Application of sewage sludge improves water and nitrogen use efficiency in alfalfa (Medicago sativa L.) under drought conditions

MARIA LAURA FIASCONARO; MANUEL SÁNCHEZ-DÍAZ; MA CARMEN ANTOLÍN

Jornada; IV Jornada de Investigación en Ciencias Experimentales y de la Salud de la Universidad de Navarra; 2011

Sewage sludge has been used as N fertilizer because it contains some of inorganic N, principally as nitrate and ammonium ions. However, sewage sludge addition to legumes could result in impaired nodule metabolism due to the presence of inorganic N from sludge. The aim of this study was to determinate the effects of sewage sludge on growth, photosynthesis, N assimilation and nodule activity of alfalfa plants under drought conditions. The experiment included three treatments: (1) plants inoculated with rhizobia and amended with sewage sludge at rate of 10% (w/w) (RS); (2) plants inoculated with rhizobia without any amendment (R); and (3) non-inoculated plants fed with ammonium nitrate (N). Two levels of irrigation were imposed: (1) well-watered and (2) drought stress during several cycles of moisture stress and recovery. Results showed that sludge-treated plants have decreased photosynthesis and N2 fixation under drought. However, there was a stimulation of the N assimilation capacity. Thus, the application of sewage sludge resulted in improved growth and led to an efficient use of resources such as water and nitrogen in alfalfa plants grown in drought stressed conditions.