Impact of Zinc and Boron on Growth, Yield and Quality of Kinnow (Citrus deliciosa x Citrus nobilis) in Sub-tropical Conditions of Punjab

Kinnow is the most preferred cultivar in Punjab due to its wider adaptability, yield and higher economic returns. However, excessive fruit drop is becoming a major cause for achieving low fruit yield. This could be attributed mainly to the lack of appropriate nutrient management for Kinnow orchards. The soil and leaf chemical analysis showed severe deficiency of Zn and B in Kinnow. Therefore the present study was carried out in the farmer’s field at Abohar, Punjab with an objective to examine the influence of micronutrients on the growth and quality of Kinnow and in order to frame the appropriate dose. The experiment was laid out in randomized block design with ten treatments and three replications. Results show that in basal dose, treatment of Zn and B (250 gm/plant) gives fruit weight (198.78 g), number of fruits (269.66), weight of fruit/plant (58.00 kg) and vitamin C (20.83%), fruit drop(33.21%) and in foliar dose, treatment of Zn (3gm) and B (2gm) gives plant height (25.40cm), number of fruits (298),weight of fruit/plant (60.00 kg) and vitamin C(17.50%), while combination treatment of basal + foliar of Zinc (250+3gm) and boron(250+2gm) significantly improved the plant height (29.46cm), fruit length (4.95cm), width (5.61cm) and vitamin C (24.16%) with lowest fruit drop of 28.48% was obtained.

Among the Citrus, Kinnow is placed at first position with respect to its area and production in India. Kinnow a mandarin hybrid (C. deliciosaTenora× C. nobilisLour.) is one of the most important and finest varieties of mandarin grown especially in North India. It has assumed great importance among North Indian growers and a large area is being brought under its cultivation particularly in Punjab, Haryana, Rajasthan and Himachal Pradesh. The area under Kinnow cultivation is 48,182 hectares with the production of 118618 lakh tonnes and the productivity of 21,607 kilos per hectare (NHB 2015-16). It is mostly grown in areas of Fazilka, Ferozpur, Muktsar and Bathinda of Punjab. Kinnow are a fair source of vitamin C and daily consumption protects mankind from scurvy. Its pulp is used to make jam, squash, juice, sauce, syrup and its outer skin can be used to make cosmetics and essence. It is the main source of peel oil, citric acid which has international market value. It is rich in fibre (Sharma et al. 2007 andAltaf, 2006). Therefore for growth, yield and quality, use of micronutrients in Kinnow fruit crop is essential as they also help in enzyme activation and biosynthesis (Edward Raja, 2009).Among micronutrients; zinc (Zn) and boron (B) have much significance due to most wide spread deficiency of these micronutrients in the citrus cultivated areas in India. Zinc is one of the important micronutrient essential for plants due to its involvement in the synthesis of tryptophan which is a precursor of indole acetic acid synthesis. Similarly, boron (B) increases pollen grain germination, pollen tube elongation, consequently fruit set percentage and finally the yield (Abd-ullah, 2006).Therefore, keeping the above factors in view the present study "Influence of zinc and boron on growth, yield and quality of Kinnow in sub-tropical conditions of Punjab" was carried out at V.P.O Ramsara Tehsil Abohar District Fazilka, Punjab during the year 2016-17.

Experimental Site
The field experiment was conducted during the years 2016-17 in the orchard of Kinnow located at V. P. O. Ramsara, Tehsil Abohar, District Fazilka, Punjab under the Horticulture department of LPU Phagwara, Punjab during the year 2016-17.In this experiment five year old trees with thirty uniform and healthy kinnow plants were chosen to check the influence of micronutrients. The soil analysis report shown in table-1 shows that kinnow orchard soils are deficient to micronutrients; therefore the current study was undertaken to frame the appropriate dose.

Observations Detail
These treatment applications were given during fruit set, pea size fruit set and after monsoon in October. The observations were recorded on yield, quality and morphological parameters. The morphological parameters regarding the tree height (cm) was recorded using measuring tape from the crown level to base of leaf apex, fruit set (%) was recorded by taking the number of fruits divided by numbers of flowers, fruit drop (%) was recorded by total number of fruits set and number of fruit dropped were counted and calculated and expressed in percent. The yield regarding average fruit weight was calculated by weighing fruit on electronic balance and the number of fruit will be counted at the time of maturity and expressed as number of fruit/plant and fruit length were measured by vernier caliper. The total fruit yield per tree was calculated by multiplying total number of fruits per tree with the average fruit weight and estimated yield hectare was calculated by multiplying total fruit yield per tree with number of plant per hectare. The quality parameters regard TSS ( 0 B) with optical refractometer, acidity (%) and ascorbic acid (%) were also recorded during the investigation. And all observation were determined by the methods described by AOAC.

