Leandro Leonardo Teichmann

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.

Adubação nitrogenada em milho pelo monitoramento do nível de nitrogênio na planta por meio do clorofilômetro

The objective of monitoring the adequate nitrogen (N) content in maize is to determine when a nutrient application becomes necessary, since the use of high doses of this nutrient may contaminate superficial and underground waters with nitrate. This experiment was conducted to evaluate the chlorophyll content in leaves, measured by a chlorophyll meter, as an indicator of the N level in maize, at four growth stages, in the state of Rio Grande do Sul, Brazil, during the growing season 1999/2000. Treatments consisted of two maize hybrids (Pioneer 32R21 and Premium) and eight nitrogen management systems. The tested variables (grain yield, N level and accumulation in leaf and plant) in the systems monitored by the chlorophyll meter did not differ in relation to the standard systems, where N was applied regardless of the readings. Monitoring of the N content in the hybrid Pioneer 32R21, reduced N applications by 50, 100 and 150 kg ha-1, respectively, in the S3, S4, and S5 systems, and in the hybrid Premium by 150 kg ha-1 in the system S5, without affecting the maize grain yield. Therefore, monitoring the N level in maize by the corresponding chlorophyll leaf content with a portable chlorophyll meter proved to be an efficient method to separate plants with N deficiency from those with an adequate level of this nutrient.

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.