Alexandre Reuber Almeida da Silva

Crescimento da cultura do girassol irrigado com diferentes tipos de água e adubação nitrogenada

The objective of the present study was to evaluate the growth of sunflower crop irrigated with different water sources (both treated wastewater and well water) and application of different rates of nitrogen fertilizer. The experiment was conducted at the Research Center of Treatment and Reuse of Sewer Water located in the municipality of Aquiraz in the State of Ceara, Brazil. The statistical design consisted of a randomized block in split-plots with four replications. In the plots, the effects of two types of irrigation water on sunflower growth parameters was evaluated and in the subplots the effects of the five irrigation levels; according to the percentage of Class A Evaporation Pan (ECA),corresponding to the multiplication of ECA by factors of 0.25, 0.50, 0.75, 1.00 and 1.25 levels were determined. In splitplots, the effects of the four rates of nitrogen (25, 50, 75 and 100 kg ha-1) on the same growth parameters were evaluated. The plant height, stem diameter and number of leaves increased lineaRLy as a function of the irrigation water levels. The parameter values obtained for wastewater were consistently higher than those obtained with well water. The capitulum diameter increased in a quadratic manner as a function of the irrigation water levels and nitrogen fertilizer rates.

Trocas gasosas em plantas de girassol submetidas à deficiência hídrica em diferentes estádios fenológicos

This study evaluated gas-exchange responses of the sunflower when subjected to water deficit at different stages of growth. The experiment was carried out at Pentecost, in the state of Ceara, in a randomized-block design of time-split plots, consisting of eight plots, three subplots and four blocks. In the plots, the periods of induction of the water deficit were evaluated at different stages of growth (vegetative, flowering and production formation), which corresponded to the occurrence of the water deficit at one, two or three stages, and in the subplots, the times of evaluation of the physiological characteristics corresponded to the end of each phase (52, 68 and 110 days after sowing, DAS). The crop was irrigated at a level equivalent to100% of the reference for evapotranspiration (ETo), and the water deficit was imposed at half the level that was used in the control treatment. The periods of evaluation influenced most of the variables analysed, except for the intrinsic efficiency of the use of water. The results for leaf temperature and for the rates of photosynthesis, transpiration, stomatal conductance, concentration of internal CO2, and the immediate and intrinsic efficiency of the use of water, showed no effects in relation to the level of water deficit evaluated regardless of the period in which these were applied. Photosynthesis and transpiration decreased with the stage of development of the crop, causing reductions in the immediate efficiency of the use of water. It was therefore concluded that the crop can be irrigated at 50% of ETo throughout the complete cycle without damage to the process of photosynthesis.This study evaluated gas-exchange responses of the sunflower when subjected to water deficit at different stages of growth. The experiment was carried out at Pentecost, in the state of Ceara, in a randomized-block design of time-split plots, consisting of eight plots, three subplots and four blocks. In the plots, the periods of induction of the water deficit were evaluated at different stages of growth (vegetative, flowering and production formation), which corresponded to the occurrence of the water deficit at one, two or three stages, and in the subplots, the times of evaluation of the physiological characteristics corresponded to the end of each phase (52, 68 and 110 days after sowing, DAS). The crop was irrigated at a level equivalent to100% of the reference for evapotranspiration (ETo), and the water deficit was imposed at half the level that was used in the control treatment. The periods of evaluation influenced most of the variables analysed, except for the intrinsic efficiency of the use of water. The results for leaf temperature and for the rates of photosynthesis, transpiration, stomatal conductance, concentration of internal CO2, and the immediate and intrinsic efficiency of the use of water, showed no effects in relation to the level of water deficit evaluated regardless of the period in which these were applied. Photosynthesis and transpiration decreased with the stage of development of the crop, causing reductions in the immediate efficiency of the use of water. It was therefore concluded that the crop can be irrigated at 50% of ETo throughout the complete cycle without damage to the process of photosynthesis.

