Valmir Gaedke Menezes

Resposta de duas cultivares de arroz irrigado à densidade de semeadura e à adubação nitrogenada

Many studies about seeding and nitrogen rates in flooded rice were carried out, but few works have studied these two factors altogether. The objective of this study was to evaluate the effect of seeding and nitrogen rates on grain yield and its components, in two flooded rice cultivars. The experiment was carried out in field conditions during the 1998/1999 and 1999/2000 growing seasons. Treatments consisted of the combinations of two flooded rice cultivars (BR-IRGA 410 and IRGA 417), four seeding rates (50, 100, 150, and 200 kg ha -1 ) and four nitrogen rates (0, 40, 80, and 120 kg ha -1 ) in a randomized blocks design with four replications. Grain yield in response to nitrogen fertilizer was not influenced by seeding rate, except in the lowest density, in the second year. Grain yield did not vary within the range of seeding rate tested. Nitrogen use efficiency was higher in BR-IRGA 410 cultivar than in IRGA 417 and it decreased with increment in N fertilizer.

Competitividade de cultivares de arroz irrigado com cultivar simuladora de arroz-vermelho

(2) Resumo - Caracteristicas morfologicas e fisiologicas de plantas cultivadas podem afetar sua habilidade competitiva com plantas daninhas. Este trabalho objetivou investigar a competitividade de cultivares de arroz irrigado (Oryza sativa L.) com cultivar simuladora de arroz-vermelho. Investigou-se na safra 2000/2001 o comportamento de oito genotipos de arroz, cultivados na presenca ou ausencia da cultivar de arroz EEA 406, que simulou infestacao de arroz-vermelho. Aos 45 e aos 60 dias apos a semeadura, avaliou-se a resposta da simuladora em relacao as cultivares de arroz. Na colheita, foram determinados estatura de planta, componentes do rendimento e produtividade das plantas. A cultivar tardia IR 841 suprimiu o crescimento da simuladora, apresentando com a cultivar superprecoce Ligeirinho as meno- res reducoes de produtividade quando em competicao. Por sua vez, as cultivares IAS 12-9 Formosa e Bluebelle permitiram maior crescimento e producao de sementes pela concorrente, tambem sofrendo as maiores reducoes de produtividade de graos na condicao de competicao. Termos para indexacao: Oryza sativa, competicao vegetal, planta daninha, manejo da cultura. Competitiveness of flooded rice cultivars with a red rice simulating cultivar Abstract - Morphologic and physiologic characteristics of crop plants can affect their competitive ability with weeds. This research aimed to investigate competitiveness of flooded rice (Oryza sativa L.) cultivars with a red rice simulating genotype. It was investigated, during the 2000/2001 warm season, the behavior of eight rice genotypes, grown in presence or absence of the rice cultivar EEA 406, simulating a red rice infestation. At 45 and 60 days after rice seeding, it was evaluated the response of red rice mimicker genotype in relation to rice cultivars. At harvest, it was determined plant height, yield components, and grain yield of the cultivars. The late season genotype IR 841 suppressed growth of the simulative cultivar, presenting, together with the very-early cultivar Ligeirinho, the lowest reductions in grain yield under competition. In opposite, IAS 12-9 Formosa and Bluebelle cultivars allowed the greatest growth and seed production by the concurrent rice, also presenting the largest decreases of grain yield under the competition condition.

Manejo de arroz vermelho através do tipo e arranjo de plantas em arroz irrigado

Red rice (Oryza sativa L.) is considered the worst weed to the rice crop in the State of Rio Grande do Sul, Brazil. The difficulty of its chemical control and the high degree of infestation in rice fields determine the necessity of developing systems for cultural control. The objective of this study was to evaluate the effects of three sowing rates, three row spacings and two irrigated rice cultivars on red rice control, grain yield and agronomic characteristics of irrigated rice under minimum tillage system. The experiment was conducted in 1994/95, at Rice Experimental Station, IRGA, Cachoeirinha/RS. The treatments consisted of row spacings of 13.5, 20 and 30 cm, sowing rates of 75, 150, and 225 kg/ha and cultivars BR-IRGA 410 and IRGA 416. The results indicated that increasing of sowing rate associated with narrowing row spacing in the taller cultivar and higher season, BR-IRGA 410, gave higher competitivity to rice with regard to red rice. The use of early season rice cultivar, IRGA 416, reduced the amount of red rice seed that fallen to the ground.

