The effects of nitrogen, boron and harvesting time on yield and alternate bearing in olive

Olive orchards cover 7000 hectares of land in Zanian province with a mean yield of 4000 kg/ha. Due to high oil content of olive huit and high quality ofits oil cultivation of olive trees is inevitable to meet development program targets. Olive is an alternate bearing tree and this characterisitic is intensified by traditional i management and date harvest. Proper harvest time and sufficient use of fertilizers, is necessary for obtaining high yield and reducing alternate bearing in olive. Therefore to investigate the effects of different nitrogen and boron rates and also harvest times on yield and alternate bearing of olive an experiment was conducted for two years (l998_l999)in Zanjan province. The experiment was randomized complete block design as factorial and 18 treatments and had three replications. Nitrogen rates were N0(without application of nitrogen), N] (split application of 500 gN/tree+foliar application of urea on two times) and N2 (soil application of 1000 gN/tree); Boron rates were B0(without application of Boron) B,(soil application of l2.5g B as Boric acid/tree + foliar application of Boric acid and two times) and B2(soil application of 25.5g B as Boric acid/tree). Harvest times were Tl(ha1yesting 50% of yield at conserving stage and 50% at oily stage) and T2(harvesting total yield at oily stage). The results obtained from analysis of variance showed that the main effects of nitrogen, boron and harvest time and their interaction effects on yield were significant. There was no significant difference in yield from one year to another and this means alternate bearing was reduced by application of experimental treatments. if The highest yield was obtained from N2B,T] treatment which was 81.2 kg/tree but this yield was not` significantly difference from those of N,B,T] and N2B2T\} treatments. According to results obtained from this experiment for improvement of nutritional status of olive trees, obtaining higher yield and reducing alternate bearing in olive soil application of 500 gN along with 75 g Boric acid /tree and foliar application of urea along with Boric acid before flowering and after fruit set is recommended in Zanjan province and areas with similar climatical conditions. Key Words: Olive, alternate bearing, nitrogen, boron and harvesting time