INTRODUCTION Sweet orange (Citrus sinensis), the 2nd most important group of citrus, constituted 23% of total citrus production (Singh, 2001) in India. Mosambi is the choicest variety due to its sweet taste and pleasant aroma. Application of water through drip irrigation along with some mulching materials may be helpful for getting quality fruits. Several workers established the usefulness of drip irrigation in citrus for better plant growth and higher production of quality fruits in addition to other economical benefits of cultivation (Deidda et al, 1994; Kanber et al, 1996; Tayde and Ingle, 1999). Very little information is available regarding the effect of drip versus basin irrigation on growth, yield and fruit quality of sweet orange. Hence, a long term investigation on the above line was carried out in laterite soil. MATERIAL AND METHODS The experiment was conducted in sub-tropical weather at the Regional Research Station, Jhargram of Bidhan Chandra Krishi Viswavidyalaya, situated at 22oN Effect of basin versus drip irrigation on quality production in Mosambi sweet orange S.N. Ghosh and P.P. Pal Department of Fruits and Orchard Management Faculty of Horticulture Bidhan Chandra Krishi Viswavidyalaya Mohanpur – 741 252, India E-mail: profsnghosh@yahoo.co.in ABSTRACT An investigation was undertaken to find out the effect of basin and drip irrigation on growth, production, fruit quality, foliar N, P, K values and soil moisture status in Mosambi sweet orange grown in laterite soil. Treatments included drip irrigation at 0.6, 0.8 and 1.0 Epan with and without black polythene mulching, basin irrigation @ 30 liter/plant at 18 days interval + black polythene mulching and control (No watering + black polythene mulching). The plants receiving irrigation at 0.8 Epan + polythene mulching resulted 136 fruits per plant with superior in fruit quality in terms of highest TSS (11.20B), sugar (8.5%) and vitamin C (47.8 mg/100ml) content. Maximum fruit weight of 166 g and diameter of 7.0 cm were recorded in the fruits of the plants which received irrigation at 1.0 Epan + polythene mulching. Foliar nitrogen content was highest (2.65%) in plants with drip irrigation at 0.8 Epan + polythene mulching while phosphorus and potassium content were non-significant among the treatments. Irrigation (drip or basin) of the plants during dry months resulted lower shoot drying as compared to no irrigation. Key words : Citrus sinensis, drip irrigation, basin irrigation, fruit yield, fruit quality, laterite soil latitude and 87oE longitude with an altitude of 78.8 MSL during 2005 to 2008 (4 consecutive years). The sweet orange cv. Mosambi were planted during 1997 at a spacing of 5x5 m. The soil of the experimental site was laterite with a pH of 5.5. The treatments consisted of : T 1 = Irrigation at 0.6 Epan; T 2 = Irrigation at 0.8 Epan; T 3 = Irrigation at 1.0 Epan; T 4 = T 1 + black polythene mulching; T 5 = T 2 + black polythene mulching; T 6 = T 3 + black polythene mulching; T 7 = Basin watering @ 30 litres/plant at 18 days interval + black polythene mulching, T 8 = Control (No watering + black polythene mulching). The basin watering @ 30 litre/plant was found to be the best for this area as proposed by Chattopadhyay and Ghosh (1992). The irrigation through drip and basin was provided from January to June in each year. The treatments were laid out in a Randomized Block Design with four replications with four plants in each replication. Four emitters/plant at four sides were placed at 90 cm away from the trunk with a discharge rate of 4 l hr-1 emitter-1. The amount of water applied was determined by employing the formula of J. Hortl. Sci. Vol. 5 (1): 25-29, 2010 26 Biswas and Mallick (1999), V = Epan x Kc x Kp x A. Where, V = volume of water applied to each plant per day (mm3); Epan = Pan Evaporation multiplied by 0.6, 0.8 or 1.0 at the irrigation level (mm/day); A = Area of wetting (mm2) [i.e., 60% of canopy area]; Kc = Crop factor (i.e., 0.8) and Kp = Pan coefficient (i.e., 0.8). The crop coefficient (Kc) was adopted from the value suggested by Doorenbos and Pruitt (1977). Thus, the amount of water required for Mosambi plant through drip in