INTRODUCTION Strawberry (Fragaria x ananassa Duch.) is one of the important small-fruit crops, belonging to the family Rosaceae. It is a rich source of vitamins, minerals and has a tantalizing flavour and aroma. The added advantage with strawberry is that it gives early and very high returns per unit area compared to other fruit crops because the crop is ready for harvest within six months from planting. Though previously concentrated in the temperate region, with advent of day-neutral cultivars, it is now profitably grown in the tropical and sub-tropical regions as well. In India, a sizeable increase in area and production of strawberry has been observed in recent years. Being highly remunerative, it has become very popular among growers, especially, closer to towns and cities. In India, Maharashtra is a leading state in production of strawberry fruits. It has also become popular in the plains and hilly areas of Himachal Pradesh, Jammu and Kashmir, Uttar Pradesh, Rajasthan, Punjab and Haryana, as a low-volume, high-priced fruit crop, in places where sufficient irrigation facilities exist. In Himachal Pradesh, strawberry cultivation has gained momentum only in the past few years and the area Evaluation of mulch colour for enhancing winter-strawberry production under polyhouse in mid-hills of Himachal Pradesh Bunty Shylla and C.L. Sharma Krishi Vigyan Kendra Dr. Y.S. Parmar University of Horticulture & Forestry Kandaghat, Solan - 173 215, Himachal Pradesh, India E-mail:shyllabunty@yahoo.com ABSTRACT Strawberry cultivation in Himachal Pradesh is mainly based on outdoor planting using hay as mulch and, very recently, using black polythene as mulch. The bulk of its production under field conditions usually occurs in April- May when market price is quite low. In an effort to make the crop remunerative through enhanced winter-production, a polyhouse experiment was set up to investigate influence of mulch colour on off-season fruiting response, fruit size and quality in strawberry (Fragaria x ananassa Duch.). Plants of cv. Chandler were planted in September, 2004. Irrigation was imposed using the given through T-Tape system, from 8.00 AM to 5.00 PM. Yellow plastic mulch significantly increased number of fruits, effected early and higher total yield compared to black or silver-over-purple plastic mulches. Un-mulched bed produced lowest yield and fruit quality. Yellow plastic mulch raised soil temperature by at least 2oC compared to the un-mulched bed. Key words: Strawberry, polyhouse, mulch colour, fruit yield, fruit quality under cultivation is 13 ha, with a total production of 89 MT (Anonymous 2006). Generally, it is planted in the second fortnight of September under open conditions by traditional methods using hay-mulch and, very recently, using black plastic mulch (to a small extent). The bulk of production under field conditions usually occurs in April-May, when the average market price is quite low. High market-price can be realized if winter-production is enhanced. Thus, the key to maintaining profitability in the strawberry industry in Himachal Pradesh (and thereby, commercialization of the crop) is enhanced winter-production. This can be done under controlled environment, along with use of micro-irrigation system and coloured mulch for better productivity and quality. With this in view, the present study was conducted to assess the effect of mulch colour on growth and cropping in strawberry and to explore the possibility of enhancing winter- production of this fruit under polyhouse. MATERIAL AND METHODS The study was conducted at the experimental farm of Department of Soil Science and Water Management, Dr. Y.S. Parmar University of Horticulture and Forestry, Solan, Himachal Pradesh, during 2004-2005. The experiment was J. Hortl. Sci. Vol. 5 (1): 34-37, 2010 35 laid out in Completely Randomized Block Design under a polyhouse with misting facilities, and the crop was irrigated through the T-Tape irrigation system. Uniform runners of cultivar ‘Chandler’ were planted in 1x1 m raised-beds at a distance of 20 x 20 cm, in the second fortnight of September with planting density of 16 plants m-2 and 4 rows per bed. Plants were mist-irrigated with tubes hanging 1.5 m above the plant-surface. Misting was terminated at 4 weeks, and then, the plants were irrigated through two T-Tape drip- irrigation tubes per bed. After 30 days of planting, the beds were covered with mulch treatments and plants were pulled up through a 5 cm dia perforation in the plastic. Treatments included three polyethylene-mulch colours: black (T 1 ); silver- over-purple (T 2 ); yellow (T 3 ), plus a bare- ground treatment i.e., control (T 4 ). The experiment was laid out in Randomized Complete Block Design with three replicates. Recommended basal doses of phosphorus (40 kg ha-1), potash (40 kg ha-1) and FYM (50 t ha-1) were applied at the time of preparation of beds. Nitrogen was applied in two equal split doses. Half the nitrogen was applied one month after planting, and the remaining half after flowering. Soil Temperatures were monitored on a daily basis, while, soil moisture was recorded at weekly intervals. Marketable fruits were harvested for early (15 December to 15 February) and total (15 December to 15 May) yield. Mean fruit weight, mean fruit size, fruit number and TSS were also recorded and subjected to statistical analysis of variance. RESULTS AND DISCUSSION All growth and yield parameters were significantly influenced by mulching through its modifying effect on hydrothermal regimes and physico-chemical properties of the soil, as also