The objective was determine the effect of cover crops on the water use efficiency and total yield of the pumpkin crop. The study was carried out on a soil called petrocalcic Paleustoll, located in the south of the rugged plain of the semi­arid Pampa region. In the same lot for three consecutive seasons, Rye (C) and rye + vetch (CV) were sown and fallow was established without cover cultivation. In this way, 6 management treatments for pumpkin cultivation were established: T1: without CC predecessor, with tillage prior to pumpkin planting, and without weed control during the pumpkin cycle. T 2: without predecessor CC with tillage prior to planting the pumpkin, with weed control (tillage and herbicide), during the pumpkin cycle. C H: Rye ancestor used as CC, with growth arrest by herbicide. C R: Rye ancestor used as CC, with growth arrest by rolling. CV H: Rye + Vetch ancestor used as CC, with growth arrest by herbicide. CV R: Rye + Vetch ancestor used as CC, with growth arrest by rolling. The results showed that on average in the 3 seasons C was higher than C V, in 22, 19 and 6% with respect to the total biomass, for the first, second and third seasons, respectively. Cover crops had higher fallow efficiency with respect to treatments without prior CC (T1 and T2). The highest pumpkin yields were over the CC, these being the ones with the lowest UC and the highest EUAt

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RESUMENLa producción hortícola en la zona de Santa Rosa, La Pampa, se realiza bajo riego, el agua dis ponible para tal fin tiene un alto contenido de sales. El objetivo de este trabajo es evaluar la res puesta del crecimiento, la actividad de la SOD y la concentración de malondialdehido, al riego con agua salina en 11 genotipos de lechuga. Se trabajó en invernáculo, y los plantines durante 54 días fueron regados con dos calidades de agua, de lluvia y con alta salinidad. Los genotipos Grand Rapid, Bermella y Boltar mostraron una reducción del peso seco del 12, 11 y 87% respectivamente y en Grand Rapid e Ice 15975 la reducción del vigor fue del 3 y 2% respectivamente. En Ice 15975, Gran Rapid y Bermella hubo un incremento de la concentración de malondialdehido del 98, 138 y 56% respectivamente ante el riego con agua salada. En Ice 15975 y Grand Rapid esta respuesta se asocia a una disminución de la actividad de la SOD. El resto de los genotipos no expresó cam bios en la concentración de malondialdehido. Estos resultados evidencian una respuesta diferencial de los genotipos en estudio, y la concentración de malondialdehido puede usarse para seleccionar genotipos de lechuga tolerantes al riego con agua con alto contenido de sales al estado de plantines. ABSTRACTHorticultural production is carried out under irrigation in the area of Santa Rosa, La Pampa pro vince, where available water sources are highly concentrated in salts. The aim of this study was to evaluate the effect of irrigation with high salt content water on growth, superoxide dismutase (SOD) activity and malondialdehyde concentration, in seedlings of 11 lettuce genotypes. The experiment was performed in a greenhouse, where the seedlings were irrigated for 54 days with two different kinds of water, one from rain as a control and another one of high salinity. Irrigation with high salinity water caused a decrease of 11, 12 and 87% in dry weight yield for Bermella, Grand Rapid and Boltar genotypes, respectively, and a vigor reduction of 2% for Ice 15975 and 3% for Grand Rapid. A the same time, irrigation treatment with high salinity resulted in plant malondialdehyde concentration in creases of 56, 98 and 138% for Bermella, Ice 15975 and Grand Rapid, respectively. In the case of the last two genotypes, their response was associated with a SOD activity decrease. The rest of the genotypes did not show changes in malondialdehyde concentration. These results evidenced a dif ferential response among the assayed lettuce varieties, and that malondialdehyde concentration can Recibido 23/. 2017. Tole rancia de plantines de distintos genotipos de lechuga (Lactuca sativa L.) al riego con agua de alto contenido en sales. Se miárida Rev. Fac. Agron. UNLPam. 27(2): 5966 be used to select genotypes tolerant to irrigation with water of high salt content at seedling stage.