Competitiveness of Semidwarf Upland Rice Cultivars against Palisadegrass (Brachiaria brizantha) and Signalgrass (B. decumbens)

Abstract

Upland rice varieties tolerant to acid soil can be sown in the acid, well-drained savannah soils of Latin Amer-When savannas in Latin America are brought into cultivation, rice ica for the profitable production of grain while grazing (Oryza sativa L.) can be sown with the perennial grasses palisadegrass land is renovated (Cadavid and Smith, 1994; Friesen, [Brachiaria brizantha (Hochst. ex A. Rich) Stapf] and signalgrass (B. decumbens Stapf) to harvest a grain crop while establishing a 1994; Guimaraes, 1993). Signalgrass and palisadegrass pasture to suppress weeds and provide grazing in subsequent years. are competitive perennial tropical grasses often un-However, these Brachiaria spp. can reduce upland rice yields. Rice dersown in rice in the savannas of Colombia, Venezuela, cultivars need to be competitive with Brachiaria spp. to maintain and Brazil (CIAT, 1990; Yokohama et al., 1999) to acyields but must allow Brachiaria spp. sufficient growth for pasture complish this goal. For the system to succeed, rice cultiestablishment. Field studies were conducted during 1994 and 1995 on vars must be sufficiently competitive to suppress the a Typic Haplustox oxisol soil in the Eastern Plains of Colombia to vigorous initial growth of the pasture, and yields must evaluate the competitiveness of upland rice cultivars and to identify be high enough to cover the cost of pasture renovation. rice traits for competitiveness. Ten (1994) and 14 (1995) upland riceRice cultivars must also be competitive enough to supcultivars were grown with and without signalgrass in 1994 and palisadegrass in 1995. Rice cultivars differed substantially in their competi-

Interferência de Brachiaria plantaginea com a cultura do arroz, cv. Primavera

“…Silva & Durigan (2009), ao avaliarem por dois anos consecutivos as relações de interferência entre plantas daninhas e o arroz de terras altas, constataram que a convivência da comunidade infestante durante todo o ciclo da cultura promoveu significativa interferência, resultando em perdas de produtividade de grãos de aproximadamente 95%. Fischer et al (2001), em campo, verificaram que a competição por luz foi o fator crítico da interferência das braquiárias (B. brizantha e B. decumbens) sobre o arroz de terras altas, com perdas na produtividade de grãos variando de 18 a 55%. Com altas densidades de planta daninha, o dano à cultura ocorre logo após a emergência, ao passo que em densidades menores as injúrias começam a partir do início do perfilhamento (Tozani et al, 1995).…”

Períodos de interferência das plantas daninhas na cultura do arroz de terras altas. II - cultivar Caiapó

“…FISCHER et al (2001) verificaram mais competitividade do arroz associada com sua habilidade para interceptação da luz. FLECK et al (2003), na cultura do arroz irrigado, constataram que a velocidade de emergência e de crescimento inicial das plântulas de arroz foram características importantes na sua habilidade competitiva.…”

Upland rice yield as affected by previous summer crop rotation (soybean or upland rice) and glyphosate management on cover crops

“…Souza et al (2006) reported allelopathic effects caused by the species Brachiaria, that can reduce crop seed germination, plant development and grain yield; similarly to what has occurred in this trial with Brachiaria ruziziensis and Brachiaria brizantha as cover crops. Fischer et al (1995Fischer et al ( , 2001, Nunes et al (2009) andCrusciol et al (2010) have added that Brachiaria spp. and Panicum spp.…”