Effect of different irrigation levels and mulching on availability of soil moisture and quality of mango (Mangifera indica L.) cv. Banganpalli

Introduction

Mango (Mangifera indica L.) belongs to the family Anacardiaceae considered as one of the most important fruits of the tropical and subtropical countries. India occupies the top position among mango growing countries of the world and produces 40.1% of the total world production. It is the premier and choicest fruit of India and undoubtedly one of the best fruits of the world. It is known as 'King of Fruits' due to its captivating flavour, irresistible taste and sweetness. Very aptly, Indians designated this fruit as the 'National Fruit' of the country.

Mango is a highly nutritive fruit. It plays an important role in balancing the human diet by providing about 64-86 calories per 100 grams of ripe fruits (Rathore et al. 2007) [35] . It is a good source of vital protective nutrients like vitamins A, B, and C, niacin and is also rich in minerals including calcium, potassium and iron. Telangana is a semi-arid area and has a predominantly hot and dry climate. Summer starts in March and reaches a peak in May with an average high temperature of 42 °C (108 °F) range. The monsoon arrives in June and lasts till September with about 755 mm (29.7 inches) of rainfall. With the global climate changes, water becomes an increasingly limiting factor for agricultural crop production. Drip irrigation is the most efficient water and nutrient delivery system for growing crops. It delivers water and nutrients directly to the plant's roots zone, in the right amounts, at the right time, so each plant gets exactly what it needs, when it needs to grow optimally. Under South Indian condition, the flower bud differentiation starts at the end of December and fruits come to maturity by May (Bhagwan et al. 2013) [4] which is coincides with severe summer. The peak water requirement of mango is during fruit development stage which coincides with March and April months in Telangana. These months experience severe water shortage in bore wells due to increased temperatures and depleting ground water. Hence, the Telangana farmers provide drip irrigation every two day in their orchards due to shortage of water which ultimately results in fruit drop and low yield. Water shortage during critical period of fruit development was earlier reported by Adak et al., 2012 in mango.

Drip irrigation system minimizes water loss through percolation and provides optimum water supply to the roots and helps in maintaining soil moisture in the rhizosphere which ultimately reduces thе plant watеr strеss (Zuazo еt al., 2011) [51] . Keeping this in view, the Government of India has been implementing PMKSY encouraging farmers to adopt micro-irrigation to expand cultivable areas under assured irrigation, improve on-farm water use efficiency, reduce wastage of water, enhance the adoption of precisionirrigation and other water saving technologies (More crop per drop). Recognizing the importance of micro-irrigation, the Telangana State government has been providing microirrigation systems to farmers on huge subsidies (80-100%) compared to other states under the PMKSY-TSMIP programme. This led to the adoption of drip irrigation by most of the farmers for irrigating crops especially the mango growing farmers of Telangana. But there are no standardized irrigation schedules for mango crop in Telangana. The irrigation requirement of mango trees mainly depends on agronomic and climatic factors of the particular zone (Naor et al., 2012) [29] . In addition to this, the water requirement during the summer season is more than the winter season (Tejero et al., 2010) [49] . Further, the flowering and fruiting season coincides with summer in mango. Therefore, the shortage of water during flowering and fruit development stages may result in flowering and fruit dropping (Pavel and De Villiers 2004) [32] . Various studies reported that fruit yield was morе with drip irrigation systеm as thе fruit paramеtеrs (lеngth, diamеtеr, numbеr of fruits, and wеight of fruit еtc), wеrе significantly affected by irrigation quantities (Levin еt al., 2017) [25] . In limited water conditions, deficit irrigation can improve water use efficiency because water is allocated properly (Spreer et al. 2009) [48] . Deficit irrigation is defined as the application of water below full crop-water requirements (evapotranspiration) and is an important tool to reduce irrigation water use. Deficit irrigation is an optimization strategy in which irrigation is applied during droughtsensitive growth stages of a crop. In this context, applying small quantities of water in pulses at frequent intervals through a drip which is known as pulse irrigation permits greater control and precision of irrigation timing and the amount of water applied. Pulse irrigation refers to the practice of irrigating for a short period then waiting for another short period and repeating this on-off cycle until the entire irrigation water is applied (Eric et al., 2004) [13] . In addition, a proper water conservation technique like mulching when coupled with this water management practice further provides an effective and efficient way to utilize applied irrigation water through soil moisture conservation. Mulches not only conserve soil moisture but along with modification of soil temperature also check the weed density (Kavino and Kaundal 2009) [17] , which ultimately increase the total and early yield (Pande et al. 2005) [23] . The practice of applying a layer of dead vegetative waste mulch on soil surface such as straw mulch and polyethene mulches to conserve soil moisture has been prevalent for a very long time in many areas. Drip irrigation and mulching offer great savings of water on account of precise and direct application of water to the root zone of plant and soil moisture conservation, respectively.

