Effect of nano-urea, urea and NAA on quality attributes of acid lime (Citrus aurantifolia) cv. Kagzi

Introduction

Acid lime (Citrus aurantifolia Swingle) is the third most important citrus fruit crop in India just after mandarins and sweet oranges. Acid lime belongs to Rutaceae family with chromosome number 2n=18. It is mainly subtropical in nature but can also be cultivated in tropical regions. The fruits of acid lime are small, round or oval in shape and polyembronic in nature. Flesh of acid lime is greenish yellow in color and fruits are juicy, highly acidic with distinctive aroma. Juice of acid lime is commonly used in human diet due to its nutritional and medicinal values as it has high sugar, fruit acids, citric acid, vitamin C and antioxidant properties (Thirugnanavel et al. 2007 and Prasad and Kumar, 2012) [20,14] . It have been estimated that each 100 g of fruit juice contain 80 g water, 26 IU vitamin A (carotene), 20 mg vitamin B 1 , 0.1 mg Riboflavin, 63 mg Vitamin C, 1.83 mg Iron, 0.16 mg copper etc which make it very essential for human health. Plants of Acid lime are medium in height, bushy and vigorous in nature with spreading branch habit. The leaves of citrus are dense, small, pale green, broadly lanceolate and normally blooms thrice in a year i.e. Ambia or Ambe bahar (Jan-Feb), Mrig Bahar (June-July) and Hasta bahar (Sept-Oct). Acid lime is being considered as a heavy feeder fruit crop, hence the productivity and quality of lime juice is directly governed by nutrients supply to the plants. Undoubtedly, balanced fertilization is the key practice for increasing productivity maintaining quality of fruits but indiscriminate and imbalance use of chemical fertilizers results in environmental disruption, soil degradation and deterioration in productivity and quality of fruits which ultimately affects the human health. Hence, appropriate strategies should be identified for application of plant nutrients to harness the potential benefits in terms of productivity and use efficiency with effective check on environmental health. This could be achieved through curtailing the amount of application, especially the highly mobile nutrients such nitrogen, and increasing the effectiveness. In this direction use of Nano fertilizers are being advocated at commercial scale in recent past as an alternative to overcome these problems. It have also been reported that foliar application of Nano urea in fruit plants as an alternative and more effective over conventional urea as it curtail the requirement of conventional urea to the extent of 50% and improve the use efficiency up to 90%. The use of bio-regulators has been highlighted as one of the most essential strategies for improving the productivity and quality of fruits through betterment in flowering, fruit set, fruit size and shape; and also curtailment in fruit drops. In light of above facts present investigation was carried out to develop the protocol for application of nitrogen, through conventional urea and nano-N molecules, and bio-regulator for getting potential benefits in acid limes.

Materials and Methods

The investigation titled "Effect of Nano-urea, Urea and NAA on growth, yield and quality of Acid lime (Citrus aurantifolia Swingle) cv. Kagzi", was carried out during 2021-2022 at the well-established Kagzi lime orchard of Fruit Research Station, Imaliya, Department of Horticulture JNKVV (MP). The study involved totalling 28 numbers of plants, spaced at regular intervals of 6 m x 6 m. The experiment included seven treatments, incorporating different concentrations of urea (2.0% and 4%), nanourea (0.2 and 0.4%) and NAA (20 ppm and 40 ppm). Two rounds of foliar spraying were administered for each treatment, first at 50% flowering, followed by the second spray after fruit set. The soil composition predominantly had a clay-loam texture with traces of heavy clay. Fruits were sampled separately from each tree at full maturity. Weights of five randomly selected mature ripe fruits from each plant were recorded. Total soluble solids (TSS) were measured by a hand refractometer and the values were corrected at 20°C (Ranganna, 1986). Titrable acidity was determined by filtrating a know quantity of blended (homogenized) pulp, diluted with distilled water, against NaOH solution (IN), using phenolphthalein as indicator and results were expressed as percentage of citric acid. TSS acid ratio was calculated by dividing the TSS value by acidity, total, reducing and non-reducing sugar from the pulp of ripe fruits was analyzed as suggested by Ranganna (1986). The experimental data were subjected to factorial analysis of variance for randomized block design and the differences tested at p < 0.05.

Results and Discussion

Total Soluble Solids ( 0 Brix) The data represents the TSS of Acid lime which was significantly influenced by the foliar application of nano-urea, Urea and NAA. The results revealed that the maximum TSS (9.11⁰Brix) was observed with the foliar application of NAA @ 20 ppm under T 6 followed by T 5 (8.88⁰Brix). However, the minimum TSS (7.61⁰Brix) was recorded under treatment T 1 (control).

Acidity percentage

The results revealed that the acidity was significantly reduced affected by treatments. The minimum acidity (5.50%) of Acid lime was recorded with foliar application of NAA @ 20 ppm under treatment T 6 and the maximum acidity (6.81%) was recorded under control (T 1 ).

