Nitrate and ammonium nutrition in chicory and rocket salad plants

Abstract

To evaluate chicory (Cichorium intybus L.) and rocket salad [Eruca vesicaria (L.) Cav.subsp. sativa (Mill.)] capability to use ammonium‐nitrogen (NH4‐N) even in the absence of nitrate‐nitrogen (NO3‐N) in the nutrient solution, and the chances they offer to reduce leaf NO3 content, cultivated rocket and two cultivars of chicory ('Frastagliata’, whose edible parts are leaves and stems, and ‘Clio’, a leaf hybrid) were hydroponically grown in a growth chamber. Three nutrient solutions with the same nitrogen (N) level (4 mM) but a different NH4‐N:NO3‐N (NH4:NO3) ratio (100:0, 50:50, and 0:100) were used. Rocket growth was inhibited by NH4 nutrition, while it reached the highest values with the NH4:NO3 ratio 50:50. Water and N‐use efficiencies increased in rocket with the increase of NO3‐N percentage in the nutrient solution. In the best conditions of N nutrition, however, rocket accumulated NO3 in leaves in a very high concentration (about 6,300 mg kg‐1 fresh mass). For all the morphological and yield features analyzed, chicory resulted to be quite unresponsive to N chemical forms, despite it took more NO3‐N than NH4‐N when N was administered in mixed form. By increasing NO3‐N percentage in the nutrient solution, NO3 leaf content increased (5,466 mg kg‐1 fresh mass with the ratio NH4:NO3 0:100). On average, both chicory cultivars accumulated 213 mg NO3 kg‐1 fresh mass with the ratio NH4:NO3 100:0 and, differently from rocket, they showed that by using NH4 produce can be obtained very low in NO3 content.