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.

Semeadura direta de genótipos de arroz irrigado em sucessão a espécies de cobertura de inverno

Resumo†n†A adoAao do sistema de semeadura direta de arroz em sucessao a espOcies de cobertura de solo no inverno O uma importante alternativa para possibilitar o cultivo em uma mesma AErea todos os anos. Com o objetivo de avaliar espOcies de cobertura do solo no inverno mais apropriadas para parti- ciparem de um sistema de sucessao de culturas com semeadura direta de genUtipos de arroz irrigado, conduziu-se um experimento na EstaAao Experimental do Arroz do Instituto Rio Grandense do Arroz, em Cachoeirinha, RS, nas estaAies de crescimento de 1996/97, 1997/98 e 1998/99. Os†tratamentos constaram de quatro genUtipos de arroz irrigado (BRS6, BR-IRGA†409, IRGA†416 e IRGA†417) insta- lados em semeadura direta, sobre parcelas com as coberturas de aveia-preta (Avena strigosa Scheib), aveia-branca (Avena sativa L.), azevOm (Lolium multiflorum Lam.), serradela nativa (Ornithopus micranthus (Benth.) Arechavaleta) e de vegetaAao espont‚nea e com solo desnudo (testemunha). Quanto ao rendimento de graos, houve interaAao entre sistemas de cobertura de solo e estaAies de crescimento. Nas†trŒs estaAies de crescimento, somente o arroz cultivado em sucessao ‡ leguminosa serradela nativa apresentou rendimento de graos similar ao obtido no sistema de cultivo convencional. Por†outro lado, o arroz cultivado em sucessao ao azevOm foi o œnico a apresentar rendimento de graos inferior em relaAao ao sistema de cultivo convencional nas trŒs estaAies de crescimento. Termos para indexaAao: plantas de cobertura, cultivo seqencial, rendimento de culturas, caracterIsti- cas agronUmicas. No-tillage system of flooded rice genotypes in succession to winter cover crops Abstract†n†The intensive use of the paddy soils in the production of flooded rice becomes more and more necessary. In this sense, the adoption of the no-till system of rice in succession to winter cover crops is an important alternative to facilitate the cultivation in the same area every year. A†trial was conducted with the purpose to identify more appropriate cover crops for cold season to participate of a succession system with no-till system of flooded rice genotypes at the EstaAao Experimental do Arroz of Instituto Rio Grandense do Arroz, in Cachoeirinha, RS, Brazil, in the 1996/97, 1997/98 and 1998/99 growing seasons. The treatments consisted of four flooded rice genotypes (BRS6, BR-IRGA†409, IRGA†416 and IRGA†417) installed in no-till system on plots with the grasses black oat (Avena strigosa Scheib), white oat (Avena sativa†L.) and rye grass (Lolium multiflorum Lam.); with the legumen iserradela nativai (Ornithopus micranthus (Benth.) Arechavaleta); with spontaneous veg- etation and with nude soil (check). For grain yield there was interaction between cover crops and growing seasons. In the three growing seasons, only the rice cultivated in succession to the legumen iserradela nativai presented similar grain yield to that one obtained in the control. On the other hand, the rice cultivated in succession to the rye grass was the only one presenting inferior grain yield in relation to the check in the three growing seasons.

