Pre-harvest management of water, nutrients along with mulch: Implications for mango post-harvest quality

Introduction

Mango (Mangifera indica L.), hailed as the "king of fruits", is one of the most important tropical and subtropical fruit crops, and occupying approximately 5.5 million hectares worldwide with an annual production exceeding 55 million tonnes (FAO, 2023). India is the largest producer, contributing nearly 45% of global output (NHB, 2025). Among Indian commercial cultivars, Banganpalli (also known as Baneshan, Safeda, or Benishan) is highly valued for its attractive golden-yellow colour, fibreless flesh, pleasant aroma, excellent sweetness, and long shelf life under ambient conditions (NHM, 2022) [20] . However, Banganpalli fruits harvested from conventionally managed orchards (flood irrigation + soil application of fertilizers) often exhibit inconsistent quality, rapid post-harvest ripening, high respiration rate, quick softening, fast chlorophyll breakdown, and short marketable life (10-12 days at ambient temperature), leading to heavy post-harvest losses estimated at 25-40% (Jilen M. Mayani. 2016) [9] . Pre-harvest factors such as water and nutrient management play a vital role in determining fruit growth, biochemical composition at harvest, and subsequent post-harvest behaviour. Water deficit during fruit development reduces cell turgor, limits photosynthate translocation, impairs mineral uptake, and results in smaller fruits with lower sugar and vitamin C content (Jilen M. Mayani. 2016) [9] . Conversely, excessive or irregular irrigation causes cracking and poor colour development (Jilen M. Mayani. 2016) [9] . Similarly, imbalanced or untimely nutrient supply, especially nitrogen (N) and potassium (K), affects carbohydrate metabolism, cell wall strength, antioxidant accumulation, and resistance to physiological disorders (Jilen M. Mayani. 2016) [9] . In recent years, drip irrigation and fertigation have emerged as powerful water-and nutrientsaving technologies in perennial fruit crops. Drip irrigation maintains optimal soil moisture in the active root zone, minimizes hydrothermal stress, enhances root proliferation, and improves nutrient use efficiency. Fertigation (application of soluble fertilizers through drip) allows precise, split, and synchronized delivery of nutrients according to crop demand, resulting in higher leaf nutrient status and better partitioning of assimilates to the fruit. Mulching further conserves soil moisture, suppresses weeds, moderates soil temperature, and reduces fruit cracking and sun scorch (Kaviyazhagan et al., 2015) [12] . Several workers have independently reported beneficial effects of drip irrigation and fertigation on fruit yield and quality of mango cultivars such as Alphonso, Dashehari, Totapuri, and Mallika (Prakash et al., 2015) [24] . However, very little information is available on their combined effect on post-harvest quality and shelf-life attributes of cv. Banganpalli, particularly under S.Emi-arid tropical conditions of southern India. Therefore, the present investigation was undertaken with the following objectives: To study the influence of different drip irrigation regimes (based on crop evapotranspiration, ETc) on fruit physico-chemical quality at harvest and during ambient storage. To evaluate the effect of varying levels of N and K applied through fertigation versus conventional soil application. To examine the synergistic effect of drip irrigation, fertigation, and mulching on biochemical constituents (TSS, sugars, ascorbic acid, acidity), respiration behaviour, fruit firmness, chlorophyll degradation, and shelf life of mango cv. Banganpalli.

Materials and Methods

Experimental site and plant material

The field experiment was conducted at the Mango Research station, Sangareddy, Sri Konda Laxman Telangana Horticultural University, Telangana, India (16° 30' N latitude and 78° 19' E longitude at an elevation of 550 m above MSL). The region has a hot S.Emi-arid climate with mean annual rainfall of 906 mm received mostly during south-west monsoon. The soil was red sandy loam with pH 7.4, low in organic carbon (0.38%), available N (182 kg ha⁻¹), P (23 kg ha⁻¹) and K (245 kg ha⁻¹). Uniform, healthy, 12-year-old mango trees cv. Banganpalli, grafted on local seedling rootstock, spaced at 10 m × 10 m, was selected for the study.

Treatments and experimental design

The experiment was laid out in a two-factor factorial randomized block design with three replications.

