Ronaldo Souza Resende

Parametrização e avaliação do modelo DSSAT/Canegro para variedades brasileiras de cana‑de‑açúcar

The objective of this work was to parameterize and to evaluate the DSSAT/Canegro model for five Brazilian sugarcane varieties. The parameterization was done using biometric and growth data from the varieties CTC 4, CTC 7, CTC 20, RB 86‑7515, and RB 83‑5486, obtained in five Brazilian locations. Local sensitivity analysis was performed for the main parameters. Model parameterization was done using the generalized likelihood uncertainty estimation (Glue) method. The predictions were evaluated using the coefficient of determination (R²), Willmotts D‑index, and the root mean square error (RMSE) as statistical indexes. CTC varieties showed D values ranging from 0.870 to 0.944 for leaf area index, stalk height, tillering, and sucrose content. The RB 83-5486 variety showed similar results for sucrose content and fresh matter mass of stalks, whereas the RB 86-7515 variety showed values ranging from 0.665 to 0.873 for all variables analyzed.

Variação de vazão de gotejadores de fluxo normal enterrados na irrigação de café

Este trabalho teve como objetivo obter informacoes sobre o desempenho de gotejadores enterrados (irrigacao subsuperficial), quanto ao aspecto de variacao de vazao em funcao da intrusao radicular da cultura do cafe. As mudas de cafe foram irrigadas por sete modelos diferentes de gotejadores de fluxo normal, instalados a duas profundidades (15 e 30 cm da superficie do solo) e em dois niveis de deplecao de agua no solo (tratamentos umido e seco). O trabalho foi conduzido em vasos e sob ambiente controlado, utilizando mudas de cafeeiro em estagio inicial de desenvolvimento. Concluiu-se que, ate os 120 dias do inicio do experimento, nao houve modelo de emissor que se destacasse quanto a penetracao de raizes e, a partir dai, diferencas na suscetibilidade dos modelos foram observadas, podendo-se agrupar os modelos avaliados em funcao do grau de reducao de vazao. Os niveis de irrigacao nao apresentaram resultados conclusivos ate 120 dias do inicio do experimento, porem, considerando todo o periodo do experimento, observaram-se evidencias de que o sistema radicular e mais agressivo na camada mais profunda de solo (30 cm) e para o tratamento umido.

Groundwater quality for irrigation purposes in Piauí River Basin in the State of Sergipe, Brazil

Groundwater use for agricultural purposes has been intensified in the State of Sergipe, mainly in the regions with more serious water shortage from surface sources. However, irrigation is still restricted to small areas like home gardens. In part, this problem is due to lack of studies on characterization of water resources, including availability and quality of groundwaters, detecting the spatial distribution of viable sources of groundwater for different uses. The potential hazards related to soil salinity and sodicity, toxicity of specific ions for crops, and clogging of components of microirrigation systems were evaluated. Physicochemical data of water from 278 deep wells located in Piaui River Basin, in the State of Sergipe, Brazil, were used considering the FAO restriction criteria for irrigation purposes. Maps of spatial distribution of groundwater quality indicators in the watershed were prepared by ordinary kriging procedures. Groundwaters showed good quality for irrigation use, mainly in the center-downstream portion of the river basin. There was a trend in increasing the salt concentration in water from the coast to inland in the Piaui River Basin area.