Material and Methods

The present investigation was carried out during two succeeding seasons i.e., 2015-16 and 2016-17 at Fruit Research Station, Sangareddy, SKLTSHU, Telangana State. The material used and methods adopted during the investigation are presented under the following heads. The climate of Sangareddy is tropical, semi-arid and dry. Ten years old bearing trees of mango cv. Banganpalli, having uniform vigor and health were selected mango orchard. Trees were spaced 8×8 m and received uniform pruning and cultural operations. Sevent two selected trees were subjected to twelve treatments combinations 1. I

Water requirement calculation of mango

Water requirement for mango crop (WR), is a function of surface area covered by plants, evaporation rate and infiltration capacity of the soil. The daily water requirement for fully grown plants was calculated as under. The average value of six years of corresponding months was taken into account and the daily water requirement for experimental plants was calculated as suggested by Shukla et al. (2001) [41] . V = Ep. Kp. Kc. Sp. Sr. Wp Where, V = Volume of water required (litre day -1 plant -1 ), Ep =Pan evaporation as measured by Class-A pan evaporimeter mm day -1 . Kc = Crop co-efficient [co-efficient during fruit development stage 0.85] Kp = Pan co-efficient (0.7) Sp = Plant to plant spacing (m) Sr = Row to row spacing (m) Wp = Fractional wetted area, which varies with different growth stage (0.3 for wider spaced crops).

Soil moisture was measured using Delta-T Devices Profile Probe (PR2). The PR2 soil moisture probe is built around patented sensing technology which provides unprecedented performance in all soil types, with minimal influence from either salinity or temperature. The specific gravity of mango fruits was determined by dividing the weight of the fruit in the air by the volume of the fruits obtained by the water displacement method (Gustafson, 1926) [15] . The total soluble solids (TSS) were determined by using the 'Erma' hand refractometer and expressed as 0 Brix. The titrable acidity was estimated in terms of per cent citric acid (Ranganna, 1986) [34] .

Where, T = Titre, N =Normality of NaOH, V1 =Volume made up (ml), V2 = Volume of extract (ml), E = Equivalent weight of acid and, W = Weight of sample (mg). TSS/Acid ratio was estimated mathematically by dividing the value of TSS with titrable acidity and the data so obtained was expressed as TSS/Acid ratio. Ascorbic acid was estimated by the procedure elicited by Ranganna (1986) [34] . Reducing sugars were determined as per Lane and Eynon (AOAC, 1965) method.Total sugars were determined as per Lane and Eynon (AOAC, 1965) method. The shelf life was determined by recording the number of days the fruits remained in good condition without spoilage in each replication during storage. When the fruit reached a stage that is unsuitable for marketing, it was considered as the end of shelf life which was judged by visual scoring. The design adopted was a randomized block design with the factorial concept. The data were subjected to statistical analysis as per the procedure out lined by Panse and Sukhatme (1985) [31] .

Results and Discussion

The data obtained for the available soil moisture was presented in The active feeder root zone area spreads up to a depth of 60 cm in mango (Bojappa and Singh, 1974) [5] . The distribution of water in the soil occurs along the hydraulic gradient between the wet and the dry soil, laterally using capillary action and vertically due to gravitation (Mahgoub et al., 2017) [26] . In the case of treatment I 2 , water was applied in smaller quantities at three intervals due to which a lower hydraulic gradient was created and the percolation was slow into the soil. This resulted in higher availability of soil moisture at all depths. In the case of treatment I 3 , with the application of bulk volume of water per irrigation with a long gap between the irrigation intervals, a greater hydraulic gradient was created, which resulted in more rapid downward movement of water recording less soil moisture content comparatively, at all studied depths. These results are in agreement with the findings of Eid et al. (2013) [12] who reported increased soil moisture in the root zone of soybean with pulse drip irrigation by applying daily water requirements in eight pulses compared to applying daily water requirements at one time. With an increase in the number of pulses, soil moisture distribution increases in the root zone which in turn increased wetted soil volume, thus the volume of available water in the root zone was more. A similar increase in moisture content in the root zone and wetted soil volume with increased irrigation pulses was also reported in orange (Abdelraouf et al., 2019) [2] , soybean (Eid et al., 2013) [12] and potato (Abdelghany, 2009) [1] . The results revealed that all mulching treatments have recorded higher soil moisture content than control treatment without mulch (M 4 ). The greater moisture content under mulch treatments compared to control was due to reduced soil surface evaporation and weed intensity due to mulching. However, black polythene mulch (M 1 ) has resulted in the highest available soil moisture at all recorded depths than other mulches paddy straw (M 2 ) and saw dust (M 3 ). This high moisture retention ability of plastic mulches could be due to limited evaporation from the soil compared to paddy straw and saw dust mulches which are inherently porous and hygroscopic. Further, the water vapors that evaporate from the soil surface were trapped on the lower side of polythene sheet, it gets condenses and drips down again into the soil surface thus increasing the soil moisture content (Khan et al.

