Investigations on determination of nutritional status of pear trees according to a new index - deviation from optimum percentage (DOP)

Abstract

This experiment was conducted in a private orchard (Kosar) in district of Shahriar of Alborz province (Iran), during 2012-2013, to determine the effects of B and Zn applied on flowers at full bloom stage on leaf macro and micronutrient contents at 90 days after full bloom (DAFB) of three pear cultivars (Spadona and Duchesse and a pear cultivar from Iranian national collection, named as Daregazi). The deviation from the optimum percentage (DOP) index of macro and micronutrients for two studied years was used to evaluate the nutritional status: optimal (DOP = 0), deficiency (DOP < 0) or excess (DOP > 0). The ΣDOP for two studied years is obtained by adding the values of DOP index irrespective of sign. The larger the ΣDOP, the greater is the intensity of imbalances among nutrients. In general, a DOP value close to the optimum level (DOP = 0) were observed in treated studied pear cultivars with B and Zn applied on flowers at full bloom stage compared with the control trees (without any application of boron and zinc). The DOPmacro and DOPmicro were, respectively, positive and negative for all of studied pear cultivars regardless of treatments. According to £DOP index (during 2012- 2013), the combination of both products (borax+zinc sulfate treatments) at full bloom stage applied on flowers of three pear cultivars (Spadona, Duchesse and Daregazi) showed better balanced nutritional values than the rest of treatments.