Experimental Design And Statistical Analysis
The data was analysed by Randomized Block Design.And (ANOVA) was calculated by the help of OPSTAT software.

RESULTS AND DISCUSSION
The basal and foliar application of zinc and boron significantly affects the growth, yield and quality parameters of Kinnow (Table-2

and 3). Basal application of Zinc and Boron
Trees with basal dose of 250 gm each of zinc and boron inT 7 basal (250gm chelated zinc+ 250gm borax)has given better results than other basal treatments T 1 (250gm chelated Zn) and T 3 (250gm borax). The fruit weight (198.78 gm), number of fruit/plant(269.66), weight of fruit/plant (58.00 kg), vitamin C (20.83%) are significantly improved by basal application of 250 gm chelated zinc + borax inbasal followed by T 1 (250gm chelated Zn) and T 3 (250gm borax) basal treatments as presented in Table -2, 3. The increase in fruit weight might be due to increased rate of cell division and cell enlargement leading to regulating metabolites in the fruit (Babu and Singh, 2001). Similar results were also obtained by Asadi and Akhlagi (2005) which are in conformity with  table-3 show thatthe maximum total soluble solid and acidity was recorded in Zn basal application on kinnow. In T 1 (basal 250 gm chelated Zinc) recorded maximum total soluble solid of 11.53 0 B and acidity of 2.63% .Zinc treated plants recorded maximum total soluble solid in kinnow because zinc is considered as one of the important micronutrient essential for plants synthesis of tryptophan which is a precursor of indole acetic acid. Similar results by Bhatnagar et al. (2015) observed maximum TSS and ascorbic acid and other quality traits.

Foliar application of Zinc and Boron
Data in table-2, 3illustrate that in foliar application T 8 foliar (3gm zinc sulphate+2gm boron) treatment gives enhanced ascorbic acid of 17.50%, weight of fruit/plant (60.00kg), number of fruit/plant (298) as compared to T 2 foliar (3gm zinc sulphate) and T 4 foliar (2gm boron). The increase in fruit size might be due to combined applications of zinc and boron because of their stimulatory effect on plant metabolism.The above results in kinnow are in line with those of Khan, Malik, Saleem & Rajwana (2009).
The observations recorded in table-3 shows that the maximum total soluble solid and acidity was recorded in Zn foliar application on kinnow. T 2 (foliar 3gm zinc sulphate) total soluble solid of 11.46 0 B and acidity of 3.46% was recorded as compared to T 5 -basal+ foliar (250gm chelated zinc+3gm zinc sulphate) treatment. Zinc has important role in starch metabolism, nucleic acid and protein biosynthesis. Similarly

Basal and Foliar application of both Zinc and Boron
The data in table-2, 3 showed that combined applications of zinc and boron in treatment T 9 (basal dose 250 gm chelated zinc+borax +foliar 3gm zinc sulphate+ 2gm boron) the maximum plant height of 29.46cm, ascorbic acid of 24.16%, fruit length of 4.95cm and fruit width of 5.61cm was observed compared to T 10 (Control) and T 5 (basal 250 gm chelated Zinc+foliar 3gm zinc sulphate) and T 6 (basal 250 gm borax+foliar 2gm boron)... These findings are also in line with the Ram and Bose (2000), as they observed the maximum height and spread of mandarin orange with spray of 0.5% zinc. Similarly Dawood et al. (2001) observed that the plant height of young tree of Washington Navel orange, Valencia orange and Balady mandarin was increased with the application of 0.4% zinc sulphate spray.
In present findings the minimum fruit drop(28.48%) was obtained in treatment T 9 (basal dose 250 gm chelated zinc+borax + foliar 3gm zinc sulphate + 2gm boron) followed by 33.21% in T 7 treatment (basal and foliar dose of 250 gm chelated zinc+ borax) was recorded compared to 57.29% in T 10

CONCLUSION
From the present study it has beenconcluded thatbasal and foliar application of 250gm each of chelated zinc and borax with 3gm zinc sulphate and 2gm boron showed better performance in plant height, fruit length, fruit width, ascorbic acid and is helpful for the reduction in fruit drop of kinnow fruit. Therefore, effective nutrientmanagement of citrus is obtained to get desired productivity and quality of fruits that involves appropriate rate, time and method of application aswell as selection of suitable combination offertilizers.