Abstract Mucuna (Stizolobium pruriens) is widely used in agriculture as a green allowance and in crop rotation, due to its ability to fix nitrogen and recover degraded areas; without embargo, there is a slow and uneven germination. This study used some classical methods, together with the use of low-frequency ultrasound to accelerate and homogenize the germination and emergence of the seeds. The experiment was carried out at the Plant Tissue Cultivation Laboratory of the Ilha Solteira Campus, São Paulo, Brazil. The design used was a completely randomized one, with five replications, in a 3x6 factorial scheme, the factors being: three pre-treatments for latency break: mechanical scarification, thermal scarification, and without scarification with six levels of ultrasound exposure: 0, 1, 2, 3, 5, 8 min, totaling 18 treatments. For eight days the germination and the initial stages of the seedlings were controlled. The method without scarification subjected to 4.5 min of ultrasound can become an excellent alternative, since it presented greater germination vigor, while 3.14 min of exposure to ultrasound were enough to improve the emergence speed, regardless of the method used in the preparation of seeds. In conclusion, only with the use of low-frequency ultrasound, it is possible to improve both the germination speed index and the germination vigor, without the need for additional treatments.

Resumen La mucuna (Stizolobium pruriens) se usa ampliamente en agricultura como abono verde y en rotación de cultivos, debido a su capacidad para fijar nitrógeno y recuperar áreas degradadas; sin embargo, tiene una germinación lenta y desigual. Este estudio utilizó algunos métodos clásicos, junto con el uso de ultrasonidos de baja frecuencia para acelerar y homogeneizar la germinación y emergencia de las semillas. El experimento se realizó en el Laboratorio de Cultivo de Tejidos Vegetales del campus Ilha Solteira, São Paulo, Brasil. El diseño utilizado fue un completamente al azar, con cinco repeticiones, en un esquema factorial 3x6, siendo los factores: tres pre-tratamientos para ruptura de la latencia: escarificación mecánica, térmica, y sin escarificación con seis niveles de exposición a ultrasonido: 0, 1, 2, 3, 5, 8 min, totalizando 18 tratamientos. Durante ocho días se controló la germinación y las etapas iniciales de las plántulas. El método sin escarificación sometido a 4.5 min de ultrasonido puede convertirse en una excelente alternativa, ya que presentó mayor vigor de germinación, mientras que 3.14 min de exposición a ultrasonido fueron suficientes para mejorar la velocidad de emergencia, independientemente del método utilizado en la preparación de semillas. En conclusión, solo con el uso de ultrasonidos de baja frecuencia es posible mejorar tanto el índice de velocidad de germinación como el vigor de germinación, sin necesidad de tratamientos adicionales.

RESUMO Na estatística experimental, a variabilidade, que permite conclusões relacionadas à precisão experimental, é geralmente demonstrada por meio do coeficiente de variação experimental (CV). O objetivo deste estudo foi avaliar a distribuição do CV em diversos experimentos de crescimento de eucalipto, comparar as faixas de classificação existentes propostas na literatura (métodos propostos por Garcia; Costa, Seraphin e Zimmermann e Pimentel-Gomes), e definir o melhor a ser utilizado como referência para cultivo de mudas de eucalipto em estufas ou cultivo protegido. Para tanto, foi realizado um teste em branco com 100 repetições e avaliações realizadas em 30, 60, 90 e 120 dias. Além disso, foram coletados dados anteriores da literatura, para fins de comparação. Os resultados obtidos foram submetidos aos testes de Shapiro-Wilk e Kolmogorov-Smirnov, e as tabelas de classificação submetidas aos testes de aderência e heterogeneidade. Como resultado, foi possível concluir que os dados obtidos com os experimentos com eucalipto na presente pesquisa não se enquadram na classificação de Pimentel-Gomes e nas tabelas obtidas por Costa, Seraphin e Zimmermann enquanto as tabelas por meio do método proposto por Garcia seriam preferencialmente utilizadas.

ABSTRACT In experimental statistics, the variability, which allows for conclusions related to experimental accuracy, is usually demonstrated by means of experimental coefficient of variation (CV). The aims of this study were to evaluate the distribution of CV in several experiments of eucalyptus growth, compare the existent classification ranges proposed in the literature (methods proposed by Garcia; Costa, Seraphin and Zimmermann, and Pimentel-Gomes), and define the better one to be used as reference for eucalyptus seedlings cultures in greenhouses or protected cultivation. For that, a blank test with 100 repetitions was conducted and evaluations were performed in 30, 60, 90 and 120 days. Moreover, previous data from literature were collected, for comparison proposes. The obtained results were submitted to Shapiro-Wilk and Kolmogorov-Smirnov tests, and the classification tables were submitted to adherence and heterogeneity tests. As a result, it was possible to conclude that data obtained with the experiments with eucalyptus in the present research did not fit the classification of Pimentel-Gomes and tables obtained by Costa, Seraphin and Zimmermann, while the tables related to the method proposed by Garcia would be preferably used.