Mário Antônio Bianchi

Tolerância à interferência de plantas competidoras e habilidade de supressão por genótipos de soja: II. Resposta de variáveis de produtividade

As perdas de produtividade das culturas em decorrencia da competicao de plantas concorrentes geralmente aumentam quanto mais semelhantes forem suas caracteristicas morfofisiologicas. O objetivo deste trabalho foi avaliar os efeitos da competicao de cultivares de soja, simulando especies daninhas dicotiledoneas, sobre cultivares de soja portadores de caracteristicas diferenciais de planta. Para isso, conduziu-se um experimento em campo, em Eldorado do Sul-RS. Os fatores e tratamentos comparados foram: tres condicoes de competicao (ausencia de plantas de soja concorrentes e presenca de plantas concorrentes do cultivar de soja BRS 205 ou Cobb); e quatro cultivares reagentes de soja a competicao (IAS 5, BR-16, CD 205 e Fepagro RS-10). Avaliaram-se variaveis relacionadas a produtividade dos cultivares e outras correlatas. Caracteristicas dissimilares em plantas de cultivares de soja, como estatura e ciclo, resultaram em habilidade competitiva diferenciada com plantas concorrentes. O cultivar de soja CD 205, de estatura elevada e ciclo tardio, mostrou alta habilidade competitiva; IAS 5, de baixa estatura e ciclo precoce, apresentou baixa tolerância a competicao, enquanto BR-16 e Fepagro RS-10 sao intermediarios. Cultivares com elevada habilidade competitiva, alem de tolerarem a competicao, preservando o potencial de produtividade, tambem suprimem a producao de graos das plantas concorrentes.

Tolerância à interferência de plantas competidoras e habilidade de supressão por cultivares de soja: I. Resposta de variáveis de crescimento

Differential morphological plant characteristics may influence competition relations between crop and weeds. The aim of this study was to evaluate the influence of plants of four soybean cultivars and two other soybean cultivars, mimicking dicotyledonous weed species, on their relationships during the vegetative growth period. Thus, two experiments were carried out: one in pots, to provide data for initial soybean plant growth; and the other in the field, to monitor plant growth characteristics. The following factors and treatments were tested in the field: three competition conditions (absence of competing plants or presence of the soybean cultivars BRS 205 or Cobb), and four soybean cultivars reagent to competition (IAS 5, BR-16, CD 205, and Fepagro RS-10). Soybean cultivars showed varied emergence speed and initial plant growth. The presence of the concurrent plants, regardless of their plant characteristics, affected soybean branching. Fepagro RS-10 and BR-16 cultivars had a fast growth during the initial development period; CD 205, on the contrary, showed slow growth during this phase. Early maturity soybean cultivars cover the soil more rapidly than late maturity cultivars, during the first 45 days of growth.

Perdas de rendimento de grãos de soja causadas por interferência de picão-preto e guanxuma

The level of reciprocal interference between weeds and crops is affected by the competing species and plant populations involved. This research was conducted in order to evaluate the possibility of using the retangular hyperbolic model for predicting soybean grain yield losses caused by beggarticks (Bidens spp.) and arrowleaf sida (Sida rhombifolia L.) infestations. To accomplish this, there were carried out two field experiments in Eldorado do Sul, RS, Brazil, during the 1999/00 and 2000/01 growing seasons. Treatments consisted of beggarticks and arrowleaf densities, which were located according to naturally ocurring population levels in the research area. Was detected that grain yield losses due to increasing densities of these weeds increased non-linearly. The retangular hyperbolic model suits better adjustments when is used grain yield losses than using soybean dry matter at flowering stage or biological yield losses. Through comparison of the parameters estimated for the adjusted model, it is concluded that beggarticks exerts greater interference in soybean than arrowleaf sida.