Factor A -Irrigation levels (drip)  I₁: Conventional surface (flood-1200 liters once in 10 days per plant) irrigation (control)  I₂: 75% of crop evapotranspiration (ETc)  I₃: 100% ETc  I₄: 125% ETc Factor B -Fertigation / fertilization levels  F₁: 100% recommended dose of N and K through soil application (control)  F₂: 50% recommended dose of N and K through fertigation  F₃: 75% recommended dose of N and K through fertigation  F₄: 100% recommended dose of N and K through fertigation Thus, there were 16 treatment combinations (4 irrigation × 4 fertilization levels) replicated thrice, making a total of 96 trees (two plants per treatment). Recommended dose of fertilizer for mango in the region is: 1000 g N, 1000 g P2O5, 1000 g K₂O and 50 kg FYM per tree per year. 500 g of N&K fertilizer applied along with phosphorus (1000 g P₂O₅) and 50 kg FYM was applied uniformly to all treatments as basal soil application during onset of Monsoon period and the remaining 500 g of N&K fertilizer applied in three splits for fertigation treatments. Urea and potassium nitrate (white) were used as sources of N and K, respectively, for both soil and fertigation treatments.

Drip irrigation was scheduled daily based on previous day's pan evaporation (Class A pan) adjusted by crop factor (Kc) and canopy coverage factor. Four drippers (8 L h⁻¹ each) were placed around each tree. Black polyethylene mulch (100 micron) was spread in the tree basin (6 m diameter) in all drip-irrigated plots to conserve moisture and control weeds.

Observations recorded

Fully mature fruits (100-120 days after fruit set, shoulder development, slight yellowing at apex) were harvested in the morning hours during second week of May in both years. Representative samples of 30 fruits per treatment per replication were kept for storage studies at ambient condition (27 ± 2 °C, 65-75% RH).

Physico-chemical parameters recorded at harvest and at 3-day intervals during storage included:  Total soluble solids (°Brix) -Hand Refractometer  Titratable acidity (%) -NaOH titration  Ascorbic acid (mg 100 g⁻¹) -2,6-dichlorophenol dye method  Total, reducing and non-reducing sugars (%) -Lane-Eynon method  Respiration rate (O₂ uptake and CO₂ evolution,% kg⁻¹ h⁻¹)static head-space method using portable gas analyser (PBI Dan sensor)  Fruit firmness (kg cm⁻²)penetrometer (8 mm probe)  Chlorophyll degradation -DA-index using DA-meter (TR Turoni, Italy)  Shelf lifenumber of days taken to reach eating-soft stage (firmness < 0.8 kg cm⁻² with full yellow colour)

Statistical analysis

The data were subjected to two-way analysis of variance (ANOVA) using OPSTAT and WASP software. Duncan Multiple Range Test (DMRT) was used to distinguish means that were significantly different at p ≤ 0.05. The results of both years followed similar trend; hence, pooled data are presented and discussed.

Results and Discussion

Ascorbic acid content (mg 100 g⁻¹) Irrigation levels significantly influenced the fruit ascorbic acid content (Table -1). The highest value was recorded at 100% ETc (I3: 46.22 mg 100 g⁻¹), statistically similar to 75% ETc (I2: 45.42 mg 100 g⁻¹) and 125% ETc (I4: 43.75 mg 100 g⁻¹), whereas the control (I1) gave the lowest (39.42 mg 100 g⁻¹). Thus, drip irrigation at 75-125% ETc significantly increased ascorbic acid compared to conventional surface irrigation, consistent with findings in sapota cv. Kalipatti (Tiwari et al., 2016) [31] , mango cv. Alphonso (Prakash et al., 2015) [24] , citrus (Mathew and Ghosh, 2004) [18] , sweet orange (Ghosh and Pal, 2010), and guava (Singh et al., 2015) [29] . This might be due to higher soil moisture under drip irrigation and mulching minimized root shrinkage, improved root-soil contact, and enhanced potassium uptake. Elevated leaf K promotes conversion of carbohydrates into amino acids and vitamins, including ascorbic acid (Borthakur and Bhattacharyya, 1996b) [4] . [23] in acid lime. The irrigation × fertilization interaction was significant ( [25,13,5,21] . These factors collectively explain the superior ascorbic acid levels observed in the present study.

TSS ( Brix)

Data revealed no significant main effect of irrigation or fertilization levels on TSS (°Brix) of mango cv. Banganpalli (Table -2). However, their interaction was significant. [27] in Nagpur mandarin, Junaid et al. (2013) [10] in guava, Koo (1984) [13] in orange, Colapietra (1987) [5] in grapes, Orphanos and Eliades (1994) [21] in Valencia orange, and Sadarunnisa et al. (2010) [25] in papaya. The increase in TSS with higher irrigation, fertigation, and mulching is attributed to sustained soil moisture, reduced hydrothermal fluctuations, and active roots throughout the season. Drip irrigation and mulching minimized root shrinkage and improved root-soil contact. Fertigation enhanced nutrient availability, raising leaf NPK content. Higher nutrient reserves might have promoted conversion of carbohydrates into amino acids and proteins, increasing leaf area, carbon assimilation, and ultimately sugar accumulation and TSS (Borthakur and Bhattacharyya, 1996b) [4] .