2015) [19] . A similar increase in soil moisture content due to black polythene mulch followed by paddy straw and paddy husk was reported by Das and Dutta (2018) [10] in mango cv. Himsagar. Improvement in soil moisture content with mulching was also reported in several other tropical fruits such as Nagpur mandarin (Shirgure et al. 2003) [39] , mango cv. Himsagar (Ghosh and Bauri, 2003) and guava cv. L-49 (Dutta and Majumder, 2009) [11] .

Regarding the interaction effect, the treatment irrigation as three pulses per day (based on 80% of volume of water) with black polyethene mulch (100 µ) (I 2 M 1 ) has recorded the highest soil moisture (%) at all recorded depths viz., at 10, 20, 30, 40, 60 and 100 cm during entire observation period from January to April whereas lowest soil moisture was recorded by the treatment three hours irrigation at two days interval (Farmer's practice) with no mulch (I 3 M 4 ) mostly.

During January, maximum soil moisture (%) available at 10, 20, 30, 40, 60 and 100 cm depths was recorded as7.84, 18.17, 36.65, 47.59, 68.36 and 97.14%, respectively with the treatment of three pulses of irrigation per day with black polyethylene mulching (I 2 M 1 ). At 10 cm soil depth, minimum soil moisture (5.67%) was recorded by all three irrigation levels combination with no mulch (I 1 M 4 , I 2 M 4 and I 3 M 4 ) whereas at 20 cm soil depth the minimum soil moisture (%) was recorded as 11.27% in the treatment three pulses irrigation per day with no mulch (I 2 M 4 ). Further, at 30 cm soil depth, minimum soil moisture (%) was recorded as 20.67% in the treatment one-time irrigation per day with

no mulch (I 1 M 4 ). At 40, 60 and 100 cm depths lowest soil moisture was recorded as 24.46, 34.04 and 48.75%, respectively in the treatment three hours irrigation at two days intervals with no mulch (I 3 M 4 ). Further, when the mean available soil moisture in the active root zone area (10-60 cm) between best treatment (pulse irrigation with black polythene mulch) (I 2 M 1 ) and farmer's practice of irrigation with no mulch (control) (I 3 M 4 ) was compared, the mean available soil moisture in I 3 M 4 was 19.25% whereas it was found as 35.72% in I 2 M 1 which is 1.86 times to that of I 3 M 4 (Fig 1). . At 10 cm soil depth, no soil moisture (0.00%) was recorded by all three irrigation levels combination with no mulch (I 1 M 4 , I 2 M 4 and I 3 M 4 ) whereas at 20 cm soil depth the minimum soil moisture (%) was recorded as 0.01% in the treatment three pulses irrigation per day with no mulch (I 2 M 4 ). Further, at 30 cm soil depth, minimum soil moisture (%) was recorded as 0.92% in the treatment one-time irrigation per day with no mulch (I 1 M 4 ). At 40, 60 and 100 cm depths lowest soil moisture was recorded as 4.28, 11.14 and 22.53%, respectively in the treatment three hours irrigation at two days intervals with no mulch (I 3 M 4 ). When the mean available soil moisture in the active root zone area (10-60 cm) between pulse irrigation with black polythene mulch (I 2 M 1 ) and farmer's practice of irrigation with no mulch (I 3 M 4 ) was compared, the mean available soil moisture in I 3 M 4 was 3.29% whereas it was found as 19.63% in I 2 M 1 which is 5.96 times to that of I 3 M 4 ( Fig 1). Further, the decrease in soil moisture availability from January to February was 34.75% in I 3 M 4 whereas it is 16.99% inI 2. M 1 . From February to March, the decrease was 39.09% in I 3 M 4 whereas it is 16.83% inI 2. M 1 and from March to April, the decrease was 56.99% in I 3 M 4 whereas it is 20.40% inI 2. M 1 .

