plot, The rate of leaf accumulation was higher as K increased. Leaf size and weight per unit area also increased, as did stomatal number and aperture. Larger epidermal cells and greater numbers per leaf were observed with high K nutrition. Percent K in plants was associated with rate of K application. Net photosynthesis rates of excised leaves increased with potassium application, but all K levels had similar light compensation points. Leaves from plants with added K had lower CO₂ compensation points, indicating higher efficiency of CO₂ assimilation. Based on these data, K appears to function both to increase the effective photosynthetic surface through greater leaf initiation and development and to increase the rate of CO₂ utilization per unit leaf area. The latter increase probably results from greater CO₂ diffusion into substomatal cavities. / Ph. D.

An incubation study was conducted to evaluate the effects of added urea, NH$ sb4$Cl, and KCl on fixation of NH$ sb4 sp{+}$ and K$ sp{+}$. A field study was carried out to observe the effects of rates and methods of added urea and KCl on the forms and distribution of N and K in soils, and on yields and nutrient uptake of silage corn. / Generally, the fixation of NH$ sb4 sp{+}$ was increased by added N but reduced by added K and vice versa. One exception was that added K increased NH$ sb4 sp{+}$ fixation when NH$ sb4$Cl was the N source. In comparison with NH$ sb4$Cl, urea resulted in greater K$ sp{+}$ fixation but less NH$ sb4 sp{+}$ fixation. / Band placement of urea and KCl showed apparent accumulation of NH$ sb4$-N and NO$ sb3$-N, and exchangeable K$ sp{+}$ in the fertilizer bands, particularly early in the growing season. On the other hand, band placement resulted in lower levels of available N and K in soil between the bands in comparison with broadcast. / Yields of silage corn and nutrient uptake values were increased by N and K fertilizers, except for one soil in the first year. Band placement of urea was superior in the case of frequent and light rainfall but inferior with dry surface soil conditions followed by a relatively large rainfall 3 or 4 days after application. In the latter condition, banding K resulted in less yields on one soil, and banding the two fertilizers together further reduced N utilization on another soil. / Additions of K suppressed Ca and Mg uptake but did not influence N uptake, whereas K uptake was usually enhanced by added N.

The effects of added potassium, K, magnesium, Mg and sulfur, S on corn grain and silage yields were investigated in the field for two years. / Due to high nutrient soil, K, Mg and S had no effects on corn grain and silage yields. However, there were trends observed in the treatment effects that were significant. Added K at 240 kg K$ sb2$O/ha increased grain yield over zero kg K$ sb2$O/ha in 1983 and Mg at 60 kg/ha increased grain yield over 30 kg/ha in 1984. In silage, 240 kg K$ sb2$O/ha increased yield over 120 and zero kg K$ sb2$O/ha in 1984. Although there was no K by Mg interaction, there was a need for added Mg to achieve higher yields. / The cumulative effect of fertilizer S at 50 kg/ha significantly reduced silage yield in 1984 over zero S treatment indicating that fertilizer S was unnecessary for corn growth by reason of high levels of soil S and sufficient S provided from precipitation and air dry deposition. S had no interaction with K and Mg because there was no need for fertilizer S to increase yields. / The antagonistic association between K and Mg was seen at the seedling, tasseling and silking stages. / There was an indication of a K by S interaction which was expressed at different stages of growth, but this effect was not evident for dry matter yields.

Complexos de caulinita intercalada com acetato de potássio estão em destaque em diversos estudos devido a sua variada aplicação na indústria. A facilidade com que ocorre o processo de intercalação do acetato de potássio na matriz da caulinita corrobora na utilização do material em muitas outras reações e produtos. Duas metodologias de intercalação foram comparadas nesse trabalho, processos mecanoquímico e por imersão. Técnicas de caracterização como Difração de Raios X de pó (DRX), Infravermelho com Transformada de Fourier (IVTF), Espectroscopia Eletrônica por Reflectância Difusa em amostras sólidas (DRUV-Vis) foram utilizadas para a verificação do material preparado. Com o intuito de obter um material possível de ser usado como um fertilizante de liberação controlada de potássio foi realizado o estudo do comportamento térmico por meio de análises térmicas de DSC/TGA/DTG e a avaliação do material após ensaio de lixiviação. Além dos métodos de intercalação, porcentagens diferentes dos reagentes foram comparadas, levando a um resultado de melhor índice de retenção antes e depois da lixiviação juntamente com a estabilidade térmica do produto de intercalação, o material obtido na metodologia de intercalação do KAc foi de 20%, em imersão em solução. / Kaolinite complexes interspersed with potassium acetate are highlighted in several studies due to its wide application in industry. The ease with which occurs intercalation process of potassium acetate kaolinite matrix from the material supports the use of many other reactions and products. Merge two procedures were compared in this work, mechanochemical reaction and the wet. Characterization techniques as X-ray powder diffraction (XRD), Fourier Transform Infrared (FTIR), Diffuse reflectance Fourier transform infrared spectroscopic on solid samples (DRUV-Vis) were used for the verification of the material prepared. In order to obtain a material can be used as a potassium fertilizer controlled release was carried out to study the thermal behavior by thermal analysis DSC / TGA / DTG and evaluation of the material after leaching test. In addition to interleaving different methods, percentages of reactants were compared, leading to a better result of the reaction rate before and after leaching along with the thermal stability of the material collating product obtained in KAc the intercalation retention at the best index was 20% by immersion in solution.