Irrigation levels significantly affected titratable acidity (Table 2). The lowest acidity was recorded in the control (I1: 0.27%), statistically similar to 100% ETc (I3: 0.28%) and 125% ETc (I4: 0.29%), whereas the highest was with 75% ETc (I2: 0.33%). Titratable acidity decreased significantly with increasing irrigation levels, consistent with findings in mango cv. Alphonso (Prakash et al., 2015) [24] . Higher irrigation maintained consistent soil moisture, enhancing stomatal conductance and CO₂ assimilation (Taiz and Zeiger, 2009) [30] . This promoted photosynthates production and accumulation of carbohydrates and hydrolytic enzymes during fruit development, accelerating starch hydrolysis into sugars and thereby reducing acidity. In contrast, water stress at 75% ETc (I2) likely limited enzyme activity, slowing conversion of organic acids and starch to sugars, resulting in higher acidity.

Fertilization treatments also significantly influenced titratable acidity. The lowest values were with 100% N and K via fertigation (F4: 0.28%), on par with 50% (F2: 0.28%) and 75% (F3: 0.30%) through fertigation, while the highest was with 100% N and K via soil application (F1: 0.32%). Fertigation at 100% N and K significantly lowered acidity compared to conventional soil application, in agreement with Pankaj (2013) [23] in acid lime and Karuna et al. (2017) [11] in Kinnow mandarin.

The irrigation × fertilization interaction was significant. The lowest acidity was recorded in control + 100% N and K via fertigation (I1F4: 0.23%), comparable to I3F2 (0.24%), I4F2 (0.25%), and I1F1 (0.25%). The highest was in I3F1 (0.36%).

Combined higher irrigation and fertigation with mulching consistently reduced titratable acidity, corroborating reports in orange (Koo, 1984) [13] , grapes (Colapietra, 1987) [5] , Valencia orange (Orphanos and Eliades, 1994) [21] , papaya (Sadarunnisa et al., 2010) [25] , Nagpur mandarin (Shirgure et al., 2016) [27] , and guava (Junaid et al., 2013) [10] . Reduced acidity under higher irrigation and fertigation with mulching is attributed to improved soil moisture and nutrient availability, which enhanced sourceto-sink translocation and plant growth (Prakash et al., 2015) [24] . This favored metabolite accumulation and starch hydrolysis into sugars during fruit ripening, thereby lowering titratable acidity.

Brix acid ratio

The Brix: acid ratio of mango cv. Banganpalli fruits as affected by irrigation and fertilization levels is shown in Table 2. Irrigation levels significantly influenced the Brix: acid ratio. The highest ratio was recorded in the control (I1: 72.39), statistically similar to 125% ETc (I4: 69.50) and 100% ETc (I3: 67.00), whereas the lowest was with 75% ETc (I2: 54.36). The ratio increased with higher irrigation levels, consistent with findings in mango cv. Alphonso (Prakash et al., 2015) [24] . Higher irrigation ensured consistent soil moisture, improved translocation of assimilates, and enhanced accumulation of carbohydrates and hydrolytic enzymes during fruit development. This accelerated starch hydrolysis into sugars, raising TSS and reducing acidity, thereby increasing the Brix: acid ratio. Fertilization treatments also significantly affected the Brix: acid ratio. The highest values were obtained with 100% N and K via fertigation (F4: 70.14), comparable to 50% via fertigation (F2: 69. 19). The lowest ratio was with 100% N and K via soil application (F1: 58.60), similar to 75% via fertigation (F3: 59.88). Fertigation significantly improved the ratio over conventional soil application, in agreement with Pankaj (2013) [23] in acid lime and Karuna et al. (2017) [11] in Kinnow mandarin. Fertigation increased nutrient availability, boosted photosynthesis, and enhanced synthesis of carbohydrates and hydrolytic enzymes. These enzymes promoted hydrolysis of starch and organic acids into sugars, raising TSS and lowering acidity, which ultimately improved the Brix: acid ratio (Shirgure et al., 2016) [27] . The irrigation × fertilization interaction was significant. The highest Brix: acid ratio was recorded in control + 100% N and K via fertigation (I1F4: 80.47), followed closely by I4F2 (83. [27] and pomegranate cv. Bhagwa (Haneef et al., 2014) [8] . The superior Brix: acid ratio under higher irrigation and fertigation with mulching resulted from greater soil moisture and nutrient availability, which strengthened source-to-sink transport and plant growth. This favored accumulation and hydrolysis of starch into sugars, increasing TSS and reducing acidity, leading to a higher Brix: acid ratio.