Irrigation as three pulses per day along with black polyethene mulch (I 2 M 1 ) has enhanced available soil moisture content due to the synergistic effect of mulching and irrigation treatment. The higher available soil moisture in the soil layers under pulse drip irrigation may be attributed to the fact that daily water requirement was met by the application of smaller quantities of water in three pulses due to which more moisture was confined in the upper layers of soil. The higher available soil moisture by pulse irrigation was further retained without any evaporation loss from the soil surface due to the presence of polythene mulch which has resulted in more soil moisture content in I 2 M 1 than other treatments. This higher moisture content under mulch treatments may be ascribed to reduced evaporation during the daytime which is the main reason for the diurnal cycle in the bare soil. Furthermore, under the plastic mulch, the evaporated moisture condenses on the lower side of the polyethene sheet and drip down again on the soil surface, consequently eliminating the diurnal cycling process of the bare soil. These observations are in accordance with the findings of Raina et al. (1998) [33] and Singh et al. (2004) [44] . Further, these results are in agreement with the findings of Eid et al. (2013) [12] who reported the increased soil moisture content due to the synergistic effect of irrigation as 8 pulses/day along with black polythene mulch in soybean. The pulse irrigation increased water movement in the horizontal direction than vertical direction hence improved soil moisture distribution and wetted soil volume in root zone and black polythene mulch decreased from evaporation process rate from the soil surface. Under control treatment, a higher hydraulic gradient was created owing to the application of bulk volume of water per irrigation with quite wider irrigation intervals, which resulted in more rapid downward movement of water reducing the available soil moisture.

Specific gravity of fruit

The data for the specific gravity of fruit was presented in Table 5. The analysis of pooled data revealed that the individual factors i.e., different levels of irrigation (I) and different mulching (M) have recorded no significant difference in specific gravity of fruit among the treatments in mango cv. Banganpalli.

Regarding the effect of irrigation levels (I), the application of irrigation as three pulses per day (I 2 ) has recorded maximum specific gravity of fruit (1.05) whereas minimum specific gravity of fruit (0.97) was recorded with farmer's practice with three hours irrigation at two days interval (I 3 ). This can be attributed to the increase in fruit weight with irrigation as three pulses per day (I 2 ). This improvement in quality parameters might be due to increased available soil moisture content (Table 1 to 4) leading to greater mobility of major nutrients to the developing fruits (sink) from leaves (source) that resulted in increased stored food material in the tissue (Singh and Rajput, 1977) [45] bearing good sized fruits with increased fruit length and breadth, which in turn increased fruit weight in the present investigation. A similar increase in fruit weight and quality of fruits with different drip irrigation regimes was also reported by Khalifa (2018) [18] in two mango cultivars Ewais and Tommy Atkins, Kumar et al. (2008) [23] in mango hybrid Arka Anmol, Shirgure (2012) [40] in Nagpur mandarin and Marathe et al.

(2018) [27] in pomegranate.

Regarding the effect of different mulching (M), mulching with black polythene (M 1 ) has recorded maximum specific gravity (1.03) which was on par with that of paddy straw mulch (M 2 ) (1.02) and sawdust mulch (M 3 ) (1.01) whereas control (no mulch) (M 4 ) has recorded minimum specific gravity (0.97). This is attributed to the increased soil moisture content (Table 1 to 4) and the resultant increased size of the fruits with more weight under black polythene mulch (M 1 ). A similar increase in fruit weight and fruit quality with mulching treatments was also reported by Das and Dutta (2018) [10] in mango cv. Himsagar, Panigrahi et al (2010) [30] in mango cv. Dashehari, Kiranshankar et al.

(2019) [20] in mango cv. Alphonso and in Nagpur mandarin by Shirgure et al. (2003) [39] .

Regarding, the interaction effect of different levels of irrigation and mulching (I × M) maximum specific gravity (1.08) of fruit was found in irrigation as three pulses per day with black polythene mulch (I 2 M 1 ) whereas three hours irrigation at two days interval with no mulch (I 3 M 4 ) has resulted in minimum specific gravity (0.94) of fruits in mango cv. Banganpalli. This is due to the synergistic effect of pulse irrigation along with mulching, which led to increased soil moisture content (Table 1 to 4) in the root zone, reduced soil temperature creating congenial conditions for better plant growth with increased availability and translocation of nutrients from source to sink resulting in increased fruit weight with good quality. These results are in agreement with findings of other workers who also reported increased fruit weight and fruit quality that includes Panigrahi et al. (2010) [30] in mango cv. Dashehari, Kiranshankar et al. (2019) [20] in mango cv. Alphonso and Shirgure et al. (2003) [39] in Nagpur mandarin.

TSS (ºBrix)

The data for the TSS (ºBrix) of fruit was presented in Table 5. The results revealed that individual factors i.e., different levels of irrigation (I) and different mulching (M) have variably affected the TSS (ºBrix) of fruit among the treatments in mango cv. Banganpalli.

Regarding the effect of irrigation levels (I), the application of irrigation as three pulses per day (I 2 ) has recorded maximum TSS of fruit (15.56 ºBrix) whereas minimum TSS of fruit (14.55 ºBrix) was recorded with farmer's practice with three hours irrigation at two days interval (I 3 ). The increase and decrease in TSS% are directly correlated with hydrolytic changes in starch and conversion of starch to sugar being an important index of the ripening process in mango (Rathore et al., 2007) [35] . There was higher and continuous available soil moisture content (Table 1 to 4) in the root zone with the treatment I 2 , due to pulse irrigation which improved the water and nutrient uptake. This improved moisture and nutrient supply and the availability of optimum soil temperature with I 2 might have promoted enzymatic activity. Improved activity of enzymes may further favour the hydrolysis of metabolites (such as organic acids) resulting in improved TSS content of fruits (Tyagi, 2021). A similar increase in fruit TSS with pulse drip irrigation was reported in Nagpur mandarin (Shirgure, 2012) [40] and orange (Abdelraouf et al., 2019) [2] .

