EFFECT OF NITROGEN, BORON AND IRON FERTILIZATION ON YIELD AND NUT QUALITY OF ´NEGRET´ HAZELNUT TREES

In a mature hazelnut orchard cv. Negret, established in La Selva del Camp, Tarragona (north-east Spain), a field experiment was set up in order to study the effect of N, B and Fe on yield and nut quality. Two fertilizer trials were conducted in the spring of five consecutive years (1999-2003) for N and three years (2001-2003) for B and Fe. These involved four N treatments (200, 150, 100, and 50 kg/ha as a control) and four B treatments (soil, 50 g/tree and 25 g/tree in March the first and second year of the trial respectively); two foliar sprays of 500 ppm in May and June; two foliar sprays of 500 ppm and soil iron chelates in May, 30 g Fe/tree; and an untreated control with five replications. The greater amount of N resulted in significantly lower production and kernel yield from hazelnut trees, whereas a B foliar and Fe chelate treatment increased production with respect to the other three treatments. Boron treatments increased kernel yield and kernel size in comparison with the untreated control. Results also suggested that current N recommendation guidelines (100 kg/ha) might be too high to obtain good yields and nut quality. It was concluded that applying 50 kg N/ha when the leaf N level was about 2.4% of the dry mass in July and two B foliar sprays with soil Fe chelates in spring was the optimum way of obtaining higher production and better nut quality.