Total sugars, non-reducing sugars, and reducing sugars Total sugars

Irrigation levels significantly affected total sugar content (Table 3). The highest values were recorded at 100% ETc (I3) and 125% ETc (I4) (both 12.98%), statistically similar to control (I1: 12.48%), while the lowest was at 75% ETc (I2: 12.09%). Fertilization treatments showed significant differences. Maximum total sugars were obtained with 100% N and K via fertigation (F4: 14.98%), comparable to 75% via fertigation (F3: 14.26%). The lowest was with 100% N and K via soil application (F1: 10.22%).

The interaction was significant. Highest total sugars were recorded in I3F4 (15.96%), followed by I4F4 (15.35%), I3F3 (14.98%), I4F3 (14.48%), and I1F4 (14.75%). The lowest was in I4F1 (9.43%), similar to several soil-applied treatments (9.93-10.58%), (Table 3).

Non-reducing sugars

Irrigation significantly influenced non-reducing sugars. Highest content was at 100% ETc (I3: 8.09%), comparable to 125% ETc (I4: 7.53%). Lowest values were at 75% ETc (I2) and control (I1) (~7.35-7.53%). Fertigation at 100% N and K (F4: 9.51%) gave the highest non-reducing sugars, followed by 75% (F3: 8.71%), while soil application (F1: 5.24%) recorded the lowest.

The interaction effect was significant, with I3F3 (10.42%), I3F4 (10.14%), and I4F4 (9.51%) showing the highest values, and I4F1 (4.15%) the lowest (Table 3).

Reducing sugars

Surprisingly, highest reducing sugars were observed at 75% ETc (I2: 5.59%), comparable to 125% ETc (I4: 5.45%), while 100% ETc (I3) gave the lowest (4.89%). Among fertilization treatments, 100% N and K via fertigation (F4: 5.93%) recorded the highest reducing sugars, followed by 75% (F3: 5.41%). Lowest values were with 50% via fertigation (F2: 4.74%) and soil application (F1: 4.97%). Interaction showed I2F4 (6.28%) as the highest, followed by I4F4, I3F4, I4F3, and I1F4 (5.77-5.84%). The lowest was I1F2 (3.90%), (Table 3). Higher irrigation (100-125% ETc) through drip, combined with mulching, significantly increased total and non-reducing sugars compared to the control or deficit irrigation (75% ETc). This is attributed to sustained soil moisture, reduced hydrothermal stress, enhanced surface rooting, and efficient uptake of N and K-key activators of enzymes involved in photosynthesis and carbohydrate metabolism. [7,3,25,26,11] . The combined effect of higher irrigation and fertigation with mulching maximized sugar accumulation through better sourceto-sink strength, sustained moisture, and nutrient supply, leading to efficient starch hydrolysis during ripening. Similar results have been reported in orange (Koo, 1984) [13] , grapes (Colapietra, 1987) [5] , Valencia orange (Orphanos and Eliades, 1994) [21] , and papaya (Sadarunnisa et al., 2010) [25] .

Respiration is a fundamental metabolic process that provides energy for various biochemical reactions in plant tissues. Aerobic respiration involves the oxidative breakdown of organic reserves into simpler molecules, primarily carbon dioxide (CO₂) and water, with the concomitant release of energy. The substrates utilised in respiration include carbohydrates, lipids, and organic acids. This process consumes oxygen (O₂) through a series of enzymatic reactions.

In climacteric fruits such as mango, ripening is marked by a dramatic increase in respiration rate (the climacteric rise), characterised by a sharp rise in CO₂ evolution and a corresponding decline in internal O₂ concentration. This climacteric rise is triggered by an autocatalytic increase in ethylene production and sensitivity (Lyons and Pratt, 1964) [17] . Under ambient conditions, a relatively constant respiratory quotient (ratio of CO₂ evolved to O₂ consumed) is typically observed, indicating the presence of physiologically active ethylene within the fruit tissues (James et al., 1961). A secondary rise in respiration, often termed "induced" respiration, may occur later during storage and is primarily caused by microbial proliferation rather than the ripening process itself (Palmer and McGlasson, 1969) [22] . Freshly harvested fruits are virtually free of microbes; however, microbial populations increase as ripening progresses (Palmer and McGlasson, 1969) [22] . Unripe fruits generally exhibit low microbial counts, possibly due to the presence of antimicrobial compounds in green tissues (Simmonds, 1963) [28] . In ripe fruits, loss of cellular integrity makes them more susceptible to infection, which can trigger secondary (microbially induced) respiration (McGlasson and Pratt, 1964) [19] . The extent of this secondary rise depends largely on cellular integrity, which is influenced by both preharvest and post-harvest factors.