Regarding the effect of different mulching (M), mulching with black polythene (M 1 ) has recorded maximum TSS of fruit (15.57 ºBrix) which was on par with that of paddy straw mulch (M 2 ) (15.36 ºBrix) and sawdust mulch (M 3 ) (15.15 ºBrix) whereas control (no mulch) (M 4 ) has recorded minimum TSS of fruit (14.13 ºBrix). It is evident from the results that all mulching treatments have recorded improved TSS content of the fruit compared to control. Improvement in TSS by mulching might be due to soil moisture conservation and increased soil water availability (Table 1 to 4) which ultimately might have caused the mobilization of soluble carbohydrates to the fruits (Samant et al. 2017) [37] . Similar improvement in fruit quality due to application of mulches has also been reported in mango hybrid 'Amrapali' (Samant et al. 2017) [37] , in mango cv. Alphonso (Kiranshankar et al., 2019) [20] , in mango cv. Himsagar (Das and Dutta, 2018) [1] and in guava by Singh et al. (2015) [46] . Regarding, the interaction effect of different levels of irrigation and mulching (I × M) maximum fruit TSS (16.18 ºBrix) was found in irrigation as three pulses per day with black polythene mulch (I 2 M 1 ) whereas three hours irrigation at two days interval with no mulch (I 3 M 4 ) has resulted in minimum TSS of fruits (13.93 ºBrix) in mango cv. Banganpalli. This is due to the synergistic effect of pulse irrigation along with mulching, which led to the increased soil moisture content in the root zone (Table 1 to 4), reduced soil temperature creating congenial conditions for better plant growth with which ultimately might have caused the mobilization of soluble carbohydrates to the fruits (Samant et al. 2017) [37] resulting in increased fruit TSS. These results are in agreement with findings of other workers who also reported increased fruit TSS with different irrigation regimes and mulching that includes Panigrahi et al (2010) [30] in mango cv. Dashehari, Kiranshankar et al. (2019) [20] in mango cv. Alphonso and Shirgure et al. (2003) [39] in Nagpur mandarin.

The data for total Sugars (%) of fruit was presented in Table 5. The results revealed that individual factors i.e., different levels of irrigation (I) and different mulching (M) have variably affected the total Sugars (%) of fruit among the treatments in mango cv. Banganpalli.

Regarding the effect of irrigation levels (I), the application of irrigation as three pulses per day (I 2 ) has recorded maximum total Sugars (12.82%) whereas minimum total sugars (11.07%) was recorded with farmer's practice with three hours irrigation at two days interval (I 3 ). The pulse irrigation treatment has resulted in higher as well as continuous soil moisture availability (Table 1 to 4) which in turn increased the water and nutrient uptake resulting in higher starch accumulation during the first stage of fruit growth, followed by conversion of starch into sugars during fruit maturation. This resulted in the increased amount of total sugars in fruits under the treatment irrigation as three pulses per day (I 2 ). A similar increase in total sugars of fruits with pulse irrigation was also reported in Nagpur mandarin (Shirgure, 2012) [40] and orange (Abdelraouf et al., 2019) [2] . Further, increased sugars content of fruits as a result of frequent drip irrigation was also reported earlier in the case of sweet orange (Singh and Singh, 1981) [43] .

Regarding the effect of different mulching (M), mulching with black polythene (M 1 ) has recorded maximum total sugars (12.82%) which was on par with that of paddy straw mulch (M 2 ) (12.47%) whereas control (no mulch) (M 4 ) has recorded minimum total sugars (10.37%). The maximum formation of sugars with the ripening of fruits is evident as the disappearance of starch as reported by Joshi and Roy (1985). Increased sugars in the present study might be due to the slow hydrolysis of starch to sugars and the gradual buildup of sugars during ripening (Kulkarni and Yewale, 2012). These findings are in close agreement with the results obtained by other workers who reported a similar increase in total sugars with mulching in mango cv. Alphonso (Kiranshankar et al., 2019) [20] , in mango cv. Himsagar (Das and Dutta, 2018) [10] , in mango (Bhushan et al., 2015) and guava (Dutta and Majumder, 2009) [11] . However, no significant change among the treatments was found regarding the total sugars of fruit with the interaction effect of different levels of irrigation and mulching (I × M) in mango cv. Banganpalli.

