Effect of Ammonium Nitrate and Free Amino Acids on the Nitrate Accumulation in Radish
Overuse of nitrogen fertilizer may result in nitrate accumulation in vegetables. The objective of this study was to determine the effect of Ammonium nitrate fertilizer and foliar application of mixed amino acids on the yield and nitrate accumulation in radish (Raphanus sativus). The experiment was based on the randomized complete blocks design and was carried out in pots filled with 6 kg of agricultural soil in factorial form with three replications. Three levels of nitrogen fertilizer (ammonium nitrate), N1: 0 mg, N2: 45 mg, N3:90 mg per one kg of soil and three levels of mixed amino acids (provided by Inagrosa company, Spain) A1: 0, A2: 1.5 and A3: 3 ml per one liter of water were used. Based on the results, the interaction effects of N fertilizer and amino acid application were significant on the yield and nitrate concentration. The results showed that the highest yield was in treatment N3A3 (2489 gr per pot) compared with the other treatments. Nitrate concentration in leaves and glands was increased with increasing the amount of ammonium nitrate. The highest concentration of nitrate in leaves was in treatment N3A1 (431 mg kg-1FW) and in glands was in treatment N3A2 (1331 mg kg-1FW). In leaves, foliar application of amino acid increased the total N and decreased the nitrate concentration. Foliar application of amino acids affected the nitrate reductase and glutamine synthetase and decreased the nitrate accumulation in leaves but had no effect on nitrate concentration of glands.