Luis Carlos Nogueira

Herbicidas no alto Rio Poxim, Sergipe e os riscos de contaminação dos recursos hídricos

Increased agricultural activity in watershed areas has been causing concern over contamination by herbicides in agricultural areas. The problem becomes more important when contamination can affect water for human consumption, as happens with water from the Poxim river, which supplies the city of Aracaju, capital of the State of Sergipe. The aim of this study was to evaluate the risk of contamination by herbicides to both surface and groundwater in the upper sub-basin of the Poxim River, and to detect the presence of the active ingredients Diuron and Ametrine up-river from the sugar-cane plantations. Risk analysis was carried out using criteria from the Environmental Protection Agency (EPA), the GUS index, and the GOSS method. It was observed that several active ingredients are at risk of leaching, demonstrating the importance of monitoring the river to control both the quality of water and the frequency and volume of herbicides used in the region. Based on the results, monitoring was carried out bi-monthly from July 2009 to July 2010 at two sampling points. Water samples were analyzed in the laboratory, where the presence of Diuron and Ametrine was noted. Water quality in the Sub-basin of the Rio Poxim is being influenced by the use of herbicides in the region. There was an increase in herbicide concentration in the surface water during the rainy season, possibly caused by soil runoff.

Storage of cut Heliconia bihai (L.) cv. Lobster Claw flowers at low temperatures

The postharvest conservation of cut Heliconia flowers is an important factor to the success of commercialization, especially with regard to exportation. In the present study, the maximal storage time of cut inflorescences of Heliconia bihai cv. Lobster Claw at two different temperatures (12 and 19 °C) was evaluated and compared to laboratory conditions (25 °C, control treatment). Changes in visual quality, fresh weight and bract color (L*, a* and b*) were determined. The visual quality of the inflorescences and fresh weight decreased with time in all treatments. Symptoms of chilling injury were observed on the inflorescences stored at 12 °C for six and eight days. Bract color was not affected by temperature, storage time or the senescence process. The results indicate that a temperature of 12 °C is not recommended for a storage time longer than four days, whereas 19 °C can be used for a storage time of up to eight days for cut inflorescences of H. bihai cv. Lobster Claw.

Influência de nitrogênio e potássio, via fertirrigação, em atributos do solo, níveis críticos foliares e produção do coqueiro-anão

Irrigated plantations of dwarf coconut for the production of coconut water have expanded considerably in Brazil. Higher yields obtained under irrigation affect the amount of N and K required by dwarf coconut, influencing the relationships between yield and soil and leaf contents of these nutrients. An experiment was set up on an Ultissol in the Brazilian Northeast coastal tablelands, following a Pan Puebla III experimental matrix in a randomized block design. Ten combinations of urea and potassium chloride were weekly injected during 52 months. Soil samples were collected in the irrigated area and leaf samples taken from the leaves 9 and 14. Soil pH, Ca and Mg contents decreased as urea doses increased. The highest electrical conductivity value was 0.65 dS m-1 in the 0_5 cm layer and it decreased with depth. Correlation coefficients between leaf K and soil K in the layers 0_5, 0_20 and 20_40 cm were very similar, indicating that layer 0_20 cm can be sampled for fertility purposes in irrigated coconut. Highest fruit weight and coconut water volume were obtained with the lowest N level, due to the lower number of nuts per tree. Nitrogen and K combinations did not influence the coconut water pH, but increased coconut water brix. The K content in the coconut water increased along the K doses; leaf K and K in the coconut water were directly related. Nitrogen and K critical levels for leaves 9 and 14 were 19.2 and 20.5 g kg-1 and 12.1 and 9.4 g kg-1, respectively. The critical level of soil K by Mehlich-1 in the 0-20 cm layer was 45 mg dm-3.

Condutividade hidráulica saturada em um solo aluvial do perímetro irrigado de São Gonçalo, PB

Field tests were carried out to characterize spatial variability of saturated hydraulic conductivity (K0) in an alluvial soil at Embrapa-cotton Experimental Station, in Sao Goncalo, Paraiba, Brazil. In an 18 ha area nineteen measurements of saturated K0 were taken within 1.0 and 1.65 m depth in the soil profile, as most of the drainage systems in the irrigated areas of the Northeast Brazilian region are installed in this depth interval. Measured K0 values varied from 0.02 to 1.71 m d-1, agreeing with other results commonly obtained for alluvial soils. The observed K0 variability results from natural soil development process, its genesis and geomorphologic complexity.