The data for reducing and non-reducing sugars (%) of fruit was presented in Tables 5 and6. The perusal of data revealed that individual factors i.e., different levels of irrigation (I) and different mulching (M) and their interaction have affected the reducing and non-reducing sugars (%) of fruit significantly among the treatments in mango cv. Banganpalli.

Regarding the effect of irrigation levels (I), the application of irrigation as three pulses per day (I 2 ) has recorded maximum reducing sugars (5.61%) and non-reducing sugars (7.21%) of fruits whereas minimum reducing sugars (4.24%) and non-reducing sugars (6.83%) was recorded with farmer's practice with three hours irrigation at two days interval (I 3 ). This is due to the high accumulation of total sugars with irrigation as three pulses per day (I 2 ) (Table 5) as discussed above. The pulse irrigation treatment has resulted in higher as well as continuous soil moisture availability (Table 1 to 4) which in turn increased the water and nutrient uptake resulting in higher starch accumulation during the first stage of fruit growth, followed by conversion of starch into sugars during fruit maturation resulting in an increased quantity of reducing and non-reducing sugars. A similar increase in sugar content with pulse irrigation was reported in Nagpur mandarin (Shirgure, 2012) [40] and orange (Abdelraouf et al., 2019) [2] .

Regarding the effect of different mulching (M), mulching with black polythene (M 1 ) has recorded maximum reducing sugars (5.61%) and non-reducing sugars (7.21%) whereas control (no mulch) (M 4 ) has recorded minimum reducing sugars (3.69%) and non-reducing sugars (6.68%). It may be because the increased soil moisture availability (Table 1 to 4) might have reduced nutrient losses and controlled weeds and improved hydrothermal regimes of the soil under black polythene mulching (Kiranshankar et al., 2019) [20] . Similar results were also observed by Kiranshankar et al., (2019) [20] in mango cv. Alphonso, Das et al., (2010) [9] in guava cv. L-49, Chakaraborty and Sadhu (1994) [7] , Singh (2005) [42] in tomato and Singh et al. (2009) [47] in mango.

Regarding the interaction effect of factors (I × M), the interaction effect of irrigation as three pulses per day with black polythene mulch (I 2 M 1 ) has recorded maximum reducing sugars (6.44%) of fruits. Minimum reducing sugars (3.42%) of fruits were recorded by the interaction of three hours irrigation at two days intervals with no mulch (I 3 M 4 ) in mango cv. Banganpalli. This is due to the synergistic effect of pulse irrigation along with mulching increased the total sugar content of the fruit as discussed above (Table 5).

Pulse drip irrigation in association with mulch reduced the water as well as nutrient losses through leaching and maintained higher availability of soil moisture to the root zone (Table 1 to 4). Further, the availability of optimum soil temperature, moisture and nutrient supply might have promoted the enzymatic activity increasing the concentration of total sugars accumulation. However, no significant change among the treatments was found regarding the non-reducing sugars of fruit with the interaction effect of different levels of irrigation and mulching (I × M) in mango cv. Banganpalli. Similar results were reported in Nagpur mandarin (Shirgure, 2012) [40] , orange (Abdelraouf et al., 2019) [2] and guava cv. L-49 (Das et al. 2010) [9] .

The data for acidity (%) of fruit was presented in Table 6.

The results revealed that individual factors i.e., different levels of irrigation (I) and different mulching (M) and their interaction have variably affected the acidity (%) of fruit among the treatments in mango cv. Banganpalli.

Regarding the effect of irrigation levels (I), the application of irrigation as three pulses per day (I 2 ) has recorded minimum acidity (0.22%) of fruits whereas maximum acidity (0.25%) was recorded with farmer's practice with three hours of irrigation at two days interval (I 3 ). This might be due to the pulse irrigation increased the area of the wet zone maintaining more available soil moisture (Table 1 to 4), reducing fertilizer filtration and increased nutrient uptake. Further, the availability of optimum soil temperature, moisture and nutrient supply might have promoted the enzymatic activity (Tyagi, 2021) reducing the organic acid content of fruits during ripening. A similar decrease in fruit acid content with pulse irrigation was reported in Nagpur mandarin (Shirgure, 2012) [40] and orange (Abdelraoufet al., 2019) [2] .

