Research Article

Effect of Nitrogen Doses and Timing on Fruit Quality of Guava in Winter

Junaid Khan* and Muhammad Sajid

Department of Horticulture, The University of Agriculture, Peshawar, Pakistan.

Received | April 23, 2024; Accepted | June 06, 2024; Published | July 25, 2024

*Correspondence | Junaid Khan, Department of Horticulture, The University of Agriculture, Peshawar, Pakistan; Email: jkhan362@gmail.com

Citation | Khan, J. and M. Sajid. 2024. Effect of nitrogen doses and timing on fruit quality of guava in winter. Sarhad Journal of Agriculture, 40(3): 848-857.

DOI | https://dx.doi.org/10.17582/journal.sja/2024/40.3.848.857

Keywords | Guava, Nitrogen, Winter guava, post-harvest, Fertilizer

Copyright: 2024 by the authors. Licensee ResearchersLinks Ltd, England, UK.

This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/).

Introduction

Guava (Psidium guajava L.) is an important crop of the Myrtaceae family. Guava trees grow well in subtropical and tropical climate. It contains high amount of ascorbic acid (McCook et al., 2012). It is the richest after orange in terms of vitamin C content (Muhammad et al., 2014). It is an important export fruit due to its nutritional value. The top exporting countries are Mexico, Thailand, India, Brazil and the Philippines, while the United States, China and the United Kingdom are the largest importers of guavas (Comtrade, 2018). Guava cultivation in Pakistan is mostly in Punjab and Sindh provinces (Khushk et al., 2009) and the punjab accounts for about 80.7% of the total production of guava across the country (Jain et al., 2001).

Pakistan climate is arid and semi-arid and soil is low in organic matter as well as alkaline calcareous. Therefore, nutrients have a great role in increasing crop production. Similarly, deficiency of nitrogen badly affect crop production in the country (Rashid and Ryan, 2004; Ibrahim et al., 2019). Nutrients have role in human health so nutrients deficiency should be take in to consideration (Welch and Graham, 2004). Nitrogen deficiency or toxicity caused different physiological malfunction and their symptoms appeared on leaves fruit and shoots. Deficiency of nitrogen in plant caused yellowing of leaves, stunted growth and thin stem (Agfact, 2002). Deficient amount of nitrogen application resulted decline growth and photosynthesis which limit fruit yield and quality (Marschner, 1995). The deficiency of nitrogen to plant is due to lake of N availability in soil. Nitrogen leaching occurred maximum during heavy summer rain fall or excess irrigation and maximum porous soil. Due to the nitrification which may cause a short term nitrogen deficiency in soil which can be relieved by dry weather condition. Rate of nutrients, time of application and its placement are very much important to increase nutrient uptake efficiency and decrease nutrient losses. Frequent nitrogen application to week or older trees may lead to nitrogen availability and decrease nitrogen deficiency (Zekri and Obereza, 2003).

Various nitrogen doses (0, 300 g and 600 g N tree-1) were applied to guava tree. It was observed that application N tree-1 at rate of 60 gram significantly improved yield and quality attributes (TSS, ascorbic acid, reducing sugar) while fruit acidity was recorded decline by highest nitrogen application (Lal and Sen, 2001; Muhammad et al., 2019). Soil application of 400 g N caused the maximum cumulative growth of the plant, maximum fruit number and highest fruit weight. Application of nitrogen improved fruit quality also increased fruit juice, TSS, acidity, total sugar (reducing and non-reducing) and ascorbic acid (Ghosh and Das, 2000). Among management factors, application of balanced fertilizer is key component that increases vegetative as well as reproductive growth leading to high productivity and standard of the produce (Jilani et al., 2021). Different levels (300 g, 600 g and 900 g N tree-1) of nitrogen was applied to guava trees. All levels significantly affected all parameters as compare to control plants. Significant effect of different nitrogen levels (0.0, 0.90, 1.36 and 1.82 kg plant-1) on fruit size and fruit weight of guava were recorded which increased with increase in nitrogen content (Singh and Singh, 1970). Nitrogen at 600 g plant-1 gave high values for weight of fruit, yield, TSS, ascorbic acid and acidity (Bhatia et al., 2001). Spray application of 15 % urea significantly increased terminal shoot length, fruit yield, diameter and length of fruit, weight of fruits, TSS, total sugar (reducing and non-reducing sugar), vitamin C content and reduced fruit acidity of guava (Dubey et al., 2001). Whereas, application of 2% urea spray significantly affected fruit yield tree-1, size of fruit, weight of fruit, total soluble solids and ascorbic acid, reduced fruit drop and decreased the acidity of ber fruits (Chauhan and Gupta, 1985). Banana plants treated with 200 g N plant-1 recorded highest plant height, pseudostem girth, number of functional leaves at shooting and leaf nitrogen content at harvest while 160 g N produced highest yield (Khan et al., 2015). However, phalsa plant treated with nitrogen at rate of 100 g revealed maximum sprout shoot-1, yield bush-1 and yield ha-1 (Kandolia and Bhuva, 1996). Peach plant treated with 450 g N tree resulted maximum plant height, fruit weight and yield (Arora et al., 1999). Urea spray at 1 or 2% increased vitamin C and TSS content of the guava fruit (Shanmugavelu, 1987). Looking the importance of nitrogen; the present research experiment was design to know the “Effect of nitrogen doses and timing on fruit quality of guava in winter” with the objectives to optimize the appropriate dose of nitrogen and timing of application for growth and fruit quality of guava crop in winter.

