Roberto Rezende

Influência da condutividade elétrica, concentração iônica e vazão de soluções nutritivas na produção de alface hidropônica

Objetivou-se, neste trabalho, estudar os efeitos de diferentes solucoes nutritivas aplicadas em duas vazoes na producao hidroponica da alface (Lactuca sativa), cultivada pelo sistema NFT (Nutritive Film Technique). O experimento foi conduzido em casa de vegetacao, na unidade de pesquisa em agricultura irrigada da Universidade Estadual de Maringa. Os tratamentos constaram de tres solucoes nutritivas com concentracoes diferentes (S1=0,8 dS/m, S2=1,2 dS/m e S3=2,5 dS/m), combinadas com duas vazoes de aplicacao (V1=0,8 L.min-1 e V2=1,2 L.min-1 ) nos canais de cultivo em esquema fatorial 3 x 2. Para avaliar o efeito dos tratamentos no desenvolvimento da cultura os dados foram submetidos a analise de variância (teste F), e os resultados avaliados atraves de teste de media de Tukey (5%). A analise dos resultados permitiu concluir que os fatores solucao e vazao nao apresentaram interacao significativa e que os maiores valores avaliados de biomassa fresca e diâmetro do caule foram obtidos no tratamento solucao 2 (CE= 1,2 dS/m).

Efeito de paclobutrazol como regulador de crescimento e produção de flores de girassol em cultivo hidropônico

Objetivou-se neste trabalho estudar os efeitos de um regulador de crescimento (paclobutrazol) sobre o crescimento e a producao de flores de girassol em vasos, crescidos sob sistema hidroponico. Foram utilizados dois genotipos de girassol (BRS Oasis e Helio 358), combinados com seis doses de paclobutrazol (0;0,5;1;2;4 e 6 mg.L-1) e substrato inerte de silica moida. A solucao nutritiva foi a de Hoagland modificada (EPSTEIN & BLOOM, 2004) e as plantas foram mantidas sob aeracao constante. Para avaliar os efeitos do paclobutrazol sobre o crescimento das plantas (altura final e diâmetro de capitulo), as variaveis foram submetidas a analise de variacao (teste F), utilizando-se rotinas do sistema SAS/STAT , aplicando-se, para os valores significativos a 5% de probabilidade e a regressao linear e nao linear para a analise dos parâmetros aferidos, em funcao das doses do regulador de crescimento. A analise dos dados permitiu concluir que ha efeito do paclobutrazol sobre o crescimento e sobre a producao de flores de girassol, reduzindo a altura final das plantas e o diâmetro dos capitulos, sendo que doses elevadas causaram deformacoes nas plantas e ma formacao nas flores. Helio 358 apresentou-se mais adequado para a producao ornamental, sendo melhor dose entre 1 e 2 mgL-1de paclobutrazol.

Lâmina ótima de irrigação do feijoeiro, com restrição de água, em função do nível de aversão ao risco do produtor

Nowadays, the rising competition for the use of water and environmental resources with consequent restrictions for farmers should change the paradigm in terms of irrigation concepts, or rather, in order to attain economical efficiency other than to supply water requirement for the crop. Therefore, taking into account the social and economical role of bean activity in Brazil, as well as the risk inherent to crop due to its high sensibility to both deficit and excessive water, the optimization methods regarding to irrigation management have become more interesting and essential. This study intends to present a way to determine the optimal water supply, considering different combinations between desired bean yield and level of risk, bringing as a result a graph with the former associated with the latter, depending on different water depths

Viabilidade de inserção dos efeitos da uniformidade de irrigação em modelos de crescimento de culturas

A study was designed to evaluate the effects of uniformity of sprinkler irrigation in maize and dry bean crops. For maize crop, the treatments consisted of five depths of water applied in two application uniformities: one high (CUC> 82%) and the other low (CUC<67%). For dry beans, the treatments consisted of four Christiansen application uniformity coefficients (CUC - 94.1, 85.6, 65.6 and 57.9%). A regression equation was adjusted for maize grain yield versus water application depth for high uniformity irrigation treatments, whereas for treatments with low irrigation uniformity in maize crop and for all treatments in dry beans the regression equations observed had very low values of R2. These data indicate that, it is impossible to introduce irrigation uniformity effects in crop growth simulation models

Crescimento de girassol como flor em vaso em função de doses de paclobutrazol

Growth of potted sunflower in response to paclobutrazol Sunflower, besides being an oil seed crop, is also grown as an ornamental plant. However , its great growth in height makes such use difficult, especially as pot flower . This study aimed to evaluate the effects of the growth regulator paclobutrazol on the growth of potted sunflowers in a hydroponic system, in pots filled with milled silica in a greenhouse. Two sunflower genotypes BRS Oasis with brown head and average height of 1,85 m and Helio 358, with yellow head and average height of 1,45 m. The rates of paclobutrazol evaluated were 0; 0.5; 1; 2; 4 and 6 mg L -1 , directly applied on the milled silica substrate. The plants were maintained in Hoagland nutrient solution under constant aeration. The experiment was arranged in a factorial complete randomized block , design with five repetitions, totaling 60 plots. The variables evaluated were plant height, dry phytomass of root, stem, leaves and heads. There was no effect of paclobutrazol on plant growth. Paclobutrazol reduced the height of cultivars Helio 358 and BRS Oasis at all rates. Rates higher than 2 mg L -1 and 4 mg L -1 reduced the growth of the genotypes BRS Oasis and Helio 358 respectively. Sensitivity to

Spatial variability and temporal stability of water storage in a cultivated tropical soil

Irrigated agricultural fields usually show variable crop water demand. If water application is done to match this spatially variable demand, the water use efficiency can be substantially improved. Soil water management by irrigation has been one of the most important factors to increase crop yield. To look for the economic viability of the process, the use of several inputs, particularly water, should be done with high efficiency levels. Historically, irrigation uniformity has been evaluated above the soil surface, in which applied water was the only factor to be taken into account. However, the crop will respond to soil water content uniformity, which can differ from the uniformity of water application. To evaluate temporal stability of spatial pattern of soil water storage (SWS), this work was done on a Brazilian clayed soil. Volumetric water content from soil surface to 0,30m depth, was measured by TDR in 80 points regularly spaced (3 x 3 m) on an experimental area cultivated with bean crop, irrigated by conventional sprinkling. The evaluations were done immediately before and after a water application by irrigation. Experimental semivariograms made from values obtained in the field showed that SWS distribution was spatially structured and strongly stable in time, being regulated mainly by intrinsic factors of the soil. In addition, obtained results showed that water application uniformity did not influence the spatial distribution pattern of SWS in these soil conditions.

Optimal irrigation depth for bean crops considering water constraints and farmer's risk aversion level

Nowadays, the rising competition for the use of water and environmental resources with consequent restrictions for farmers should change the paradigm in terms of irrigation concepts, or rather, in order to attain economical efficiency other than to supply water requirement for the crop. Therefore, taking into account the social and economical role of bean activity in Brazil, as well as the risk inherent to crop due to its high sensibility to both deficit and excessive water, the optimization methods regarding to irrigation management have become more interesting and essential. This study intends to present a way to determine the optimal water supply, considering different combinations between desired bean yield and level of risk, bringing as a result a graph with the former associated with the latter, depending on different water depths