Regarding the effect of different mulching (M), mulching with black polythene (M 1 ) has recorded minimum acidity (0.22%) whereas control (no mulch) (M 4 ) has recorded maximum acidity (0.26%). Organic acids accumulation during the early stages of fruit development is directly related to the supply of substrates for the maintenance of respiration processes during the development (Seymour et al., 2013). During fruit ripening, breakdown of stored carbohydrates to sugars coupled with reductions in acidity occur alongside increases in flavour and aroma volatiles (Klee and Giovannoni, 2011; Cherian et al., 2014). Different mulches significantly decreased the acid content of fruit. This might be due to the better nutrient uptake from soil solution due to increased soil moisture availability (Table 1 to 4) especially due to the effect of leaf potassium and an increased rate of photosynthesis which cumulatively improved the fruit quality (Dutta and Majumdar, 2009) [11] reducing the levels of organic acids during ripening. A similar decrease in titratable acidity of fruits with mulching treatments has been reported by Das and Dutta (2018) [10] in mango cv. Himsagar with black polythene mulch, Dutta and Majumdar (2009) [11] with black polythene and paddy straw mulching in guava and Das et al. (2010) [9] in guava cv. L-49 with paddy straw mulch.

Regarding the interaction effect of factors (I × M), the interaction effect of irrigation as three pulses per day with black polythene mulch (I 2 M 1 ) has recorded minimum acidity (0.20%) of fruits which was on par with the interaction effect of irrigation as three pulses per day with paddy straw mulch (I 2 M 2 ) (0.21%) and with interaction effect of irrigation as three pulses per day with sawdust mulch (I 2 M 3 ) (0.21%). Maximum acidity (0.27%) of fruits was recorded by the interaction of three hours irrigation at two days intervals with no mulch (I 3 M 4 ) in mango cv. Banganpalli. In the present study, the interaction of pulse drip irrigation (I 2 ) with all mulch treatments (M 1 , M 2 , M 3 ) has recorded less acidity of fruits. Pulse drip irrigation in association with mulch reduced the water as well as nutrient losses through leaching and surface run-off and subsequently augmented their availability and uptake. The application of pulse drip irrigations in tandem with mulch maintained higher availability of soil moisture in the root zone (Table 1 to 4). Further, the availability of optimum soil temperature, moisture and nutrient supply might have promoted the enzymatic activity. Improved activity of enzymes may further favour the hydrolysis of metabolites (such as organic acids) (Tyagi, 2021) reducing the organic acids content during ripening thus recording lower acidity of fruits. Similar results were reported in Nagpur mandarin (Shirgure, 2012) [40] , orange (Abdelraoufet al., 2019) [2] and guava cv. L-49 (Das et al. 2010) [9] .

Sugar and Acid ratio

The data for the sugar and acid ratio of fruits was presented in Table 6. The analysis of pooled data revealed that individual factors i.e., different levels of irrigation (I) and different mulching (M) and their interaction have significantly affected the sugar and acid ratio of fruits among the treatments in mango cv. Banganpalli.

Regarding the effect of irrigation levels (I), the application of irrigation as three pulses per day (I 2 ) has recorded maximum sugar and acid ratio (72.29) of fruits whereas minimum (58.98) was recorded with farmer's practice with three hours irrigation at two days interval (I 3 ). The higher sugar to acidity ratio is the indicator of the sweetness of the fruit. If the sugar to acid ratio is high means the fruits have more sugars and less acidity. The increased value of sugar and acid ratio in the present study is because of the increased sugars content (Table 5) and reduced acidity of fruits (Table 6) as discussed above with pulse irrigation. This is due to the pulse irrigation increased the area of the wet zone with increased availability of soil moisture (Table 1 to 4) reducing fertilizer filtration and increased nutrient uptake. Further, the availability of optimum soil temperature, moisture and nutrient supply might have promoted the enzymatic activity (Tyagi, 2021) increasing the sugar concentration and organic acid conversion during fruits during ripening. A similar increase in the sugar and acid ratio of fruits with pulse irrigation was also reported in Nagpur mandarin (Shirgure, 2012) [40] and orange (Abdelraouf et al., 2019) [2] .

Regarding the effect of different mulching (M), mulching with black polythene (M 1 ) has recorded maximum sugar and acid ratio (71.78) whereas control (no mulch) (M 4 ) has recorded minimum sugar and acid ratio (54.50). Different mulches significantly decreased the acid content (Table 6) and increased sugar content (Table 5) of fruit as discussed above. This might be due to the mulching that might have prevented the loss of water from the soil through evaporation and better conserved the soil moisture resulting in increased soil moisture availability (Table 1 to 4). This in turn increased uptake of leaf potassium and an increased rate of photosynthesis which cumulatively improved the fruit quality (Dutta and Majumdar, 2009) [11] reducing the levels of organic acids and increased sugar accumulation during ripening. A similar increase in sugar and acid ratio of fruits with mulching treatments has been reported by Das and Dutta (2018) [10] in mango cv. Himsagar with black polythene mulch, Dutta and Majumdar (2009) [11] with black polythene and paddy straw mulching in guava and Das et al.

(2010) [9] in guava cv. L-49 with paddy straw mulch.