Materials and Methods

The research experiment was conducted at village, Gher Khan, District, Haripur during 2017-2018. The research was designed in Randomized Complete Block Design (RCBD) with split plot arrangement. The experiment consist of two factor with application time having main plot and nitrogen levels was kept with sub plot. Total 12 treatments were used which were replicated thrice. There were total 36 treatments in experiment. Guava trees cv. ‘Allahabad Safeda’ of eight-year-old were selected for experiment. Except control all trees were applied with nitrogen during growing season to fulfill the nutrient requirement of winter season guava fruit. Cultural practices (weeding, hoeing etc) were regularly performed during experiment. Nitrogen doses were applied to guava trees in two split doses, the first dose at start of the month and second at dose mid-month. Urea was used a source of nitrogen while recommended doses of phosphorus (SSP) and potash (SOP) were also applied to all trees. There were two factors i-e, Factor A. Time of Application, September (1st and 15th), October (1st and 15th), November (1st and 15th), Factor B. Nitrogen, N0= 0 Kg ha-1, N1= 75 Kg ha-1, N2= 150 Kg ha-1 and N3= 225 Kg ha-1).

The following quality parameters were examined during research.

Fruit firmness (kg cm-2): Fruit firmness of guava fruits were calculated in randomly selected fruits through Penetrometer and average fruit firmness was recorded.

Total soluble solids (oBrix): The Total soluble solids were examined through Brix refractometer for each treatment of all replication. Drop was taken from juice and placed on clean slab of a oBrix refractometer which is equipped with (%) sugar scale and then readings for average total soluble solids were calculated.

Titrable acidity (%): The titrable acidity was determined by using standard procedure of association official analytical chemists (A.O.A.C), 1984.

Ascorbic acid (C6H8O6): 1 ml sample of guava juice was taken and then diluted it in solution of 1 N oxalic acid (C2H2O4). The sample was then titrated against standard dye solutions and ascorbic acid was measured for randomly selected fruits.

TSS-acid ratio: The following formula was used to determine TSS-acid ratio of the sample.

TSS-acid ratio = TSS/percent acidity

Percent reducing and non-reducing sugars

Reducing and non-reducing sugars were examined by using the method of Lane and Eynon, as reported in Iqtidar and Saleemullah (2004).

Statistical analysis

The recorded data of all the parameters were analyzed through statistical software “Statistix-8.1” to determine the significance of the differences obtained by the experimental treatments. The difference among treatments means were examined by least significant difference (LSD) test at 5% level of probability (Steel and Torrie, 1980).

Results and Discussion

Fruit firmness (kg cm-2)

Analysis of variance presented that time of application has non-significantly affected fruit firmness of guava while nitrogen doses and its interaction with time of application significantly (P<0.05) affected guava fruit firmness. Early to delay in nitrogen application, significantly decreased fruit firmness where maximum fruit firmness (1.95 kg cm-2) was recorded in guava fruit trees treated with nitrogen during September which was statistically similar to fruit firmness (1.91 kg cm-2) recorded in guava trees treated with nitrogen during October. The minimum fruit firmness (1.76 kg cm-2) of guava fruits were recorded in trees treated with nitrogen during November. As concerned nitrogen doses, fruit firmness of guava ranged from 1.52 to 2.00 kg cm-2. The maximum fruit firmness (2.00 kg cm-2) was recorded in control trees (0 kg N ha-1) while minimum fruit firmness (1.52 kg cm-2) of guava fruits were observed trees treated with 225 kg N ha-1. With regard to interaction, highest guava fruit firmness (2.24 kg cm-2) was observed in guava fruit trees treated with nitrogen in September while lowest fruit firmness (1.24 kg cm-2) was observed in guava trees treated with 225 kg ha-1 in November (Figure 1).

 

It is thought that higher doses of nitrogen negatively affect fruit quality. The level of nitrogen fertilizer increase so fruit firmness is going to decline. High N doses generally reduced color development and flesh firmness in apple trees (Souza et al., 2013; Hoying et al., 2004; Nava et al., 2007). Nitrogen fertilization affect quality of various fruits (Locascio et al., 1984). High N supply typically induces higher growth rates, fruits are grown to larger size, but the supply of other constituents, particularly of phloem-immobile Ca, does not increase, resulting in dilution affects So, N in perennial fruit crops does not accumulate in fruits as nitrate, as it is not phloem-mobile. N is translocated as amino acids which brings us to the next aspect. It is argued that N tends to move the C skeletons away from structural metabolism to protein metabolism (Marschner, 1995). Fruit firmness in apple is closely related to cellulose which is why high N supply tends to reduce fruit firmness. The present results confirm the results of Drake et al. (2002) who recorded highest fruit firmness in apple by use of lowest nitrogen rate.