No description available.

No description available.

A técnica da aplicação da fertirrigação está ganhando aceitação, principalmente nos sistemas de irrigação por gotejamento, devido às vantagens que apresenta como a possibilidade de controlar a nutrição das plantas, como é o caso do potássio, que é um dos fertilizantes mais empregados. Porém, a descrição do transporte de água e solutos sob condições reais apresenta grande complexidade, além dos altos custos envolvidos nas pesquisas de campo. Portanto, o presente trabalho teve como objetivo desenvolver um modelo matemático para simular o deslocamento simultâneo de água e potássio no solo aplicado sob fonte pontual. O estudo foi executado em três fases: desenvolvimento do modelo, validação experimental e análise de sensibilidade. A modelagem esteve baseada na solução numérica das equações que regem o movimento de água e o transporte de solutos no solo, aplicados a partir de fonte pontiforme, permitindo assim determinar a distribuição de água e dos solutos no solo em função tanto do espaço quanto do tempo. Estas equações foram resolvidas considerando um sistema de volumes de controle, caracterizado pelas dimensões radial e vertical, asumindo que o bulbo úmido está composto por uma série de anéis concêntricos. A validação do modelo foi conduzida no Laboratório de Física de Solo e em uma estufa plástica do Departamento de Engenharia Rural da Escola Superior de Agricultura "Luiz de Queiroz", da Universidade de São Paulo, em Piracicaba. A análise de sensibilidade foi feita com respeito às variações individuais da condutividade hidráulica do solo saturado, umidade inicial e saturada do solo, dispersividade, fator de retardamento e vazão do emissor. Foi obtido um bom ajuste entre os valores simulados pelo modelo e os observados, indicando que o movimento e distribuição de água e potássio aplicados via irrigação por gotejamento podem ser modelados matematicamente a partir da solução das equações de fluxo transiente mediante o uso do método dos volumes de controle. O resultado da análise de sensibilidade revelou que o modelo, com relação à distribuição de água, é bastante sensivel à umidade de saturação e inicial do solo. A respeito da distribuição de potássio, é bastante sensível a variações negativas da condutividade hidráulica do solo saturado, vazão do gotejador e fator de retardamento do solo, e pouco sensível às variações da dispersividade do solo. / The technique of fertigation application is winning acceptance, mainly in trickle irrigation, due to the advantages that it presents as the possibility of controlling the nutrition of the plants, as the case of the potassium, that is one of the most used fertilizers. However, the description of the transport of water and solute under real conditions presents great complexity, besides the high costs involved in the field researches. Therefore, the present work had as objective develop a mathematical model to simulate the simultaneous displacement of water and potassium applied in the soil under a punctual source. The study was executed in three phases: model development, experimental validation and sensibility analysis. The modeling was based on the numeric solution of the equations that govern the movement of water and the solute transport in the soil, applied from a punctual source, allowing to determine the distribution of water and of the solute in the soil in function of the space and time. These equations were resolved considering a system of control volumes, characterized by the radial and vertical dimensions, considering that the humid bulb is composed for a series of concentric rings. The validation of the model was driven at Soil Physics Laboratory and in a plastic greenhouse of the Department of Rural Engineering of the Escola Superior de Agricultura "Luiz of Queiroz", of the São Paulo University, in Piracicaba - Brazil. The sensibility analysis was made with regard to the individual variations of the saturated soil hydraulic conductivity, initial and saturated soil humidity, dispersivity, retardation factor and emitter flow. It was obtained a good adjustment among the model simulated values and the observed ones, indicating that the movement and distribution of water and potassium applied in trickle irrigation can be modeled mathematically by the solution of the transient flow equations by using the control volumes method. The result of the sensibility analysis revealed that the model is quite sensitive to the soil saturation and initial humidity, regarding the distribution of water. Regarding the potassium distribution, it is quite sensitive to negative variations of soil saturated hydraulic conductivity, emitter flow and retardation factor of the soil, and little sensitive to the variations of the soil dispersivity.