RESUMEN El glifosato y la atrazina son dos herbicidas utilizados en todo el mundo para garantizar una alta productividad en diferentes tipos de cultivos. A pesar de la importancia de los herbicidas, su aplicación puede causar efectos negativos en organismos no objetivo, incluyendo bacterias usadas en control biológico y fijación biológica de nitrógeno. Por lo tanto, esta investigación tuvo como objetivo analizar el efecto in vitro del glifosato y la atrazina sobre el crecimiento de las bacterias Azospirillum brasilense, Bacillus subtilis, Bacillus thuringiensis, Chromobacterium subtsugae y Saccharopolyspora spinosa. El diseño utilizado fue completamente al azar y las dosis de los herbicidas evaluadas fueron 1.0, 2.0, 3.0 y 4.0 L ha-1. Los resultados mostraron que el glifosato y la atrazina afectaron el desarrollo de las bacterias estudiadas. La atrazina tiene un efecto lineal creciente entre las dosis utilizadas y la inhibición del crecimiento bacteriano. Por lo tanto, la dosis de 4.0 L ha-1 de este herbicida fue la que mostró la mayor inhibición de crecimiento de bacterias, mientras que el glifosato a una dosis de 2.0 L ha-1 mostró la más alta inhibición de crecimiento de bacterias en comparación con las dosis de 1.0, 3.0 y 4.0 L ha-1.

ABSTRACT Glyphosate and atrazine are two herbicides used worldwide to ensure high yields in different types of crops. Despite the importance of herbicides, their application may have negative effects on non-target organisms, including bacteria used in biological control and biological nitrogen fixation. Therefore, this research aimed to analyze the in vitro effect of glyphosate and atrazine on the growth of bacteria Azospirillum brasilense, Bacillus subtilis, Bacillus thuringiensis, Chromobacterium subtsugae, and Saccharopolyspora spinosa. The design used was completely randomized, and the doses of the herbicides evaluated were 1.0, 2.0, 3.0 and 4.0 L ha-1. The results showed that glyphosate and atrazine affected the development of the bacteria under study. Atrazine showed a lineal increasing effect between the doses used and inhibition of bacterial growth. Therefore, the dose of 4.0 L ha-1 of this herbicide was the one that showed the highest inhibition of bacteria, whereas glyphosate at a dose of 2.0 L ha-1 showed the highest inhibition of bacteria compared to doses of 1.0, 3.0 and 4.0 L ha-1.

RESUMO A mesorregião sudeste paraense é importante produtora de soja, e o cultivo em safrinha pode incrementar a produção agrícola local. No entanto, na região, predominam Latossolos de textura média a muito argilosa, os quais, apesar de adequados ao uso agrícola, possuem, naturalmente, baixos níveis de fósforo disponível. Objetivou-se avaliar a produtividade de feijão-caupi [Vigna unguiculata (L.) Walp] em safrinha sob doses de fósforo residual em Latossolo Amarelo. Foram instalados dois experimentos em condições de campo. O delineamento experimental foi em blocos casualizados, com 5 tratamentos (residuais de 0, 50, 100, 150 e 200 kg ha-1 de P2O5) e 4 repetições. O primeiro experimento consistiu de cultivo de feijão-caupi em safrinha após a safra da soja, com as doses fosfatadas fornecidas durante o plantio da soja, e o segundo de feijão-caupi em safrinha após a safra do arroz, com as doses fosfatadas fornecidas durante o plantio do arroz. Avaliaram-se o peso de mil grãos e produção de vagens, cascas e grãos. Houve maior produção de vagens e cascas em área com residual de fósforo. A maior produtividade foi obtida no residual da dose de 200 kg ha-1 de P2O5, atingindo-se produtividades de grãos de 1.256 kg ha-1 após a safra da soja e 885 kg ha-1 após a safra do arroz.

ABSTRACT The southeastern mesoregion of the Brazilian Pará state is an important soybean producer, and the second-crop system can increase the local agricultural production. However, Latosols with medium to very clayey texture predominate in the region and, despite being suitable for farming, they naturally have low levels of available phosphorus (P). This study aimed to evaluate the yield of second-crop cowpea [Vigna unguiculata (L.) Walp] under doses of residual P in a Yellow-Latosol. Two experiments were installed under field conditions. The experimental design was randomized blocks, with five treatments (residuals of 0, 50, 100, 150 and 200 kg ha-1 of P2O5) and four replications. The first experiment consisted of cultivating second-crop cowpea after the soybean harvest, with phosphate doses provided during the soybean planting, and the second of second-crop cowpea after the rice harvest, with phosphate doses provided during the rice planting. The 1,000-grain weight and production of pods, husks and grains were evaluated. The production of pods and husks were higher in the area with residual P. The highest yield was obtained in the residual dose of 200 kg ha-1 of P2O5, reaching a grain yield of 1,256 kg ha-1 after the soybean harvest and 885 kg ha-1 after the rice harvest.

ABSTRACT Using biological inputs to improve the efficiency of nitrogen fertilizers represents an alternative for the cultivation of grasses in tropical regions. Azospirillum brasilense is a species of plant growth promoting bacteria widely studied and used in inoculants. Thus, this study aimed to evaluate the performance of Mombasa grass ( Megathyrsus maximus ) in association with A. brasilense and nitrogen (N) fertilization. The study was conducted under field conditions in Araguaína-Tocantins State, between December 2017 and May 2018. The treatments were arranged in randomized blocks, in a 5 × 2 factorial arrangement, with five doses of N fertilization (0, 25, 50, 75, and 100 kg ha-1) combined with two inoculation treatments (inoculated and non inoculated), in four replicates. For the number of tillers and root production, the inoculation efficiency varied as a function of the supplied N doses. However, the percentage of leaf N was higher for inoculated plants regardless of the application of nitrogen. In the absence of nitrogen fertilization, it was possible to increase forage production by up to 36 % with inoculation.