Total Soluble Solids (oBrix)

Total soluble solid of guava fruits were significantly affected by time of application and nitrogen doses. The interaction of time of application and nitrogen doses was found non-significant (P<0.05) (Table 1). Mean table 1 presented that guava fruit trees fertilized during September produced highest TSS (10.32 oBrix) which was statistically similar to TSS (10.28 oBrix) of guava fruit trees fertilized during October. The guava fruit trees fertilized during November showed lowest TSS (10.10 oBrix). Furthermore, the means for nitrogen doses showed that highest TSS (10.55 oBrix) were recorded in guava fruit trees applied with 75 kg N ha-1 which was closely followed by TSS (10.42 oBrix) of guava fruit trees applied with nitrogen at 150 kg ha-1. Moreover, the lowest TSS (9.85 oBrix) were produced in untreated trees (Control trees).

The increase in TSS of guava fruit trees treated with nutrients in September might be correlated with higher fruit weight which contain maximum TSS. Struik et al. (1989a) examined that optimum temperature increases photosynthesis that enhanced vegetative growth of plant which plays a vital role in better translocation of sugars into fruit tissues. Further these are similar to the the findings of Calderon et al. (2004) and Fidler (1973). The fruit color and TSS affected negatively by nitrogen application (Nava et al., 2007). The present research indicated that higher rates of nitrogen beyond optimum level cause reduction in total soluble solids of guava. These finding are in line with those reported by other researchers working with orange, grape fruit and date palm (Dawoud, 1991; Smith, 1969). The content of TSS shows declined trend with application of nitrogen fertilizer. This might be due to high self-shading caused by excessive vegetative growth due to nitrogen application. The application of nitrogen fertilizer to apple tree resulted heavy vegetative growth and decrease light shedding on fruit surface which affect TSS content of apple fruit (Dris et al., 1999; Drake et al., 2002). However, the observed values of TSS contents were within the range with high nitrogen dose. The present findings proved the results of Paula et al. (1991) that higher doses of nitrogen reduce TSS of guava fruit.

 

Table 1: Fruit firmness, TSS, titratable acidity and TSS-acid ratio of guava as affected by nitrogen doses and its time of application.

Treatments	Fruit firmness (kg cm-2)	TSS (oBrix)	Titratable acidity (%)	TSS-acid ratio
Time of application
September	1.95	10.32 a	0.29	30.89
October	1.91	10.28 a	0.33	35.46
November	1.76	10.10 b	0.35	37.37
LSD (P< 0.05)	NS	0.16	NS	NS
Nitrogen doses (kg ha-1)
Control	2.00 b	9.851 c	0.41 a	27.17 c
75	2.16 a	10.55 a	0.34 b	33.30 b
150	1.81 c	10.42 a	0.28 c	38.09 a
225	1.52 d	10.12 b	0.26 c	39.72 a
LSD (P< 0.05)	0.032	0.25	0.03	3.47
Interaction N-doses × Time of application	Fig. 1	NS	NS	NS

Means followed by different letters are significantly different at 5% level of significance by using LSD test, NS= Non-significant

 

Titratable Acidity (%)

The data for titratable acidity revealed that nitrogen doses significantly (P<0.05) affected titratble acidity of guava fruits whereas the alone affect of application time and its interaction with nitrogen doses were found non-significant. The mean table 1 revealed that guava fruit trees of control treatment (unfertilized) showed higher titratable acidity (0.41%) while increasing the rate of nitrogen dose (75 to 225 Kg ha-1) significantly decreased titratable acidity from 0.34 to 0.26%.

The decrease TA might be due to the conversion of the organic acids into sugars during fruit ripening. Increasing nitrogen rates produced bigger size fruits but it adversely affects fruit quality like titrable acidity (Spironello et al., 2004). The present findings are in agreement with the findings of Jones (1999) who investigated that fruit quality is negatively affected by nitrogen fertilizer and reduction in acidity with increased nitrogen doses in tomato. The present results are supported by Bashir and Abu-Goukh (2003) and Mitra and Bose (1985) that TTA decreases by application of nitrogen.

TSS-acid ratio

Table 1 shows that nitrogen doses significantly affected TSS-acid ratio of guava fruits (P<0.05). Moreover, time of application and the interaction between time of application and nitrogen doses were non-significant for TSS-acid ratio (Table 1). Mean presented that increasing nitrogen dose (75 to 225 kg ha-1) significantly increased TSS-acid ratio (33.30 to 39.72). The TSS-acid ratio of 225 kg N ha-1 was statistically similar with TSS-acid ratio (38.09) of guava fruits tree treated with 150 kg N ha-1 (Table 1). The guava fruits tree of control treatment (Untreated plants) had TSS-acid ratio of 27.17.