Características de plantas de soja que conferem habilidade competitiva com plantas daninhas

In order to identify morphological characteristics in soybean plants that define greater competitive ability against weeds, two experiments were carried out. The first experiment was installed in Cruz Alta, RS, where soybean competed against forage radish (Raphanus sativus), and the other in Eldorado do Sul, RS, where the crop competed against beggar ticks (Bidens spp.) and arrow leaf sida (Sida rhombifolia). Results multiple linear regression and correlation analysis demonstrated that soybean plants holding with higher stem dry matter of (including leaves) at 45 days after emergency, higher dry matter of shoot at 60 days after emergency, and greater grain yield, granted superior competitiveness of soybean with forage radish. When competitors were weeds hairy beggarticks and arrowleaf sida, soybean stem dry matter (with the leaves), soil coverage by crop canopy, and grain yield, arose as the traits that conferred greater competitive ability to the crop. Plant height, branch number and branch length have also contributed for higher competition ability in soybean.

Interferência de plantas concorrentes em arroz irrigado modificada por métodos culturais

The optimization of a weed control program depends on early and reliable prediction of the impact of weeds on crop yield. This research aimed to evaluate the effects of rice cultivars and plant arrangements on flooded rice grain yield loss and to identify the explicative variable that provides the best adjustment to the model tested. Two field experiments were carried out during the 2000/2001 growing season. Treatments consisted of three rice cultivars (BRS-38 Ligeirinho, IRGA 417, and BR-IRGA 409), two row widths (15 and 25 cm), and plant populations (ten and six levels for the first and second experiments, respectively) of the rice cultivar EEA 406, mimicking red rice infestation.. Data were analyzed using the non - linear regression model of rectangular hyperbole, adjusted independently for the three studied factors. Results of the first experiment were used to evaluate data adjustment to the model and results of the second to validate the model generated in the first. IRGA 417 cultivar presented greater competitive ability than the other two. Reduction of row width increased the ability of rice cultivars to compete with the concurrent genotype. The rectangular hyperbolic model was suitable to estimate flooded rice grain yield loss due to interference of concurrent plants. The explicative variable leaf area of EEA 406 cultivar, in general, was equivalent to plant population as an independent variable in the mathematical model tested.

Comparação de modelos matemáticos na estimativa das perdas de produtividade de grãos em arroz irrigado

The objectives of this work were to compare mathematical models and identify, among morphologic variables, the one better adjusted to rice grain yield losses by interference of EEA 406 cultivar, simulating red rice. Four experiments were carried out, one in the field and the others in a greenhouse. Rice cultivars BRS-38 Ligeirinho, IRGA 417, and BR-IRGA 409, were studied in the field in row widths of 15 and 25 cm, and populations (ten levels) of concurrent cultivar. In greenhouse, tests in monocultures were carried out in a replacement series model. Data analysis were accomplished with application of linear and non linear regression models. The best adjustment of rice grain yield losses data was attained using the model with two parameters. Leaf area and soil coverage estimated better grain yield loss than dry weight of the simulating cultivar. The models show that reduction of crop row width increases the competitive ability of rice cultivars in relation to the concurrent genotypes.

Partição da competição por recursos do solo e radiação solar entre cultivares de soja e genótipos concorrentes

Plants compete for environmental resources located below and over soil surface. Physical separation of competition allows understanding the relative importance of each fraction, as well as identifying possible differences among species. The aim of this research was to separate the individual effects resulting from competition for soil or solar radiation resources, between soybean and concurrent plants. Thus, experiments using pots were carried out at UFRGS, in Porto Alegre-RS, in 2001 and 2002. The treatments tested resulted from the combinations of two concurrent genotypes (crop and competitor) and four competition conditions (absence of competition, competition for soil and solar radiation, competition for soil resources, and competition for solar radiation). Soybean cultivars IAS 5 and Fepagro RS 10 represented the crop, whereas radish forage and the soybean cultivar Fundacep 33 were the competitors tested. Morpho-physiological variables were evaluated in the soybean plants and radish forage. Growth of the soybean plants was most affected by soil resources competition, with RS 10 cultivar being more competitive than IAS 5.Radish forage did not interfere in the growth of soybean cultivars but it benefited from soybean presence.