Respiration Rate of Mango cv. Banganpalli Fruits during Storage

Respiration rate was measured as oxygen uptake (O₂% kg⁻¹ fresh mass h⁻¹) and carbon dioxide evolution (CO₂% kg⁻¹ fresh mass h⁻¹). The data (Tables 4 to 6) exhibited a typical climacteric pattern, with a sharp rise in CO₂ evolution and a corresponding decline in internal O₂ concentration between the 3rd and 6th day after harvest, followed by a gradual decline thereafter.

Oxygen Uptake (O₂% kg⁻¹ fresh mass h⁻¹); (Table 4&5) On the day of harvest Significant differences were observed among irrigation levels. The highest O₂ uptake was recorded with 75% ETc (I₂: 15.3), which was statistically at par with 125% ETc (I₄: 15.1) and control (I₁: 15.1). The lowest was with 100% ETc (I₃: 14.4). Among fertigation treatments, the highest O₂ uptake occurred with 75% N and K through fertigation (F₃: 15.5), followed by 100% N and K through fertigation (F₄: 14.9) and 100% N and K applied through soil (F₁: 14.9). The lowest was with 50% N and K through fertigation (F₂: 14.5). Interaction effects were significant. The highest value was recorded in I₄F₃ (125% ETc + 75% N and K fertigation: 16.5), at par with I₃F₃ (100% ETc + 75% N and K fertigation: 15.8). The lowest was in I₃F₂ (100% ETc + 50% N and K fertigation: 13.8).

rd day of storage

The highest O₂ uptake among irrigation levels was in the control (I₁: 12.7), followed by 100% ETc (I₃: 9.4), at par with 75% ETc (I₂: 9.5). The lowest was with 125% ETc (I₄: 8.4). Among fertigation treatments, the highest value was with 100% N and K applied through soil (F₁: 10.6), followed by 50% N and K through fertigation (F₂: 10.2). The lowest was with 75% N and K through fertigation (F₃: 9.2). The highest interaction value was in I₁F₁ (control + 100% N and K through soil: 14.4), at par with I₂F₂ (75% ETc + 50% N and K fertigation: 14.3). The lowest was in I₄F₂ (125% ETc + 50% N and K fertigation: 7.0).

th day of storage

The highest O₂ uptake among irrigation levels was in the control (I₁: 11.8), followed by 100% ETc (I₃: 9.4), at par with 75% ETc (I₂: 9.2). The lowest was with 125% ETc (I₄: 8.3). Among fertigation treatments, the highest value was with 100% N and K applied through soil (F₁: 10.1), followed by 50% N and K through fertigation (F₂: 10.0). The lowest was with 75% N and K through fertigation (F₃: 9.0). The highest interaction value was in I₁F₁ (13.7), at par with I₂F₂ (13.2). The lowest was in I₂F₃ (75% ETc + 75% N and K fertigation: 5.9).

th day of storage

The highest O₂ uptake among irrigation levels was in the control (I₁: 13.7), followed by 125% ETc (I₄: 12.1). The lowest was with 100% ETc (I₃: 11.5). Among fertigation treatments, the highest value was with 100% N and K applied through soil (F₁: 14.1), followed by 50% N and K through fertigation (F₂: 12.7). The lowest was with 75% N and K through fertigation (F₃: 10.1). The highest interaction value was in I₁F₁ (15.3), at par with I₂F₂ (15.1). The lowest was in I₂F₃ (7.3).

th day of storage

The highest O₂ uptake among irrigation levels was in the control (I₁: 11.4), followed by 100% ETc (I₃: 10.5), at par with 125% ETc (I₄: 10.4). The lowest was with 75% ETc (I₂: 8.7). Among fertigation treatments, the highest value was with 100% N and K applied through soil (F₁: 12.0), followed by 50% N and K through fertigation (F₂: 10.5). The lowest was with 75% N and K through fertigation (F₃: 9.1). The highest interaction value was in I₁F₁ (14.1), at par with I₃F₁ (14.0). The lowest was in I₂F₃ (7.0).