Nitrogen application affects the content of some sugars, amino acids, and ascorbic acid which can influence the taste and flavor of fruits (Lee and Kaddar, 2000; Alcobendas et al., 2013). The present results show significant increase of TSS-acid ratio over control are in accordance with the results of Lima et al. (2008) who reported that higher doses of N treatment showed the highest total soluble solids concentration and TSS-acid ratio but the lowest titratable acidity (acid content) at ripening, while control treatment resulted opposite trend. The increased TSS content might be due to further synthesis and accumulation of photosynthates in the fruits (Murata, 1977) and Color development is associated with a loss of texture, increasing sugar content and decreasing acidity (Rana, 2006). Present results are supported by Lal and Sen (2001) who reported that TSS-acid ratio is linearly increased by increasing nitrogen fertilizer.

Ascorbic acid (mg 100g-1)

The statistical analysis showed that application time (AT) and nitrogen doses (ND) significantly (P<0.05) affected ascorbic acid (AA) of guava, whereas the interaction of application time (AT) and nitrogen doses (ND) were found non-significant for ascorbic acid (AA) of guava (Table 2). Guava fruit trees treated with nitrogen in September recorded maximum ascorbic acid (207.59 mg 100g-1) content which was statistically similar with ascorbic acid (206.31 mg 100g-1) of guava fruit trees treated in October. The minimum ascorbic acid (200.49 mg 100g-1) content of guava fruit trees were recorded in trees treated in November. Revealing the means for nitrogen doses, increasing nitrogen doses from untreated 75 to 150 Kg ha-1 significantly increase ascorbic acid of guava from 203.46 mg 100g-1 to 217.76 mg 100g-1 respectively. The ascorbic acid observed at 150 kg N ha-1 was statistically similar with ascorbic acid (212.42 mg 100g-1) observed in guava fruit trees applied with 225 Kg N ha-1. The control plants (Untreated plants) were observed for minimum ascorbic acid (185.55 mg 100g-1) content.

Ascorbic acid of guava fruits were found higher in the trees that were treated with nutrient in September could be related to better vegetative growth of the plant and its complete crop maturity due to appropriate temperature and photoperiod that boosted the photosynthesis of plant and produced maximum assimilates and translocation to fruit tissues. Similar findings were observed by Ali et al. (2003) in citrus and Burton et al. (1989) in their investigation. Moreover, Ascorbic acid content increases as soil content increases. The ripe guava fruit contain high ascorbic acid contents, which includes dehydroascorbic acid and L-ascorbic acid (Gomez and Lajolo, 2008). L-ascorbic acid (AsA) improve nutritional quality of the fruit as it works as powerful antioxidant and minimize oxidative stress (Gallie, 2013; Huang et al., 2014). Current study revealed that control trees are going through stress due to no fertilization and gives less ascorbic acid content while it is higher at optimum level but again decline due to high nitrogen fertilizer stress. These results also support the results of Shin et al. (2005) who investigated that hydrogen peroxide (H2O2) in guava was high when there was low level of nitrogen but the level of hydrogen peroxide was slowly decreased by increasing application of nitrogen up to optimum level. Possibly, the use of smallest nitrogen dose caused nutrient deficiency related to stress, like resulting high ROS level as observed for the H2O2. In addition, at higher N doses, the H2O2 content began to increase. The present results are in conformity with the findings of Marschner (2012), Zhao et al. (2015) and Ochoa-Velasco et al. (2016) that application of high nitrogen doses during cultivation tends to decrease the values of ascorbic acid contents in various fruits. Liang et al. (2013) also reported that Recycling enzymes of ascorbic acid, such as enzyme MDHAR, which may be up-regulated in response to Nitrogen deficiency as a mechanism for the removal of the ROS. The similar behavior was recorded herein for ‘Paluma’ guava, regarding the enzyme MDHAR activity. On another side, the application of nitrogen in highest amount possibly reduced the functions of MDHAR enzyme which could contribute in decreasing the amount of ascorbic acid content.

 

Table 2: Ascorbic acid (mg 100g-1), reducing sugar and non-reducing sugar of guava as affected by nitrogen doses and its time of application.

Treatments	Ascorbic acid (mg 100g-1)	Reducing sugar (%)	Non-reducing sugar (%)
Time of application
September	207.59 a	5.78	4.74
October	206.31 a	5.66	4.66
November	200.49 b	5.52	4.48
LSD (P<0.05)	5.42	NS	NS
Nitrogen doses (kg ha-1)
Control	185.55 c	5.35 c	4.30 b
75	203.46 b	5.63 b	4.80 a
150	217.76 a	5.85 a	4.77 a
225	212.42 ab	5.77 a	4.63 a
LSD (P<0.05)	10.38	0.09	0.20
Interaction N-doses × Time of application	NS	NS	NS

Means followed by different letters are significantly different at 5% level of significance by using LSD test, NS= Non-significant

 

Reducing sugar (%)

Analysis of variance Table 2 presented a significant (P<0.05) response of reducing sugar to nitrogen doses. However, the alone affect of application time and the interaction of nitrogen doses and application was recorded non-significant for reducing sugar of guava (Table 2). Maximum reducing sugar (5.85%) was noted in guava fruit trees fertilized with nitrogen at the rate of 150 kg N ha-1 which was statistically similar to reducing sugar (5.77%) noted in guava fruit trees fertilized with 225 kg N ha-1 nitrogen. Control trees where nitrogen doses were not applied gave reducing sugar of 5.35%.

