-(How and why to measure the germination process?). In the last two centuries, papers have been published including measurements of the germination process. High diversity of mathematical expressions has made comparisons between papers and some times the interpretation of results difficult. Thus, in this paper is included a review about measurements of the germination process, with an analysis of the several mathematical expressions included in the specific literature, recovering the history, sense, and limitations of some germination measurements. Among the measurements included in this paper are the germinability, germination time, coefficient of uniformity of germination (CUG), coefficient of variation of the germination time (CV t ), germination rate (mean rate, weighted mean rate, coefficient of velocity, germination rate of George, Timson's index, GV or Czabator's index; Throneberry and Smith's method and its adaptations, including Maguire's rate; ERI or emergence rate index, germination index, and its modifications), uncertainty associated to the distribution of the relative frequency of germination (U), and synchronization index (Z). The limits of the germination measurements were included to make the interpretation and decisions during comparisons easier. Time, rate, homogeneity, and synchrony are aspects that can be measured, informing the dynamics of the germination process. These characteristics are important not only for physiologists and seed technologists, but also for ecologists because it is possible to predict the degree of successful of a species based on the capacity of their harvest seed to spread the germination through time, permitting the recruitment in the environment of some part of the seedlings formed.Key words -germinability, germination rate, germination synchrony, germination time, germination uniformity RESUMO -(Como e por que medir o processo de germinação?). Nos dois últimos séculos, trabalhos têm sido publicados incluindo medidas do processo de germinação. A diversidade das expressões matemáticas existente na literatura tem tornado difícil comparações entre os trabalhos e, algumas vezes, a interpretação dos resultados. Assim, este trabalho apresenta uma revisão sobre medidas de germinação, incluindo a análise de várias expressões matemáticas contidas na literatura específica. Entre as medidas analisadas estão a germinabilidade, tempo de germinação, coeficiente de uniformidade de germinação (CUG), coeficiente de variação do tempo de germinação (CV t ), velocidade de germinação (velocidade média, velocidade média ponderada, coeficiente de velocidade, velocidade de germinação de George, índice de Timson, GV ou índice de Czabator; método de Throneberry e Smith e suas adaptações, incluindo a velocidade de Maguire; ERI ou índice de velocidade de emergência, índice de germinação e suas modificações), incerteza associada à distribuição das freqüências relativas de germinação (U) e índice de sincronia (Z). Os limites dessas medidas foram incluídos para facilitar a interpretação...

-(Calculating germination measurements and organizing spreadsheets). With the objective to minimize diffi culties for beginners we are proposing the use of a conventional spreadsheet for the calculations of the main germination (or emergence) measurements, the organization of the fi nal data for the statistical analysis and some electronic commands involved in these steps.Key words -germination rate, germination time, seed germination, synchrony, uncertainty RESUMO -(Calculando medidas de germinação e organizando planilhas eletrônicas). Com o objetivo de minimizar as difi culdades dos iniciantes, estamos propondo o uso de planilhas eletrônicas convencionais para o cálculo das principais medidas de germinação (ou emergência), a organização dos dados fi nais para a análise estatística e alguns comandos eletrônicos envolvidos nesses passos.Palavras-chave -germinação de sementes, incerteza, sincronia, tempo de germinação, velocidade de germinação

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Influência da cultura antecessora e da adubação nitrogenada na produtividade de milho em sistema plantio direto

The beneficial effects of silicon (Si) fertilization have been observed for several plant species, especially when submitted to stress, either biotic or abiotic. Among the possible reasons for the greater adaptability and resistance of brachiaria grass in areas of low fertility soils in Brazilian savanna, stands its capacity of absorbing and accumulating Si in aerial parts. To evaluate the effect of Si on dry matter yield of Brachiaria decumbens Stapf and Brachiaria brizantha Hochst, grown under two soil moisture regimes, a trial was set up in a completely randomized design factorial scheme (5 × 2 × 2), with five Si rates: (0; 242; 484; 968 and 1,452 kg ha-1), two soil water tensions (60% and 80% of field capacity) and the two brachiaria species. The experiment was installed in a greenhouse, using one of the most representative soils in the region under cerrado, Typic Haplustox. Both brachiaria species can be considered Si-accumulating plants, since they present high Si contents in their aerial parts. Application of Si to the soil increased the contents of this element in both grass species but did not change their tolerance to water deficit, and did not affect dry matter yield.