Efluente de esgoto doméstico tratado e reutilizado como fonte hídrica alternativa para a produção de cana-de-açúcar

Com base no consumo hidrico excessivo na producao agricola e da expansao do cultivo da cana-de-acucar impulsionada pela crescente demanda de etanol, tem-se questionado em relacao a um uso mais racional da agua de irrigacao e ao reuso de agua na producao agricola. Desta forma objetivou-se, com o presente trabalho, avaliar os efeitos do reuso de efluente de esgoto domestico tratado na irrigacao da cana-de-acucar. O estudo foi conduzido no Centro de Pesquisa sobre Tratamento e Reuso de Aguas Residuarias, em Aquiraz, CE. O delineamento experimental adotado foi o de blocos ao acaso, no esquema de parcelas subdivididas, com quatro repeticoes. Nas parcelas avaliaram-se os efeitos de dois tipos de agua (agua potavel e esgoto domestico tratado); e nas subparcelas se alocaram cinco lâminas de irrigacao baseadas em percentuais da evaporacao medida em um tanque do tipo classe A (ECA). Concluiu-se que a agua residuaria proporcionou o maior potencial produtivo de colmos (272,1 Mg ha-1) e a maior densidade de plantas (126.000 plantas ha-1). O aumento das lâminas de irrigacao proporcionou incrementos no potencial produtivo e na densidade de plantas, independente do tipo de agua.

Morfologia e fitomassa do girassol cultivado com déficits hidricos em diferentes estádios de desenvolvimento

The objective of the present study was to evaluate the morphology, biomass production and biomass partition of sunflower (Multissol cultivar) when subjected to water deficit at Pentecoste, CE - Brazil. An experimental design in randomized blocks was used as split plots in time (8 x 3) with four replications, with the treatments defined by the development stage for application of water deficit vegetative, flowering and formation of production stages corresponding to the occurrence of water deficit at stages 1, 2 or 3 and three evaluation periods at 52, 68 and 110 days after sowing. The plant height, number of leaves and stem diameter were negatively influenced by the isolated effects of the water deficits and evaluation periods. The water deficits and evaluation periods interacted and affected the leaf area, dry mass of leaves, petiole, stem, head and total. The best response in terms of growth and biomass production occurred in the treatment presenting no water deficit throughout the cycle. The irrigation deficits did not change the biomass partition. The irrigation level equivalent to 50% of the ETo compromised morphology and biomass production, when applied at any development stage.

RESPOSTAS FISIOLÓGICAS DE PLANTAS DE COQUEIRO ANÃO SOB DEFICIÊNCIA HÍDRICA, EM SOLOS AFETADOS POR SAIS

The objective of this study was to characterize the physiological acclimation responses of young plants of the dwarf coconut cultivar ̳Jiqui Green‘ associated with tolerance to conditions of multiple abiotic stresses (drought and soil salinity), acting either independently or in combination. The study was conducted under controlled conditions and evaluated the following parameters: leaf gas exchange, quantum yield of chlorophyll a fluorescence, and relative contents of total chlorophyll (SPAD index). The experiment was conducted under a randomized block experimental design, in a split plot arrangement. In the plots, plants were exposed to different levels of water stress, by imposing potential crop evapotranspiration replacement levels equivalent to 100%, 80%, 60%, 40%, and 20%, whereas in subplots, plants were exposed to different levels of soil salinity (1.72, 6.25, 25.80, and 40.70 dS m). Physiological mechanisms were effectively limited when water deficit and salinity acted separately and/or together. Compared with soil salinity, water stress was more effective in reducing the measured physiological parameters. The magnitudes of the responses of plants to water supply and salinity depended on the intensity of stress and evaluation period. The physiological acclimation responses of plants were mainly related to stomatal regulation. The coconut tree has a number of physiological adjustment mechanisms that give the species partial tolerance to drought stress and/or salt, thereby enabling it to revegetate salinated areas, provided that its water requirements are at least partially met.