Reducing sugars which is consist of more than 65% of the TSS are important for tree growth and regulate tree movements by providing energy to the tree (Wang and Tang, 2014). Maximum reducing sugar by nitrogen application could be attributed to the role of nitrogen in different energy sources such as amino acid and amino sugar (Prasade and Mali, 2000). Decrease in reducing sugar at higher doses of nitrogen might be due to toxicity level, it decreases other nutrient molecule and enzymes which help in the synthesis of these quality parameters (Kaul and Bhatanagar, 2006). The current results are matched with the results of Bhatia et al. (2001) who revealed that nitrogen help in uptake of other nutrients which enhance the guava fruit quality. Kashyap et al. (2012) also support the current study as well.

Non reducing sugar (%)

It is evident from the Anova Table 2 that nitrogen doses (ND) significantly(P<0.05) affected (P<0.05) non-reducing sugar of guava fruit. Moreover, the separate affect of application time (AT) and the interaction of ATxND was non-significant for non-reducing sugar of guava. The data for nitrogen doses showed that highest non-reducing sugar (4.80%) was determined in guava fruit trees supplied with 75 kg N ha-1 which was statistically at par to non reducing sugar (4.77 and 4.63%) of guava fruit trees supplied with 150 and 225 kg N ha-1. The lowest non-reducing sugar (4.30%) was determined in unfertilized (Nitrogen) guava trees.

Maximum non reducing sugar was observed in guava fruit treated with nitrogen fertilizer. It might be due to nitrogen action which favored the soluble solids increase through sugar translocation from leaves to fruits to maximum amount of TSS available in fruit (Souza et al., 2010). Non-reducing sugars significantly increased by increasing nitrogen dose. These findings are in agreement with the reports of Dudi et al. (2005) in Kinnow mandarin, Kashyap et al. (2012) and Ghosh et al. (2012) in pomegranate. Another possible reason of increased in non-reducing sugar could be the transformation of complex polysaccharide into simple sugar. The fruit content contents could easily be described by the fact that urea improve the process of photosynthesis which led to carbohydrate accumulation and helped to enhance sugar content of the fruit. Lal et al. (2000) findings in guava also in agreement with the present results.

Conclusions and Recommendations

It was concluded from the results of the current experiment; that guava trees cv. ‘Allahabad Safeda’ treated with nitrogen during the month of September showed better quality attributes than other treatments. Maximum reducing sugar and non-reducing sugars were noted in trees treated with nitrogen at 150 kg ha-1. However, maximum TSS-acid ratio and ascorbic acid were observed in trees treated with nitrogen at 225 kg ha-1. The maximum TSS and fruit firmness were recorded in trees treated with 75 kg N ha-1, while maximum titratable acidity was observed in trees of control treatment. The interaction of nitrogen application at various timing significantly affected fruit firmness of guava while rest of parameters showed non-significant affect.

On the basis of above conclusions, it is recommended that the guava trees cv. ‘Allahabad Safeda’ should be treated with nitrogen during the month of September to produced quality guava fruit during winter season and nitrogen dose at the rate of 150 kg ha-1 should be applied to guava trees during early season (September) to obtain better fruit during winter season.

Acknowledgements

I would like to acknowledge and give my warmest thanks to my supervisor, Prof. Dr. Muhammad Sajid for his valuable guidance throughout this research study. I am also thankful to the Orchard Farms, Haripur (KP) for their logistic support.

Novelty Statement

Optimum application of nitrogen fertilizer to guava in winter season enhances the quality of guava fruits.

Author’s Contribution

Junaid Khan: Principal author and PhD Scholar, who did research, analysis and wrote draft of this MS.

Sajid Khan: Major Supervisor, who provided all technical guidelines in the whole study program.

Conflict of interest

The authors have declared no conflict of interest.

References

Agfact. 2002. Citrus nutrition. 2nd ed. NSW Department of Primary Industries, Australia.

Alcobendas, R., J.M. Mirás-Avalos, J.J. Alarcón and E. Nicolás. 2013. Effects of irrigation and fruit position on size, colour, firmness and sugar contents of fruits in a mid-late maturing peach cultivar. Sci. Hortic., 164(164): 340-347. https://doi.org/10.1016/j.scienta.2013.09.048

Ali A., A. Rab and A.S. Hussain. 2003. Yield and nutrients profile of potato tubers at various stages of development. Asian J. Plant Sci., 2: 247-250. https://doi.org/10.3923/ajps.2003.247.250

Arora, R.L., S. Tripathi and R. Singh. 1999. Effect of nitrogen on leaf mineral nutrient status, growth and fruiting in Peach. Indian J. Hort., 56(4): 286-284

Bashir, H.A. and A.A. Abu-Goukh. 2003. Compositional changes during guava fruit ripening. Food Chem. Columbus, 80(4): 557-563. https://doi.org/10.1016/S0308-8146(02)00345-X

Bhatia, S.K., V.P. Ahlawat, A.K. Gupta and G.S. Rana. 2001. Physico-chemical attributes of guava as affected by nitrogen application. Haryana J. Hort. Sci., 30(1-2): 65-66.

