The effect of nitrogen and phosphorus fertilization on yield, some fruit characteristics, hormone concentrations, and alternate bearing in pistachio

This research was carried out in order to determine the effects of nitrogen and phosphorus fertilization on yield, some fruit characteristics, hormone concentrations, and alternate bearing in pistachio (Pistacia vera L.) cv. ‘Kırmızı’ grafted on P. vera over 3 consecutive years. Nitrogen was applied at the rate of 0 (control), 800, 1000, and 1200 g tree^- 1, and phosphorus was applied at the rate of 0 (control), 200, 400, and 600 g tree^-1 into the soil. As a result, although yield mostly decreased and nut weight increased, especially in the 2nd year (‘off’ year), considerable interactions among fertilizer rates were determined for only nut weight, auxin, gibberellic acid, and zeatin concentrations (P ≤ 0.05). For all parameters investigated in this study, a stable and regular effect of fertilizers applied into the soil was not observed, probably because of this species’ characteristics. Therefore, further research, including longer treatment periods, is needed to determine the effects of fertilizers.