Growth of leguminous plants used as green manure under different salt levels in irrigation water/Crescimento de leguminosas utilizadas na adubacao verde em diferentes niveis de sais na agua de irrigacao

This study had the objective to evaluate the influence of salinity on the growth of legumenous species commonly used as green manure. An experiment was conducted in a greenhouse in the year of 2010 set up in 5 x 2 factorial in randomized blocks. Treatments were composed of five levels of salt (0.8, 1.6, 2, 4, 3.2 and 4.0 dS [m.sup.-1] at 25°C) in irrigation water and two legumenous species: Crotalaria juncea and Crotalaria spectabilis. Sodium chloride was added in the irrigation water and plants were irrigated manually on alternate days, based on water consumption of the previous day. The morpho-physiological parameters--plant height, stem diameter and number of leaves, were evaluated. Absolute growth rates and relative growth rates were adjusted to the regression models. Plants of Crotalaria juncea were not affected with salt levels used in this study. Depressive effect of salt levels was observed at 40 days for plant height, stem diameter and number of leaves of Crotalaria spectabilis, with linear response for plant height and quadratic for stem diameter and number of leaves. Key words: salinity cover crops biometry Objetivou-se, com este trabalho, avaliar a influencia da salinidade no crescimento de especies de leguminosas comumente utilizadas como adubacao verde. Conduziu-se um experimento em ambiente protegido, no ano de 2010, em blocos ao acaso, no esquema fatorial 5 x 2. Os tratamentos foram cinco niveis de sais (0,8, 1,6, 2,4, 3,2 e 4,0 dS [m.sup.-1] a 25°C) e duas leguminosas: Crotalaria juncea e Crotalaria spectabilis. A agua de irrigacao foi preparada com a adicao de NaCl e as irrigacoes foram feitas manualmente, em dias alternados, com base no consumo de agua das plantas na irrigacao anterior. Avaliaram-se os componentes morfofisiologicos--altura de plantas, diametro do caule e numero de folhas. Plantas de Crotalaria juncea nao foram afetadas pelos niveis de sais utilizados neste trabalho. Observou-se efeito depreciativo dos niveis de sais aos 40 dias, para altura de plantas, diametro do caule e numero de folhas da Crotalaria spectabilis, com resposta linear para altura de planta e quadratica para diametro do caule e numero de folhas. Palavras-chave: salinidade plantas de cobertura biometria