January to June (Average of 4 years) has been presented below: The vegetative growth parameters viz., height, basal girth and spread of sweet orange plants under different treatments were recorded at the beginning and at completion of the experiments and the growth was expressed as percentage of promotion. Observation on fruit retention from marble stage to harvest and number of fruits per plant at maturity was made. Physico-chemical analysis of fruit was based on ten randomly selected mature fruits from each plant. For chemical analysis of the fruits, the methods were followed as described by A. O. A. C. (1990). Leaf N was Month Pan Interval Water evaporation watering requirement/plant (cm) (days) (litres) 1.0 0.8 0.6 Epan Epan Epan January 0.23 3 9.1 7.3 5.5 February 0.33 2 8.7 7.0 5.2 March 0.47 0 6.2 5.0 3.7 April 0.57 0 7.5 6.0 4.5 May 0.60 0 7.9 6.3 4.7 June 0.53 0 7.0 5.6 4.2 determined using micro-kjeldahl method, P by vandomolybdophosphoric acid method and K by flame photometer. Foliar N, P and K content from different treatments was estimated during last 2 years and average was mentioned. The dry shoots and branches available after pruning of the plants in December were weighed separately to know the condition of the plants under different treatments. RESULTS AND DISCUSSION Judicious application of water directly to the root zone could improve plant growth and development as observed in Table 1. All growth parameters of Mosambi plants were directly proportional to the amount of irrigation water applied through drip. As the amount of irrigation water increased, the growth of plants with respect to height, girth and canopy spread also proportionately increased and the findings was in consonance with Castle and Lopez (1993). Mulching the plant with black polythene also had a great influence on growth characters. It was observed that plant respond well when irrigated at 1.0 Epan as compared to 0.6 and 0.8 Epan, but mulching with black polythene further enhanced the rate of growth. Pruning of dry shoots is considered to be one of the cultural practices in sweet orange cultivation as shoots are dried up every year due to various reasons. It was found from the results in Table 1 that irrigated plants (drip or basin) showed lower shoot drying as compared to control plants (no watering) and indicated that regular watering in dry periods is not only needed for fruit production but also for maintenance of plant health and vigor. Unlike vegetative growth, fruit production did not proportionately increase with the increase in amount of irrigation water (Table 2). The pooled data of 4 years showed that the plants under T 5 gave highest production (136 fruits plant-1) closely followed by T 6 (133.5 fruits plant-1). The Table 1. Effect of drip versus basin irrigation on plant growth in Mosambi sweet orange Treatment- Plant growth (percent promotion) Pruned dry Height Basal girth Plant spread shoot (kg) East-West North-South T 1 = Irrigation through drip at 0.6 Epan 38.3 50.0 87.1 105.3 2.1 T 2 = Irrigation through drip at 0.8 Epan 44.9 50.6 97.6 110.9 2.0 T 3 = Irrigation through drip at 1.0 Epan 45.0 56.4 114.6 124.8 0.7 T 4 = T 1 + Black polythene mulch 44.0 54.4 107.2 114.2 0.9 T 5 = T 2 + Black polythene mulch 52.1 64.0 113.6 120.8 1.5 T 6 = T 3 + Black polythene mulch 67.3 67.5 143.4 131.2 1.9 T 7 = Basin watering + Black polythene mulch 35.4 49.3 84.4 85.2 0.6 T 8 = Control 31.5 49.0 79.3 78.8 2.9 CD (P=0.05) 4.2 2.5 3.4 3.2 0.4 J. Hortl. Sci. Vol. 5 (1): 25-29, 2010 Ghosh and Pal 27 plants under T 8 resulted lowest fruit production and was about to half of the fruits produced by T 5 . The highest fruit production under T 5 may be due to maximum fruit retention (68.6%) which consequently resulted in the maximum number of fruits per plant. It is clear from the result (Table 2) that a regular and low amount of moisture supply is essential for retention of more number of fruits in sweet orange as compared to sudden application of high amount of water (T 7 ). It is well established that water is very much essential during growth and development of fruits as water helps mobilization of nutrients and food materials to