ESTABLISHMENT OF YOUNG “DWARF GREEN” COCONUT PLANTS IN SOIL AFFECTED BY SALTS AND UNDER WATER DEFICIT

The aim was to analyze the establishment of young “Green Dwarf” coconut plants in soils affected by salts and under water stress, by evaluating leaf area, biomass production and allocation. In the experiment, conducted in protected environment in Fortaleza, CE, in statistical design of randomized blocks in a split plot arrangement, the effects of different water deficit levels (plots) were evaluated, by imposing different percentages of replacement of water losses by potential crop evapotranspiration - ETpc (20, 40, 60, 80 and 100%), associated with subplots consisting of increasing soil salinity levels (1.72, 6.25, 25.80 and 40.70 dS m-1) provided by soil collected at different parts of the Morada Nova Irrigated Perimeter - PIMN. Leaf area and biomass production were sharply reduced by the conditions of water stress and high soil salinity, apparently being more critical to the crop under water restriction condition. The degree of water stress can increase the susceptibility to salinity and plants can be considered, in general terms, as moderately tolerant to the effects of salinity, when combined with water deficiency. Coconut seedlings show full capacity of establishment in PIMN saline soils, corresponding to the level of electrical conductivity of 6.50 dS m-1, but only when the water supply remains adequate. For higher salinity levels, plants survive, but their size is reduced by around 50%, even when fully irrigated.

Ion accumulation in young plants of the ‘green dwarf’ coconut under water and salt stress

Water scarcity and salinity are two major limitations on agricultural production. The aim of this study was to investigate the biochemical mechanisms associated with the separate and/or concurrent effects of water deficit and soil salinity on young plants of the ‘green dwarf’ coconut from the responses of ion accumulation (potassium, sodium and chloride) in the leaves and roots. The experiment was carried out in a screened greenhouse in Fortaleza, in the State of Ceara, Brazil. A randomised complete block statistical design was used in a scheme of treatments in subdivided plots, to evaluate the effects of different levels of water deficiency (plots) using different percentages for the replacement of water lost through potential crop evapotranspiration (20, 40, 60, 80 and 100%), associated with sub-plots comprising increasing levels of soil salinity (1.72, 6.25 , 25.80 and 40.70 dS m-1) found in soils collected in the Morada Nova Irrigated Perimeter (Morada Nova/Limoeiro do Norte, Ceara). Under conditions of water scarcity, K+ is maintained and/or accumulated in the leaves; while in the roots, levels are jointly affected by water deficiency and soil salinity, where these stress agents act in an antagonistic way on the K+ content. Conditions of salt stress lead to increases in the levels of Na+ both in the leaves and especially in the roots. The Cl- ion content of the leaves and roots responds to the interaction between water deficiency and salinity, demonstrating synergy in the relationship between stress agents. The accumulation of inorganic solutes in the leaves and roots of the coconut follows the order: Cl- > K+ > Na+.

Energy analysis of ethanol from sugarcane irrigated with treated domestic sewage

Using energy balance methodology, this study compared the sustainability of ethanol synthesis from sugarcane irrigated with different replacement levels based on the evaporation estimated in a Class A pan (ECA), using treated domestic sewage effluent and groundwater as the water source, in Aquiraz, in the State of Ceara. The adopted statistical design was of randomised blocks in split plots, with four replications. Two water sources (treated sewage effluent and groundwater) were evaluated in the plots, and five irrigation levels (50, 75, 100, 125 and 150% of the ECA) were evaluated in the split plots. Irrigation with treated domestic sewage effluent results in greater energy expenditure. The irrigation depth relative to 150% of the ECA expends the most energy, irrespective of the water source. Irrigation with treated domestic sewage effluent gives a higher energy yield (368.9 GJ ha-1) through the application of a depth of 781.4 mm, while for irrigation with groundwater, 937.6 mm (150% of the ECA) is the best recommended depth for obtaining the highest energy yield (276.9 GJ ha-1). Domestic sewage effluent gives the best energy return, and its use in systems of crop-production is viable.