RESUMO Os bioestimulantes são complexos que promovem o equilíbrio hormonal das plantas, favorecendo a expressão do seu potencial genético, estimulando o crescimento da parte aérea e do sistema radicular. O uso desses reguladores vegetais em cultivos agrícolas pode causar aumentos quantitativos e qualitativos da produção das culturas. Diante disso, o objetivo deste estudo foi avaliar o efeito de bioestimulante comercial no crescimento inicial da mandioca. Adotou-se esquema fatorial 2 x 5, correspondente a duas cultivares de mandioca (Cacau-UFV e Coimbra) e a cinco concentrações do bioestimulante (0, 4, 8, 12 e 16 mL L-1). Aos 90 dias após o plantio, avaliaram-se área foliar, altura da planta, diâmetro do caule, número de folhas e as matérias secas de raízes, caule, folhas e total. O bioestimulante promoveu incrementos lineares da altura de planta, do número de folhas, da área foliar, das matérias secas de caule, folhas, raízes e total. A cultivar Cacau-UFV apresentou maior crescimento que a cultivar Coimbra. O uso do bioestimulante na cultura da mandioca estimula o crescimento inicial da cultura.

ABSTRACT Biostimulants are complex substances that promote hormonal balance in plants, favor the genetic potential expression, and enhance growth of shoots and root system. The use of these plant growth promoters in crops can increase quantitatively and qualitatively crop production. Therefore, the aim of this study was to evaluate the effect of a commercial biostimulant on the initial growth of cassava. The experiment was arranged in a 2 x 5 factorial design, corresponding to two cassava cultivars (Cacau-UFV and Coimbra) and five biostimulant concentrations (0, 4, 8, 12 and 16 mL L-1). At 90 days after planting, the characteristics leaf area, plant height, stem diameter, leaf number, total dry matter and dry matter of roots, stems and leaves were evaluated. The biostimulant promoted linear increases in plant height, leaf number, leaf area, total dry matter, dry matter of stems, leaves and roots. The cultivar Cacau-UFV had a higher growth rate than the cultivar Coimbra. The growth promoter stimulated the early growth of the cassava crop.

Os fertilizantes podem ser usados para alterar as relações de competitividade, de modo a favorecer as espécies cultivadas, desde que as espécies competidoras apresentem respostas diferenciadas à aplicação de nutrientes. Por essas razões, objetivou-se, com este trabalho, avaliar o crescimento do picão preto (Bidens pilosa L.), da braquiária (Brachiaria decumbens Stapf) e da mandioca (Manihot esculenta Crantz), cultivados sob diferentes quantidades de fósforo fornecidas no plantio. Para isso, foi conduzido experimento em casa de vegetação, em arranjo fatorial 3x4, sendo o primeiro fator constituído pelas espécies estudadas, combinadas com quatro níveis de adubação fosfatadas (0, 80,800 e 4.000 kg ha-1 de P2O5), no delineamento em blocos casualizados, com cinco repetições. A aplicação do fertilizante fosfatado promoveu maior crescimento das espécies avaliadas, sendo que a mandioca apresentou maior crescimento da parte área com o aumento da disponibilidade de fósforo. De maneira geral, as plantas daninhas apresentaram maiores respostas às menores doses de fósforo.

Fertilizers may be used to change the competitive relations, favoring the crop species, providing the competing species have different responses to the nutrient application. Thus, the aim of this study was to evaluate the growth of Cassava plant, Bidens pilosa L. and Brachiaria decumbens Stapf, as a function of the amount of P supplied at planting. The experiment was conducted in a greenhouse and the, treatments were arranged in a 3 x 4 factorial, involving the three species studied and four levels of phosphate fertilization (absence of P2O5, 80 kg ha-1, 800 kg ha-1 and 4000 kg ha-1 P2O5, equivalent to 0, 1, 10 and 50 times the phosphorus dose recommended, respectively). A randomized block design was used, with five replications. The application of phosphate fertilizer promoted larger growth of the species evaluated, and cassava had higher growth of the shoot with the increased availability of phosphorus. In general, weeds showed higher responses to lower doses of phosphorus.

Dry matter yield and chemical composition of forage grasses harvested from an area degraded by urban solid waste deposits were evaluated. A split-plot scheme in a randomized block design with four replicates was used, with five grasses in the plots and three harvests in the subplots. The mineral content and extraction and heavy metal concentration were evaluated in the second cut, using a randomized block design with five grasses and four replicates. The grasses were Brachiaria decumbens cv. Basilisk, Brachiaria ruziziensis, Brachiaria brizantha cv. Marandu and cv. Xaraés, and Panicum maximum cv. Tanzânia, cut at 42 days of regrowth. The dry matter yield per cut reached 1,480 kg ha-1; the minimum crude protein content was 9.5% and the average neutral detergent fiber content was 62.3%. The dry matter yield of grasses was satisfactory, and may be an alternative for rehabilitating areas degraded by solid waste deposits. The concentration of heavy metals in the plants was below toxicity levels; the chemical composition was appropriate, except for phosphorus. The rehabilitated areas may therefore be used for grazing.