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The cultivation of hybrid rice is a technology that allows for an increase in grain yield of 30% relative to the grain yield of conventional cultivars. However, the main challenge for this technology is related to seed production, which has high production costs and low seed yields. Therefore, agronomic techniques that could enhance flowering synchrony of parental lines in the field are essential for an efficient production system of hybrid rice seeds. The objective of this work was to study the effects of sowing depth, plant density and fertilization with nitrogen or phosphorus as potential techniques to increase the pollen availability in the field and, consequently, the flowering synchrony between parental lines in the production of hybrid rice seeds. The experiments were conducted during two growing seasons in the Central Region of Brazil. All of the experiments were conducted as a randomized complete block in a split plot scheme; however, the experiment with P fertilization had a factorial design. Our research allow inferring that nitrogen fertilization technique applied to the soil or foliar at the time of panicle differentiation does not affect the time of onset of flowering of rice varieties INTA Puitá CL and L106R, which are potential R lines for the production of hybrid rice. Agronomic techniques of variation in sowing depth, seeding rate and the phosphate fertilization affect the time of onset of flowering from 10 to 19 degree-days, which could represent two days in the crop cycle, for the line L106R. Such techniques constitute potential alternatives for use in hybrid rice seed production systems and could be applied in alternated blocks of R lines in the field to obtain longer periods of pollen availability in the field.

Entre os fatores que afetam a emergencia das plântulas e o estabelecimento da cultura estao a germinacao e o vigor das sementes, que tem influencia importante sobre o estabelecimento da populacao de plantas e o seu desenvolvimento inicial, podendo afetar a produtividade da cultura. Neste contexto, o objetivo deste trabalho foi avaliar os efeitos do vigor de sementes de lotes de sementes de feijao-comum sobre a produtividade da cultura. Os tratamentos consistiram de seis lotes de sementes de feijao-comum, que foram compostos por diferentes combinacoes de sementes de alto e baixo vigor. Os lotes de sementes foram avaliados por meio de testes de germinacao e de vigor (primeira contagem de germinacao, condutividade eletrica e envelhecimento acelerado). Um experimento de campo foi conduzido em delineamento em blocos casualizados, com parcelas de seis linhas de cinco metros e, foram avaliados pela produtividade de graos na colheita. Pelos dados obtidos concluiu-se que o vigor das sementes afeta a produtividade da cultura do feijao-comum; o uso de sementes com baixo vigor resulta em perdas de produtividade de ate 20%.