Using adequate sample size in experimental units improves the efficiency of the research. In the agricultural year of 2004/2005, an experiment was conducted in Santa Maria, Rio Grande do Sul State, Brazil, with the objective of estimating sample size for the following traits: ear length, ear and cob diameter, ear weight, weight of grains per ear, cob weight and the weight of 100 grains, number of grain rows per ear, number of grains per ear and length of grains for two single hybrids (P30F33 and P Flex), two threeway hybrids (AG8021 and DG501) and two double hybrids (AG2060 and DKB701) of maize. For a 5% (D5) precision, the weight traits (dehusked ear weight, weight of grains per ear, cob weight and weight of 100 grains) can be sampled with 21 ears; the size traits (ear length, ear diameter, cob diameter and grain length) with eight ears; and the number traits (number of grain and rows) with 13 ears. Sample size varies as a function of ear trait and the type of hybrid i.e. single, three-way or double. Genetic variability among ears does not correspond to the increasing genetic variability i.e. single, three-way and double for the sample size of traits per ear.

In the Brazilian state of Rio Grande do Sul, rice (Oryza sativa L.) is predominantly grown using continuous flood irrigation, which requires large quantities of fresh water. Due to increasing scarcity and demand for water, modern agricultural systems need to produce more food with less water. The objective of this study was to evaluate the effect of different irrigation management systems on water use efficiency, quantity of water loss due to runoff, and rice grain yield. The experiments were conducted from 2007 through 2010 at an experimental station of the Plant Protection Department of the Universidade Federal de Santa Maria, Rio Grande do Sul state, Brazil, on an Albaqualf sandy‐loam soil. Treatments consisted of two irrigation management systems: continuous flooding (CF) at approximately a 10‐cm flood depth and intermittent irrigation (II) where the flood was allowed to fully subside before being re‐established to a 10‐cm depth. Intermittent irrigation increased storage of rainwater by reducing runoff water by 56% compared with CF. In addition, II reduced irrigation water use by 22 to 76% resulting in a 15 to 346% increase in water use efficiency (WUE). Rice yield was not affected by II compared with CF. Intermittent irrigation provides greater water conservation, does not reduce rice yield compared with CF, and improves the WUE of rice.

Risco de contaminação das águas de superfície e subterrâneas por agrotóxicos recomendados para a cultura do arroz irrigado.Ciência Rural, v.42, n.10, out, 2012. Ciência Rural, Santa Maria, v.42, n.10, p.1715-1721, out, 2012

Cold stress reduces bispyribac-sodium absorption and metabolism in rice, but has no effect on translocation.

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