Regarding the interaction effect of factors (I × M), the interaction effect of irrigation as three pulses per day with black polythene mulch (I 2 M 1 ) has recorded maximum sugar and acid ratio (80.54) of fruits. The minimum sugar and acid ratio (52.69) of fruits was recorded by the interaction of three hours irrigation at two days intervals with no mulch (I 3 M 4 ) in mango cv. Banganpalli. This is due to the synergistic effect of pulse irrigation along with mulching which resulted in increased sugar content (Table 5) and reduced acidity (Table 6) of the fruits. These results are in agreement with the findings of Marathe et al., (2018) [27] in pomegranate and Das et al. (2010) [9] in guava cv. L-49.

Shelf life of fruits

The data for the shelf life of fruits was presented in Table 6.

The analysis of pooled data revealed that the individual factors i.e., different levels of irrigation (I) and different mulching (M) have variably affected the shelf life of fruits in mango cv. Banganpalli.

Regarding the effect of irrigation levels (I), the application of irrigation as three pulses per day (I 2 ) has recorded the maximum shelf life of fruits (12.69 days) whereas minimum shelf life (11.09 days) was recorded with farmer's practice with three hours irrigation at two days interval (I 3 ). This could be due to better availability of soil moisture (Table 1 to 4) and nutrients throughout the plant growth and fruiting period with pulse irrigation as discussed above. The quality improvement is mainly due to potassium as it is an enzyme activator and plays an important role in photosynthesis, respiration and synthesis of starch and protein (Marschner 1995) [28] . It also influences the regulation of water in the cell controlling water loss through transpiration (Salisbury and Rose 1992) [36] thus recording more shelf life of fruits. Similar results with improved quality of fruits with pulse irrigation were also reported in Nagpur mandarin (Shirgure, 2012) [40] and orange (Abdelraouf et al., 2019) [2] .

Regarding the effect of different mulching (M), mulching with black polythene (M 1 ) has recorded maximum shelf life of fruits (12.70 days) which was on par with that of paddy straw mulch (M 2 ) (12.37 days) whereas control (no mulch) (M 4 ) has recorded minimum shelf life (10.45 days). From the above results, it is evident that the positive influence of different mulches on yield and fruit quality parameters such as fruit weight, fruit length and breadth, yield and biochemical composition of fruit with increased shelf life was founded with the application of black polythene mulch followed by paddy straw in the present study. An increase in fruit quality with mulching might be due to better conservation of soil moisture, the effect of leaf potassium and an increased rate of photosynthesis which cumulatively improved the fruit quality (Das and Dutta, 2018) [10] . Such beneficial effect of mulching was also observed by Das and Dutta (2018) [10] with black polythene mulch in mango cv. Himsagar and by Das et al. (2010) [9] with paddy straw followed by black polythene mulch in guava cv. L-49 reported that the mulching treatment significantly increases the growth of plants which subsequently increase the fruit physical characters and biochemical composition resulting in better quality fruits. Bhusan et al. also reported that black polythene mulching significantly increased the TSS, reducing sugar, total sugar, reduce acidity and effectively decrease physiological loss in weight resulting in better storage life of mango cv. Amrapali, mulching in guava and Das et al. (2010) [9] in guava cv. L-49 with paddy straw mulch.

Regarding interaction effect of factors (I × M), the interaction effect of irrigation as three pulses per day with black polythene mulch (I 2 M 1 ) has recorded maximum shelf life of fruits (13.66 days) whereas three hours irrigation at two days interval with no mulch (I 3 M 4 ) has resulted in minimum shelf life (10.12 days). This is attributed to the synergistic effect of pulse irrigation along with black polythene mulching which resulted in improved growth of plants which subsequently increase the fruit physical characters and biochemical composition resulting in better quality fruits with more shelf life. These results are in conformity with findings of Shirgure, (2012) [40] in Nagpur mandarin, Abdelraouf et al., (2019) [2] in orange and Das and Dutta (2018) [10] in mango cv. Himsagar.

Summary and Conclusion

The present study has indicated that the interaction effect of different mulching and irrigation levels on soil physical properties, the treatment irrigation as three pulses per day with black polyethene mulch (I 2 M 1 ) has recorded the highest soil moisture (%) at all recorded depths during the entire critical fruit growth and development period i.e., from January to April. The synergistic effect of pulse irrigation along with black polyethene mulch, which led to the increase in soil moisture content in the root zone reduce soil temperature created congenial conditions for better plant growth with which ultimately might have caused the mobilization of soluble carbohydrates and macro and micro nutrients which are essential for the improvement of fruit quality during fruit growth and development. Hence, the interaction effect of irrigation as three pulses per day with black polyethene mulch (I 2 M 1 ) found significant influence resulting in good quality fruits with maximum specific gravity, TSS, reducing sugars and sugar-acid ratio with improved flavour recording minimum titratable acidity and maximum shelf life of fruits.

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