Vladirene Macedo Vieira

Desempenho agronômico a campo de híbridos de milho inoculados com Azospirillum

O uso de inoculantes na cultura do milho tem sido cada vez mais valorizado, em vista dos beneficios que pode trazer a cultura, como a fixacao biologica do nitrogenio e o aumento da quantidade de raizes. Isto pode melhorar a absorcao de agua e nutrientes pela planta, contribuindo para o desenvolvimento do milho, principalmente em periodos de seca. Este estudo foi desenvolvido com o objetivo de avaliar, em condicoes de campo, as caracteristicas agronomicas e o rendimento de graos de hibridos de milho, inoculados, ou nao, com uma mistura de tres especies de Azospirillum (A. brasilense, A. lipoferum, A. oryzae). Foram avaliados o teor relativo de clorofila nas folhas, a altura de planta, a senescencia foliar, os componentes de rendimento de graos, o teor de N, a materia seca da parte aerea das plantas e o numero mais provavel de bacterias diazotroficas na rizosfera das plantas. A inoculacao manteve o teor de clorofila significativamente maior ate o estadio R3 das plantas, para os tres hibridos testados, aumentou o rendimento da materia seca da parte aerea, dos hibridos AS 1575 e SHS 5050, o peso de 1000 graos, para o hibrido P32R48 e altura, para o AS 1575. Houve interacao entre os genotipos de milho e as bacterias inoculadas, visto que, cada hibrido testado respondeu de forma diferente a inoculacao. A inoculacao de Azospirillum em milho demonstrou estimular o desenvolvimento das plantas no periodo vegetativo, aumentando a probabilidade de obter-se um estande de plantas uniforme, maior resistencia ao estresse e maior concentracao de clorofila nas folhas.

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.

Densidade de plantas de milho híbrido em semeadura precoce no Rio Grande do Sul

A escolha da densidade de plantas e a sua adequacao a epoca de semeadura sao praticas de manejo importantes na determinacao do rendimento de graos de milho. Este trabalho foi realizado a fim de avaliar os efeitos da densidade de plantas sobre o rendimento de graos e seus componentes em dois hibridos cultivados em semeadura precoce (agosto) no Rio Grande do Sul. O experimento foi conduzido em Eldorado do Sul, em 2006/07. Os tratamentos consistiram de quatro densidades de plantas (5,5; 7,3; 9,1 e 11pl m-2) e dois hibridos, um de folhas decumbentes (Dow 2B587) e outro de folhas eretas (NB 4214). A semeadura foi realizada em 22 de agosto de 2006. O rendimento de graos do hibrido de folhas decumbentes aumentou linearmente com o incremento na densidade de 5,5 ate 11pl m-2, alcancando 16t ha-1. Ja no hibrido de folhas eretas, o rendimento aumentou de forma quadratica, sendo maximizado na densidade de 9,4pl m-2. O numero de espigas por metro quadrado foi o componente que melhor explicou o aumento da produtividade com o incremento na densidade de plantas. O uso de densidades superiores a 9pl m-2 e uma estrategia efetiva para aumentar o rendimento de graos sob alto nivel de manejo em semeadura precoce (agosto).

Estratégias de manejo da palha de azevém para cultivo do arroz irrigado em sucessão

The adoption of crop rotation and crop sequence systems is one of the fundamental prerequisites for the sustainability of agricultural production. Therefore, the objective of this study was to evaluate the effects of ryegrass desiccation time and nitrogen fertilizer applied at sowing of irrigated rice, in succession, as a management strategy in irrigated rice cultivation. The field experiment was carried out in two growing seasons (2008/09 and 2009/10), in Cachoeirinha, State of Rio Grande do Sul, Brazil, on a typical dystrophic Ta Haplic Gleysol. The design was a randomized complete block, with three replications. The treatments, laid out in split plots, consisted of four periods of ryegrass desiccation (90, 70, 50 and 30 days before sowing rice in the first year, and 49, 34, 19 and 6 in the second year of cultivation), and five nitrogen fertilization systems of rice, consisting of a combination of four N rates applied at sowing (0, 10, 20, and 40 kg ha-1) and four N rates as top dressing (150, 140, 130, and 110 kg ha-1), resulting in a total of 150 kg ha-1, plus a control without N application throughout the crop cycle. The initial establishment of rice plants grown in succession was not affected by the presence of upright-standing dry ryegrass plants. In both years, rice grain yield was not influenced by the desiccation time of ryegrass nor the N rate applied at sowing.

Práticas de manejo integradas para produção de arroz irrigado

The objective of this work was to perform a technical and financial evaluation of integrated management practices for lowland rice (Oryza sativa). The experiment was carried out in Cachoeirinha, in the state of Rio Grande do Sul, Brazil. A randomized block design with split-split plots with four replications was used.The three growing seasons (2003/2004, 2004/2005, and 2006/2007) were the main plots, the sowing dates (preferential and late) were the split plots, and the management practice systems (low, average, high and veryhigh) were thes plit-split plots. The management practice systems varied in terms of seeding rate, fertilizer rate, herbicide rate, nitrogen fertilizer topdress management, and irrigation management. The grain yield and financial return responses to the improvement of management practices were greater at the preferential sowing date, at the end of October, than on the first week of December. At the preferential sowing date, the financial return increased with the improvement of management practices, due to the increased income resulting from the higher grain yield.