Pedro Luiz Terra Lima

Cargas superficiais da fração argila de solos influenciadas pela vinhaça e fósforo

Effects of vinasse, P sorption and the interaction vinasse-phosphorus on zeta potential and point of zero charge (PZC) as well as the effects of vinasse on P sorption on clay-fraction samples from two soils were evaluated. The vinasse and P sorption influenced the surface charge of clay fraction of both soils. Sorption of P increased negative charges from soil particles reducing PZC. These effects were more pronounced when clay fraction was previously treated with vinasse. Vinasse treatment reduced P sorption, probably due to coating of P-adsorption sites and by enhancing the negative charges.

Ni-GDC Nanocomposite Material Prepared by Aqueous Based Tape Casting

In this work aqueous-based tape casting was used to produce Ni-GDC substrates. Rheological properties of the slurries were measured at room temperature. The acrylic-based suspensions showed a pseudoplastic behavior and remained stable and homogeneous. Tapes with thickness between 100 and 220 um were produced and showed smooth and homogeneous surfaces and good flexibility. Sintered tapes showed good density and porosity values.

DINÂMICA DAS CARACTERÍSTICAS QUÍMICAS DE UM SUBSTRATO FLORESTAL EXPOSTO À IRRIGAÇÃO

The quality of seedlings produced at forest nurseries is related to several factors, including irrigation and the used substrate. Both have as their purposes the production of quality seedlings in a short time period, but over-irrigation can negatively affect the substrate nutrient content. This work aimed to evaluate the chemical characteristics dynamics of a forest substrate subjected to successive irrigation at sub-irrigation tanks in two plastic tubes sizes. To this end, plastic tubes of 110 and 300 cm³ were placed, containing forest substrate without the presence of new seedlings at two sub-irrigation tanks with recirculation, one for each tube size, built at Universidade Federal de Lavras. It was set up completely randomized design with two replications, being the treatment levels 0,6, 12, 18, 24 and 30 irrigations, five per day. The substrate chemical characteristics were evaluated: pH, phosphorus, potassium, iron, zinc, manganese, copper, calcium, magnesium, aluminum, boron, sulfur, effective CEC, organic matter and electrical conductivity. Additionally, before the irrigations counted as treatment, water samples were taken to check for possible changes in the quality of irrigation recycled water after successive irrigations. The sub-irrigations provided only changes in the potassium concentration in the substrate in both tubes, and most of the chemical characteristics assessed on the substrate were unchanged as a sub-irrigation function.

VELOCITY AND KINETIC ENERGY OF RAINDROPS BY A DYNAMIC RAIN GAGE

Abstract. Knowledge of raindrop velocity is very important to calculate kinetic energy and, therefore, erosivity either by natural rains or by sprinkler irrigation systems. Several methods are used to estimate kinetic energy, being the majority, based on rain intensity. This research presents a new method able to measure the drop velocity, designated as Dynamic Rain Gage System (DRGS). Simulated rains were investigated even under windy conditions to measure the velocity of drops and their kinetic energy, at International Center of Eremology at Ghent University in Belgium. Results were compared to data obtained by a LASER disdrometer (PARSIVEL) and it can be concluded that this new method is very accurate for evaluating velocity or kinetic energy of rains. Conditions were simulated to vary rain intensity by increasing the water pressure from 1.0 to 1.5 and 2.0 bars; wind velocity set to zero and to 6.4 m/s horizontally; different vertical distance from the sprayers and positions (under sprayer and in between sprayers). These variations allowed investigating the effects of wind and rain intensity on velocity and kinetic energy of raindrops. Measurements of velocity and rain intensity at ICE wind tunnel allows concluding that the UFLA DRGS can potentially measure the drop velocity since, by turning on all directions, might better integrate the velocity vectors compared to the Parsivel LASER system. Winds such as 6.4 m s-1 can decrease the kinetic energy of rain under the sprayer and increase it under and between sprayers.

Germination and early growth of physic nut submitted to levels of salinity

Two experiments were conducted to evaluate the effect of salinity on early physic nut plant development. In the first trial, physic nut seeds were exposed to seven levels of salinity (0, 2, 4, 6, 8, 10 and 12dS m-1) with eight repetitions, using a substrate of paper soaked with solutions of CaCl2 and KCl. The treatments were evaluated based on the initial germination, total percentage of germination, and time necessary to germination of 50% of the seeds. Increased salinity reduced the first germination count and delayed the time to 50% germination. From 10dS m-1, there was a reduction in germination percentage. The second trial evaluated the effect of salinity on the growth of physic nut seeds. This trial, carried out inside a greenhouse, with a completely randomized design, was composed of five salinity treatments (0.02, 2, 4, 6 and 8dS m-1) with 5 replications. It was observed that salinity levels above 2dS m-1 affected plant development. The current study suggests that salinity management is an important factor to be considered to achieve the potential productivity of physic nut.