Abstract: This study was conducted with the objective assessing the effect of ammonium nitrate fertilizer applied 0, 100, 200, 300, 400 and 500 kg N ha -1 on nitrogen uptake and accumulation of rocket plant in the field conditions. It was determined total nitrogen NO3-N, NO2-N contents of leaves. Highest yield was determined at the parcels that received 300 kg N ha -1. In this study, the highest leaf NO3-N (205.6-795.3 ppm) and NO2-N (0.019-0.154 ppm) contents was measured in the parcels that received the highest N (500kg ha -1) dose.
Introduction
Rocket is a very anthautic herbaceous plant consumed in many of the Mediterrean countries as a salad for its leaves and India and China as an oil crop for its seed (Vaughan, 1970), which is utilized in human nutrition and in drug industry (Vural et al., 2000; Bianco and Boari, 1996).
Likewise spinach and lettuce exceeding concentrations of nitrite (NO2) and nitrate (NO3) in rocket leaves also threaten human health. Infact, methemoglobinia kind of cancer risk increases.
It is analyzed high amounts of Nitrate of rocket in Italia market (Cerrutti et al., 1996; Santamaria et al., 1998b). Hakerlerler et al. (1993) and Venter (1978) reported that over fertilization with nitrogen (N) results in NO2 and NO3 accumulation in leaves.
The objective of this study to examine the NO3 and NO2 accumulations in rocket leaves fertilized under different rates of nitrogen.
Materials and Methods
A trial was performed in the experimental fields one years of Odemis Vocational School, Ege University, where 5 rates of N(0-100-200-300-400 and 500 kg ha-1) were in corporated into 2 m2 parcels, ½ at preseeding and the second half 40 days later in the form of ammonium nitrate. Phosphorus (P2O5) and Potassium (K2O) were applied at 150 kg ha-1 rates in the forms of triple super phosphate and potassium sulphate, respectively. Rocket seeds were sown on 11.01.2001 harvested on 21.03.2001.
A soil sample was taken from the experimental field and analyzed according to standard methods (Bingham, 1949; Bremner, 1965; Lindsay and Norvell, 1978). Leaves were harvest and analyzed for their total N (Kacar, 1972), for NO3-N (Balks and Reekers, 1960) and NO2-N (Bremner, 1965 and Hildebradt, 1976). Yield was determined and statistically analyzed according to Acikgoz (1993).
Results and Discussion
Experimental soil (Table 1) was slightly acidic in pH, poor in CaCO3(%), sandy loam in texture, poor in organic matter, total N (%) and had no salinity problem (Bouyoucos, 1962 and Loue’, 1968).
Highest yield was determined at the parcels that received 300 kg N ha-1 (Table 2). On the other hand, highest leaf N content (4.2-6.5 %) was measured in 500 kg N ha-1 treatment. Infact, leaf N contents were found higher than the normal threshold values given by Bergmann (1988). Esiyok et al. (1998) report that the highest yield was obtained at the 160 kg ha-1 N treatment and the highest leaf N was at the 240 kg ha-1 treatment of the 20th harvest.
In this study, the highest leaf NO3-N (205.6-795.3 ppm) and NO2-N (0.019-0.154 ppm) contents was measured in the parcels that received the highest N (500 kg ha-1) dose. However, these values were lower than the measurements (1500mg kg-1, fresh weight) of Ruckenbauer (1985). In this regard, Bergmann (1998) cited NO3 contents of chicory and similar crops as 1500 mg kg-1 (fresh weight). Result showed that enhanced N rates affected the yield, total N and NO3-N contents significantly at 1% level.
| Table 1: | Physical and chemical properties of experimental soil |
| Table 2: | The effect of nitrogen fertilization on yield and nitrogen accumulation in rocket |
| Means followed by the same letters did not differ significantly at 1 % levels of probability | |
Santamaria et al. (1998a) said that highest NO3 contents in their studies were measured in the NO4: NO3 (50:50) treatment. Moreover, highest yield and largest leaf areas were also determined in these same parcels. They also reported that NO3-N contents as 6440-6081 mg kg-1 fresh material which are relatively higher than the results of our study. Similar results were found by Malakouti et al. (1999), who speculate a consistency between N rates and NO3 accumulations in the plants. European Union Food Commission (CECSCF, 1992) states the daily acceptable intake level of NO3 and NO2 as 0-3.65 and 0-0.07 mg kg -1, respectively. Similarly, FAO and WHO Food Commission (IEFCA) report the weurege daily NO3 and NO2 intake of a 60 kg person as 220-440 mg and 16-32 mg, respectively (Corre and Breimer, 1979). Dich et al. (1996) claim that NO3 intake the leafy vegetables should not exceed 72-94%.
In conclusion, 300 kg N ha-1 gave the highest yield. Even though no toxicity was measured, total N, NO3-N and NO2-N contents of the rocket increased parallel with the increasing N rates.