Spurred Anoda (Anoda cristata) Competition in Narrow- and Wide-Row Soybean (Glycine max)¹

Abstract

The effect of spurred anoda competition in narrow- (35 cm) and wide-row (70 cm) soybean was studied in field experiments for 2 yr. Vigorous early soybean growth in narrow- compared with wide-row soybean resulted in lower radiation transmitted through the canopy, which can partially account for greater competitiveness of narrow-row than wide-row soybean. Soybean plant height was not significantly influenced by the row spacing. Relative yield total (RYT), which is the relationship between yield in mixtures and in monocultures of the crop or the weed and indicates resource complementarity, was equal to 1 with 12 spurred anoda/m2 in the year with less precipitation. Regardless of the row spacing, spurred anoda gave resource use complementarity with the crop (RYT > 1) in all other treatments; therefore, partial avoidance of competition in mixed species was evident. Soybean aggressivity, which takes into account the effect of competition on both the crop and the weed and indicates competitive ability, decreased with weed density in both row spacings. Soybean yield loss at harvest was linearly related to relative dry weight 40 d after planting. Weed-free narrow- and wide-row soybean produced similar yields. In the presence of the spurred anoda, soybean yield was greater in narrow-row compared with wide-row soybean only in the most humid year. A management system that uses quick canopy closure with narrow-row soybean can provide excellent soybean yield and suppression of low spurred anoda densities.

Proporção entre plantas de soja e plantas competidoras e as relações de interferência mútua

“…Nesse caso, o nabo foi mais agressivo que a soja. Esse comportamento mostra que uma espécie é mais agressiva que a outra e contribui mais que o esperado para o rendimento total (RADOSEVICH, 1987).…”

“…Nos Ensaios V e VI, em que o cultivar "Fundacep 33" foi o competidor, não houve diferenças significativas em PR dos cultivares de soja, em relação às produtividades equivalentes (Tabela 1), o que significa que não há efeito de uma espécie sobre a outra ou que a habilidade das espécies em interferir uma sobre a outra é equivalente (RADOSEVICH, 1987). Nesses experimentos, também não ocorreram diferenças para número de nós, estatura de planta e matéria seca foliar dos cultivares de soja (Tabela 2).…”

“…Para analisar a MPA da cultura e do competidor, foi utilizado o método da análise gráfica da produtividade relativa (RADOSEVICH, 1987;ROUSH et al, 1989;COUSENS, 1991). Esse procedimento, também chamado de método convencional para experimentos substitutivos, consiste na construção de um diagrama com base na produtividade relativa (PR) e na produtividade relativa total (PRT) nas proporções 0, 25, 50, 75 e 100% do genótipo X e do Y.…”

“…(malva-de-crista), Euphorbia heterophylla L. (leiteira) e Ipomoea ramosissima (Poir.) Choysy (corda-de-viola) evitam, ao menos em parte, a competição com a cultura (PURICELLI et al, 2003;RIZZARDI et al, 2004).…”

Effects of Changes in Flax (Linum usitatissimumL.) Density and Interseeding with Red Clover (Trifolium pratenseL.) on the Competitive Ability of Flax Against Brassica Weeds

“…Competitive ability can vary among crops (Satorre and Snaydon 1992) according to the community of weeds present (Doll 1997) or between cultivars of the same species, as pointed out by Husrev and Zandstra (2005) in wheat (Triticum aestivum L.), and Begna et al (2001) in corn (Zea mays). The competitive ability can also be modified by the availability of resources (Guglielmini et al 2000), cultural practices (Gonzalez Ponce and Santín 2001;Puricelli et al 2003;Puricelli and Faccini 2005), or changes in the density of sowing (Stevenson and Wright 1996). The results recorded in these experiments carried out with different crops or under different conditions may not be valid for flax, which requires the search for alternatives to improve its competitive ability.…”