Burton, W.G. 1989. The Potato. 3th edition. John Wiley & Sons, New York, USA. pp. 742.

Cabrera R.M., M.E. Saltveit and K. Owens. 1992. Cucumber cultivars differ in their response to chilling temperatures. J. Am. Soc. Hortic. Sci., 11795): 802-807. https://doi.org/10.21273/JASHS.117.5.802

Calderon, Z.G., A.N. Lakso and R.M. Piccioni. 2004. Temperature effects on fruit and shoot growth in the apple (Malus domestica) early in the season. XXVI Intl. Hort. Congr.: Key Processes in the Growth and Cropping of Deciduous Fruit and Nut Trees. Acta Hort., 636: 447-453 https://doi.org/10.17660/ActaHortic.2004.636.54

Chauhan, K.S. and A.K. Gupta. 1985. Effect of foliar application of urea on the fruit drop and physico-chemical composition of Ber (Z. mauritiana Lamk.) fruits under arid conditions. Haryana J. Hort. Sci., 14(1-2): 9-11.

Comtrade, H.S. 2018. Selected commodities: 080450 (Guavas, mangoes and mangosteens, fresh or dried) http://comtrade.un.org/db/ce/ceSnapshot.aspx?p=all&px=H1&cc= 080450

Dawoud, H.D. 1991. The effect of nitrogen fertilizer application on growth productivity and fruit quality guava. Annual Report of New Halfa Research Station-ARC Sudan. 209-214

Drake, S.R., J.T. Raese and T.J. Smith. 2002. Time of nitrogen application and its influence on ‘Golden delicious’ apple yield and fruit quality. J. Plant Nutr., 25: 143-157. https://doi.org/10.1081/PLN-100108786

Dris, R., R. Niskanen and E. Fallahi. 1999. Relationships between leaf and fruit minerals and fruit quality attributes of apples grown under northern conditions. J. Plant Nutr., 22:1839-1851. https://doi.org/10.1080/01904169909365760

Dudi, O.P., S. Singh, S. Baloda and D. Singh. 2005. Effect of nitrogen and FYM on fruit quality and yield of Kinnow mandarin. Haryana J. Horti. Sci., 34(3-4): 224-226.

Dubey, A.K., D.B. Singh and D. Neeru. 2001. Effect of foliar spray of urea on fruit yield and quality of guava (Psidium guajava L.). Prog. Hort., 33(1): 37-40

Gallie, D.R. 2013. L-ascorbic Acid: A multifunctional molecule supporting plant growth and development. Scientifica (Cairo). 79: 59-64. https://doi.org/10.1155/2013/795964

Ghosh, S.N. and B.R. Das. 2000. Effect of nitrogen and potassium on growth, yield and physico-chemical properties of kinnow Mandarin grown in rainfed laterite soil. The Hort. J., 13(1): 37-45.

Ghosh, S.N., B. Bera, S. Roy, and A. Kundu. 2012. Integrated nutrient management in pomegranate grown in laterite soil. Indian J. Hortic., 69(3): 333-337.

Gomez, M.L. and F.M. Lajolo. 2008. Ascorbic acid metabolism in fruits: activity of enzymes involved in synthesis and degradation during ripening in mango and guava. J. Sci. Food Agric., 88(5): 756–762. https://doi.org/10.1002/jsfa.3042

He, Z.L.D.V., A.K. Calvert, A.K. Alva and Y.C. Li. 2000. Management of nutrients in citrus production systems in Florida. An overview. Soil Crop Sci. Fla. Proc. 59: 2-10.

Hoying, S., M. Fargione and K. Iungerman. 2004. Diagnosing apple tree nutritional status: leaf analysis interpretation and deficiency symptoms. New York Fruit Quarterly, 12(11): 16-19.

Huang, M., Q. Xu. and X.X. Deng. 2014. L-Ascorbic acid metabolism during fruit development in an ascorbaterich fruit crop chestnut rose (Rosa roxburghii Tratt). J. Plant Physiol., 171 (14): 1205-1216. https://doi.org/10.1016/j.jplph.2014.03.010

Ibrahim, M., J. Ali, M.A. Raza, I.U. Rahman, I.A. Khan, S.A. Khan, J. Khan, A. Rehman and Attaullah. 2019. Wheat productivity in response to ridge sowing and nitrogen application on rain fed condition. Pure Appl. Biol., 8(1):523-529.

Iqtidar, A.K. and Saleemullah. 2004. Text book of Chemistry One. (Bioanalytical Chemistry). National book foundation. Islamabad. Pakistan. 39-40.

Jain, N., K. Dhawan, K, Malhotra, S. Siddiqui and R. Singh. 2001. Compositional and enzymatic changes in guava (Psidium guajava L.) fruits during ripening. Acta Physiol. Plant, 23(3): 357-362. https://doi.org/10.1007/s11738-001-0044-7

Jilani. T. A., Waseem, K., Shirani, J., Kamran, S., Jilani, M.S., Ahmad, T., Manan, A., Ullah, S., Nazim, K and Jilani, H. 2021. Rationalization of bio-slurry and chemical fertilizer combinations for growth and pod yield of pea (Pisum sativum L.) under two growing seasons. Inte. J. Emerg. Technol., 12(1): 139-147.