the growing fruits. Increase in fruit production due to irrigation through drip was also reported by Tayde and Ingle (1999) who found that drip method of irrigation produced significantly maximum yield of bigger size fruits. It was further noted that number of fruits plant-1 was decreased from 2008. It might have been due to reduction of economic life of the plants which were raised on the rootstock like rough lemon (Citrus jambhiri). It was already established that productivity of sweet orange would be decreased from 10-15 years of orchard life if rough lemon is used as rootstock (Chohan et al, 1980). Fruit weight and size was significantly increased with the increase in volume of water (Table 3) and the effect was enhanced with the black polythene mulching. Maximum fruit weight (168 g) and size (7.0 cm) were measured from the plants in T 6 followed by the plants in T 5 . Minimum fruit weight (114 g) and size (5.8 cm) were noticed from control plants where no irrigation was provided. These observations were in line with the findings of Sepaskhah and Kashefipur (1986) who obtained highest yield in sweet lime under drip irrigation at 0.75 Epan while, maximum weight of fruit, pulp and juice percentage resulted from higher water application through drip. Larger fruit size in drip irrigated plants may be due to constant available soil moisture during fruit development stage (Brestler, 1977). The juice recovery percentage (Table 3) was significantly increased with the increase in amount of water and highest juice recovery (60.2%) was found from the plants in T 6 followed by T 5 (57.6%). The lowest juice recovery was noted from control plants (45.5%). Patil et al (1997) also noted more juice and less pomace in the fruits of Nagpur mandarin under drip system. It is evident from the data in table 3 that total soluble solids content was significantly improved due to irrigation Table 2. Effect of drip versus basin irrigation on fruit yield in Mosambi sweet orange Treatment Number of fruits/plant Fruit@ 2005 2006 2007 2008 Pooled retention (%) T 1 = Irrigation through drip at 0.6 Epan 61 98 125 100 96.0 53.6(47.06) T 2 = Irrigation through drip at 0.8 Epan 68 120 170 115 118.3 69.2(56.29) T 3 = Irrigation through drip at 1.0 Epan 52 118 135 110 103.8 67.5(55.24) T 4 = T 1 + Black polythene mulch 76 105 150 100 107.8 66.4(54.57) T 5 = T 2 + Black polythene mulch 99 130 190 125 136.0 68.6(55.92) T 6 = T 3 + Black polythene mulch 86 126 192 130 133.5 67.9(55.49) T 7 = Basin watering + Black polythene mulch 50 90 126 95 90.3 51.2(45.69) T 8 = Control 36 85 80 82 70.8 45.4(42.36) CD (P=0.05) 10.2 4.1 7.5 4.5 3.8 4.8 * Figures in the parantheses are angular transformed values @ From marble stage to harvest Table 3. Effect of drip versus basin irrigation on physico-chemical characteristics of fruits in Mosambi sweet orange Treatment Fruit Fruit Juice Total Total Acidity Vitamin weight diameter recovery soluble sugar (%) C mg/ (g) (cm) (%) solids (%) 100 ml (0Brix) (juice) T 1 = Irrigation through drip at 0.6 Epan 132 6.5 46.0 (42.71) 8.5 7.4 0.40 45.0 T 2 = Irrigation through drip at 0.8 Epan 138 6.5 52.2 (46.26) 9.0 7.5 0.39 45.5 T 3 = Irrigation through drip at 1.0 Epan 144 6.8 56.0 (48.45) 10.1 8.0 0.39 45.8 T 4 = T 1 + Black polythene mulch 139 6.6 56.0 (48.45) 10.0 8.0 0.35 47.5 T 5 = T 2 + Black polythene mulch 155 6.9 57.6 (49.37) 11.2 8.5 0.36 47.8 T 6 = T 3 + Black polythene mulch 168 7.0 60.2 (50.89) 10.2 8.1 0.36 47.6 T 7 = Basin watering + Black polythene mulch 146 6.7 48.0 (43.85) 8.4 7.4 0.39 44.5 T 8 = Control 114 5.8 45.5 (42.42) 7.9 7.3 0.38 42.1 CD (P=0.05) 3.5 0.2 2.4 0.4 N.S. N.S. 1.3 * Figures in the parantheses are angular transformed values J. Hortl. Sci. Vol. 5 (1): 25-29, 2010 Effect of type of irrigation on sweet orange production 28 either through drip or basin and it was maximum in fruits of the plants in T 5 (11.20B) followed by the plants in T 6 (10.20B). This observation corroborated with the findings obtained by Tayde and Ingle (1999) who recorded higher TSS content in the fruits of drip irrigated plants than other methods. The total sugar and acidity content in the fruits were not significantly