reported by various workers (Monescu and Ciofu, 1970; Tripathi and Katiyar, 1984; Poling,1994). These are also very efficient in reducing competition from weeds for nutrients and water (Shylla et al, 2005). Mulch-colour markedly affected plant growth and cropping and these results are in agreement with findings of Mohamed (2002). It was possible to produce fruits of good size and taste during winter months under polyhouse, wherein the environment (Fig. 3) was quite favourable for growth and harvest of good quality fruits starting from December. A perusal of data presented in Table 1 and Fig. 1 reveals that maximum average berry weight (13.22 g), length (45.32 mm) and breadth (27.54 mm) was recorded under black polythene mulch which was statistically at par with silver-on-purple polythene mulch (Gupta and Acharya, 1993; Himerlick et al, 1993; Gupta and Acharya, 1994). This may be attributed to better soil hydrothermal regimes (Fig. 3-5), better moisture conservation and suppression of weeds in a crop mulched with black polythene rather than with other mulches (Badiyala and Aggarwal, 1981; Tarara, 2000; Sharma and Sharma, 2004). Maximum number of fruits per m2 was recorded under yellow polythene mulch, which was statistically different from all other treatments. This may be attributed to better moisture conservation, optimum soil temperature and nutrient supply in weed-free plots during fruit development in strawberry. Marumoto et al (1991) also reported a positive influence of soil temperature and mulch on growth and cropping in strawberry. Black polythene mulch improved fruit quality as indicated by increased total Table 1. Major effects of mulch colour on growth, yield and quality of strawberry grown under polyhouse Treatment Berry Berry length Berry diameter Fruit number/m2 TSS(%) Early yield Total yield weight(g) (mm) (mm) (Q/ha) (Q/ha) T 1 = Black polythene much 13.22 45.32 27.54 27.20 10.00 48.81 104.94 T 2 = Silver-over-purple 13.22 43.74 24.67 25.60 10.20 51.85 111.48 polythene mulch T 3 = Yellow polythene mulch 13.12 41.58 23.59 35.00 8.00 7.61 143.30 T 4 = Control (bare-ground) 11.37 40.80 22.89 15.60 9.00 31.47 76.98 CD (P=0.05) 0.09 0.59 1.08 5.96 0.87 17.31 26.98 T 1 = Black polythene much, T 2 = Silver-over-purple polythene mulch, T 3 = Yellow polythene mulch, T 4 = Control (bare-ground) Fig 1. Effect of mulch-colour on fruit quality in polyhouse-grown strawberry J. Hortl. Sci. Vol. 5 (1): 34-37, 2010 Mulch colour and winter-strawberry production under polyhouse 36 soluble solids (Fig. 2). This effect may be attributed to increased soil temperature (Fig. 4) and optimum soil moisture (Fig. 5), which may have led to early fruit-ripening. These results are in accordance with findings of Hassan et al (2000) Shylla and Chauhan (2004) also reported maximum TSS, minimum acidity, maximum TSS/acid ratio, with black polythene mulch. Fruit size, weight and TSS were low in bare-ground, which is congruent with findings of Hassan et al (2000) and Shylla & Chauhan (2004). Early yield as well as maximum total yield was observed under yellow polythene mulch, though the fruits were less sweet than in other treatments. This may be attributed to the fact that yellow- coloured sheets faded to a white under polyhouse conditions. Similar results of highest yields for ‘Chandler’ with white- on-black mulch were reported by Himerlick et al (1993). When the effect of black plastic mulch on early and total yield is compared to that in silver-on-purple plastic mulch, the latter resulted in earlier and greater total yield, though these were statistically at par. Mohamed (2002), however, reported silver-on-purple (S/P) plastic mulch to significantly Fig 2. Effect of mulch colour on fruit yield and TSS of polyhouse grown strawberry Fig 3. Environmental parameters under polyhouse Fig 4. Effect of mulch colour on soil temperature of polyhouse grown strawberry increase early and total yield over clear or black mulch. Besides black polythene mulch, increase in yield using coloured plastic mulch has also been reported by various workers in strawberry (Fear and Nonnecke, 1989; Albregts and Chandler, 1993; Himelrick et al, 1993; Mohamed, 2002). Plants on bare-ground had poorest growth and cropping performance, which is in conformity with findings of Hassan et al (2000) and Shylla and Chauhan (2004). Under polyhouse conditions, maximum and earliest yields were observed under yellow polythene mulch, while, better quality fruits were obtained under black polythene mulch. Till date, strawberry cultivation in the mid-hill zone of Himachal Pradesh is practiced only in open fields where bulk of the fruit production usually occurs in April-May, fetching a low price in the market. Hence, results obtained in the present trial offer a possibility of producing off-season, good quality strawberry under polyhouse during winter months in the mid-hill zone of Himachal Pradesh. This can fetch a better price and prove to be highly remunerative to strawberry farmers. Fig 5. Effect of mulch colour on soil moisture of polyhouse grown strawberry J. Hortl. Sci. Vol. 5 (1): 34-37, 2010 Bunty Shylla and Sharma 37 ACKNOWLEDGEMENT The authors are highly grateful to National Committee on Plasticulture Applications in Horticulture (NCPAH), New Delhi, for providing financial assistance. 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Effect of mulches on thermal regime of soil. Soil Tillage Res., 4:381- 390 (MS Received 16 June 2009, Revised 20 May 2010) J. Hortl. Sci. Vol. 5 (1): 34-37, 2010 Mulch colour and winter-strawberry production under polyhouse