Jones, J.B. 1999. Tomato Plant Culture in the Field, Greenhouse and Home Garden (Florida, USA). 199.

Kandolia, S.H. and H.P. Bhuva. 1996. Response of different levels of pruning and nitrogen on growth and yield of Phalsa (Grewia asiatica L.) Indian J. Hort., 53(1): 32-34.

Kashyap, P., K.K. Pramanick, K.K. Meena and V. Meena. 2012. Effect of N and P application on yield and quality of Pomegranate. Indian J. Hort., 69(3): 322-327.

Kaul, M.K. and P. Bhatanagar. 2006. Nutritional studies in kinnow. Indian J. Arid Hortic., 1(1): 23-24.

Khan, J., I. Ahmad., N. Mehmood., H. Khan., S. M. Khan., H. Raza., N. Zeb and A. A. Syed. 2015. Influence of cormel sizes and nitrogen uptake for enhancing growth of gladiolus. Int. J. Biosci., 7(2): 152-158. https://doi.org/10.12692/ijb/7.2.152-158

Khushk, A.K., A. Memon and M. Lashari. 2009. Factors affecting guava production in Pakistan. J. Agric. Res., 47(2): 201-210.

Lal, G. and N.L. Sen. 2001. Effect of N, Zn and Mn fertilization on fruit quality of guava (Psidium guajava L.) c.v. Allahabad Safeda. Haryana J. Hort. Sci., 30 (3- 4): 209-210.

Lal, G., N. Sen NL, R. Jat. 2000. Yield and leaf nutrient composition of guava as influenced by nutrients. Indian J. Hort., 57(2):130-132.

Lee, S.K. and A.A. Kader. 2000. Technology. Preharvest and postharvest factors influencing vitamin C content of horticultural crops. Postharvest Biol. Tech., 20(3): 207-209. https://doi.org/10.1016/S0925-5214(00)00133-2

Liang, C., J. Tian and H. Liao. 2013. Proteomics dissection of plant responses to mineral nutrient deficiency. Proteomics, 13(3-4): 624-636. https://doi.org/10.1002/pmic.201200263

Lima, M.A., C.L.H. Bassoi, D.J. Silva, P.D.S. Santos, P.D.C. Paes, P.R.D.A. Ribeiro and B.F. Dantas. 2008. Effect of levels of nitrogen and potassium on yield and fruit maturation of irrigated guava trees in the SAO Francisco Valley. Rev. Bras. Frutic., 30(1): 246-250. https://doi.org/10.1590/S0100-29452008000100045

Locascio, S.J., W.J. Wiltbank, D.D Gull. and D.N. Maynard. 1984. Fruit and vegetable quality as affected by nitrogen nutrition. In: Nitrogen in Crop Production. Ed Hauck, R.D. 617-626. https://doi.org/10.2134/1990.nitrogenincropproduction.c42

Marschner, H. 1995. Mineral nutrition of higher plants. 2nd ed. London: Academic Press. 889.

Marschner, H. 2012. Mineral Nutrition of Higher Plants. 3rd Ed. (London, UK: Academic Press).

Massignam, A.M., S.C. Chapman, G.L. Hammer and S. Fukai. 2009. Physiological determinants of maize and sunflower achene yield as affected by nitrogen supply.
Field Crops Res., 113: 256-267. https://doi.org/10.1016/j.fcr.2009.06.001

Maust, B.E. and J.G. Williamson. 1994. Nitrogen nutrition of containerized citrus nursery plants. J. Am. Soc. Hort. Sci., 119: 195-201. https://doi.org/10.21273/JASHS.119.2.195

McCook, R.K.P., M.G. Nair, P.C. Facey and F.C.S. Bowen. 2012. Nutritional and nutraceutical comparison of Jamaican Psidium cattleianum (Strawberry guava) and Psidium guajava (Common guava) fruits. Food Chem., 134(2): 1069-1073. https://doi.org/10.1016/j.foodchem.2012.03.018

Mitra, S.K. and T.K. Bose. 1985.Effect of varying levels of nitrogen, phosphorus and potassium on yield and quality of guava (Psidium guajava L.) var. L-49. South Indian Hort. 33: 286-92.

Muhammad Ibrahim, J. Ali, M.A. Raza, I. urRahman, I.A. Khan, S.A. Khan, J. Khan, A. Rehman and Attaullah. 2019. Wheat productivity in response to ridge sowing and nitrogen application on rainfed condition. Pure Appl. Biol., 8(1): 523-529.

Muhammad, S., I. Ashiru, D. Ibrahim, A. Kanoma, I. Sani and S. Garba. 2014. Effect of ripening stage on vitamin C content in selected fruits. Int. J. Agric. For. Fish., 2(3): 60-65.