differ among the treatments, however, vitamin C content in fruits varied significantly due to different treatments and it was highest by fruits of the plants received drip irrigation in T 5 (47.8 mg/100ml) closely followed T 6 (47.6 mg/100 ml). Sepeskhah and Kashefipur (1994) also recorded higher vitamin C content in drip irrigated plants. The vitamin C content was lowest in fruits of the plants with no irrigation (42.1 mg/100 ml). Foliar N, P and K content was analyzed to know the leaf nutrient status under different treatments as it has been established that fruit yield and quality is very much related with the N, P and K values of leaf (Bhargava, 1999). It was found that N, P and K values in all the treatments were in optimum range (Ghosh, 2004). The nitrogen content was significantly highest (2.65%) in the plants with irrigation at 0.8 Epan + black polythene mulching followed by in plants (2.40%) with irrigation at 1.0 Epan + black polythene mulching. The phosphorus and potassium content in the leaves were not varied significantly among the treatments (Table 4). ACKNOWLEDGEMENT The authors are thankful to the Department of Food Processing Industries and Horticulture, Government of West Bengal for providing financial assistance for the study. Thanks are also to the Associate Director of Research, Regional Research Station, B.C.K.V., Jhargram for providing all sorts of help and cooperation for carrying out the investigation smoothly. REFERENCES A.O.A.C. 1990. Official Method of Analysis. Assoc. Official Analytical Chemists. 15th Edn. Washington, D.C., U.S.A. Bhargava, B.S. 1999. Leaf analysis for diagnosing nutrients need in fruit crops. Ind. Hort., 43:6-8 Biswas, R.K. and Mallick, S. 1999. Performance of drip irrigation in papaya cultivation in new alluvial agroclimatic zone of West Bengal. Ann. Agril. Res., 20:116-117 Brestler, E. 1977. Trickle irrigation : Principle and application to water management. Adv. Agron., 29:343-393 Castle, J.R. and Lopez, J.G. 1993. Response of young Clementine citrus trees to drip irrigation. Citrus Sub- tropical Fruit J., 735:313-323 Chattopadhyay, N. and Ghosh, S.N. 1992. Studies on the interval of watering during dry period on fruit retention, yield and quality of sweet orange cv. Mosambi under rainfed condition. Orissa J. Hort., 20(Special): 60-63 Chohan, G.S., Thatai, S.K. and Sharma, J.N. 1980. The influence of rootstocks on tree growth, yield and fruit quality of Valencia orange in Punjab. Ind. J. Hort., 37:41-44 Deidda, P., Filigheddu, M.R. and Dettori, S. 1994. Progress report on influence of irrigation system on yield and fruit quality in Valencia orange. Proc. 7th Int’l. Citrus Cong., Italy, 8-13 March, 1994 Doorenbos, J. and Pruitt, W.O. 1977. Crop water requirements. Irrigation and Drainage. F.A.O.U.N., Rome, Italy, paper No. 24. Ghosh, S.N. 2004. Integrated Management Practices for sweet orange production under rainfed laterite soil of West Bengal, India. Proc. Int’l. Soc. Citriculture, pp. 551-557 Kanber, R., Koksal, H., Onder, S. and Eylen, M. 1996. Effects of different irrigation methods on yield, evaporation and root development of young orange Table 4. Effect of drip versus basin irrigation on foliar NPK status of Mosambi sweet orange Treatment Foliar content (per cent dry weight basis) Nitrogen Phosphorus Potassium T 1 = Irrigation 2.00 (8.13) 0.10 (1.81) 1.20 (6.29) through drip at 0.6 Epan T 2 = Irrigation 2.10 (8.33) 0.12 (1.81) 1.30 (6.55) through drip at 0.8 Epan T 3 = Irrigation 2.20 (8.53) 0.12 (1.81) 1.40 (6.80) through drip at 1.0 Epan T 4 = T 1 + Black 2.30 (8.72) 0.12 (1.81) 1.40 (6.80) polythene mulch T 5 = T 2 + Black 2.65 (9.28) 0.16 (2.56) 1.80 (7.71) polythene mulch T 6 = T 3 + Black 2.40 (8.91) 0.16 (2.56) 1.70 (7.49) polythene mulch T 7 = Basin watering 1.98 (8.12) 0.14 (1.81) 1.20 (6.29) + Black polythene mulch T 8 = Control 1.90 (7.92) 0.10 (1.81) 1.10 (6.02) CD (P=0.05) 0.25 N.S N.S * Figures in the parantheses are angular transformed values J. Hortl. Sci. Vol. 5 (1): 25-29, 2010 Ghosh and Pal 29 trees. Turkish J. Agri. Forestry, 20:163-172 Patil, V.S., Damke, M.M. and Panchbhai, D.M. 1997. 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