Response of alfalfa (Medicago sativa L.) to diurnal and nocturnal saline sprinkler irrigations. II: shoot ion content and yield relationships

摘要

When using saline waters, sprinkling irrigation at night is a recommended practice to reduce evaporation, salt absorption by the wetted leaves and its negative effects on crops. We measured shoot ion concentrations (Cl super(-), Na super(+) and K super(+)) and total dry matter (TDM) in alfalfa subject to diurnal and nocturnal saline sprinkler irrigations and established potential relationships among them. The work was carried out along the 2004-2006 growing seasons using EC waters from 0.5 to 5.6dSm super(-1). Saline sprinkling irrigations linearly increased shoot Cl super(-) and Na super(+) and decreased shoot K super(+). Even though daytime evaporation was much higher than nigh-time, shoot ion accumulation and TDM were similar in the diurnal and nocturnal irrigations. The salinity tolerance of alfalfa decreased in year 2006 due to increases in shoot Cl super(-) and, particularly, shoot Na super(+). The lower threshold for shoot Na super(+) (276meqkg super(-1)) than for shoot Cl super(-) (726meqkg super(-1)) shows that alfalfa is more sensitive to Na super(+) than to Cl super(-), and that Na super(+) accumulation is the preponderant cause of alfalfa yield decline after 3 years of sprinkling with saline waters.