Produção de girassol sob estresse salino e adubação nitrogenada

Abstract

RESUMOA limitada disponibilidade de águas de baixa salinidade na região semiárida brasileira faz com que os produtores utilizem, na irrigação, águas com teores salinos de moderado a alto. Considerando que o girassol (Helianthus annuus L.) vem ganhando destaque nessa região por se caracterizar como fonte potencial de energia renovável, realizou-se esta pesquisa visando avaliar a sua produção sob diferentes níveis de salinidade da água de irrigação (CEa) e doses de adubação nitrogenada, em experimento conduzido em casa de vegetação da Universidade Federal de Campina Grande (UFCG), entre julho e outubro de 2009. Utilizou-se a aleatorização em bloco, testando-se cinco níveis de CEa (0,5 -controle; 1,6; 2,7; 3,8; e 4,9 dS m -1 ) e quatro doses de adubação nitrogenada (50, 75, 100 e 125 % da dose indicada para ensaios em vaso), em esquema fatorial 5 x 4, com três repetições. A salinidade da água de irrigação e a adubação nitrogenada afetam as plantas de girassol de forma independente. A salinidade da água de irrigação a partir de 0,5 dS m -1 altera linear e negativamente a área foliar, a matéria seca da parte aérea e das raízes, a massa e produção total de aquênios e o índice de colheita, enquanto a duração do ciclo da cultura e o intervalo do tempo entre a formação e maturação fisiológica dos aquênios diminuem e sua massa aumenta com as doses de N. Termos de indexação:Helianthus annuus L., produtividade, condutividade elétrica.

Gas exchange and production of sunflower (Helianthus annuus L.) irrigated with water of different salinity, cationic nature and nitrogen doses

“…Excess of salts in water, independently of their cationic nature, cause damage to various physiological and biochemical processes such as respiration, photosynthesis, protein synthesis and lipid metabolism, and may also lead the plant to a state of water stress with loss of water to the external environment and to suffer from toxicity, which will result in serious damage to the growth and production of plants (Esteves& Suzuki, 2008). Corroborating with the results obtained Nobre et al (2011) found that the effect of irrigation with water of different saline levels and nitrogen rates on sunflower growth and flowering, decreased both internal and external diameterof capitulum. According to Figure2B, the phytomass of the capitulum with achenes (PCA) of the plants differed significantly due to the use of water with different cationic nature, and the highest value (88.03 g) was obtained using water of the treatment S 1 (control).…”

“…For the factor N doses (ND), there was no significant influence for any of the studied variables, while the interaction (S x ND) showed to significance only for the dry phytomass of the capitulum (DPC). Nobre et al (2011) evaluating the production of sunflower cv. Embrapa 122 / V-2000 cultivated under different irrigation water salinity levels (ECw: 0.5 to 4.9 dS m -1 , prepared with addition of NaCl) and nitrogen fertilization rates, also observed no interaction between these factors for any production variable evaluated.…”

“…Such decrease in DPC is attributed to the osmotic effect of the dissolved salts, which reduce the osmotic potential of the soil solution and inhibit the movement of water to the cells, characterizing the water stress, besides the possibility of occurrence of ionic toxicity, nutritional imbalance, or both, due to the excessive accumulation of certain ions in the plant tissues (Flowers, 2004). In an experiment conducted in greenhouse with the sunflower cultivar Embrapa 122/V-2000 irrigated with waters of different salinity levels (0.5 to 4.9 dS m -1 ), Nobre et al (2011) observed that the production of achenes was negatively affected by the increase in the electrical conductivity of the irrigation water.…”

“…In order to minimize the effects of salinity on sunflower growth and yield, various strategies have been studied, particularly the use of nitrogen (N) fertilizers (Biscaro et al, 2008;Nobre et al, 2010;Nobre et al, 2011). Since N is a macronutrient required in large amount by the agricultural crops, it is among the main management techniques (Miller & Cramer, 2004) because of its participation in the formation of protein, amino acids and other compounds important for plant metabolism (Barhoumi et al, 2010).…”

Impact of Saline Conditions and Nitrogen Fertilization on Citrus Production and Gas Exchanges

“…On the other hand, the application of ammonium (NH 4 + ) can contribute to a higher absorption of anions and, in salt-affected soils with high amounts of chlorides, NH 4 + will be absorbed preferentially, causing lower damages to plants. Preliminary results have been observed in experiments with castor bean (SOARES et al, 2013;LIMA et al, 2014) and sunflower (NOBRE et al, 2011;NOBRE et al, 2014).…”