The lowest CO₂ evolution among irrigation levels was with 75% ETc (I₂: 4.8), at par with 100% ETc (I₃: 4.9). The highest was in the control (I₁: 5.6). Among fertigation treatments, the lowest was with 50% N and K through fertigation (F₂: 4.8), followed by 75% N and K through fertigation (F₃: 5.0). The highest was with 100% N and K applied through soil (F₁: 5.4). The lowest interaction value was in I₃F₂ (100% ETc + 50% N and K fertigation: 4.2), at par with I2F3 (4.3). The highest values (5.8) were recorded in I3F1, I1F3, and I4F4.

rd day of storage

The lowest CO2 evolution among irrigation levels was with 100% ETc (I3: 7.1), followed by control (I1: 7.6). The highest was with 125% ETc (I4: 8.4). Among fertigation treatments, the lowest was with 100% N and K through fertigation (F4: 6.7), followed by 75% N and K through fertigation (F3: 7.6). The highest was with 50% N and K through fertigation (F2: 8.9). The lowest interaction values were in I2F4 (6.1) and I4F4 (6.0). The highest was in I4F2 (125% ETc + 100% N and K through soil: 11.2).

th day of storage (climacteric peak)

The lowest CO2 evolution among irrigation levels was in the control (I1: 6.6), followed by 100% ETc (I3: 7.7), at par with 125% ETc (I4: 7.8). The highest was with 75% ETc (I2: 8.0). Among fertigation treatments, the lowest was with 75% N and K through fertigation (F3: 5.5), followed by 100% N and K through fertigation (F4: 6.3). The highest was with 100% N and K applied through soil (F1: 9.4). The lowest interaction value was in I1F3 (3.0), followed by I2F4 (4.2). The highest was in I4F2 (12.1).

th day of storage

The lowest CO2 evolution among irrigation levels was in the control (I1: 5.5). The highest was with 100% ETc (I3: 6.5), at par with 125% ETc (I4: 6.4). Among fertigation treatments, the lowest was with 75% N and K through fertigation (F3: 5.6). The highest (6.5) was recorded in both F1 and F2. The lowest interaction values (4.1) were in I4F3 and I2F4. The highest was in I4F2 (8.2).

th day of storage

The lowest CO2 evolution among irrigation levels was in the control (I1: 6.8), followed by 75% ETc (I2: 7.2). The highest was with 100% ETc (I3: 8.7). Among fertigation treatments, the lowest was with 75% N and K through fertigation (F3: 6.7), followed by 100% N and K through fertigation (F4: 7.3). The highest was with 50% N and K through fertigation (F2: 8.5). The lowest interaction value was in I4F3 (5.1), followed by I1F3 (5.9). The highest was in I3F1 (9.9). The results on gas composition (O2 and Co2% kg fresh mass -1 h - 1 ) of mango fruits after application of different levels irrigation and fertilization treatments are presented in the has shown increased respiration rate along with early second raise in O2 consumption, it means fruits ripened early and there after fruits started degrading due to it the induced respiration triggered. This may be due to poor cell wall integrity affected by improper irrigation and nutrition has resulted in reduced synthesis of antimicrobial and antioxidant compounds. Further, the reduced fruit firmness, increased chlorophyll degradation which ultimately increased the respiration rate led to reduced shelf life of fruits in the present investigation.

The data revealed that there is no significant difference among different levels of irrigation with respect to firmness of fruit on 12 th day of storage. Fertilization treatments significantly affected fruit firmness on day 12 of storage. Highest firmness occurred with 75% N-K fertigation (F3: 2.65 kg cm⁻²), followed by 100% fertigation (F4: 1.58 kg cm⁻²); lowest was with 50% fertigation (F2: 0.97 kg cm⁻²). Higher fertigation levels markedly retained firmness compared to conventional soil fertilization. This is attributed to greater nutrient reserves from improved uptake via fertigation, enhanced photosynthesis, increased food reserves, and higher pectin synthesis -all strengthening cell-wall integrity (Junaid et al., 2013 in guava) [10] .

The irrigation × fertilization interaction significantly affected fruit firmness on day 12 of storage. Highest firmness occurred with 125% ETc + 75% N-K fertigation (I4F3: 3.3 kg cm⁻²), comparable to 100% ETc + 75% N-K fertigation (I3F3: 3.1 kg cm⁻²), control + 75% N-K fertigation (I1F3: 3.1 kg cm⁻²), and control + 100% soil-applied N-K (I1F1: 3.0 kg cm⁻²). Lowest firmness was in control + 50% fertigation (I1F2: 0.3 kg cm⁻²). Combined higher irrigation and fertigation markedly improved firmness retention compared to conventional practices. This resulted from sustained soil moisture, enhanced nutrient availability and uptake, higher nutrient reserves, increased photosynthesis, greater photosynthate accumulation, and elevated pectin synthesisall strengthening cell-wall integrity (Junaid et al., 2013 in guava) [10] .