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-(Anacardium humile A. St.-Hil. (Anacardiaceae) seedling emergence evaluated by means of small samples). Anacardium humile has low capacity for fruit production, limiting the application of experimental techniques, broadly used in the analysis of seed germination. Thus, the purpose of this paper was to introduce the statistical theory of small samples to the study of the seedling emergence of this species. Cashew nuts of different individuals were randomly collected, being submitted to scarification by abrasion of the pericarp near the pedicel; scarification in the same manner followed by washing in water for 24 hours, and intact cashew nuts as control treatment. The cashew nuts (50 per treatment) were sowed at 1 cm depth, in vermiculite moistened with distilled water at field capacity. The experiment was carried out under continuous fluorescent white lamps (21.8 μmol m -2 s -1 ), at 25 ºC. The emergence (%) presented approximated normal distribution for all treatments and they did not differ significantly by Student t test (emergence between 70% and 76%). Seedlings emerged from scarified cashew nuts washed in water presented shorter mean emergence time (16.3 days) and consequently higher mean emergence rate (0.0613 day -1 ) in relation to the other treatments. The uncertainty values far from zero (I ≥ 3.28 bits) and values of Z near zero (Z ≤ 0.095) indicated low seedling emergence synchrony for this species. The results obtained showed that by using reduced number of cashew nuts it was possible to infer about seedling emergence process without violation of the statistical principles and assumptions.Key words -cashew nut, emergence measurements, normal distribution, Student t test RESUMO -(Emergência de plântulas de Anacardium humile A. St.-Hil. (Anacardiaceae) avaliada por meio de amostras pequenas). Anacardium humile possui baixa capacidade de produção de frutos, o que limita a aplicação de técnicas experimentais, amplamente utilizadas na análise da germinação. Assim, o objetivo do trabalho foi introduzir a teoria estatística de amostras pequenas ao estudo da emergência de plântulas da espécie. Núculas foram aleatoriamente coletadas de diferentes indivíduos, sendo submetidas à escarificação por abrasão do pericarpo na região junto ao pedicelo; escarificação na mesma região, seguida de lavagem em água corrente por 24 horas e núculas intactas como controle. As núculas (50 por tratamento) foram semeadas a 1 cm de profundidade, em vermiculita umedecida com água destilada à capacidade de campo, contida em bandejas de plástico. O teste de emergência foi conduzido sob luz branca fluorescente contínua, a 21,8 μmol m -2 s -1 e 25 ºC. O percentual de emergência apresentou distribuição normal aproximada para todos os tratamentos que, quando comparados pelo teste t de "Student", não diferiram significativamente (emergência entre 70% e 76%). Plântulas emergidas a partir de núculas escarificadas e posteriormente lavadas apresentaram menor tempo médio (16,3 dias) e conseqüentemente maior velocidade média de emergên...

-(Germination of newly collected diaspores of Myracrodruon urundeuva Allemão (Anacardiaceae) occurring in the cerrado of Central Brazil). Myracrodruon urundeuva occurs in Northeast, Southeast, and West Center Brazilian regions, being considered as a vulnerable species to extinction. Diaspores collected in the Araguari River valley, MG, were used in three experiments, in a completely randomized design, with five replications of 50 diaspores each one. In the first and second experiments, germination boxes with vermiculite moistened with distilled water, GA 3 and cytokinin at 1, 10, 100 µg mL -1 , and 0.2% KNO 3 were used as treatments. The first experiment was conducted under continuous fluorescent white lamps and the second in darkness. In the third experiment the diaspores were moistened with distilled water and stratified during one to six days at 4-5 °C in darkness. Control treatment was constituted by diaspores moistened with water, without stratification. For the experiments conducted under light conditions, data were collected observing the embryo protrusion every 24 hours; in darkness conditions counting was processed after seven days from the beginning of the experiment. Under continuous light, diaspores treated with 1 µg.mL -1 GA 3 were more homogeneous (CV t = 17.13%) and synchronized (Z = 0.64) in relation to the other treatments. The germinability ranged from 52.8% to 60% and occurred between two and three days. In darkness condition, germinability ranged from 50.4% to 58.8% and under stratification, from 49.6% to 61.2%. For the experiment testing stratification, the lowest mean time, the highest rate and germination uniformity were registered for diaspores stratified during six days. Although the germination process had been fast, low germinability indicates that new investigations are necessary to the sustainable exploration of this species.Key words -germination measurements, growth regulators, stratification RESUMO -(Germinação de diásporos recém-colhidos de Myracrodruon urundeuva Allemão (Anacardiaceae) ocorrente no cerrado do Brasil Central). Myracrodruon urundeuva distribui-se no nordeste, sudeste e centro-oeste brasileiro, sendo considerada uma espécie vulnerável à extinção. Diásporos coletados no vale do Rio Araguari, MG, foram utilizados em três experimentos, em delineamento inteiramente casualizado, cada um deles com cinco repetições de 50 diásporos. No primeiro e segundo experimentos, utilizou-se gerbox com vermiculita umedecida com água destilada, GA 3 e citocinina a 1, 10, e 100 µg.mL -1 e KNO 3 a 0,2%, o primeiro mantido sob luz branca fluorescente contínua e o segundo no escuro. No terceiro experimento, os diásporos foram umedecidos com água e estratificados por um a seis dias a 4-5 °C, no escuro; no controle os diásporos não foram estratificados. A cada 24 horas observou-se a protrusão do embrião nos experimentos mantidos sob luz e, aos sete dias, na ausência de luz. Sob luz contínua, diásporos tratados com GA 3 1 µg.mL -1 foram mais homogêneos (CV t = 17,13%) e sincronizados...