Time filter

Source Type

de Sousa K.A.,Programa de Pos Graduacao em Ciencias Agrarias | Resende O.,Instituto Federal Goiano campus | Chaves T.H.,Curso de Agronomia do IF Goiano campus | Costa L.M.,Pos Graduacao em Ciencias Agrarias
Revista Ciencia Agronomica | Year: 2011

A study aimed at determining the best mathematical model to describe the drying of forage-turnip seeds, along with the diffusion coefficient and activation energy under different air-conditions, was carried out in a randomized design with four replications. Seeds were harvested, having a moisture content of 0.36 (decimal bs) and then dried to 0.09 (decimal bs) in an experimental dryer at controlled temperatures of 30; 40; 50; 60 and 70 °C and relative humidities of 47.3; 26.2; 12.0; 10.1 and 5.1%, respectively. The effective coefficient of diffusion was calculated by F-test variance analysis and regression, adopting a 5% level of probability. The conclusion was reached that among the models analyzed, that of Midilli best fit the drying curves of forage-turnip seeds. The effective diffusion coefficient increases with temperature, with values of between 3.23 x 10-11 and 10.42 x 10-11 m2 s-1 for a temperature range of from 30 to 70 °C. The relationship between the coefficient of diffusion and drying temperature can be described by the Arrhenius equation which gives an activation energy of 24.78 kJ mol-1 for liquid diffusion in the drying process of forage-turnip seeds.

Sangoi L.,Santa Catarina State University | Schmitt A.,Programa de Pos Graduacao em Ciencias Agrarias | Vieira J.,Programa de Pos Graduacao em Ciencias Agrarias | Vargas V.P.,Programa de Pos Graduacao em Ciencias Agrarias | And 2 more authors.
Ciencia Rural | Year: 2012

Historically, tillers have been considered detrimental to maize because they do not produce ears and may act as sinks competing for carbohydrates with the main stem. This work was carried out aiming to evaluate the effect of tiller removal on maize grain yield at different sowing dates. The experiment was set during the 2006/07 and 2008/09 growing seasons. A randomized complete block design disposed in split-plots was used. Two sowing dates were tested in the main plots: second half of October (recommended) and second half of December (late). Four tiller's fates were evaluated in the split-plots: tiller removal when the main stem had six expanded leaves (V6), nine expanded leaves (V9), fifteen expanded leaves (V15) and tiller maintenance until harvesting. Hybrid P30F53 was sowed at 55,000 plants ha-1, with a row spacing of 0.7m. The percentage of plants with tillers and the number of tillers per plant were higher when maize was sown in October than in December. There was no grain yield difference between treatments where tillers were preserved and those where they were removed at V6, V9 or V15, regardless of sowing date. Such behavior demonstrates that tillers are not sinks that compromise maize agronomic performance. Furthermore, tillers may contribute positively to grain yield when maize is sown in October.

Coelho C.M.M.,Santa Catarina State University | Souza C.A.,CAV | Zilio M.,Programa de Pos Graduacao em Ciencias Agrarias | Michels A.F.,Programa de Pos Graduacao em Ciencias Agrarias
Semina:Ciencias Agrarias | Year: 2012

An early harvest reduces the time that the seeds stay in the field under the effect of biotic and abiotic factors, which are responsible for their deterioration. So, the objective of this work was to determine the effect of pre-harvest desiccant application on the yield and physiological quality of common bean seeds. The experimental layout was completely random, the desiccant used was paraquat (400 g ha-1 a.i.), on a combination of three genotypes: 'BAF55', 'BAF84' and 'BAF112' (commercial black cv. IPR88-Uirapurú) with three plant desiccation periods (26, 30, 34 days after flowering (DAF)), and a control (plants not desiccated). Post-harvest, productivity was estimated and, soon after, germination tests were carried out with and without accelerated ageing; main root radical length and hypocotyls length were measured as well as electrical conductivity. The desiccation maintenance the cell membrane integrity in the 'BAF112' and 'BAF55' genotypes when the paraquat was sprayed at 26 DAF. The results showed that the two landrace beans genotypes outperformed the commercial one in terms of seed yield and that the seeds produced were of higher physiological quality in terms of membrane integrity. The landraces 'BAF55' and 'BAF84' showed yield higher than commercial ('BAF112'). The early of the harvest through desiccant sprayed on plants 26 DAF did not adversely affect the yield or physiological quality of harvest bean seeds.

Discover hidden collaborations