DA-index

The results on DA-index of mango fruits after application of different levels irrigation and fertilization treatments are presented in the Table-10 to 11. The changes in fruit colour can be assessed with the DA-index (difference of absorbance-index), which measures the level of chlorophyll-a in the flesh of the fruit just under the skin. Generally DA index values decreases with fruit ripens as chlorophyll degrades (Amaya and Janet, 2018) [1] . Irrigation levels significantly influenced DA-index of mango cv. Banganpalli on day 12 of storage ( [6] in blueberry. This delay is attributed to sustained soil moisture, which enhanced nutrient uptake, photosynthesis, carbon assimilation, sugar accumulation (Borthakur and Bhattacharyya, 1996b) [4] , cell-wall integrity, fruit firmness, antioxidant synthesis (ascorbic acid), and suppressed respiration. These factors collectively slowed chlorophyll breakdown (DA-index ≥0.45 on day 9; Tables 10&11).

Fertilization treatments significantly affected DA-index on day 12 of storage. Highest values occurred with 75% N-K fertigation (F3: 0.58), comparable to 100% fertigation (F4: 0.51); lowest was with 50% fertigation (F2: 0.29, mislabeled as F1 in original). Fertigation markedly increased DA-index (delayed chlorophyll degradation) compared to conventional soil fertilization. This is attributed to readily available nutrients via fertigation, which boosted photosynthesis, photosynthates accumulation, pectin-like substance production, ascorbic acid levels, antioxidant activity, and cell-wall integritycollectively slowing chlorophyll breakdown and improving fruit quality. Similar results were reported by Kumar et al. (2010) [15] in papaya.

The irrigation × fertilization interaction significantly affected DA-index on day 12 of storage (

The data (Table 12) revealed significant differences in shelf life of mango cv. Banganpalli among irrigation levels. Maximum shelf life was recorded at 125% ETc (I4: 12.73 days), statistically similar to 100% ETc (I3: 12.69 days), while minimum was at 75% ETc (I2: 10.96 days). Higher irrigation levels significantly extended shelf life compared to the control. Similar results were reported by David et al. (2012) [6] in blueberry. Longer shelf life under higher drip irrigation is attributed to sustained soil moisture, which improved mineral nutrient availability, enhanced photosynthesis and carbon assimilation, and increased accumulation of sugars and other metabolites (Borthakur and Bhattacharyya, 1996b) [4] . This led to greater fruit firmness, slower chlorophyll degradation, and suppressed respiration, collectively delaying ripening and senescence. Shorter shelf life in the control resulted from water stress, which reduces fruit quality relative to well-watered trees.

Fertilization treatments significantly affected shelf life of mango fruits. Maximum shelf life was recorded with 75% N-K fertigation (F3: 13.04 days), statistically similar to 100% fertigation (F4: 12.68 days). Minimum values occurred with 50% fertigation (F2: 11.07 days) and soil application (F1: 11.43 days). Similar extensions in shelf life with higher fertigation have been reported by Kumar et al. (2010) [15] in papaya.

