Influence of crop cycle and nitrogen fertilizer formon yield and nitrate content in differentspecies of vegetables

Research was carried out in Latina province (Italy) on rocket, radish and zucchini grown under tunnel. Ten treatments, obtained by the factorial combination of two crop cycles (autumn-winter and winter-spring) and six nitrogen fertilizer forms (organic, organic-mineral, mineral in three modes, control with no nitrogen fertilization) were compared. The effects of these treatments were evaluated in terms of yield and nitrate content in the edible organs. In rocket, no significant difference in yield was detected between the autumn-winter and winter- spring crop cycles, although the former cycle resulted in a higher leaf nitrate content. The organic fertilizer treatment and the N-unfertilized control gave the lowest yields, but the mineral fertilizers caused the highest leaf nitrate accumulation. Radish yield did not vary between the two crop cycles, but the hypocotyl nitrate content was higher in the autumn-winter cycle. The crops fertilized with the two highest mineral supplies produced the highest yields, compared with the organic or organic-mineral treatments. In the autumn-winter crop, the mineral N fertilization resulted in the highest hypocotyl nitrate content, whereas in the winter-spring crop only the highest mineral N dose caused a higher nitrate content compared with the organic fertilizer. The highest zucchini yield was obtained from the winter-spring cycle at the two highest mineral fertilizer supplies. In the autumnwinter crop the highest mineral nitrogen dose resulted in the highest fruit nitrate content, while in winter-spring the two highest supplies caused this effect.