TSS/Acid ratio

The results revealed that the maximum TSS/ acid ratio (1.66) was recorded in treatment T 6 (foliar spray of NAA @ 20 ppm) while the minimum TSS/acid ratio was recorded under control.

It is clear from the data that the ascorbic acid was significantly affected by various treatments. The results revealed that the maximum ascorbic acid (45.91 mg/100 g) was recorded under the treatment T 6 (foliar spray of NAA @ 20 ppm) while the minimum ascorbic acid (36.96 mg/100 g) was recorded under control (T 1 ).

Juice percentage

It is clear from the data that the juice% was significantly influenced by the foliar spray of various treatments of different concentrations. The result revealed that the maximum juice content (53.86%) was recorded under the treatment T 6 (foliar spray of NAA @ 20 ppm). However, the minimum juice content (43.90%) was noted under control T 1.

Total sugar

The effect of various treatments on total sugar% was found to be highly significant. The results revealed that the maximum total sugar content (1.26%) was noted in treatment T 6 (foliar application of NAA @ 20ppm). However, the minimum total sugar (0.90%) was observed in T 1 (Control).

Reducing sugar

Reducing sugar content of Acid lime was significantly improved under the effect of different treatments. The results revealed that the maximum reducing sugar (0.69%) was noted under treatment T 6 (foliar spray of NAA @ 20 ppm) which was found to be at par with the treatment T 5 (0.68%) while the minimum reducing content (0.51%) was observed in control (T 1 ).

Non-Reducing sugar

It is clear from the data that the non-reducing sugar was found significantly maximum (0.57%) with the spray of NAA @ 20 ppm under treatment T 6 which was found to be significantly at par with treatment T 5 (0.55%). However, the minimum non-reducing sugar content (0.39%) was observed in T 1 (control).

Discussion

Effect of Nano-urea, Urea and NAA on quality attributes of Acid lime It was found that the TSS of Acid lime was increased significantly with the application of foliar spray of 20 ppm NAA under treatment T 6 (9.11⁰Brix) followed by foliar spray of 0.4% Nanourea (8.88⁰Brix). However, the minimum TSS (7.61⁰Brix) was recorded under treatment T 1 (control). The increase in TSS might be due to the increased mobilization of carbohydrates from the source to the sink (fruits) by auxin. The fact that NAA boost the activity of the enzyme α-amylase, which led to improved total soluble solid content and the conversion of starch into sugar might be the possibility. In addition, NAA also regulate enzymatic activity and the enzymes that break down carbohydrates into simple sugar. Similar, findings were reported by Pandey (1999) [12] in ber. Similar effects of NAA were also reported by Makhija et al. (1990) [10] and Bal et al. (1998) [1] in ber. Singh and Sandhu (1987) [17] had also found increase in TSS content of grapes due to application of NAA. Maximum ascorbic acid (45.91 mg/100 g) was noted under the treatment T 6 (foliar spray of NAA @ 20 ppm) which was found to be at par with T 3 (foliar spray of Urea @ 4%) while the minimum ascorbic acid (36.96 mg/100 g) was recorded under T 1 (control).The increment in ascorbic acid content with the foliar spray of NAA 20 ppm may be due to perpetual synthesis of glucose-6-phosphate throughout the growth and development period of Acid lime which is the precursor of vitamin C. Similar findings were done by Pandey (1999) [12] in ber. Maximum total sugar content (1.26%), reducing sugar (0.69%) and non-reducing sugar (0.57%) was noted with the foliar application of NAA @ 20 ppm under treatment T 6 while the minimum total sugar (0.90%), reducing sugar (0.51%) and nonreducing sugar (0.39%) was recorded in T 1 (Control).

The results observed in the preceding chapter revealed that the acidity was significantly reduced affected by treatments. The minimum acidity (5.50%) of Acid lime was recorded with foliar application of NAA @ 20 ppm and the maximum acidity (6.81%) was recorded under control (T 1 ) followed by T 2 i.e. foliar application of 2% urea (6.26%). This might be caused by the fact that NAA aids in the process of photosynthesis, which causes higher accumulations of polysaccharides and oligosaccharides. In addition to this, it regulates the enzymatic activities, which increases sugars and TSS as a result of which fruit acidity is decreased. (IIyas et al., 2015). The findings of Debaje et al.( 2011) [3] , Jain et al.( 2014) [6] in Nagpur Mandarin, and Kumar et al.

(2015) [8] in guava are also in agreement with these results. Therefore, the decrease in the titrable acidity was mainly due to the increase in TSS. Maximum (53.86%) juice content was recorded under the treatment T 6 (foliar spray of NAA @ 20 ppm). However, the minimum (43.90%) juice content was noted under control T 1. It was observed that the juice content of Acid lime was greatly influenced by the treatment. The increase in juice content might be due to auxin, which is involved in the synthesis of α-amylase which is responsible for converting starch to sugars and consequently result in increase in osmotic pressure of the cell which led to accumulation of water. The same outcome was discovered by Sandhu (2013) [15] . The results revealed that the maximum TSS/ acid ratio (1.66) was recorded in treatment T 6 (foliar spray of NAA @ 20 ppm) while the minimum (1.12) TSS/acid ratio was recorded under control (T 1 ). This may be due to rapid translocation of sugars from leaves to developing fruits and synthesis of cell wall material. Thus, it can be concluded that among the various treatments, T 6

(foliar spray of 20ppm NAA) showed the maximum betterment in the quality attributes of Acid lime.