Fertigation markedly prolonged shelf life compared to conventional soil fertilization. This is attributed to higher nutrient reserves from improved uptake via fertigation, leading to enhanced photosynthesis, greater accumulation of food reserves, increased pectin synthesis, stronger cell-wall integrity, higher fruit firmness, slower chlorophyll degradation, and suppressed respiration. These factors collectively delayed senescence and extended shelf life. The combined application of irrigation and fertilization significantly affected shelf life of mango cv. Banganpalli. Maximum shelf life was recorded in 100% ETc + 100% N-K fertigation (I3F4: 14.75 days), statistically similar to 125% ETc + 75% N-K fertigation (I4F3: 14.45 days) and 125% ETc + 100% N-K fertigation (I4F4: 14.00 days). Minimum shelf life occurred in 75% ETc + 50% N-K fertigation (I2F2: 10.58 days). This study demonstrates that higher irrigation and fertigation levels, combined with mulching, significantly extended shelf life compared to conventional practices. The extension is attributed to optimal soil moisture and timely nutrient supply via split fertigation, which enhanced nutrient uptake, leaf nutrient reserves, photosynthesis, photosynthates accumulation, pectin synthesis, and cell-wall integrity. These factors increased fruit firmness, slowed chlorophyll degradation, and suppressed respiration, collectively delaying senescence has resulted in prolonging shelf life of mango. F1-100% (500 g) N and K applied through soil; F2-50% (250 g) N and K applied through fertigation; F3-75% (375 g) N and K applied through fertigation; F4-100% (500 g) N and K applied through fertigation; I1-(Control) irrigated with 1200 liters of water tree - 1 at 10 days intervals. F1-100% (500 g) N and K applied through soil; F2-50% (250 g) N and K applied through fertigation; F3-75% (375 g) N and K applied through fertigation; F4-100% (500 g) N and K applied through fertigation; I1-(Control) irrigated with 1200 liters of water tree - 1 at 10 days intervals. F1-100% (500 g) N and K applied through soil; F2-50% (250 g) N and K applied through fertigation; F3-75% (375 g) N and K applied through fertigation; F4-100% (500 g) N and K applied through fertigation; I1-(Control) irrigated with 1200 liters of water tree -1 at 10 days intervals. F1-100% (500 g) N and K applied through soil; F2-50% (250 g) N and K applied through fertigation; F3-75% (375 g) N and K applied through fertigation; F4-100% (500 g) N and K applied through fertigation; I1-(Control) irrigated with 1200 liters of water tree -1 at 10 days intervals. F1-100% (500 g) N and K applied through soil; F2-50% (250 g) N and K applied through fertigation; F3-75% (375 g) N and K applied through fertigation; F4-100% (500 g) N and K applied through fertigation; I1-(Control) irrigated with 1200 liters of water tree -1 at 10 days intervals. F1-100% (500 g) N and K applied through soil; F2-50% (250 g) N and K applied through fertigation; F3-75% (375 g) N and K applied through fertigation; F4-100% (500 g) N and K applied through fertigation; I1-(Control) irrigated with 1200 liters of water tree -1 at 10 days intervals. F1-100% (500 g) N and K applied through soil; F2-50% (250 g) N and K applied through fertigation; F3-(375 g) N and K applied through fertigation; F4-100% (500 g) N and K applied through fertigation; I1-(Control) irrigated with 1200 liters of water tree -1 at 10 days intervals. F1-100% (500 g) N and K applied through soil; F2-50% (250 g) N and K applied through fertigation; F3-75% (375 g) N and K applied through fertigation; F4-100% (500 g) N and K applied through fertigation; I1-(Control) irrigated with 1200 liters of water tree -1 at 10 days intervals. F1-100% (500 g) N and K applied through soil; F2-50% (250 g) N and K applied through fertigation; F3-75% (375 g) N and K applied through fertigation; F4-100% (500 g) N and K applied through fertigation; I1-(Control) irrigated with 1200 liters of water tree -1 at 10 days intervals. F1-100% (500 g) N and K applied through soil; F2-50% (250 g) N and K applied through fertigation; F3-75% (375 g) N and K applied through fertigation; F4-100% (500 g) N and K applied through fertigation; I1-(Control) irrigated with 1200 liters of water tree -1 at 10 days intervals. not differ significantly F1-100% (500 g) N and K applied through soil; F2-50% (250 g) N K applied through fertigation; F3-75% (375 g) N and K applied through fertigation; F4-100% (500 g) N and K applied through fertigation; I1-(Control) irrigated with 1200 liters of water tree -1 at 10 days intervals. . F1-100% (500 g) N and K applied through soil; F2-50% (250 g) N and K applied through fertigation; F3-75% (375 g) N and K applied through fertigation; F4-100% (500 g) N and K applied through fertigation; I1-(Control) irrigated with 1200 liters of water tree -1 at 10 days intervals.

Conclusion

Pre-harvest management through drip irrigation at 100-125% ETc combined with 75-100% recommended N and K applied via fertigation and mulching consistently produced mango cv. Banganpalli fruits of superior physicochemical quality and markedly extended post-harvest shelf life under ambient conditions. These practices enhanced TSS, total and nonreducing sugars, ascorbic acid content, and Brix: acid ratio while reducing titratable acidity. During storage, they delayed the climacteric peak, suppressed respiration rate, maintained higher fruit firmness, slowed chlorophyll degradation, and prolonged marketable life by 3-4 days compared to conventional flood irrigation and soil fertilization. The beneficial effects are primarily due to optimal and continuous soil moisture, improved nutrient availability and uptake, higher leaf nutrient status, enhanced photosynthesis and assimilate partitioning, increased synthesis of structural and protective compounds, and better cellular integrity. Therefore, adoption of drip irrigation at 100-125% ETc along with 75-100% N-K fertigation and mulching is strongly recommended as a sustainable pre-harvest practice to achieve premium fruit quality and longer post-harvest life in mango cv. Banganpalli.

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