NITRATE AND AMMONIUM NUTRITION IN CHICORY AND ROCKET SALAD PLANTS

To evaluate chicory (Cichorium intybus L.) and rocket salad [Eruca ves icaria (L.) Cav.subsp. sativa (Mill.)] capability to use ammonium-nitr ogen (NH4-N) even in the absence of nitrate-nitrogen (NO3-N) in the nu trient solution, and the chances they offer to reduce leaf NO3, conten t, cultivated rocket and two cultivars of chicory ('Frastagliata', who se edible parts are leaves and stems, and 'Clio', a leaf hybrid) were hydroponically grown in a growth chamber. Three nutrient solutions wit h 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 inhi bited by NH4 nutrition, while it reached the highest values with the N H4:NO3 ratio 50:50. Water and N-use efficiencies increased in rocket w ith the increase of NO3-N percentage in the nutrient solution. In the best conditions of N nutrition, however, rocket accumulated NO3 in lea ves in a very high concentration (about 6,300 mg kg(-1) fresh mass). F or all the morphological and yield features analyzed, chicory resulted to be quite unresponsive to N chemical forms, despite it took more NO 3-N than NH4-N when N was administered in mixed form. By increasing NO 3-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, b oth chicory cultivars accumulated 213 mg NO3 kg(-1) fresh mass with th e ratio NH4:NO3 100:0 and, differently from rocket, they showed that b y using NH4 produce can be obtained very low in NO3 content.