Murata, T. 1977. Studies on the Postharvest Physiology and Storage of Citrus Fruit VII. Acid Metabolism in Satsuma Mandarin Fruit during Storage. J. Japanese Soc. Hort. Sci., 46(2): 283-287. https://doi.org/10.2503/jjshs.46.283

Natale, W., E.L.M. Coutinho, A.E. Boaretto, F.M. Pereira. 1994. La fertilisation azotée du goyavier. Fruits, 49:205-10.

Nava, G., A.R. Dechen and G.R. Nachtigall. 2007. Nitrogen and potassium fertilization affect apple fruit quality in southern Brazil. Commun. Soil Sci. Plant Anal., 39(1-2): 96-107. https://doi.org/10.1080/00103620701759038

Ochoa-Velasco, C.E., R. Valadez-Blanco, R. Salas-Coronado, F. Sustaita-Rivera, B. Hernández-Carlos, S. Garcıa-Ortega and N. F. Santos-Sánchez. 2016. Effect of nitrogen fertilization and Bacillus licheniformis biofertilizer addition on the antioxidants compounds and antioxidant activity of greenhouse cultivated tomato fruits (Solanum lycopersicum L. var. Sheva). Sci. Horti., (Amsterdam) 201: 338-34. https://doi.org/10.1016/j.scienta.2016.02.015

Paula, M.B., V.D. Carvalho., F.D. Nogueira and L.F.S. Souza. 1991. Effect of liming, potassium and nitrogen on the production and quality of pineapple fruit.
Pesqui. Agropecu. Bras., 26: 1337-1343.

Prasade, R.N. and P.C. Mali. 2000. Effect of different levels of nitrogen on quality characters of Pomegranate fruit. Haryana J. Hort. Sci., 29(3-4): 186-187.

Rana, M.K. 2006. Ripening changes in fruits and vegetables-a review. Haryana J. Hort. Sci., 35(3/4): 271-279.

Rashid, A. and J. Ryan. 2004. Macronutrients constraints to crop production in soils with Mediterranean-type characteristics. J. Plant Nutr., 27: 959-975. https://doi.org/10.1081/PLN-120037530

Shanmugavelu, K.G. 1987. Production technology of fruit crops. S.B.A. Publication, Kolkata. pp. 22-31

Shin, R., R.H. Berg and D.P. Schachtman. 2005. Reactive oxygen species and root hairs in Arabidopsis root response to nitrogen, phosphorus and potassium deficiency. Plant Cell Physiol., 46 (8): 1350-1357. https://doi.org/10.1093/pcp/pci145

Singh, H.P. and G. Singh. 2007. Nutrient and water management in guava. Proc. 1st Interna. Guava Sym., CISH, Lucknow. Acta Hort., 735: 389-397. https://doi.org/10.17660/ActaHortic.2007.735.55

Smith, P.F. 1969. Effect of nitrogen rates and timing of application on march grapefruit in florida. Proceedings of the first international citrus symposium 3: 1559-1567.

Souza, F., L.C. Argenta, G. Nava, P.R. Ernani and C.V.T. Amarante. 2013. Quality of ‘Fuji’ apples affected by nitrogen and potassium fertilization in two soil types. Rev. Bras. Frutic., 35(1): 305-315. https://doi.org/10.1590/S0100-29452013000100035

Souza, J.A.R., D.A. Moreira, P.A. Ferreira and A.T. Matos. 2010. Availability of table tomato fruits produced with effluent from the primary treatment of waste water from agricultural production. Eng. Agric., 18: 198-207. https://doi.org/10.13083/1414-3984.v18n03a02

Spironello, A., J.A. Quaggio, L.A.J. Teixeira, P.R. furlani and J.M.M. Sigristp. 2004. Pineapple yield and fruit quality effected by NPK fertilization in a tropical soil. Rev. Bras. Frutic. Jaboticaba, 1: 155-159. https://doi.org/10.1590/S0100-29452004000100041

Steel, R.G.D. and Torrie. 1980. Principles and Procedures of Statistics, Second Edition, New York: McGraw-Hill

Struik, P.C., J. Geertsema and C. Custers. 1989a. Effect of shoots, root and stolon temperature on development of potato plant (I). Potato Res. 32: 133- 141 https://doi.org/10.1007/BF02358225

Wang, J. and Z. Tang. 2014. The regulation of Soluble suger in the growth and development of Plants. Bot. Res., 3: 71-76. https://doi.org/10.12677/BR.2014.33011

Welch, R.M. and R.D. Graham. 2004. Breeding for micronutrients in staple food crops from a human nutrition perspective. J. Exp. Bot., 55: 353-364. https://doi.org/10.1093/jxb/erh064

Zekri, M. and T.A. Obreza. 2003. Macronutrient deficiencies in citrus: nitrogen, phosphorus, and potassium. University of Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, EDIS. 1-3. https://doi.org/10.32473/edis-ss420-2003

Zhao, W., X. Yang, H. Yu, W. Jiang, N. Sun, X. Liu, X. Zhang, Y. Wang and X. Gu. 2015. RNA-Seq-based transcriptome profiling of early nitrogen deficiency response in cucumber seedlings provides new insight into the putative nitrogen regulatory network. Plant Cell Physiol., 56 (3): 455–467. https://doi.org/10.1093/pcp/pcu172