The feasibility for replacement of urea with nitrogen nano-chelated fertilizer in olive (Olea europaea L.) orchards

Nitrogen is an important element in the life of a plant. A wide range of nitrogen-containing compounds is available in the world market, with different formulations and efficiencies. Urea is present in most fertilizer applications; however, nano-nitrogen products are becoming popular although there is only limited information on their field efficiency. Thus, this paper studied the foliar application with two sources of nitrogen (urea and nano-chelated nitrogen fertilizer) on 15-year-old ‘Zard’ olive trees. Fertilizers were used during the bud-swelling stage, before blooming, pit hardening stage, and shortly after harvest of table olive, at the concentration of 2.21 (U1) and 2.95 (U2) g urea, 6 (nano-N1) and 8 (nano-N2) g nano-chelated nitrogen, corresponding to 1.02 g (U1 and nano-U1) and 1.36 g (U2 and nano-N2) pure nitrogen per liter. Results revealed that the nano-N1 treatment increased the fruit set. However, fruit yield efficiency increased using U1 in both years. Fruit consuming-quality attributes were affected mainly by U1 treatment. Mineral elements, chlorophyll and carbohydrate contents of leaves were affected during summer and fall by nitrogen treatments. The maximum oil percentage was achieved by nano-N2 treatment. However, oil yield increased with increasing fruit load as a result of applying U1. It seems that urea, due to rapid absorption compared with slow-released nano-nitrogen, provided requiring assimilates in the growing season so that especially in the first year the yield and mineral composition improved. However, in the second year, both types of fertilizers led to improved nutrient status. Further research is recommended for application of nano-chelated nitrogen fertilizer in olive orchards.