Conclusion

On the basis of result obtained in present experiment, it can be concluded that treatments, the foliar application of T 6 (foliar spray of 20 ppm NAA) was effective in enhancing quality parameters.

Acknowledgement

The author wishes to acknowledge the support and facilities provided by the Head of the Department of Horticulture at the College of agriculture Jabalpur to carry out the present investigation.

References

1. Bal JS, Randhawa JS, Singh SN. Effect of NAA on fruit characters and quality of ber cv. 'Umran'. Haryana Journal of Horticultural Sciences. 1998;1(1-2):20-23.
2. Chermahini SA, Moallemi N, Nabati DA, Shafieizargar AR. Winter application of foliar urea can promote some quantitative and qualitative characters of flower and fruit set of Valencia orange trees. Journal of Food, Agriculture and Environment. 2011;9(1):252-255.
3. Debaje PP, Shinde ED, Ingale HV. Effect of plant growth regulator and nutrients on quality of acid lime. The Asian Journal of Agricultural and Horticultural Research. 2011;6(1):253-255.
4. Etehadnejad F, Aboutalebi A. Evaluating the effects of foliar application of nitrogen and zinc on yield increasing and quality improvement of apple cv. 'Golab Kohanz'. Indian Journal of Fundamental and Applied Life Sciences. 2014;4:125-129.
5. Ilyas A, Yasin AM, Mumtaz H, Muhammad A, Aashid A, Ali K. Effect of micronutrients (Zn, Cu and B) on photosynthetic and fruit yield attributes of Citrus reticulata Blanco var. Kinnow. Pakistan Journal of Botany. 2015;47(4):1241-1247.
6. Jain MC, Choudhary HD, Sharma MK, Singh B. Yield and quality attributes of Nagpur mandarin as affected by use of different plant growth regulators. Environment and Ecology. 2014;32(3):1141-1145.
7. Jat G, Kacha HL. Response of guava to foliar application of urea and zinc on fruit set, yield and quality. Journal of Agricultural Research. 2014;1(2):86-91.
8. Kumar J, Kumar R, Rai R, Mishra S. Response of 'Pant Prabhat' guava trees to foliar sprays of zinc, boron, calcium and potassium at different plant growth stages. The Bioscan. 2015;10(2):495-498.
9. Lovatt CJ. Improving fruit set and yield of 'Hass' avocado with a spring application of boron and/or urea to the bloom. California Avocado Society Yearbook. 1994;78:167-173.
10. Makhija M, Chandra A, Yamdagni R. Note on quality improvement by nutrients spray in ber cv. 'Gola'. Current Agriculture. 1990;14:73-74.
11. Mazumdar BC, Bhatt DNV. Effect of pre-harvest application of GA and ethrel on sweet orange (Citrus sinensis Osbeck) fruits. Progressive Horticulture. 1976;8(2):89-91.
12. Pandey V. Effect of NAA and GA3 spray on fruit retention, growth, yield and quality of ber (Zizyphus mauritiana L. amk.) cv. Banarasi Karaka. Orissa Journal of Horticulture. 1999;27(1):69-73.
13. Parmar JM, Karetha KM, Rathod PJ. Effect of foliar spray of urea and zinc on growth and flowering attributes of guava (Psidium guajava) cv. Bhavnagar Red. Advance Research Journal of Crop Improvement. 2014;5(2):140-143.
14. Prasad S, Kumar U. A handbook of fruit production. Agrobios; 2012. p. 654-659.
15. Sandhu S. Improving lemon [Citrus limon (L.) Burm.] quality using growth regulators. Journal of Horticultural Sciences. 2013;8(1):88-90.
16. Singh AK, Rajput CBS. Effect of GA3, BA and calcium on the chemical properties of fruit in mango (Mangifera indica L.). Punjab Horticulture Journal. 1988;28(3-4):159-163.
17. Singh K, Sandhu AS. Berry thinning in Perlette grapes through pre-bloom application of Planofix (NAA) and GA3. Punjab Horticulture Journal. 1987;27(1-2):34-36.
18. Stiles WC. Effects of nutritional factors on regular cropping of apple. HortTechnology. 1999;9:328-331.
19. Syamal MM, Singh SK, Singh BP. Effect of urea and zinc on growth, flowering, fruiting and fruit quality of Kagzi lime. Environment and Ecology. 2008;26(3):1036-1038.
20. Thirugnanavel A, Amutha R, Baby Rani W, Indira K, Mareeswari S, Muthulaksmi S. Studies on regulation of flowering in acid lime (Citrus aurantifolia Swingle). Research Journal of Agricultural and Biological Sciences. 2007;3(4):239-241.