Elio L. da Silva

Avaliação hidráulica de um sistema de irrigação localizada de baixa pressão, projetado pelo software "bubbler"

This work was done with the objective of evaluating a low-pressure irrigation system (bubbler system), under field conditions. This evaluation consisted of a study divided in two phases: in the first, the hydraulic design of the irrigation system was elaborated with the use of the software named Bubbler version 1.1; while, in the second phase the installation and the field tests were done. Volumetric tests were accomplished in each emission hose to determine: the flow variation, the coefficients of uniformity, and the application efficiency. It was established the heights of the emitter hose exit at 0.77; 0.71; 0.68 and 0.67 m, on the field, following the recommendation of the software. The tests showed a Christiansens Uniformity Coefficient (CUC) of 96.64%, a Distribution Uniformity (DU) of 95.85% and an Application Efficiency (AE) of 86.98%. The system in the field provided a medium sewage of 64.8 L h-1 against 79.2 L h-1 established by the program. The found values for sewage differed from the values designed by the software, due to variation on pipe diameters and head losses (longitudinal and local), resulting in a standard deviation of 0.23 m.

Crescimento inicial do cafeeiro irrigado com água salina e salinização do solo

The coffee crop is expanding to new areas with not enough studies about its response to saline irrigation water. The initial growth of coffee plant was evaluated, in greenhouse at the Engineering Department of the Federal University of Lavras (UFLA), under different levels of irrigation water salinity. The completely randomized design was used with 6 treatments (S0 = 0.0 dS m-1, S1 = 0.6 dS m-1, S2 = 1.2 dS m-1, S3 = 1.8 dS m-1, S4 = 2.4 dS m-1 and S5 = 3.0 dS m-1) and 4 replications. The irrigation was accomplished according to soil water retention curve and resistance block reading, restoring the soil water content to its field capacity. It was verified that water salinity affected the plants characteristics significantly. The water salinity above 1.2 dS m-1 caused damage to plant development resulting, in some cases, in death of plants. The leaf area of plant was the variable most affected by salinity of irrigation water. By the end of the experiment, the soil was classified as saline-sodic.

Variabilidade espacial de atributos físicos de um latossolo vermelho distroférrico, submetido a diferentes manejos

The study of the spatial variability of soil attributes can help in the determination of a specific management strategy that enhances agricultural productivity. The present study aimed at the evaluation of a possible influence of the soil management on spatial variability of a Dystroferric Red Latosol (Oxisol) physical properties. The study was carried out in 2002, in three adjacent areas, in Lavras, Minas Gerais state, Brazil, with the following management systems: A1 - fallowing for three years; A2 - recently planted coffee plants and A3 - area with three-year-old coffee plants. One hundred and eighty-eight grid points were sampled at distances of 1, 5 and 10 m. Disturbed soil samples were collected at each sampling point in the 0-20 cm layer to evaluate the clay, silt, and sand contents and particle density. Data were analyzed by classical statistics (Sisvar software) and geo-statistics (GeoR software). It was concluded that management and land position influenced the spatial variability of the studied attributes, and the widest range of semivariograms was found in the areas with greatest soil disturbance. On average, silt and particle density presented the largest and smallest variation coefficients, respectively.

Uso do cilindro infiltrômetro único em diferentes solos

Infiltrometer ring (IAC) has been the most used way for the soil intake rate determination, although the best result comes from the technique using no pressure head, like in rainfall simulator, for application in sprinkler irrigation. The objective of this work was the evaluation of a single ring infiltrometer (ICU) comparing its data with those from an IAC and rainfall simulator. The evaluation was done in two types of soils, Dystrophic Dusky Red Latosol and Cambisol, using an ICU with diameter of 0.20 m and 0.50 m high, with hydraulic heads varying from 0.03 m to 0.30 m with intervals of 0.03 m and three repetitions. It was used, for comparison, an IAC with diameters of 0.30 m and 0.90 m, with three replications and hydraulic heads of 0.05 m and 0.10 m. The rainfall simulator utilized had an area of 1.0 m2 with two sprinklers. It was observed that, the elevation of hydraulic head in the ICU promoted an increase in the water flow into the soil, in a polynomial model, for both soils. The IAC may underestimate or upperestimate the real values of final intake rate, depending on the soil and the hydraulic head. The soil water intake rate can be estimate, with no pressure head, using an ICU with a desired pressure since a correction factor is applied according to the soil type.

Difusividade e condutividade hidráulica não saturada de substratos

A quantificacao dos processos hidraulicos que ocorrem dentro do recipiente durante e entre irrigacoes, e essencial para a gestao eficaz da irrigacao e adubacao em substratos. Os testes foram feitos no laboratorio de hidraulica da Universidade Federal de Lavras com o objetivo de determinar a condutividade hidraulica nao saturada de substratos usando-se o metodo proposto por Bruce & Klute (1956) em seis substratos (S1, S2, S3, S4, S5 e S6) com quatro repeticoes. Foram realizados ensaios de fluxo horizontal visando estimar a difusividade e, por seu meio, a condutividade hidraulica nao saturada (K(θ)). A taxa com que a umidade avanca no espaco e no tempo ocorre de maneira diferenciada entre os substratos avaliados destacando-se os substratos S5 (casca de pinus, vermiculita e turfa) e S2 (cinza, turfa e outros materiais), que tiveram menor e maior difusividade, respectivamente. Apos o aumento da tensao ocorre uma nitida diminuicao da K(θ), especialmente no substrato S3 (casca de pinus e terra vegetal) enquanto para o substrato S5 os valores foram tao pequenos que nao se destacam dentre os demais. A condutividade hidraulica nao saturada aumenta com o aumento da umidade, de forma exponencial.