Papéis do arranjo de plantas e do cultivar de soja no resultado da interferência com plantas competidoras

Abstract

RESUMO -O uso combinado de cultivar competitivo e de arranjo equidistante de plantas pode incrementar a habilidade competitiva das culturas com plantas daninhas. Conduziramse dois experimentos em campo na Estação Experimental Agronômica da UFRGS, em Eldorado do Sul-RS, durante o ano agrícola 2001/02, com o objetivo de caracterizar a contribuição do cultivar e do espaçamento entre fileiras para a competitividade da soja com plantas concorrentes. No experimento 1, testaram-se condições de competição (ausência ou presença do cultivar de soja Fundacep 33, simulando planta daninha), espaçamentos entre fileiras (25 e 50 cm) e seis cultivares de soja reagentes. No experimento 2, compararam-se condições de competição (ausência ou presença de plantas daninhas dicotiledôneas), espaçamentos entre fileiras (25 e 50 cm) e cultivares de soja (IAS 5 e Fepagro RS 10). O cultivar Fepagro RS 10 apresenta características de planta que o destacam quanto à habilidade em competir com plantas daninhas, como plantas mais altas, com mais matéria seca, com maior razão de massa foliar e que proporcionam maior cobertura do solo, além de figurar entre os cultivares mais produtivos. O espaçamento reduzido entre fileiras proporciona cobertura precoce do solo pela soja, reduz a população e a matéria seca das plantas daninhas e mantém ou incrementa a produtividade de grãos de soja.Palavras-chave: Glycine max, espaçamento entre fileiras, competitividade, plantas daninhas, Bidens spp., Sida rhombifolia.ABSTRACT -The use of a soybean cultivar with competitive ability combined with an equidistant plant population distribution can enhance the competitive ability of crops against weeds. Two field experiments were carried out at the Agronomic Experimental Station of the Federal University of Rio Grande do Sul, in Eldorado do Sul-RS, during the 2001/2002 growing season, aiming to characterize the contribution of the cultivar and row spacing to soybean competitiveness against weeds. Experiment 1 tested the competitive conditions expressed by the presence or absence of the soybean cultivar FUNDACEP 33 simulating the weed, row spacing (25 and 50 cm) and six reacting soybean cultivars. Experiment 2 tested the competitiveness conditions expressed by the presence or absence of dicotyledonous weeds, row spacing (25 and 50 cm) and soybean cultivars (IAS 5 and FEPAGRO RS 10). Besides ranking among the best producing cultivars, FEPAGRO RS 10 shows characteristics of a plant able to compete with weeds, especially taller weeds with higher dry matter and foliar mass ratio, providing a better soil coverage. Reduced row spacing allows earlier soybean soil coverage, decreases weed population and dry matter, and maintains or increases soybean grain yield.

Competitive ability of soybean cultivars with horseweed (Conyza bonariensis)

“…Often, the selection of more productive cultivars in the absence of competition, also results in more productive cultivars under competition (Bianchi et al, 2010). In this regard, it is noteworthy that the cultivar BMX Apollo RR is one of those who have been showing greater productive potential in the southwest region of Paraná.…”

Weed Management in the Soybean Crop

“…Differences in competitive ability between soybean cultivars with weeds have been reported by Bussan et al [12]; Jannink et al [9]; Lamego et al [13]; Bianchi et al [14] and Fleck et al [15]. Suitable conditions for crop planting, such as moist soil, proper and uniform planting depth, close contact between seed and soil, as well as certified quality seeds, are essential to ensure competitive advantage to the crop by promoting the rapid emergence and establishment of uniform populations.…”

“…The set of morphological and physiological traits of cultivars defines its ability to compete with weeds for environmental resources [31,14]. However, the competitive ability of cultivars can be altered by agronomic practices [32].…”

“…On the other hand, weed species with fast emergence, like the ones from Genus Brachiaria, Digitaria, Euphorbia, Bidens and Raphanus, among others, are able to compete earlier for environmental resources in relation to soybean [34,13,14,35]. Rizzardi et al [36], studying competition between soybean and Euphorbia heterophylla, Ipomoea ramosissima, Bidens pilosa or Sida rhombifolia, reported that several management practices can minimize their interference on soybeans, like the use of more competitive cultivars, correction of soil fertility and the adequacy of the arrangement of plants.…”

Physiology of Crops and Weeds Under Biotic and Abiotic Stresses

“…Several studies of competition between crops and weed species were conducted and the results of these studies are being applied at planning of integrated management practices such as crop rotation, succession, crop-livestock integration and winter crops as tools for suppressing weed occurrence (Severino, 2005;Ceccon, 2007). Most of these studies allow modeling the dynamics of weeds infestation in certain crops and optimizing the system as a whole, based in dry mass accumulation, plants height, number of tillers or branches, number of inflorescences and other directly measured variables (Galon et al, 2007;Fleck et al, 2008;Bianchi et al, 2010).…”