Produtividade de arroz irrigado e eficiência da adubação nitrogenada influenciadas pela época da semeadura

The potential grain yield of late flooded rice is important for decision making of producers. Yields of rice crops sown after the recommended period are restricted due to unfavorable climatic conditions. The objective of this research was to evaluate grain yield and agronomic, technical and economic efficiency of broadcast nitrogen for flooded rice sown in December in the state of Rio Grande do Sul, Brazil. The field experiment was carried out in 2005/2006, in Cachoeirinha. Treatments consisted of two sowing dates, recommended (November) and late (December), four seeding rates (50, 100, 150, and 200 kg ha-1) and four nitrogen levels (0, 60, 120, and 180 kg ha-1). The experiment had a randomized block design using split plots with three replications. Rice grain yield and response to nitrogen topdressing were reduced by the late sowing date. The doses for maximum technical and economic efficiency were reduced with the sowing delay, and nitrogen agronomic efficiency was reduced with the sowing delay and N fertilizer dose. The number of panicles m-2 did not respond to nitrogen broadcast and was one of the most limiting yield components.

Resposta de genótipos de arroz irrigado ao arranjo de plantas

O aumento do rendimento de graos do arroz irrigado pode ser buscado atraves da manipulacao do arranjo de plantas. Oxa0objetivo desta pesquisa foi determinar a resposta de genotipos de arroz irrigado, com distintos tipos de planta e potenciais de rendimento, ao espacamento entre linhas e a densidade de semeadura. Conduziram-se tres experimentos no campo, no sistema de cultivo convencional, em Cachoeirinha, RS, nos anos agricolas de 1994/95, 1997/98 e 1998/99. Noxa0primeiro ano, os tratamentos constituiram-se de tres espacamentos entre linhas (12,5, 20 e 30xa0cm), de tres densidades de semeadura (75, 150 e 225xa0kg/ha) e de duas cultivares (BRIRGAxa0410 e IRGAxa0416). Nosxa0outros dois experimentos, os tratamentos constaram de quatro espacamentos entre linhas (12,5, 20, 30 e 40xa0cm), tres densidades de semeadura (30, 90 e 150xa0kg/ha), e de quatro genotipos de arroz irrigado (linhagem 959, hibrido XL5 e as cultivares BRIRGAxa0410 e IRGAxa0416). Nosxa0tres anos, a reducao do espacamento entre linhas aumentou o rendimento de graos, independentemente do genotipo de arroz irrigado. Sob condicoes de cultivo com controle de plantas daninhas e de adequado manejo da irrigacao, pode-se reduzir a densidade de semeadura.

Interferência do arroz vermelho no rendimento de engenho de cultivares de arroz irrigado

Red rice is considered the weed that cause the most significam damage to rice fields in the State of Rio Grande does Soul, Brazil. The presence of red rice grains associated with the grains of the commercial rice cultivars contribute to reduce the physical quality of the rice because reduce the milling yield and increase the number of grains chalky and with white pearly. This experiment was developed with the purpose of determining the effect of different quantities of retrace in the sample on the milling yield of three cultivars of irrigated rice with grains fine long class. The treatments consisted of different proportions in the samples (0, 5, 10, 15, 20, 25, 50, 75 and 100%) of grains red rice and grains of the rice cultivars BR-JRGA 410, IRGA 416 and IRGA 417. As the quantity of grains of red rice increased in the sample in the milling process, the whole grain yield and total milling yield decreased linearly, white the yield of broken grains increased linear fly for all cultivars.

Caracterização de biótipos de arroz-vermelho em lavouras de arroz no Estado do Rio Grande do Sul

