Abstract
The ability of plants to produce high fruit yield and quality depends on the utilization of reserved carbohydrates and
photosynthetic activity of plants at initial stages of bud sprouting and flowering. Optimum dose of N is essential for this
mechanism. Therefore, different doses of N (600, 900 and 1200g per plant) along with 120 mL of 8% humic acid (HA) per
plant were applied in three equal installments (before flowering, after fruit setting and fruit development stages). Growth
parameters, C:N ratio, photosynthetic activities and their effects on yield and quality of ‘Kinnow’ fruit of these plants were
compared with the control plants receiving recommended dose of N (1200g) applied in two equal installments (before
flowering and at fruit setting). Source of fertilizers for nitrogen, phosphorus and potassium and method of their application
was kept same in all treatments. Results revealed that plants receiving N dose of 900g with 120 ml of 8% humic acid showed
the best utilization of carbohydrates which was also found directly correlated with photosynthesis. This treatment depicted
increase in photosynthesis and maintenance in C:N ratio of plant at fruit setting stage. It was noted that maintenance of
carbohydrates at flowering time, during fruit setting and harvesting stages (13.51, 13.44 and 13.39%, respectively) showed
promising results on fruit development (956 fruit per plant) and quality of Kinnow. Maximum TSS (12.20 °Brix), ascorbic
acid (44.96mg100g
-1), total sugars (13.69%), phenolic compounds (398.5mg GAE100g
-1) and antioxidants (90.13 Ic µgL
-1)
were also recorded in the fruits of plant treated with 900g N and 120 mL HA. The dose of N (900g and 120mL HA) in three
equal splits (before flowering, fruit setting and fruit maturation) along with recommended doses of P and K (each 600g per
plant) were found effective to build synergism between photosynthetic and C:N ratio which resulted in enhancing fruit yield
and quality of ‘Kinnow’ mandarin.
