Evaluation of different rates of nitrogen, phosphorus and potassium on fruits Antioxidant traits of blackberry cultivars in greenhouse

Black berries (Rubus fruticosis aggr.) with more than 700 species are from worldwide and Iran small fruits. In addition of its wild relatives, there are breeded thorny and thornless cultivars which are under cultivation in the south region of Caspian Sea.Using chemical fertilizers is fastest method to compensate plants requirement to nutritional elements. Based on literature review, application of NPK will change the length of primocane, number and length of auxillary buds and flower number of inflorescence in blackberry, its yield component and antioxidant chracteristics, positively. The goal of this research was to evaluate the effect of different levels of nitrogen, phosphorus and potassium on three thorny blackberry cultivars.

This experiment performed in pots at Quancet greenhouse as completely random design in factorial. First factor included cultivar with three levels (Slivan, Marion and Tupy as early, mid and late ripening, respectivly) and second factor as fertilization in six rates (N0P0K0،N50P0K0، N50P0K25، N50P0K50، N50P25K50 &N50P12.5K25) in three replications. The measured traits included fruit quantitative charactristics like as weight, length and diameter (size), fruit qualitative traits like as Brix and titrable acidity, druplet traits as weight and precent of druplet material, number and weight of seed and antioxidant traits of juice (Antioxidant activity from Diphenyl-2-picrylhydrazyl method, phenol, flavenoiid and vitamin C).

Results showed that early ripen cultivar included the highest fruit weight, TSS and seed dry weight of 5 fruits (7.8g, 12.9% and 0.598g, respectively) in N50P0K25 which resulted the highest fresh and dry weight in seeds of fruits for late ripening cultivar as 2.528 & 0.607g. The most titrable acidity observed in late ripen cultivar and N50P0K0 treatment. The maximum weight of druplet, highest druplet matter precent achieved in early and mid ripening cultivars for N50P0K25 treatment which have been resulted highest anthocyanin rate in mid and late ripen cultivars. In oxidant stop precent and phenol rate of late ripen cultivar was higher than others. The most vitamin C was observed in N50P25K50 tretment and increase in nutrient affected this parameter and other phytochemical traits like as anthocyanin, negatively.

In the traits whihc related to reproductive growth and fruit, early ripen cultivar showed effectiveness than others significantly. However, in nutritional value (antioxidant traits) late ripen cultivar was better. Treatment with N50P0K25 in early ripen cultivar improved TSS, druplet weight, druplet matter and taste in compare to other treatments, significantly. late ripen cultivar was better. Treatment with N50P0K25 in early ripen cultivar improved TSS, druplet weight, druplet matter and taste in compare to other treatments, significantly.