O presente trabalho teve por objetivo avaliar caracteristicas morfofisiologicas de alguns biotipos de arroz-vermelho ocorrentes em lavouras de arroz no Estado do Rio Grande do Sul. Para isso, conduziu-se um experimento na Estacao Experimental do Arroz do Instituto Rio-Grandense do Arroz, durante a estacao de crescimento 1996/97. Os tratamentos constituiram-se dos seguintes biotipos de arroz-vermelho, segundo caracteristicas de graos: graos longo-finos, de casca clara, com ou sem arista; graos longo-finos, de casca preta; graos medios, de casca clara, provenientes de dois locais (Santo Antonio da Patrulha e Cachoeira do Sul); e graos curtos, de casca clara ou de casca preta. Como padroes comparativos foram utilizados os cultivares de arroz BR-IRGA 410 e IRGA 416. As variaveis avaliadas foram: estatura de planta, afilhamento, area foliar da folha bandeira, area foliar por planta, comprimento da panicula, numeros de espiguetas e de graos por panicula, esterilidade de espiguetas, relacao comprimento/largura de grao, peso medio de graos, producao de graos por planta e germinacao de sementes. Os biotipos de arroz-vermelho avaliados diferiram dos cultivares de arroz para as caracteristicas morfofisiologicas investigadas. De modo geral, para essas caracteristicas, nao se verificaram diferencas acentuadas entre biotipos possuidores de graos curtos, entre biotipos com graos medios e entre aqueles com graos longo-finos, de casca clara. Caracteristicas assemelhadas de dormencia apresentadas pelos biotipos de arroz-vermelho com graos longo-finos e de casca clara, com os cultivares de arroz, permitem inferir que aqueles sofreram cruzamentos com genotipos de arroz cultivado.

Supressão da produção de sementes de arroz-vermelho pela aplicação de herbicidas em arroz irrigado

(3) Resumo - A similaridade morfologica existente entre arroz-vermelho e arroz cultivado, associada a prolifica producao de sementes pelo arroz daninho e ao degrane dos graos com elevado teor de umida- de, sao fatores que contribuem para sua infestacao em lavouras de arroz. O objetivo deste trabalho foi investigar a supressao da producao de sementes viaveis, pelo arroz-vermelho, a fim de reduzir o seu banco de sementes no solo. Para isso, conduziram-se experimentos no campo e em laboratorio, nas estacoes de crescimento 1997/98 e 1998/99, utilizando-se os herbicidas nao-seletivos glyphosate, glufosinate e paraquat, aplicados em duas epocas e em duas doses, e o regulador de crescimento, hidrazida maleica, testado em duas epocas. Incluiu-se uma testemunha que nao recebeu aplicacao. Utilizou-se a cultivar de arroz IRGA-416, que cresceu na presenca de elevada infestacao de arroz- vermelho. Os produtos quimicos foram aplicados na fase de maturacao fisiologica da cultura. As variaveis avaliadas no arroz-vermelho foram: numero de colmos sem panicula, com paniculas normais e estereis, esterilidade de espiguetas, producao de sementes, peso medio de graos e germinacao de sementes. Os herbicidas glyphosate, glufosinate e paraquat podem ser usados seletivamente para suprimir a pro- ducao de sementes de arroz-vermelho, quando aplicados na fase de maturacao do arroz irrigado. A adocao desta tecnologia depende de haver diferenca de ciclo do arroz-vermelho em relacao ao cultivado, pela utilizacao de cultivares de arroz de ciclo precoce ou superprecoce. Termos para indexacao: Oryza sativa, dessecantes, controle de plantas daninhas, substâncias de cresci- mento vegetal. Suppression of red rice seed production by herbicides applied to irrigated rice Abstract - Morphological similarity between red rice and cultivated rice, associated with a prolific seed production by weedy rice and to grain dehiscence with high moisture content, are factors that contribute to its invasion in rice fields. The objective of this research was to investigate the suppression of viable seed production by red rice, with the intent of reducing its seed bank in the soil. With this purpose, field and laboratory experiments were carried out during the growing seasons of 1997/98 and 1998/99, utilizing the non-selective herbicides glyphosate, glufosinate, and paraquat, applied at two times and at two rates, and the growth regulator maleic hydrazide, tested at two times. A control with- out chemical treatment was included. The rice cultivar tested was IRGA-416, grown in the presence of a high red rice infestation. The chemicals were applied at physiological maturity of cultivated rice. Variables evaluated in red rice were: numbers of stems without panicle, with normal panicles, and sterile ones, spikelets sterility, seed production, seed weight and germination. The herbicides glyphosate, glufosinate, and paraquat can be used selectively in order to suppress red rice seed production when applied during maturity phase of cultivated rice. Adoption of this technology depends on existence of difference between maturity of cultivated and weedy rice, through use of early maturity rice cultivars.